* Re: [PATCH v3] epoll.7: clarify the event distribution under edge-triggered mode
From: 潘少 @ 2024-07-31 15:22 UTC (permalink / raw)
To: Alejandro Colomar; +Cc: Michael Kerrisk, linux-man, linux-api
In-Reply-To: <l5ezb77kqvbmypsvv4nek7ce46sghrm6ox6zbeq7hzd6j2ouv2@mhaihw3rkwjl>
Hi Alejandro,
I believe I've found a more suitable place to put this added clarification sentence. Please check out the [PATCH v4], thanks!
-----------
Best regards,
Andy Pan
^ permalink raw reply
* [PATCH v4] epoll.7: clarify the event distribution under edge-triggered mode
From: Andy Pan via B4 Relay @ 2024-07-31 15:17 UTC (permalink / raw)
To: Alejandro Colomar; +Cc: linux-man, linux-api, mtk.manpages, Andy Pan, Andy Pan
From: Andy Pan <i@andypan.me>
For the moment, the edge-triggered epoll generates an event for each
receipt of a chunk of data, that is to say, epoll_wait() will return
and tell us a monitored file descriptor is ready whenever there is a
new activity on that FD since we were last informed about that FD.
This is not a real _edge_ implementation for epoll, but it's been
working this way for years and plenty of projects are relying on it
to eliminate the overhead of one system call of read(2) per wakeup event.
There are several renowned open-source projects relying on this feature
for notification function (with eventfd): register eventfd with EPOLLET
and avoid calling read(2) on the eventfd when there is wakeup event (eventfd being written).
Examples: nginx [1], netty [2], tokio [3], libevent [4], ect. [5]
These projects are widely used in today's Internet infrastructures.
Thus, changing this behavior of epoll ET will fundamentally break them
and cause a significant negative impact.
Linux has changed it for pipe before [6], breaking some Android libraries,
which had got "reverted" somehow. [7] [8]
Nevertheless, the paragraph in the manual pages describing this
characteristic of epoll ET seems ambiguous, I think a more explict
sentence should be used to clarify it. We're improving the notification
mechanism for libuv recently by exploiting this feature with eventfd,
which brings us a significant performance boost. [9]
Therefore, we (as well as the maintainers of nginx, netty, tokio, etc.)
would have a sense of security to build an enhanced notification function
based on this feature if there is a guarantee of retaining this implementation
of epoll ET for the backward compatibility in the man pages.
[1]: https://github.com/nginx/nginx/blob/efc6a217b92985a1ee211b6bb7337cd2f62deb90/src/event/modules/ngx_epoll_module.c#L386-L457
[2]: https://github.com/netty/netty/pull/9192
[3]: https://github.com/tokio-rs/mio/blob/309daae21ecb1d46203a7dbc0cf4c80310240cba/src/sys/unix/waker.rs#L111-L143
[4]: https://github.com/libevent/libevent/blob/525f5d0a14c9c103be750f2ca175328c25505ea4/event.c#L2597-L2614
[5]: https://github.com/libuv/libuv/pull/4400#issuecomment-2123798748
[6]: https://lkml.iu.edu/hypermail/linux/kernel/2010.1/04363.html
[7]: https://github.com/torvalds/linux/commit/3a34b13a88caeb2800ab44a4918f230041b37dd9
[8]: https://github.com/torvalds/linux/commit/3b844826b6c6affa80755254da322b017358a2f4
[9]: https://github.com/libuv/libuv/pull/4400#issuecomment-2103232402
Signed-off-by: Andy Pan <i@andypan.me>
---
Changes in v4:
- Move the added sentence elsewhere to make more sense
- Link to v3: https://lore.kernel.org/r/20240730-epoll-et-desc-v3-1-6aa81b1c400d@andypan.me
Changes in v3:
- Updated the git commit description
- Link to v2: https://lore.kernel.org/r/20240727-epoll-et-desc-v2-1-c99b2ac66775@andypan.me
Changes in v2:
- Added the git commit description based on feedback
- Link to v1: https://lore.kernel.org/r/20240727-epoll-et-desc-v1-1-390bafc678b9@andypan.me
---
man/man7/epoll.7 | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/man/man7/epoll.7 b/man/man7/epoll.7
index 951500131..a7235971d 100644
--- a/man/man7/epoll.7
+++ b/man/man7/epoll.7
@@ -121,7 +121,8 @@ .SS Level-triggered and edge-triggered
meanwhile the remote peer might be expecting a response based on the
data it already sent.
The reason for this is that edge-triggered mode
-delivers events only when changes occur on the monitored file descriptor.
+delivers events only when changes occur on the monitored file descriptor,
+that is, an event will only be generated upon each receipt of a chunk of data.
So, in step
.B 5
the caller might end up waiting for some data that is already present inside
---
base-commit: cbc0a111e4dceea2037c51098de33e6bc8c16a5c
change-id: 20240727-epoll-et-desc-04ea9a590f3b
Best regards,
--
Andy Pan <i@andypan.me>
^ permalink raw reply related
* [PATCH RFT v7 9/9] selftests/clone3: Test shadow stack support
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook
In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org>
Add basic test coverage for specifying the shadow stack for a newly
created thread via clone3(), including coverage of the newly extended
argument structure. We check that a user specified shadow stack can be
provided, and that invalid combinations of parameters are rejected.
In order to facilitate testing on systems without userspace shadow stack
support we manually enable shadow stacks on startup, this is architecture
specific due to the use of an arch_prctl() on x86. Due to interactions with
potential userspace locking of features we actually detect support for
shadow stacks on the running system by attempting to allocate a shadow
stack page during initialisation using map_shadow_stack(), warning if this
succeeds when the enable failed.
In order to allow testing of user configured shadow stacks on
architectures with that feature we need to ensure that we do not return
from the function where the clone3() syscall is called in the child
process, doing so would trigger a shadow stack underflow. To do this we
use inline assembly rather than the standard syscall wrapper to call
clone3(). In order to avoid surprises we also use a syscall rather than
the libc exit() function., this should be overly cautious.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
tools/testing/selftests/clone3/clone3.c | 134 +++++++++++++++++++++-
tools/testing/selftests/clone3/clone3_selftests.h | 38 ++++++
2 files changed, 171 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c
index 26221661e9ae..81c2e8648e8b 100644
--- a/tools/testing/selftests/clone3/clone3.c
+++ b/tools/testing/selftests/clone3/clone3.c
@@ -3,6 +3,7 @@
/* Based on Christian Brauner's clone3() example */
#define _GNU_SOURCE
+#include <asm/mman.h>
#include <errno.h>
#include <inttypes.h>
#include <linux/types.h>
@@ -11,6 +12,7 @@
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
+#include <sys/mman.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/un.h>
@@ -19,8 +21,12 @@
#include <sched.h>
#include "../kselftest.h"
+#include "../ksft_shstk.h"
#include "clone3_selftests.h"
+static bool shadow_stack_supported;
+static size_t max_supported_args_size;
+
enum test_mode {
CLONE3_ARGS_NO_TEST,
CLONE3_ARGS_ALL_0,
@@ -28,6 +34,10 @@ enum test_mode {
CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG,
CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG,
CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG,
+ CLONE3_ARGS_SHADOW_STACK,
+ CLONE3_ARGS_SHADOW_STACK_NO_SIZE,
+ CLONE3_ARGS_SHADOW_STACK_NO_POINTER,
+ CLONE3_ARGS_SHADOW_STACK_NO_TOKEN,
};
typedef bool (*filter_function)(void);
@@ -44,6 +54,44 @@ struct test {
filter_function filter;
};
+
+/*
+ * We check for shadow stack support by attempting to use
+ * map_shadow_stack() since features may have been locked by the
+ * dynamic linker resulting in spurious errors when we attempt to
+ * enable on startup. We warn if the enable failed.
+ */
+static void test_shadow_stack_supported(void)
+{
+ long ret;
+
+ ret = syscall(__NR_map_shadow_stack, 0, getpagesize(), 0);
+ if (ret == -1) {
+ ksft_print_msg("map_shadow_stack() not supported\n");
+ } else if ((void *)ret == MAP_FAILED) {
+ ksft_print_msg("Failed to map shadow stack\n");
+ } else {
+ ksft_print_msg("Shadow stack supportd\n");
+ shadow_stack_supported = true;
+
+ if (!shadow_stack_enabled)
+ ksft_print_msg("Mapped but did not enable shadow stack\n");
+ }
+}
+
+static unsigned long long get_shadow_stack_page(unsigned long flags)
+{
+ unsigned long long page;
+
+ page = syscall(__NR_map_shadow_stack, 0, getpagesize(), flags);
+ if ((void *)page == MAP_FAILED) {
+ ksft_print_msg("map_shadow_stack() failed: %d\n", errno);
+ return 0;
+ }
+
+ return page;
+}
+
static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
{
struct __clone_args args = {
@@ -89,6 +137,21 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
case CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG:
args.exit_signal = 0x00000000000000f0ULL;
break;
+ case CLONE3_ARGS_SHADOW_STACK:
+ /* We need to specify a normal stack too to avoid corruption */
+ args.shadow_stack = get_shadow_stack_page(SHADOW_STACK_SET_TOKEN);
+ args.shadow_stack_size = getpagesize();
+ break;
+ case CLONE3_ARGS_SHADOW_STACK_NO_POINTER:
+ args.shadow_stack_size = getpagesize();
+ break;
+ case CLONE3_ARGS_SHADOW_STACK_NO_SIZE:
+ args.shadow_stack = get_shadow_stack_page(SHADOW_STACK_SET_TOKEN);
+ break;
+ case CLONE3_ARGS_SHADOW_STACK_NO_TOKEN:
+ args.shadow_stack = get_shadow_stack_page(0);
+ args.shadow_stack_size = getpagesize();
+ break;
}
memcpy(&args_ext.args, &args, sizeof(struct __clone_args));
@@ -102,7 +165,12 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
if (pid == 0) {
ksft_print_msg("I am the child, my PID is %d\n", getpid());
- _exit(EXIT_SUCCESS);
+ /*
+ * Use a raw syscall to ensure we don't get issues
+ * with manually specified shadow stack and exit handlers.
+ */
+ syscall(__NR_exit, EXIT_SUCCESS);
+ ksft_print_msg("CHILD FAILED TO EXIT PID is %d\n", getpid());
}
ksft_print_msg("I am the parent (%d). My child's pid is %d\n",
@@ -191,6 +259,26 @@ static bool no_timenamespace(void)
return true;
}
+static bool have_shadow_stack(void)
+{
+ if (shadow_stack_supported) {
+ ksft_print_msg("Shadow stack supported\n");
+ return true;
+ }
+
+ return false;
+}
+
+static bool no_shadow_stack(void)
+{
+ if (!shadow_stack_supported) {
+ ksft_print_msg("Shadow stack not supported\n");
+ return true;
+ }
+
+ return false;
+}
+
static size_t page_size_plus_8(void)
{
return getpagesize() + 8;
@@ -334,6 +422,47 @@ static const struct test tests[] = {
.expected = -EINVAL,
.test_mode = CLONE3_ARGS_NO_TEST,
},
+ {
+ .name = "Shadow stack on system with shadow stack",
+ .size = 0,
+ .expected = 0,
+ .e2big_valid = true,
+ .test_mode = CLONE3_ARGS_SHADOW_STACK,
+ .filter = no_shadow_stack,
+ },
+ {
+ .name = "Shadow stack with no pointer",
+ .size = 0,
+ .expected = -EINVAL,
+ .e2big_valid = true,
+ .test_mode = CLONE3_ARGS_SHADOW_STACK_NO_POINTER,
+ },
+ {
+ .name = "Shadow stack with no size",
+ .size = 0,
+ .expected = -EINVAL,
+ .e2big_valid = true,
+ .test_mode = CLONE3_ARGS_SHADOW_STACK_NO_SIZE,
+ .filter = no_shadow_stack,
+ },
+ {
+ .name = "Shadow stack with no token",
+ .flags = CLONE_VM,
+ .size = 0,
+ .expected = SIGSEGV,
+ .e2big_valid = true,
+ .test_mode = CLONE3_ARGS_SHADOW_STACK_NO_TOKEN,
+ .filter = no_shadow_stack,
+ },
+ {
+ .name = "Shadow stack on system without shadow stack",
+ .flags = CLONE_VM,
+ .size = 0,
+ .expected = -EINVAL,
+ .e2big_valid = true,
+ .test_mode = CLONE3_ARGS_SHADOW_STACK,
+ .filter = have_shadow_stack,
+ },
};
int main(int argc, char *argv[])
@@ -341,9 +470,12 @@ int main(int argc, char *argv[])
size_t size;
int i;
+ enable_shadow_stack();
+
ksft_print_header();
ksft_set_plan(ARRAY_SIZE(tests));
test_clone3_supported();
+ test_shadow_stack_supported();
for (i = 0; i < ARRAY_SIZE(tests); i++)
test_clone3(&tests[i]);
diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/testing/selftests/clone3/clone3_selftests.h
index 39b5dcba663c..38d82934668a 100644
--- a/tools/testing/selftests/clone3/clone3_selftests.h
+++ b/tools/testing/selftests/clone3/clone3_selftests.h
@@ -31,12 +31,50 @@ struct __clone_args {
__aligned_u64 set_tid;
__aligned_u64 set_tid_size;
__aligned_u64 cgroup;
+#ifndef CLONE_ARGS_SIZE_VER2
+#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */
+#endif
+ __aligned_u64 shadow_stack;
+ __aligned_u64 shadow_stack_size;
+#ifndef CLONE_ARGS_SIZE_VER3
+#define CLONE_ARGS_SIZE_VER3 104 /* sizeof fourth published struct */
+#endif
};
+/*
+ * For architectures with shadow stack support we need to be
+ * absolutely sure that the clone3() syscall will be inline and not a
+ * function call so we open code.
+ */
+#ifdef __x86_64__
+static pid_t __always_inline sys_clone3(struct __clone_args *args, size_t size)
+{
+ long ret;
+ register long _num __asm__ ("rax") = __NR_clone3;
+ register long _args __asm__ ("rdi") = (long)(args);
+ register long _size __asm__ ("rsi") = (long)(size);
+
+ __asm__ volatile (
+ "syscall\n"
+ : "=a"(ret)
+ : "r"(_args), "r"(_size),
+ "0"(_num)
+ : "rcx", "r11", "memory", "cc"
+ );
+
+ if (ret < 0) {
+ errno = -ret;
+ return -1;
+ }
+
+ return ret;
+}
+#else
static pid_t sys_clone3(struct __clone_args *args, size_t size)
{
return syscall(__NR_clone3, args, size);
}
+#endif
static inline void test_clone3_supported(void)
{
--
2.39.2
^ permalink raw reply related
* [PATCH RFT v7 8/9] selftests/clone3: Allow tests to flag if -E2BIG is a valid error code
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook
In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org>
The clone_args structure is extensible, with the syscall passing in the
length of the structure. Inside the kernel we use copy_struct_from_user()
to read the struct but this has the unfortunate side effect of silently
accepting some overrun in the structure size providing the extra data is
all zeros. This means that we can't discover the clone3() features that
the running kernel supports by simply probing with various struct sizes.
We need to check this for the benefit of test systems which run newer
kselftests on old kernels.
Add a flag which can be set on a test to indicate that clone3() may return
-E2BIG due to the use of newer struct versions. Currently no tests need
this but it will become an issue for testing clone3() support for shadow
stacks, the support for shadow stacks is already present on x86.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
tools/testing/selftests/clone3/clone3.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c
index 3b3a08e6a34d..26221661e9ae 100644
--- a/tools/testing/selftests/clone3/clone3.c
+++ b/tools/testing/selftests/clone3/clone3.c
@@ -39,6 +39,7 @@ struct test {
size_t size;
size_function size_function;
int expected;
+ bool e2big_valid;
enum test_mode test_mode;
filter_function filter;
};
@@ -153,6 +154,11 @@ static void test_clone3(const struct test *test)
ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n",
getpid(), ret, test->expected);
if (ret != test->expected) {
+ if (test->e2big_valid && ret == -E2BIG) {
+ ksft_print_msg("Test reported -E2BIG\n");
+ ksft_test_result_skip("%s\n", test->name);
+ return;
+ }
ksft_print_msg(
"[%d] Result (%d) is different than expected (%d)\n",
getpid(), ret, test->expected);
--
2.39.2
^ permalink raw reply related
* [PATCH RFT v7 7/9] selftests/clone3: Explicitly handle child exits due to signals
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook
In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org>
In order to improve diagnostics and allow tests to explicitly look for
signals check to see if the child exited due to a signal and if it did
print the code and return it as a positive value, distinct from the
negative errnos currently returned.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
tools/testing/selftests/clone3/clone3.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c
index e066b201fa64..3b3a08e6a34d 100644
--- a/tools/testing/selftests/clone3/clone3.c
+++ b/tools/testing/selftests/clone3/clone3.c
@@ -111,6 +111,13 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
ksft_print_msg("waitpid() returned %s\n", strerror(errno));
return -errno;
}
+
+ if (WIFSIGNALED(status)) {
+ ksft_print_msg("Child exited with signal %d\n",
+ WTERMSIG(status));
+ return WTERMSIG(status);
+ }
+
if (!WIFEXITED(status)) {
ksft_print_msg("Child did not exit normally, status 0x%x\n",
status);
--
2.39.2
^ permalink raw reply related
* [PATCH RFT v7 6/9] selftests/clone3: Factor more of main loop into test_clone3()
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook
In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org>
In order to make it easier to add more configuration for the tests and
more support for runtime detection of when tests can be run pass the
structure describing the tests into test_clone3() rather than picking
the arguments out of it and have that function do all the per-test work.
No functional change.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
tools/testing/selftests/clone3/clone3.c | 77 ++++++++++++++++-----------------
1 file changed, 37 insertions(+), 40 deletions(-)
diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c
index e61f07973ce5..e066b201fa64 100644
--- a/tools/testing/selftests/clone3/clone3.c
+++ b/tools/testing/selftests/clone3/clone3.c
@@ -30,6 +30,19 @@ enum test_mode {
CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG,
};
+typedef bool (*filter_function)(void);
+typedef size_t (*size_function)(void);
+
+struct test {
+ const char *name;
+ uint64_t flags;
+ size_t size;
+ size_function size_function;
+ int expected;
+ enum test_mode test_mode;
+ filter_function filter;
+};
+
static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
{
struct __clone_args args = {
@@ -109,30 +122,40 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
return 0;
}
-static bool test_clone3(uint64_t flags, size_t size, int expected,
- enum test_mode test_mode)
+static void test_clone3(const struct test *test)
{
+ size_t size;
int ret;
+ if (test->filter && test->filter()) {
+ ksft_test_result_skip("%s\n", test->name);
+ return;
+ }
+
+ if (test->size_function)
+ size = test->size_function();
+ else
+ size = test->size;
+
+ ksft_print_msg("Running test '%s'\n", test->name);
+
ksft_print_msg(
"[%d] Trying clone3() with flags %#" PRIx64 " (size %zu)\n",
- getpid(), flags, size);
- ret = call_clone3(flags, size, test_mode);
+ getpid(), test->flags, size);
+ ret = call_clone3(test->flags, size, test->test_mode);
ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n",
- getpid(), ret, expected);
- if (ret != expected) {
+ getpid(), ret, test->expected);
+ if (ret != test->expected) {
ksft_print_msg(
"[%d] Result (%d) is different than expected (%d)\n",
- getpid(), ret, expected);
- return false;
+ getpid(), ret, test->expected);
+ ksft_test_result_fail("%s\n", test->name);
+ return;
}
- return true;
+ ksft_test_result_pass("%s\n", test->name);
}
-typedef bool (*filter_function)(void);
-typedef size_t (*size_function)(void);
-
static bool not_root(void)
{
if (getuid() != 0) {
@@ -160,16 +183,6 @@ static size_t page_size_plus_8(void)
return getpagesize() + 8;
}
-struct test {
- const char *name;
- uint64_t flags;
- size_t size;
- size_function size_function;
- int expected;
- enum test_mode test_mode;
- filter_function filter;
-};
-
static const struct test tests[] = {
{
.name = "simple clone3()",
@@ -319,24 +332,8 @@ int main(int argc, char *argv[])
ksft_set_plan(ARRAY_SIZE(tests));
test_clone3_supported();
- for (i = 0; i < ARRAY_SIZE(tests); i++) {
- if (tests[i].filter && tests[i].filter()) {
- ksft_test_result_skip("%s\n", tests[i].name);
- continue;
- }
-
- if (tests[i].size_function)
- size = tests[i].size_function();
- else
- size = tests[i].size;
-
- ksft_print_msg("Running test '%s'\n", tests[i].name);
-
- ksft_test_result(test_clone3(tests[i].flags, size,
- tests[i].expected,
- tests[i].test_mode),
- "%s\n", tests[i].name);
- }
+ for (i = 0; i < ARRAY_SIZE(tests); i++)
+ test_clone3(&tests[i]);
ksft_finished();
}
--
2.39.2
^ permalink raw reply related
* [PATCH RFT v7 5/9] selftests/clone3: Remove redundant flushes of output streams
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook
In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org>
Since there were widespread issues with output not being flushed the
kselftest framework was modified to explicitly set the output streams
unbuffered in commit 58e2847ad2e6 ("selftests: line buffer test
program's stdout") so there is no need to explicitly flush in the clone3
tests.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
tools/testing/selftests/clone3/clone3_selftests.h | 2 --
1 file changed, 2 deletions(-)
diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/testing/selftests/clone3/clone3_selftests.h
index 3d2663fe50ba..39b5dcba663c 100644
--- a/tools/testing/selftests/clone3/clone3_selftests.h
+++ b/tools/testing/selftests/clone3/clone3_selftests.h
@@ -35,8 +35,6 @@ struct __clone_args {
static pid_t sys_clone3(struct __clone_args *args, size_t size)
{
- fflush(stdout);
- fflush(stderr);
return syscall(__NR_clone3, args, size);
}
--
2.39.2
^ permalink raw reply related
* [PATCH RFT v7 4/9] fork: Add shadow stack support to clone3()
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook
In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org>
Unlike with the normal stack there is no API for configuring the the shadow
stack for a new thread, instead the kernel will dynamically allocate a new
shadow stack with the same size as the normal stack. This appears to be due
to the shadow stack series having been in development since before the more
extensible clone3() was added rather than anything more deliberate.
Add parameters to clone3() specifying the location and size of a shadow
stack for the newly created process. If no shadow stack is specified
then the existing implicit allocation behaviour is maintained.
If a stack is specified then it is required to have an architecture
defined token placed on the stack, this will be consumed by the new
task. If the token is not provided then this will be reported as a
segmentation fault with si_code SEGV_CPERR, as a runtime shadow stack
protection error would be. This allows architectures to implement the
validation of the token in the child process context.
If the architecture does not support shadow stacks the shadow stack
parameters must be zero, architectures that do support the feature are
expected to enforce the same requirement on individual systems that lack
shadow stack support.
Update the existing x86 implementation to pay attention to the newly added
arguments, in order to maintain compatibility we use the existing behaviour
if no shadow stack is specified. Minimal validation is done of the supplied
parameters, detailed enforcement is left to when the thread is executed.
Since we are now using more fields from the kernel_clone_args we pass that
into the shadow stack code rather than individual fields.
At present this implementation does not consume the shadow stack token
atomically as would be desirable, it uses a separate read and write.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/x86/include/asm/shstk.h | 11 +++--
arch/x86/kernel/process.c | 2 +-
arch/x86/kernel/shstk.c | 104 +++++++++++++++++++++++++++++++++----------
include/linux/sched/task.h | 13 ++++++
include/uapi/linux/sched.h | 13 ++++--
kernel/fork.c | 76 ++++++++++++++++++++++++++-----
6 files changed, 176 insertions(+), 43 deletions(-)
diff --git a/arch/x86/include/asm/shstk.h b/arch/x86/include/asm/shstk.h
index 4cb77e004615..252feeda6999 100644
--- a/arch/x86/include/asm/shstk.h
+++ b/arch/x86/include/asm/shstk.h
@@ -6,6 +6,7 @@
#include <linux/types.h>
struct task_struct;
+struct kernel_clone_args;
struct ksignal;
#ifdef CONFIG_X86_USER_SHADOW_STACK
@@ -16,8 +17,8 @@ struct thread_shstk {
long shstk_prctl(struct task_struct *task, int option, unsigned long arg2);
void reset_thread_features(void);
-unsigned long shstk_alloc_thread_stack(struct task_struct *p, unsigned long clone_flags,
- unsigned long stack_size);
+unsigned long shstk_alloc_thread_stack(struct task_struct *p,
+ const struct kernel_clone_args *args);
void shstk_free(struct task_struct *p);
int setup_signal_shadow_stack(struct ksignal *ksig);
int restore_signal_shadow_stack(void);
@@ -28,8 +29,10 @@ static inline long shstk_prctl(struct task_struct *task, int option,
unsigned long arg2) { return -EINVAL; }
static inline void reset_thread_features(void) {}
static inline unsigned long shstk_alloc_thread_stack(struct task_struct *p,
- unsigned long clone_flags,
- unsigned long stack_size) { return 0; }
+ const struct kernel_clone_args *args)
+{
+ return 0;
+}
static inline void shstk_free(struct task_struct *p) {}
static inline int setup_signal_shadow_stack(struct ksignal *ksig) { return 0; }
static inline int restore_signal_shadow_stack(void) { return 0; }
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index f63f8fd00a91..59456ab8d93f 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -207,7 +207,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
* is disabled, new_ssp will remain 0, and fpu_clone() will know not to
* update it.
*/
- new_ssp = shstk_alloc_thread_stack(p, clone_flags, args->stack_size);
+ new_ssp = shstk_alloc_thread_stack(p, args);
if (IS_ERR_VALUE(new_ssp))
return PTR_ERR((void *)new_ssp);
diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
index 059685612362..1755fa21e6fb 100644
--- a/arch/x86/kernel/shstk.c
+++ b/arch/x86/kernel/shstk.c
@@ -191,44 +191,102 @@ void reset_thread_features(void)
current->thread.features_locked = 0;
}
-unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags,
- unsigned long stack_size)
+int arch_shstk_post_fork(struct task_struct *t, struct kernel_clone_args *args)
+{
+ /*
+ * SSP is aligned, so reserved bits and mode bit are a zero, just mark
+ * the token 64-bit.
+ */
+ struct mm_struct *mm;
+ unsigned long addr;
+ u64 expected;
+ u64 val;
+ int ret = -EINVAL;;
+
+ addr = args->shadow_stack + args->shadow_stack_size - sizeof(u64);
+ expected = (addr - SS_FRAME_SIZE) | BIT(0);
+
+ mm = get_task_mm(t);
+ if (!mm)
+ return -EFAULT;
+
+ /* This should really be an atomic cmpxchg. It is not. */
+ if (access_remote_vm(mm, addr, &val, sizeof(val),
+ FOLL_FORCE) != sizeof(val))
+ goto out;
+
+ if (val != expected)
+ goto out;
+ val = 0;
+ if (access_remote_vm(mm, addr, &val, sizeof(val),
+ FOLL_FORCE | FOLL_WRITE) != sizeof(val))
+ goto out;
+
+ ret = 0;
+
+out:
+ mmput(mm);
+ return ret;
+}
+
+unsigned long shstk_alloc_thread_stack(struct task_struct *tsk,
+ const struct kernel_clone_args *args)
{
struct thread_shstk *shstk = &tsk->thread.shstk;
+ unsigned long clone_flags = args->flags;
unsigned long addr, size;
/*
* If shadow stack is not enabled on the new thread, skip any
- * switch to a new shadow stack.
+ * implicit switch to a new shadow stack and reject attempts to
+ * explciitly specify one.
*/
- if (!features_enabled(ARCH_SHSTK_SHSTK))
- return 0;
+ if (!features_enabled(ARCH_SHSTK_SHSTK)) {
+ if (args->shadow_stack || args->shadow_stack_size)
+ return (unsigned long)ERR_PTR(-EINVAL);
- /*
- * For CLONE_VFORK the child will share the parents shadow stack.
- * Make sure to clear the internal tracking of the thread shadow
- * stack so the freeing logic run for child knows to leave it alone.
- */
- if (clone_flags & CLONE_VFORK) {
- shstk->base = 0;
- shstk->size = 0;
return 0;
}
/*
- * For !CLONE_VM the child will use a copy of the parents shadow
- * stack.
+ * If the user specified a shadow stack then do some basic
+ * validation and use it, otherwise fall back to a default
+ * shadow stack size if the clone_flags don't indicate an
+ * allocation is unneeded.
*/
- if (!(clone_flags & CLONE_VM))
- return 0;
+ if (args->shadow_stack) {
+ addr = args->shadow_stack;
+ size = args->shadow_stack_size;
+ } else {
+ /*
+ * For CLONE_VFORK the child will share the parents
+ * shadow stack. Make sure to clear the internal
+ * tracking of the thread shadow stack so the freeing
+ * logic run for child knows to leave it alone.
+ */
+ if (clone_flags & CLONE_VFORK) {
+ shstk->base = 0;
+ shstk->size = 0;
+ return 0;
+ }
- size = adjust_shstk_size(stack_size);
- addr = alloc_shstk(0, size, 0, false);
- if (IS_ERR_VALUE(addr))
- return addr;
+ /*
+ * For !CLONE_VM the child will use a copy of the
+ * parents shadow stack.
+ */
+ if (!(clone_flags & CLONE_VM))
+ return 0;
- shstk->base = addr;
- shstk->size = size;
+ size = args->stack_size;
+ size = adjust_shstk_size(size);
+ addr = alloc_shstk(0, size, 0, false);
+ if (IS_ERR_VALUE(addr))
+ return addr;
+
+ /* We allocated the shadow stack, we should deallocate it. */
+ shstk->base = addr;
+ shstk->size = size;
+ }
return addr + size;
}
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index d362aacf9f89..56b2013d7fe5 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -43,6 +43,8 @@ struct kernel_clone_args {
void *fn_arg;
struct cgroup *cgrp;
struct css_set *cset;
+ unsigned long shadow_stack;
+ unsigned long shadow_stack_size;
};
/*
@@ -230,4 +232,15 @@ static inline void task_unlock(struct task_struct *p)
DEFINE_GUARD(task_lock, struct task_struct *, task_lock(_T), task_unlock(_T))
+#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
+int arch_shstk_post_fork(struct task_struct *p,
+ struct kernel_clone_args *args);
+#else
+static inline int arch_shstk_post_fork(struct task_struct *p,
+ struct kernel_clone_args *args)
+{
+ return 0;
+}
+#endif
+
#endif /* _LINUX_SCHED_TASK_H */
diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
index 3bac0a8ceab2..8b7af52548fd 100644
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -84,6 +84,10 @@
* kernel's limit of nested PID namespaces.
* @cgroup: If CLONE_INTO_CGROUP is specified set this to
* a file descriptor for the cgroup.
+ * @shadow_stack: Pointer to the memory allocated for the child
+ * shadow stack.
+ * @shadow_stack_size: Specify the size of the shadow stack for
+ * the child process.
*
* The structure is versioned by size and thus extensible.
* New struct members must go at the end of the struct and
@@ -101,12 +105,15 @@ struct clone_args {
__aligned_u64 set_tid;
__aligned_u64 set_tid_size;
__aligned_u64 cgroup;
+ __aligned_u64 shadow_stack;
+ __aligned_u64 shadow_stack_size;
};
#endif
-#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
-#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */
-#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */
+#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
+#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */
+#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */
+#define CLONE_ARGS_SIZE_VER3 104 /* sizeof fourth published struct */
/*
* Scheduling policies
diff --git a/kernel/fork.c b/kernel/fork.c
index cc760491f201..18278c72681c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -128,6 +128,11 @@
*/
#define MAX_THREADS FUTEX_TID_MASK
+/*
+ * Require that shadow stacks can store at least one element
+ */
+#define SHADOW_STACK_SIZE_MIN sizeof(void *)
+
/*
* Protected counters by write_lock_irq(&tasklist_lock)
*/
@@ -2729,6 +2734,19 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
return copy_process(NULL, 0, node, &args);
}
+static void shstk_post_fork(struct task_struct *p,
+ struct kernel_clone_args *args)
+{
+ if (!IS_ENABLED(CONFIG_ARCH_HAS_USER_SHADOW_STACK))
+ return;
+
+ if (!args->shadow_stack)
+ return;
+
+ if (arch_shstk_post_fork(p, args) != 0)
+ force_sig_fault_to_task(SIGSEGV, SEGV_CPERR, NULL, p);
+}
+
/*
* Ok, this is the main fork-routine.
*
@@ -2790,6 +2808,8 @@ pid_t kernel_clone(struct kernel_clone_args *args)
*/
trace_sched_process_fork(current, p);
+ shstk_post_fork(p, args);
+
pid = get_task_pid(p, PIDTYPE_PID);
nr = pid_vnr(pid);
@@ -2939,7 +2959,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
CLONE_ARGS_SIZE_VER1);
BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
CLONE_ARGS_SIZE_VER2);
- BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
+ BUILD_BUG_ON(offsetofend(struct clone_args, shadow_stack_size) !=
+ CLONE_ARGS_SIZE_VER3);
+ BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER3);
if (unlikely(usize > PAGE_SIZE))
return -E2BIG;
@@ -2972,16 +2994,18 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
return -EINVAL;
*kargs = (struct kernel_clone_args){
- .flags = args.flags,
- .pidfd = u64_to_user_ptr(args.pidfd),
- .child_tid = u64_to_user_ptr(args.child_tid),
- .parent_tid = u64_to_user_ptr(args.parent_tid),
- .exit_signal = args.exit_signal,
- .stack = args.stack,
- .stack_size = args.stack_size,
- .tls = args.tls,
- .set_tid_size = args.set_tid_size,
- .cgroup = args.cgroup,
+ .flags = args.flags,
+ .pidfd = u64_to_user_ptr(args.pidfd),
+ .child_tid = u64_to_user_ptr(args.child_tid),
+ .parent_tid = u64_to_user_ptr(args.parent_tid),
+ .exit_signal = args.exit_signal,
+ .stack = args.stack,
+ .stack_size = args.stack_size,
+ .tls = args.tls,
+ .set_tid_size = args.set_tid_size,
+ .cgroup = args.cgroup,
+ .shadow_stack = args.shadow_stack,
+ .shadow_stack_size = args.shadow_stack_size,
};
if (args.set_tid &&
@@ -3022,6 +3046,34 @@ static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
return true;
}
+/**
+ * clone3_shadow_stack_valid - check and prepare shadow stack
+ * @kargs: kernel clone args
+ *
+ * Verify that shadow stacks are only enabled if supported.
+ */
+static inline bool clone3_shadow_stack_valid(struct kernel_clone_args *kargs)
+{
+ if (kargs->shadow_stack) {
+ if (!kargs->shadow_stack_size)
+ return false;
+
+ if (kargs->shadow_stack_size < SHADOW_STACK_SIZE_MIN)
+ return false;
+
+ if (kargs->shadow_stack_size > rlimit(RLIMIT_STACK))
+ return false;
+
+ /*
+ * The architecture must check support on the specific
+ * machine.
+ */
+ return IS_ENABLED(CONFIG_ARCH_HAS_USER_SHADOW_STACK);
+ } else {
+ return !kargs->shadow_stack_size;
+ }
+}
+
static bool clone3_args_valid(struct kernel_clone_args *kargs)
{
/* Verify that no unknown flags are passed along. */
@@ -3044,7 +3096,7 @@ static bool clone3_args_valid(struct kernel_clone_args *kargs)
kargs->exit_signal)
return false;
- if (!clone3_stack_valid(kargs))
+ if (!clone3_stack_valid(kargs) || !clone3_shadow_stack_valid(kargs))
return false;
return true;
--
2.39.2
^ permalink raw reply related
* [PATCH RFT v7 3/9] mm: Introduce ARCH_HAS_USER_SHADOW_STACK
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook,
David Hildenbrand
In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org>
Since multiple architectures have support for shadow stacks and we need to
select support for this feature in several places in the generic code
provide a generic config option that the architectures can select.
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Deepak Gupta <debug@rivosinc.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/x86/Kconfig | 1 +
fs/proc/task_mmu.c | 2 +-
include/linux/mm.h | 2 +-
mm/Kconfig | 6 ++++++
4 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 007bab9f2a0e..320e1f411163 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1957,6 +1957,7 @@ config X86_USER_SHADOW_STACK
depends on AS_WRUSS
depends on X86_64
select ARCH_USES_HIGH_VMA_FLAGS
+ select ARCH_HAS_USER_SHADOW_STACK
select X86_CET
help
Shadow stack protection is a hardware feature that detects function
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 5f171ad7b436..0ea49725f524 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -984,7 +984,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
[ilog2(VM_UFFD_MINOR)] = "ui",
#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
-#ifdef CONFIG_X86_USER_SHADOW_STACK
+#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
[ilog2(VM_SHADOW_STACK)] = "ss",
#endif
#ifdef CONFIG_64BIT
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c4b238a20b76..3357625c1db3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -342,7 +342,7 @@ extern unsigned int kobjsize(const void *objp);
#endif
#endif /* CONFIG_ARCH_HAS_PKEYS */
-#ifdef CONFIG_X86_USER_SHADOW_STACK
+#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
/*
* VM_SHADOW_STACK should not be set with VM_SHARED because of lack of
* support core mm.
diff --git a/mm/Kconfig b/mm/Kconfig
index b72e7d040f78..3167be663bca 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1263,6 +1263,12 @@ config IOMMU_MM_DATA
config EXECMEM
bool
+config ARCH_HAS_USER_SHADOW_STACK
+ bool
+ help
+ The architecture has hardware support for userspace shadow call
+ stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss).
+
source "mm/damon/Kconfig"
endmenu
--
2.39.2
^ permalink raw reply related
* [PATCH RFT v7 2/9] selftests: Provide helper header for shadow stack testing
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook
In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org>
While almost all users of shadow stacks should be relying on the dynamic
linker and libc to enable the feature there are several low level test
programs where it is useful to enable without any libc support, allowing
testing without full system enablement. This low level testing is helpful
during bringup of the support itself, and also in enabling coverage by
automated testing without needing all system components in the target root
filesystems to have enablement.
Provide a header with helpers for this purpose, intended for use only by
test programs directly exercising shadow stack interfaces.
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
tools/testing/selftests/ksft_shstk.h | 63 ++++++++++++++++++++++++++++++++++++
1 file changed, 63 insertions(+)
diff --git a/tools/testing/selftests/ksft_shstk.h b/tools/testing/selftests/ksft_shstk.h
new file mode 100644
index 000000000000..85d0747c1802
--- /dev/null
+++ b/tools/testing/selftests/ksft_shstk.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Helpers for shadow stack enablement, this is intended to only be
+ * used by low level test programs directly exercising interfaces for
+ * working with shadow stacks.
+ *
+ * Copyright (C) 2024 ARM Ltd.
+ */
+
+#ifndef __KSFT_SHSTK_H
+#define __KSFT_SHSTK_H
+
+#include <asm/mman.h>
+
+/* This is currently only defined for x86 */
+#ifndef SHADOW_STACK_SET_TOKEN
+#define SHADOW_STACK_SET_TOKEN (1ULL << 0)
+#endif
+
+static bool shadow_stack_enabled;
+
+#ifdef __x86_64__
+#define ARCH_SHSTK_ENABLE 0x5001
+#define ARCH_SHSTK_SHSTK (1ULL << 0)
+
+#define ARCH_PRCTL(arg1, arg2) \
+({ \
+ long _ret; \
+ register long _num asm("eax") = __NR_arch_prctl; \
+ register long _arg1 asm("rdi") = (long)(arg1); \
+ register long _arg2 asm("rsi") = (long)(arg2); \
+ \
+ asm volatile ( \
+ "syscall\n" \
+ : "=a"(_ret) \
+ : "r"(_arg1), "r"(_arg2), \
+ "0"(_num) \
+ : "rcx", "r11", "memory", "cc" \
+ ); \
+ _ret; \
+})
+
+#define ENABLE_SHADOW_STACK
+static inline __attribute__((always_inline)) void enable_shadow_stack(void)
+{
+ int ret = ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK);
+ if (ret == 0)
+ shadow_stack_enabled = true;
+}
+
+#endif
+
+#ifndef __NR_map_shadow_stack
+#define __NR_map_shadow_stack 453
+#endif
+
+#ifndef ENABLE_SHADOW_STACK
+static inline void enable_shadow_stack(void) { }
+#endif
+
+#endif
+
+
--
2.39.2
^ permalink raw reply related
* [PATCH RFT v7 1/9] Documentation: userspace-api: Add shadow stack API documentation
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook
In-Reply-To: <20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org>
There are a number of architectures with shadow stack features which we are
presenting to userspace with as consistent an API as we can (though there
are some architecture specifics). Especially given that there are some
important considerations for userspace code interacting directly with the
feature let's provide some documentation covering the common aspects.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
Documentation/userspace-api/index.rst | 1 +
Documentation/userspace-api/shadow_stack.rst | 41 ++++++++++++++++++++++++++++
2 files changed, 42 insertions(+)
diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst
index 274cc7546efc..c39709bfba2c 100644
--- a/Documentation/userspace-api/index.rst
+++ b/Documentation/userspace-api/index.rst
@@ -59,6 +59,7 @@ Everything else
ELF
netlink/index
+ shadow_stack
sysfs-platform_profile
vduse
futex2
diff --git a/Documentation/userspace-api/shadow_stack.rst b/Documentation/userspace-api/shadow_stack.rst
new file mode 100644
index 000000000000..c576ad3d7ec1
--- /dev/null
+++ b/Documentation/userspace-api/shadow_stack.rst
@@ -0,0 +1,41 @@
+=============
+Shadow Stacks
+=============
+
+Introduction
+============
+
+Several architectures have features which provide backward edge
+control flow protection through a hardware maintained stack, only
+writeable by userspace through very limited operations. This feature
+is referred to as shadow stacks on Linux, on x86 it is part of Intel
+Control Enforcement Technology (CET), on arm64 it is Guarded Control
+Stacks feature (FEAT_GCS) and for RISC-V it is the Zicfiss extension.
+It is expected that this feature will normally be managed by the
+system dynamic linker and libc in ways broadly transparent to
+application code, this document covers interfaces and considerations.
+
+
+Enabling
+========
+
+Shadow stacks default to disabled when a userspace process is
+executed, they can be enabled for the current thread with a syscall:
+
+ - For x86 the ARCH_SHSTK_ENABLE arch_prctl()
+
+It is expected that this will normally be done by the dynamic linker.
+Any new threads created by a thread with shadow stacks enabled will
+themselves have shadow stacks enabled.
+
+
+Enablement considerations
+=========================
+
+- Returning from the function that enables shadow stacks without first
+ disabling them will cause a shadow stack exception. This includes
+ any syscall wrapper or other library functions, the syscall will need
+ to be inlined.
+- A lock feature allows userspace to prevent disabling of shadow stacks.
+- Those that change the stack context like longjmp() or use of ucontext
+ changes on signal return will need support from libc.
--
2.39.2
^ permalink raw reply related
* [PATCH RFT v7 0/9] fork: Support shadow stacks in clone3()
From: Mark Brown @ 2024-07-31 12:14 UTC (permalink / raw)
To: Rick P. Edgecombe, Deepak Gupta, Szabolcs Nagy, H.J. Lu,
Florian Weimer, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira, Valentin Schneider,
Christian Brauner, Shuah Khan
Cc: linux-kernel, Catalin Marinas, Will Deacon, jannh, bsegall,
linux-kselftest, linux-api, Mark Brown, Kees Cook,
David Hildenbrand
The kernel has recently added support for shadow stacks, currently
x86 only using their CET feature but both arm64 and RISC-V have
equivalent features (GCS and Zicfiss respectively), I am actively
working on GCS[1]. With shadow stacks the hardware maintains an
additional stack containing only the return addresses for branch
instructions which is not generally writeable by userspace and ensures
that any returns are to the recorded addresses. This provides some
protection against ROP attacks and making it easier to collect call
stacks. These shadow stacks are allocated in the address space of the
userspace process.
Our API for shadow stacks does not currently offer userspace any
flexiblity for managing the allocation of shadow stacks for newly
created threads, instead the kernel allocates a new shadow stack with
the same size as the normal stack whenever a thread is created with the
feature enabled. The stacks allocated in this way are freed by the
kernel when the thread exits or shadow stacks are disabled for the
thread. This lack of flexibility and control isn't ideal, in the vast
majority of cases the shadow stack will be over allocated and the
implicit allocation and deallocation is not consistent with other
interfaces. As far as I can tell the interface is done in this manner
mainly because the shadow stack patches were in development since before
clone3() was implemented.
Since clone3() is readily extensible let's add support for specifying a
shadow stack when creating a new thread or process in a similar manner
to how the normal stack is specified, keeping the current implicit
allocation behaviour if one is not specified either with clone3() or
through the use of clone(). The user must provide a shadow stack
address and size, this must point to memory mapped for use as a shadow
stackby map_shadow_stack() with a shadow stack token at the top of the
stack.
Please note that the x86 portions of this code are build tested only, I
don't appear to have a system that can run CET avaible to me, I have
done testing with an integration into my pending work for GCS. There is
some possibility that the arm64 implementation may require the use of
clone3() and explicit userspace allocation of shadow stacks, this is
still under discussion.
Please further note that the token consumption done by clone3() is not
currently implemented in an atomic fashion, Rick indicated that he would
look into fixing this if people are OK with the implementation.
A new architecture feature Kconfig option for shadow stacks is added as
here, this was suggested as part of the review comments for the arm64
GCS series and since we need to detect if shadow stacks are supported it
seemed sensible to roll it in here.
[1] https://lore.kernel.org/r/20231009-arm64-gcs-v6-0-78e55deaa4dd@kernel.org/
Signed-off-by: Mark Brown <broonie@kernel.org>
---
Changes in v7:
- Rebase onto v6.11-rc1.
- Typo fixes.
- Link to v6: https://lore.kernel.org/r/20240623-clone3-shadow-stack-v6-0-9ee7783b1fb9@kernel.org
Changes in v6:
- Rebase onto v6.10-rc3.
- Ensure we don't try to free the parent shadow stack in error paths of
x86 arch code.
- Spelling fixes in userspace API document.
- Additional cleanups and improvements to the clone3() tests to support
the shadow stack tests.
- Link to v5: https://lore.kernel.org/r/20240203-clone3-shadow-stack-v5-0-322c69598e4b@kernel.org
Changes in v5:
- Rebase onto v6.8-rc2.
- Rework ABI to have the user allocate the shadow stack memory with
map_shadow_stack() and a token.
- Force inlining of the x86 shadow stack enablement.
- Move shadow stack enablement out into a shared header for reuse by
other tests.
- Link to v4: https://lore.kernel.org/r/20231128-clone3-shadow-stack-v4-0-8b28ffe4f676@kernel.org
Changes in v4:
- Formatting changes.
- Use a define for minimum shadow stack size and move some basic
validation to fork.c.
- Link to v3: https://lore.kernel.org/r/20231120-clone3-shadow-stack-v3-0-a7b8ed3e2acc@kernel.org
Changes in v3:
- Rebase onto v6.7-rc2.
- Remove stale shadow_stack in internal kargs.
- If a shadow stack is specified unconditionally use it regardless of
CLONE_ parameters.
- Force enable shadow stacks in the selftest.
- Update changelogs for RISC-V feature rename.
- Link to v2: https://lore.kernel.org/r/20231114-clone3-shadow-stack-v2-0-b613f8681155@kernel.org
Changes in v2:
- Rebase onto v6.7-rc1.
- Remove ability to provide preallocated shadow stack, just specify the
desired size.
- Link to v1: https://lore.kernel.org/r/20231023-clone3-shadow-stack-v1-0-d867d0b5d4d0@kernel.org
---
Mark Brown (9):
Documentation: userspace-api: Add shadow stack API documentation
selftests: Provide helper header for shadow stack testing
mm: Introduce ARCH_HAS_USER_SHADOW_STACK
fork: Add shadow stack support to clone3()
selftests/clone3: Remove redundant flushes of output streams
selftests/clone3: Factor more of main loop into test_clone3()
selftests/clone3: Explicitly handle child exits due to signals
selftests/clone3: Allow tests to flag if -E2BIG is a valid error code
selftests/clone3: Test shadow stack support
Documentation/userspace-api/index.rst | 1 +
Documentation/userspace-api/shadow_stack.rst | 41 ++++
arch/x86/Kconfig | 1 +
arch/x86/include/asm/shstk.h | 11 +-
arch/x86/kernel/process.c | 2 +-
arch/x86/kernel/shstk.c | 104 +++++++---
fs/proc/task_mmu.c | 2 +-
include/linux/mm.h | 2 +-
include/linux/sched/task.h | 13 ++
include/uapi/linux/sched.h | 13 +-
kernel/fork.c | 76 ++++++--
mm/Kconfig | 6 +
tools/testing/selftests/clone3/clone3.c | 224 ++++++++++++++++++----
tools/testing/selftests/clone3/clone3_selftests.h | 40 +++-
tools/testing/selftests/ksft_shstk.h | 63 ++++++
15 files changed, 511 insertions(+), 88 deletions(-)
---
base-commit: 8400291e289ee6b2bf9779ff1c83a291501f017b
change-id: 20231019-clone3-shadow-stack-15d40d2bf536
Best regards,
--
Mark Brown <broonie@kernel.org>
^ permalink raw reply
* Re: [PATCH v3] epoll.7: clarify the event distribution under edge-triggered mode
From: 潘少 @ 2024-07-31 11:21 UTC (permalink / raw)
To: Alejandro Colomar, Michael Kerrisk; +Cc: linux-man, linux-api
In-Reply-To: <l3suz7pnchnpnd5hhpxk5xqdikdxevp3dsybmhlcmzu6yih66s@zxuvoiunfqwl>
OK, I get your point now. In that case, should I start a new paragraph where I put the clarification? If so, where would you suggest I begin writing that new paragraph? Thanks! (Sorry for the duplicate email if you've already got my last one, it got rejected by the email gourps of linux-man and linux-api due to HTML content in that email, so I'm sending it again with only plain text.)
Best regards,
Andy Pan
^ permalink raw reply
* Re: [PATCH v3] epoll.7: clarify the event distribution under edge-triggered mode
From: Alejandro Colomar @ 2024-07-31 11:21 UTC (permalink / raw)
To: i@andypan.me; +Cc: mtk.manpages, linux-man, linux-api
In-Reply-To: <DD88B2A8DED5353D+137af5bf-158d-4e1e-b4ae-c4262434f8a6@Spark>
[-- Attachment #1: Type: text/plain, Size: 457 bytes --]
Hi Andy,
On Wed, Jul 31, 2024 at 07:16:38PM GMT, i@andypan.me wrote:
> OK, I get your point now. In that case, should I start a new paragraph
> where I put the clarification? If so, where would you suggest I begin
> writing that new paragraph? Thanks!
Thank you! I don't have an opinion at the moment. Feel free to chose
where you want; we'll see.
Cheers,
Alex
>
> Best regards,
> Andy Pan
--
<https://www.alejandro-colomar.es/>
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^ permalink raw reply
* Re: [PATCH v3] epoll.7: clarify the event distribution under edge-triggered mode
From: Alejandro Colomar @ 2024-07-31 11:07 UTC (permalink / raw)
To: 潘少, Michael Kerrisk; +Cc: linux-man, linux-api
In-Reply-To: <tencent_311E460546C884C26FB32E3C@qq.com>
[-- Attachment #1: Type: text/plain, Size: 1529 bytes --]
[TO += mtk]
Archive: <https://lore.kernel.org/linux-man/tencent_311E460546C884C26FB32E3C@qq.com/T/>
Hi,
On Wed, Jul 31, 2024 at 06:54:26PM GMT, 潘少 wrote:
> Hi Alejandro,
> > Since even with edge-triggered epoll, multiple events can be
> > generated upon receipt of multiple chunks of data, the caller has
> > the option to specify the EPOLLONESHOT flag, to tell epoll to
> > disable the associated file descriptor after the receipt of an
> > event with epoll_wait(2). When the EPOLLONESHOT flag is
> > specified, it is the caller's responsibility to rearm the file
> > descriptor using epoll_ctl(2) with EPOLL_CTL_MOD.
>
> This paragraph in man pages of epoll starts with "Since even with
> edge-triggered epoll", thus I assume the following sentences of
> "multiple events can be generated upon receipt of multiple chunks of
> data" and "that is, an event will be generated upon each receipt of a
> chunk of data" ought to be talking about EPOLLET naturally. Have I
> misunderstood something?
I understand it as:
Since _even_ with edge-triggered epoll [and thus also with other
epolls], multiple events can be generated ...
the stuff after the comma applied to at least more than one epoll typer.;
That's maybe why it's so generic.
However, I think a clarification like to one you suggest could be
appropriate in the page. I've added Michael to this mail, who may be
better placed to help with these APIs.
Have a lovely day!
Alex
--
<https://www.alejandro-colomar.es/>
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^ permalink raw reply
* Re: [PATCH v3] epoll.7: clarify the event distribution under edge-triggered mode
From: 潘少 @ 2024-07-31 10:54 UTC (permalink / raw)
To: Alejandro Colomar; +Cc: linux-man, linux-api
In-Reply-To: <2yb4zrih5esl3qldowd34ojg7mjq3xqjmqvq5bb5y6ru4x7rv5@p6ahw4ztu5cf>
Hi Alejandro,
> Since even with edge-triggered epoll, multiple events can be
> generated upon receipt of multiple chunks of data, the caller has
> the option to specify the EPOLLONESHOT flag, to tell epoll to
> disable the associated file descriptor after the receipt of an
> event with epoll_wait(2). When the EPOLLONESHOT flag is
> specified, it is the caller's responsibility to rearm the file
> descriptor using epoll_ctl(2) with EPOLL_CTL_MOD.
This paragraph in man pages of epoll starts with "Since even with edge-triggered epoll", thus I assume the following sentences of "multiple events can be generated upon receipt of multiple chunks of data" and "that is, an event will be generated upon each receipt of a chunk of data" ought to be talking about EPOLLET naturally. Have I misunderstood something?
^ permalink raw reply
* Re: [PATCH v3] epoll.7: clarify the event distribution under edge-triggered mode
From: Alejandro Colomar @ 2024-07-31 10:39 UTC (permalink / raw)
To: i; +Cc: linux-man, linux-api
In-Reply-To: <20240730-epoll-et-desc-v3-1-6aa81b1c400d@andypan.me>
[-- Attachment #1: Type: text/plain, Size: 4169 bytes --]
Hi Andy,
On Tue, Jul 30, 2024 at 10:48:28AM GMT, Andy Pan via B4 Relay wrote:
> From: Andy Pan <i@andypan.me>
>
> For the moment, the edge-triggered epoll generates an event for each
> receipt of a chunk of data, that is to say, epoll_wait() will return
> and tell us a monitored file descriptor is ready whenever there is a
> new activity on that FD since we were last informed about that FD.
> This is not a real _edge_ implementation for epoll, but it's been
> working this way for years and plenty of projects are relying on it
> to eliminate the overhead of one system call of read(2) per wakeup event.
>
> There are several renowned open-source projects relying on this feature
> for notification function (with eventfd): register eventfd with EPOLLET
> and avoid calling read(2) on the eventfd when there is wakeup event (eventfd being written).
> Examples: nginx [1], netty [2], tokio [3], libevent [4], ect. [5]
> These projects are widely used in today's Internet infrastructures.
> Thus, changing this behavior of epoll ET will fundamentally break them
> and cause a significant negative impact.
> Linux has changed it for pipe before [6], breaking some Android libraries,
> which had got "reverted" somehow. [7] [8]
>
> Nevertheless, the paragraph in the manual pages describing this
> characteristic of epoll ET seems ambiguous, I think a more explict
> sentence should be used to clarify it. We're improving the notification
> mechanism for libuv recently by exploiting this feature with eventfd,
> which brings us a significant performance boost. [9]
>
> Therefore, we (as well as the maintainers of nginx, netty, tokio, etc.)
> would have a sense of security to build an enhanced notification function
> based on this feature if there is a guarantee of retaining this implementation
> of epoll ET for the backward compatibility in the man pages.
>
> [1]: https://github.com/nginx/nginx/blob/efc6a217b92985a1ee211b6bb7337cd2f62deb90/src/event/modules/ngx_epoll_module.c#L386-L457
> [2]: https://github.com/netty/netty/pull/9192
> [3]: https://github.com/tokio-rs/mio/blob/309daae21ecb1d46203a7dbc0cf4c80310240cba/src/sys/unix/waker.rs#L111-L143
> [4]: https://github.com/libevent/libevent/blob/525f5d0a14c9c103be750f2ca175328c25505ea4/event.c#L2597-L2614
> [5]: https://github.com/libuv/libuv/pull/4400#issuecomment-2123798748
> [6]: https://lkml.iu.edu/hypermail/linux/kernel/2010.1/04363.html
> [7]: https://github.com/torvalds/linux/commit/3a34b13a88caeb2800ab44a4918f230041b37dd9
> [8]: https://github.com/torvalds/linux/commit/3b844826b6c6affa80755254da322b017358a2f4
> [9]: https://github.com/libuv/libuv/pull/4400#issuecomment-2103232402
>
> Signed-off-by: Andy Pan <i@andypan.me>
> ---
> Changes in v3:
> - Updated the git commit description
> - Link to v2: https://lore.kernel.org/r/20240727-epoll-et-desc-v2-1-c99b2ac66775@andypan.me
>
> Changes in v2:
> - Added the git commit description based on feedback
> - Link to v1: https://lore.kernel.org/r/20240727-epoll-et-desc-v1-1-390bafc678b9@andypan.me
> ---
> man/man7/epoll.7 | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/man/man7/epoll.7 b/man/man7/epoll.7
> index 951500131..361d9db99 100644
> --- a/man/man7/epoll.7
> +++ b/man/man7/epoll.7
> @@ -172,6 +172,7 @@ .SS Level-triggered and edge-triggered
> Since even with edge-triggered
> .BR epoll ,
This paragraph is not only about EPOLLET.
> multiple events can be generated upon receipt of multiple chunks of data,
> +that is, an event will be generated upon each receipt of a chunk of data,
Is this strictly true in all modes? The commit message seems to say
that this is the behavior of EPOLLET, but this paragraph is not only
about EPOLLET. Is this correct here, or should it go somewhere else?
Have a lovely day!
Alex
> the caller has the option to specify the
> .B EPOLLONESHOT
> flag, to tell
>
> ---
> base-commit: cbc0a111e4dceea2037c51098de33e6bc8c16a5c
> change-id: 20240727-epoll-et-desc-04ea9a590f3b
>
> Best regards,
> --
> Andy Pan <i@andypan.me>
>
>
--
<https://www.alejandro-colomar.es/>
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^ permalink raw reply
* Re: [PATCH v3] usb: gadget: f_fs: add capability for dfu run-time descriptor
From: Greg Kroah-Hartman @ 2024-07-31 8:27 UTC (permalink / raw)
To: Chris Wulff
Cc: linux-usb@vger.kernel.org, Christian Brauner, Paul Cercueil,
Jan Kara, Jeff Layton, Dmitry Antipov, David Sands,
linux-kernel@vger.kernel.org, linux-api@vger.kernel.org
In-Reply-To: <CO1PR17MB54197F118CBC8783D289B97DE1102@CO1PR17MB5419.namprd17.prod.outlook.com>
On Wed, Apr 24, 2024 at 10:14:58PM +0000, Chris Wulff wrote:
> From: David Sands <david.sands@biamp.com>
>
> Add the ability for FunctionFS driver to be able to create DFU Run-Time
> descriptors.
Don't you need some userspace documentation for this as well?
> --- a/include/uapi/linux/usb/ch9.h
> +++ b/include/uapi/linux/usb/ch9.h
> @@ -254,6 +254,9 @@ struct usb_ctrlrequest {
> #define USB_DT_DEVICE_CAPABILITY 0x10
> #define USB_DT_WIRELESS_ENDPOINT_COMP 0x11
> #define USB_DT_WIRE_ADAPTER 0x21
> +/* From USB Device Firmware Upgrade Specification, Revision 1.1 */
> +#define USB_DT_DFU_FUNCTIONAL 0x21
So USB_DT_WIRE_ADAPTER and USB_DT_DFU_FUNCTIONAL are the same? That
seems wrong.
> +/* these are from the Wireless USB spec */
What spec? What "these"?
> #define USB_DT_RPIPE 0x22
> #define USB_DT_CS_RADIO_CONTROL 0x23
> /* From the T10 UAS specification */
> @@ -263,6 +266,7 @@ struct usb_ctrlrequest {
> /* From the USB 3.1 spec */
> #define USB_DT_SSP_ISOC_ENDPOINT_COMP 0x31
>
> +
> /* Conventional codes for class-specific descriptors. The convention is
> * defined in the USB "Common Class" Spec (3.11). Individual class specs
> * are authoritative for their usage, not the "common class" writeup.
Unneeded change?
> @@ -329,9 +333,10 @@ struct usb_device_descriptor {
> #define USB_CLASS_USB_TYPE_C_BRIDGE 0x12
> #define USB_CLASS_MISC 0xef
> #define USB_CLASS_APP_SPEC 0xfe
> -#define USB_CLASS_VENDOR_SPEC 0xff
> +#define USB_SUBCLASS_DFU 0x01
>
> -#define USB_SUBCLASS_VENDOR_SPEC 0xff
> +#define USB_CLASS_VENDOR_SPEC 0xff
> +#define USB_SUBCLASS_VENDOR_SPEC 0xff
Why reorder these?
>
> /*-------------------------------------------------------------------------*/
>
> diff --git a/include/uapi/linux/usb/functionfs.h b/include/uapi/linux/usb/functionfs.h
> index 9f88de9c3d66..6d2061500184 100644
> --- a/include/uapi/linux/usb/functionfs.h
> +++ b/include/uapi/linux/usb/functionfs.h
> @@ -37,6 +37,31 @@ struct usb_endpoint_descriptor_no_audio {
> __u8 bInterval;
> } __attribute__((packed));
>
> +/**
> + * struct usb_dfu_functional_descriptor - DFU Functional descriptor
> + * @bLength: Size of the descriptor (bytes)
> + * @bDescriptorType: USB_DT_DFU_FUNCTIONAL
> + * @bmAttributes: DFU attributes
> + * @wDetachTimeOut: Maximum time to wait after DFU_DETACH (ms, le16)
> + * @wTransferSize: Maximum number of bytes per control-write (le16)
> + * @bcdDFUVersion: DFU Spec version (BCD, le16)
> + */
> +struct usb_dfu_functional_descriptor {
> + __u8 bLength;
> + __u8 bDescriptorType;
> + __u8 bmAttributes;
> + __le16 wDetachTimeOut;
> + __le16 wTransferSize;
> + __le16 bcdDFUVersion;
> +} __attribute__ ((packed));
> +
> +/* from DFU functional descriptor bmAttributes */
> +#define DFU_FUNC_ATT_WILL_DETACH (1 << 3)
> +#define DFU_FUNC_ATT_MANIFEST_TOLERANT (1 << 2)
> +#define DFU_FUNC_ATT_CAN_UPLOAD (1 << 1)
> +#define DFU_FUNC_ATT_CAN_DOWNLOAD (1 << 0)
Please use proper BIT macros here to make this more obvious. And in
sorted order?
thanks,
greg k-h
^ permalink raw reply
* Re:[PATCH v3] epoll.7: clarify the event distribution under edge-triggered mode
From: 潘少 @ 2024-07-31 8:10 UTC (permalink / raw)
To: i, Alejandro Colomar; +Cc: linux-man, linux-api
Hi all,
Would someone have a moment to take a look at this?
^ permalink raw reply
* Re: [PATCH 7/8] fs: add an ioctl to get the mnt ns id from nsfs
From: Christian Brauner @ 2024-07-31 5:51 UTC (permalink / raw)
To: Dmitry V. Levin; +Cc: Josef Bacik, linux-fsdevel, linux-api, kernel-team
In-Reply-To: <20240730164554.GA18486@altlinux.org>
[-- Attachment #1: Type: text/plain, Size: 2301 bytes --]
On Tue, Jul 30, 2024 at 07:45:54PM GMT, Dmitry V. Levin wrote:
> Hi,
>
> On Mon, Jun 24, 2024 at 11:49:50AM -0400, Josef Bacik wrote:
> > In order to utilize the listmount() and statmount() extensions that
> > allow us to call them on different namespaces we need a way to get the
> > mnt namespace id from user space. Add an ioctl to nsfs that will allow
> > us to extract the mnt namespace id in order to make these new extensions
> > usable.
> >
> > Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> > ---
> > fs/nsfs.c | 14 ++++++++++++++
> > include/uapi/linux/nsfs.h | 2 ++
> > 2 files changed, 16 insertions(+)
> >
> > diff --git a/fs/nsfs.c b/fs/nsfs.c
> > index 07e22a15ef02..af352dadffe1 100644
> > --- a/fs/nsfs.c
> > +++ b/fs/nsfs.c
> > @@ -12,6 +12,7 @@
> > #include <linux/nsfs.h>
> > #include <linux/uaccess.h>
> >
> > +#include "mount.h"
> > #include "internal.h"
> >
> > static struct vfsmount *nsfs_mnt;
> > @@ -143,6 +144,19 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
> > argp = (uid_t __user *) arg;
> > uid = from_kuid_munged(current_user_ns(), user_ns->owner);
> > return put_user(uid, argp);
> > + case NS_GET_MNTNS_ID: {
> > + struct mnt_namespace *mnt_ns;
> > + __u64 __user *idp;
> > + __u64 id;
> > +
> > + if (ns->ops->type != CLONE_NEWNS)
> > + return -EINVAL;
> > +
> > + mnt_ns = container_of(ns, struct mnt_namespace, ns);
> > + idp = (__u64 __user *)arg;
> > + id = mnt_ns->seq;
> > + return put_user(id, idp);
> > + }
> > default:
> > return -ENOTTY;
> > }
> > diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
> > index a0c8552b64ee..56e8b1639b98 100644
> > --- a/include/uapi/linux/nsfs.h
> > +++ b/include/uapi/linux/nsfs.h
> > @@ -15,5 +15,7 @@
> > #define NS_GET_NSTYPE _IO(NSIO, 0x3)
> > /* Get owner UID (in the caller's user namespace) for a user namespace */
> > #define NS_GET_OWNER_UID _IO(NSIO, 0x4)
> > +/* Get the id for a mount namespace */
> > +#define NS_GET_MNTNS_ID _IO(NSIO, 0x5)
>
> As the kernel is writing an object of type __u64,
> this has to be defined to _IOR(NSIO, 0x5, __u64) instead,
> see the corresponding comments in uapi/asm-generic/ioctl.h file.
Thanks for spotting that. I've pushed a fix to vfs.fixes. See the
appended patch.
[-- Attachment #2: 0001-nsfs-fix-ioctl-declaration.patch --]
[-- Type: text/x-diff, Size: 1357 bytes --]
From c43a484ddff73f92739f0167c738eb6fd2df78b7 Mon Sep 17 00:00:00 2001
From: Christian Brauner <brauner@kernel.org>
Date: Wed, 31 Jul 2024 07:47:27 +0200
Subject: [PATCH] nsfs: fix ioctl declaration
The kernel is writing an object of type __u64, so the ioctl has to be
defined to _IOR(NSIO, 0x5, __u64) instead of _IO(NSIO, 0x5).
Reported-by: Dmitry V. Levin <ldv@strace.io>
Link: https://lore.kernel.org/r/20240730164554.GA18486@altlinux.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
include/uapi/linux/nsfs.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
index b133211331f6..5fad3d0fcd70 100644
--- a/include/uapi/linux/nsfs.h
+++ b/include/uapi/linux/nsfs.h
@@ -3,6 +3,7 @@
#define __LINUX_NSFS_H
#include <linux/ioctl.h>
+#include <linux/types.h>
#define NSIO 0xb7
@@ -16,7 +17,7 @@
/* Get owner UID (in the caller's user namespace) for a user namespace */
#define NS_GET_OWNER_UID _IO(NSIO, 0x4)
/* Get the id for a mount namespace */
-#define NS_GET_MNTNS_ID _IO(NSIO, 0x5)
+#define NS_GET_MNTNS_ID _IOR(NSIO, 0x5, __u64)
/* Translate pid from target pid namespace into the caller's pid namespace. */
#define NS_GET_PID_FROM_PIDNS _IOR(NSIO, 0x6, int)
/* Return thread-group leader id of pid in the callers pid namespace. */
--
2.43.0
^ permalink raw reply related
* [PATCH net-next v8 3/3] selftests: add MSG_ZEROCOPY msg_control notification test
From: zijianzhang @ 2024-07-30 18:41 UTC (permalink / raw)
To: netdev
Cc: linux-api, willemdebruijn.kernel, almasrymina, edumazet, davem,
kuba, pabeni, dsahern, axboe, shuah, linux-kselftest, cong.wang,
xiaochun.lu, Zijian Zhang
In-Reply-To: <20240730184120.4089835-1-zijianzhang@bytedance.com>
From: Zijian Zhang <zijianzhang@bytedance.com>
We update selftests/net/msg_zerocopy.c to accommodate the new mechanism,
cfg_notification_limit has the same semantics for both methods. Test
results are as follows, we update skb_orphan_frags_rx to the same as
skb_orphan_frags to support zerocopy in the localhost test.
cfg_notification_limit = 1, both method get notifications after 1 calling
of sendmsg. In this case, the new method has around 17% cpu savings in TCP
and 23% cpu savings in UDP.
+---------------------+---------+---------+---------+---------+
| Test Type / Protocol| TCP v4 | TCP v6 | UDP v4 | UDP v6 |
+---------------------+---------+---------+---------+---------+
| ZCopy (MB) | 7523 | 7706 | 7489 | 7304 |
+---------------------+---------+---------+---------+---------+
| New ZCopy (MB) | 8834 | 8993 | 9053 | 9228 |
+---------------------+---------+---------+---------+---------+
| New ZCopy / ZCopy | 117.42% | 116.70% | 120.88% | 126.34% |
+---------------------+---------+---------+---------+---------+
cfg_notification_limit = 32, both get notifications after 32 calling of
sendmsg, which means more chances to coalesce notifications, and less
overhead of poll + recvmsg for the original method. In this case, the new
method has around 7% cpu savings in TCP and slightly better cpu usage in
UDP. In the env of selftest, notifications of TCP are more likely to be
out of order than UDP, it's easier to coalesce more notifications in UDP.
The original method can get one notification with range of 32 in a recvmsg
most of the time. In TCP, most notifications' range is around 2, so the
original method needs around 16 recvmsgs to get notified in one round.
That's the reason for the "New ZCopy / ZCopy" diff in TCP and UDP here.
+---------------------+---------+---------+---------+---------+
| Test Type / Protocol| TCP v4 | TCP v6 | UDP v4 | UDP v6 |
+---------------------+---------+---------+---------+---------+
| ZCopy (MB) | 8842 | 8735 | 10072 | 9380 |
+---------------------+---------+---------+---------+---------+
| New ZCopy (MB) | 9366 | 9477 | 10108 | 9385 |
+---------------------+---------+---------+---------+---------+
| New ZCopy / ZCopy | 106.00% | 108.28% | 100.31% | 100.01% |
+---------------------+---------+---------+---------+---------+
In conclusion, when notification interval is small or notifications are
hard to be coalesced, the new mechanism is highly recommended. Otherwise,
the performance gain from the new mechanism is very limited.
Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Signed-off-by: Xiaochun Lu <xiaochun.lu@bytedance.com>
---
tools/testing/selftests/net/msg_zerocopy.c | 101 ++++++++++++++++++--
tools/testing/selftests/net/msg_zerocopy.sh | 1 +
2 files changed, 95 insertions(+), 7 deletions(-)
diff --git a/tools/testing/selftests/net/msg_zerocopy.c b/tools/testing/selftests/net/msg_zerocopy.c
index 7ea5fb28c93d..cf227f0011b5 100644
--- a/tools/testing/selftests/net/msg_zerocopy.c
+++ b/tools/testing/selftests/net/msg_zerocopy.c
@@ -66,6 +66,10 @@
#define SO_ZEROCOPY 60
#endif
+#ifndef SCM_ZC_NOTIFICATION
+#define SCM_ZC_NOTIFICATION 78
+#endif
+
#ifndef SO_EE_CODE_ZEROCOPY_COPIED
#define SO_EE_CODE_ZEROCOPY_COPIED 1
#endif
@@ -74,6 +78,14 @@
#define MSG_ZEROCOPY 0x4000000
#endif
+#define ZC_INFO_ARR_SIZE (ZC_NOTIFICATION_MAX * sizeof(struct zc_info_elem))
+#define ZC_INFO_SIZE (sizeof(struct zc_info) + ZC_INFO_ARR_SIZE)
+
+enum notification_type {
+ MSG_ZEROCOPY_NOTIFY_ERRQUEUE = 1,
+ MSG_ZEROCOPY_NOTIFY_SENDMSG = 2,
+};
+
static int cfg_cork;
static bool cfg_cork_mixed;
static int cfg_cpu = -1; /* default: pin to last cpu */
@@ -86,7 +98,7 @@ static int cfg_runtime_ms = 4200;
static int cfg_verbose;
static int cfg_waittime_ms = 500;
static int cfg_notification_limit = 32;
-static bool cfg_zerocopy;
+static enum notification_type cfg_zerocopy;
static socklen_t cfg_alen;
static struct sockaddr_storage cfg_dst_addr;
@@ -97,6 +109,8 @@ static long packets, bytes, completions, expected_completions;
static int zerocopied = -1;
static uint32_t next_completion;
static uint32_t sends_since_notify;
+static char zc_ckbuf[CMSG_SPACE(ZC_INFO_SIZE)];
+static bool added_zcopy_info;
static unsigned long gettimeofday_ms(void)
{
@@ -182,7 +196,26 @@ static void add_zcopy_cookie(struct msghdr *msg, uint32_t cookie)
memcpy(CMSG_DATA(cm), &cookie, sizeof(cookie));
}
-static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
+static void add_zcopy_info(struct msghdr *msg)
+{
+ struct zc_info *zc_info;
+ struct cmsghdr *cm;
+
+ if (!msg->msg_control)
+ error(1, errno, "NULL user arg");
+ cm = (struct cmsghdr *)msg->msg_control;
+ cm->cmsg_len = CMSG_LEN(ZC_INFO_SIZE);
+ cm->cmsg_level = SOL_SOCKET;
+ cm->cmsg_type = SCM_ZC_NOTIFICATION;
+
+ zc_info = (struct zc_info *)CMSG_DATA(cm);
+ zc_info->size = ZC_NOTIFICATION_MAX;
+
+ added_zcopy_info = true;
+}
+
+static bool do_sendmsg(int fd, struct msghdr *msg,
+ enum notification_type do_zerocopy, int domain)
{
int ret, len, i, flags;
static uint32_t cookie;
@@ -200,6 +233,12 @@ static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
msg->msg_controllen = CMSG_SPACE(sizeof(cookie));
msg->msg_control = (struct cmsghdr *)ckbuf;
add_zcopy_cookie(msg, ++cookie);
+ } else if (do_zerocopy == MSG_ZEROCOPY_NOTIFY_SENDMSG &&
+ sends_since_notify + 1 >= cfg_notification_limit) {
+ memset(&msg->msg_control, 0, sizeof(msg->msg_control));
+ msg->msg_controllen = CMSG_SPACE(ZC_INFO_SIZE);
+ msg->msg_control = (struct cmsghdr *)zc_ckbuf;
+ add_zcopy_info(msg);
}
}
@@ -218,7 +257,7 @@ static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
if (do_zerocopy && ret)
expected_completions++;
}
- if (do_zerocopy && domain == PF_RDS) {
+ if (msg->msg_control) {
msg->msg_control = NULL;
msg->msg_controllen = 0;
}
@@ -466,6 +505,44 @@ static void do_recv_completions(int fd, int domain)
sends_since_notify = 0;
}
+static void do_recv_completions2(void)
+{
+ struct cmsghdr *cm = (struct cmsghdr *)zc_ckbuf;
+ struct zc_info *zc_info;
+ __u32 hi, lo, range;
+ __u8 zerocopy;
+ int i;
+
+ zc_info = (struct zc_info *)CMSG_DATA(cm);
+ for (i = 0; i < zc_info->size; i++) {
+ hi = zc_info->arr[i].hi;
+ lo = zc_info->arr[i].lo;
+ zerocopy = zc_info->arr[i].zerocopy;
+ range = hi - lo + 1;
+
+ if (cfg_verbose && lo != next_completion)
+ fprintf(stderr, "gap: %u..%u does not append to %u\n",
+ lo, hi, next_completion);
+ next_completion = hi + 1;
+
+ if (zerocopied == -1) {
+ zerocopied = zerocopy;
+ } else if (zerocopied != zerocopy) {
+ fprintf(stderr, "serr: inconsistent\n");
+ zerocopied = zerocopy;
+ }
+
+ completions += range;
+ sends_since_notify -= range;
+
+ if (cfg_verbose >= 2)
+ fprintf(stderr, "completed: %u (h=%u l=%u)\n",
+ range, hi, lo);
+ }
+
+ added_zcopy_info = false;
+}
+
/* Wait for all remaining completions on the errqueue */
static void do_recv_remaining_completions(int fd, int domain)
{
@@ -553,11 +630,16 @@ static void do_tx(int domain, int type, int protocol)
else
do_sendmsg(fd, &msg, cfg_zerocopy, domain);
- if (cfg_zerocopy && sends_since_notify >= cfg_notification_limit)
+ if (cfg_zerocopy == MSG_ZEROCOPY_NOTIFY_ERRQUEUE &&
+ sends_since_notify >= cfg_notification_limit)
do_recv_completions(fd, domain);
+ if (cfg_zerocopy == MSG_ZEROCOPY_NOTIFY_SENDMSG &&
+ added_zcopy_info)
+ do_recv_completions2();
+
while (!do_poll(fd, POLLOUT)) {
- if (cfg_zerocopy)
+ if (cfg_zerocopy == MSG_ZEROCOPY_NOTIFY_ERRQUEUE)
do_recv_completions(fd, domain);
}
@@ -715,7 +797,7 @@ static void parse_opts(int argc, char **argv)
cfg_payload_len = max_payload_len;
- while ((c = getopt(argc, argv, "46c:C:D:i:l:mp:rs:S:t:vz")) != -1) {
+ while ((c = getopt(argc, argv, "46c:C:D:i:l:mnp:rs:S:t:vz")) != -1) {
switch (c) {
case '4':
if (cfg_family != PF_UNSPEC)
@@ -749,6 +831,9 @@ static void parse_opts(int argc, char **argv)
case 'm':
cfg_cork_mixed = true;
break;
+ case 'n':
+ cfg_zerocopy = MSG_ZEROCOPY_NOTIFY_SENDMSG;
+ break;
case 'p':
cfg_port = strtoul(optarg, NULL, 0);
break;
@@ -768,7 +853,7 @@ static void parse_opts(int argc, char **argv)
cfg_verbose++;
break;
case 'z':
- cfg_zerocopy = true;
+ cfg_zerocopy = MSG_ZEROCOPY_NOTIFY_ERRQUEUE;
break;
}
}
@@ -779,6 +864,8 @@ static void parse_opts(int argc, char **argv)
error(1, 0, "-D <server addr> required for PF_RDS\n");
if (!cfg_rx && !saddr)
error(1, 0, "-S <client addr> required for PF_RDS\n");
+ if (cfg_zerocopy == MSG_ZEROCOPY_NOTIFY_SENDMSG)
+ error(1, 0, "PF_RDS does not support ZC_NOTIF_SENDMSG");
}
setup_sockaddr(cfg_family, daddr, &cfg_dst_addr);
setup_sockaddr(cfg_family, saddr, &cfg_src_addr);
diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
index 89c22f5320e0..022a6936d86f 100755
--- a/tools/testing/selftests/net/msg_zerocopy.sh
+++ b/tools/testing/selftests/net/msg_zerocopy.sh
@@ -118,4 +118,5 @@ do_test() {
do_test "${EXTRA_ARGS}"
do_test "-z ${EXTRA_ARGS}"
+do_test "-n ${EXTRA_ARGS}"
echo ok
--
2.20.1
^ permalink raw reply related
* [PATCH net-next v8 2/3] sock: add MSG_ZEROCOPY notification mechanism based on msg_control
From: zijianzhang @ 2024-07-30 18:41 UTC (permalink / raw)
To: netdev
Cc: linux-api, willemdebruijn.kernel, almasrymina, edumazet, davem,
kuba, pabeni, dsahern, axboe, shuah, linux-kselftest, cong.wang,
xiaochun.lu, Zijian Zhang
In-Reply-To: <20240730184120.4089835-1-zijianzhang@bytedance.com>
From: Zijian Zhang <zijianzhang@bytedance.com>
The MSG_ZEROCOPY flag enables copy avoidance for socket send calls.
However, zerocopy is not a free lunch. Apart from the management of user
pages, the combination of poll + recvmsg to receive notifications incurs
unignorable overhead in the applications. We try to mitigate this overhead
with a new notification mechanism based on msg_control. Leveraging the
general framework to copy cmsgs to the user space, we copy zerocopy
notifications to the user upon returning of sendmsgs.
Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Signed-off-by: Xiaochun Lu <xiaochun.lu@bytedance.com>
---
arch/alpha/include/uapi/asm/socket.h | 2 +
arch/mips/include/uapi/asm/socket.h | 2 +
arch/parisc/include/uapi/asm/socket.h | 2 +
arch/sparc/include/uapi/asm/socket.h | 2 +
include/linux/socket.h | 2 +-
include/uapi/asm-generic/socket.h | 2 +
include/uapi/linux/socket.h | 23 +++++++++
net/core/sock.c | 72 +++++++++++++++++++++++++--
8 files changed, 102 insertions(+), 5 deletions(-)
diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
index e94f621903fe..7c32d9dbe47f 100644
--- a/arch/alpha/include/uapi/asm/socket.h
+++ b/arch/alpha/include/uapi/asm/socket.h
@@ -140,6 +140,8 @@
#define SO_PASSPIDFD 76
#define SO_PEERPIDFD 77
+#define SCM_ZC_NOTIFICATION 78
+
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64
diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
index 60ebaed28a4c..3f7fade998cb 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -151,6 +151,8 @@
#define SO_PASSPIDFD 76
#define SO_PEERPIDFD 77
+#define SCM_ZC_NOTIFICATION 78
+
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64
diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
index be264c2b1a11..77f5bee0fdc9 100644
--- a/arch/parisc/include/uapi/asm/socket.h
+++ b/arch/parisc/include/uapi/asm/socket.h
@@ -132,6 +132,8 @@
#define SO_PASSPIDFD 0x404A
#define SO_PEERPIDFD 0x404B
+#define SCM_ZC_NOTIFICATION 0x404C
+
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64
diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
index 682da3714686..eb44fc515b45 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++ b/arch/sparc/include/uapi/asm/socket.h
@@ -133,6 +133,8 @@
#define SO_PASSPIDFD 0x0055
#define SO_PEERPIDFD 0x0056
+#define SCM_ZC_NOTIFICATION 0x0057
+
#if !defined(__KERNEL__)
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 40173c919d0f..71e3c6ebfed5 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -171,7 +171,7 @@ static inline struct cmsghdr * cmsg_nxthdr (struct msghdr *__msg, struct cmsghdr
static inline bool cmsg_copy_to_user(struct cmsghdr *__cmsg)
{
- return 0;
+ return __cmsg->cmsg_type == SCM_ZC_NOTIFICATION;
}
static inline size_t msg_data_left(struct msghdr *msg)
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index 8ce8a39a1e5f..02e9159c7944 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -135,6 +135,8 @@
#define SO_PASSPIDFD 76
#define SO_PEERPIDFD 77
+#define SCM_ZC_NOTIFICATION 78
+
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))
diff --git a/include/uapi/linux/socket.h b/include/uapi/linux/socket.h
index d3fcd3b5ec53..b5b5fa9febb1 100644
--- a/include/uapi/linux/socket.h
+++ b/include/uapi/linux/socket.h
@@ -2,6 +2,8 @@
#ifndef _UAPI_LINUX_SOCKET_H
#define _UAPI_LINUX_SOCKET_H
+#include <linux/types.h>
+
/*
* Desired design of maximum size and alignment (see RFC2553)
*/
@@ -35,4 +37,25 @@ struct __kernel_sockaddr_storage {
#define SOCK_TXREHASH_DISABLED 0
#define SOCK_TXREHASH_ENABLED 1
+#define ZC_NOTIFICATION_MAX 16
+
+/*
+ * A zc_info_elem represents a completion notification for sendmsgs in range
+ * lo to high, zerocopy represents whether the underlying transmission is
+ * zerocopy or not.
+ */
+struct zc_info_elem {
+ __u32 lo;
+ __u32 hi;
+ __u8 zerocopy;
+};
+
+/*
+ * zc_info is the struct used for the SCM_ZC_NOTIFICATION control message.
+ */
+struct zc_info {
+ __u32 size; /* size of the zc_info_elem arr */
+ struct zc_info_elem arr[];
+};
+
#endif /* _UAPI_LINUX_SOCKET_H */
diff --git a/net/core/sock.c b/net/core/sock.c
index b2cbe753af1d..37b1b12623ee 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1481,10 +1481,12 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
ret = -EOPNOTSUPP;
}
if (!ret) {
- if (val < 0 || val > 1)
+ if (val < 0 || val > 1) {
ret = -EINVAL;
- else
+ } else {
sock_valbool_flag(sk, SOCK_ZEROCOPY, valbool);
+ static_branch_enable(&tx_copy_cmsg_to_user_key);
+ }
}
break;
@@ -2826,8 +2828,8 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
}
EXPORT_SYMBOL(sock_alloc_send_pskb);
-int __sock_cmsg_send(struct sock *sk, struct msghdr *msg __always_unused,
- struct cmsghdr *cmsg, struct sockcm_cookie *sockc)
+int __sock_cmsg_send(struct sock *sk, struct msghdr *msg, struct cmsghdr *cmsg,
+ struct sockcm_cookie *sockc)
{
u32 tsflags;
@@ -2863,6 +2865,68 @@ int __sock_cmsg_send(struct sock *sk, struct msghdr *msg __always_unused,
case SCM_RIGHTS:
case SCM_CREDENTIALS:
break;
+ case SCM_ZC_NOTIFICATION: {
+ struct zc_info *zc = CMSG_DATA(cmsg);
+ struct sk_buff_head *q, local_q;
+ int cmsg_data_len, i = 0;
+ unsigned long flags;
+ struct sk_buff *skb;
+
+ if (!sock_flag(sk, SOCK_ZEROCOPY) || sk->sk_family == PF_RDS)
+ return -EINVAL;
+
+ cmsg_data_len = cmsg->cmsg_len - sizeof(struct cmsghdr);
+ if (cmsg_data_len < sizeof(struct zc_info))
+ return -EINVAL;
+
+ if (zc->size > ZC_NOTIFICATION_MAX ||
+ (cmsg_data_len - sizeof(struct zc_info)) !=
+ (zc->size * sizeof(struct zc_info_elem)))
+ return -EINVAL;
+
+ q = &sk->sk_error_queue;
+ skb_queue_head_init(&local_q);
+
+ /* Get zerocopy error messages from sk_error_queue, and add them
+ * to a local queue for later processing. This minimizes the
+ * code while the spinlock is held and irq is disabled.
+ */
+ spin_lock_irqsave(&q->lock, flags);
+ skb = skb_peek(q);
+ while (skb && i < zc->size) {
+ struct sk_buff *skb_next = skb_peek_next(skb, q);
+ struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);
+
+ if (serr->ee.ee_errno != 0 ||
+ serr->ee.ee_origin != SO_EE_ORIGIN_ZEROCOPY) {
+ skb = skb_next;
+ continue;
+ }
+
+ __skb_unlink(skb, q);
+ __skb_queue_tail(&local_q, skb);
+ skb = skb_next;
+ i++;
+ }
+ spin_unlock_irqrestore(&q->lock, flags);
+
+ i = 0;
+ while ((skb = skb_peek(&local_q)) != NULL) {
+ struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);
+
+ zc->arr[i].hi = serr->ee.ee_data;
+ zc->arr[i].lo = serr->ee.ee_info;
+ zc->arr[i].zerocopy = !(serr->ee.ee_code
+ & SO_EE_CODE_ZEROCOPY_COPIED);
+ __skb_unlink(skb, &local_q);
+ consume_skb(skb);
+ i++;
+ }
+
+ zc->size = i;
+ msg->msg_control_copy_to_user = true;
+ break;
+ }
default:
return -EINVAL;
}
--
2.20.1
^ permalink raw reply related
* [PATCH net-next v8 1/3] sock: support copying cmsgs to the user space in sendmsg
From: zijianzhang @ 2024-07-30 18:41 UTC (permalink / raw)
To: netdev
Cc: linux-api, willemdebruijn.kernel, almasrymina, edumazet, davem,
kuba, pabeni, dsahern, axboe, shuah, linux-kselftest, cong.wang,
xiaochun.lu, Zijian Zhang
In-Reply-To: <20240730184120.4089835-1-zijianzhang@bytedance.com>
From: Zijian Zhang <zijianzhang@bytedance.com>
Users can pass msg_control as a placeholder to recvmsg, and get some info
from the kernel upon returning of it, but it's not available for sendmsg.
Recvmsg uses put_cmsg to copy info back to the user, while ____sys_sendmsg
creates a kernel copy of msg_control and passes that to the callees,
put_cmsg in sendmsg path will write into this kernel buffer.
If users want to get info after returning of sendmsg, they typically have
to call recvmsg on the MSG_ERRQUEUE of the socket, incurring extra system
call overhead. This commit supports copying cmsg from the kernel space to
the user space upon returning of sendmsg to mitigate this overhead.
Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Signed-off-by: Xiaochun Lu <xiaochun.lu@bytedance.com>
---
include/linux/socket.h | 8 ++++++
include/net/sock.h | 2 +-
net/core/sock.c | 6 ++--
net/ipv4/ip_sockglue.c | 2 +-
net/ipv6/datagram.c | 2 +-
net/socket.c | 63 ++++++++++++++++++++++++++++++++++++++----
6 files changed, 72 insertions(+), 11 deletions(-)
diff --git a/include/linux/socket.h b/include/linux/socket.h
index df9cdb8bbfb8..40173c919d0f 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -71,6 +71,7 @@ struct msghdr {
void __user *msg_control_user;
};
bool msg_control_is_user : 1;
+ bool msg_control_copy_to_user : 1;
bool msg_get_inq : 1;/* return INQ after receive */
unsigned int msg_flags; /* flags on received message */
__kernel_size_t msg_controllen; /* ancillary data buffer length */
@@ -168,6 +169,11 @@ static inline struct cmsghdr * cmsg_nxthdr (struct msghdr *__msg, struct cmsghdr
return __cmsg_nxthdr(__msg->msg_control, __msg->msg_controllen, __cmsg);
}
+static inline bool cmsg_copy_to_user(struct cmsghdr *__cmsg)
+{
+ return 0;
+}
+
static inline size_t msg_data_left(struct msghdr *msg)
{
return iov_iter_count(&msg->msg_iter);
@@ -396,6 +402,8 @@ struct timespec64;
struct __kernel_timespec;
struct old_timespec32;
+DECLARE_STATIC_KEY_FALSE(tx_copy_cmsg_to_user_key);
+
struct scm_timestamping_internal {
struct timespec64 ts[3];
};
diff --git a/include/net/sock.h b/include/net/sock.h
index cce23ac4d514..9c728287d21d 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1804,7 +1804,7 @@ static inline void sockcm_init(struct sockcm_cookie *sockc,
};
}
-int __sock_cmsg_send(struct sock *sk, struct cmsghdr *cmsg,
+int __sock_cmsg_send(struct sock *sk, struct msghdr *msg, struct cmsghdr *cmsg,
struct sockcm_cookie *sockc);
int sock_cmsg_send(struct sock *sk, struct msghdr *msg,
struct sockcm_cookie *sockc);
diff --git a/net/core/sock.c b/net/core/sock.c
index 9abc4fe25953..b2cbe753af1d 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2826,8 +2826,8 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
}
EXPORT_SYMBOL(sock_alloc_send_pskb);
-int __sock_cmsg_send(struct sock *sk, struct cmsghdr *cmsg,
- struct sockcm_cookie *sockc)
+int __sock_cmsg_send(struct sock *sk, struct msghdr *msg __always_unused,
+ struct cmsghdr *cmsg, struct sockcm_cookie *sockc)
{
u32 tsflags;
@@ -2881,7 +2881,7 @@ int sock_cmsg_send(struct sock *sk, struct msghdr *msg,
return -EINVAL;
if (cmsg->cmsg_level != SOL_SOCKET)
continue;
- ret = __sock_cmsg_send(sk, cmsg, sockc);
+ ret = __sock_cmsg_send(sk, msg, cmsg, sockc);
if (ret)
return ret;
}
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index cf377377b52d..6360b8ba9c84 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -267,7 +267,7 @@ int ip_cmsg_send(struct sock *sk, struct msghdr *msg, struct ipcm_cookie *ipc,
}
#endif
if (cmsg->cmsg_level == SOL_SOCKET) {
- err = __sock_cmsg_send(sk, cmsg, &ipc->sockc);
+ err = __sock_cmsg_send(sk, msg, cmsg, &ipc->sockc);
if (err)
return err;
continue;
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index fff78496803d..c9ae30acf895 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -777,7 +777,7 @@ int ip6_datagram_send_ctl(struct net *net, struct sock *sk,
}
if (cmsg->cmsg_level == SOL_SOCKET) {
- err = __sock_cmsg_send(sk, cmsg, &ipc6->sockc);
+ err = __sock_cmsg_send(sk, msg, cmsg, &ipc6->sockc);
if (err)
return err;
continue;
diff --git a/net/socket.c b/net/socket.c
index fcbdd5bc47ac..4b65ac92045a 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2537,8 +2537,49 @@ static int copy_msghdr_from_user(struct msghdr *kmsg,
return err < 0 ? err : 0;
}
-static int ____sys_sendmsg(struct socket *sock, struct msghdr *msg_sys,
- unsigned int flags, struct used_address *used_address,
+DEFINE_STATIC_KEY_FALSE(tx_copy_cmsg_to_user_key);
+
+static int sendmsg_copy_cmsg_to_user(struct msghdr *msg_sys,
+ struct user_msghdr __user *umsg)
+{
+ struct compat_msghdr __user *umsg_compat =
+ (struct compat_msghdr __user *)umsg;
+ unsigned int flags = msg_sys->msg_flags;
+ struct msghdr msg_user = *msg_sys;
+ unsigned long cmsg_ptr;
+ struct cmsghdr *cmsg;
+ int err;
+
+ msg_user.msg_control_is_user = true;
+ msg_user.msg_control_user = umsg->msg_control;
+ cmsg_ptr = (unsigned long)msg_user.msg_control;
+ for_each_cmsghdr(cmsg, msg_sys) {
+ if (!CMSG_OK(msg_sys, cmsg))
+ break;
+ if (!cmsg_copy_to_user(cmsg))
+ continue;
+ err = put_cmsg(&msg_user, cmsg->cmsg_level, cmsg->cmsg_type,
+ cmsg->cmsg_len - sizeof(*cmsg), CMSG_DATA(cmsg));
+ if (err)
+ return err;
+ }
+
+ err = __put_user((msg_sys->msg_flags & ~MSG_CMSG_COMPAT),
+ COMPAT_FLAGS(umsg));
+ if (err)
+ return err;
+ if (MSG_CMSG_COMPAT & flags)
+ err = __put_user((unsigned long)msg_user.msg_control - cmsg_ptr,
+ &umsg_compat->msg_controllen);
+ else
+ err = __put_user((unsigned long)msg_user.msg_control - cmsg_ptr,
+ &umsg->msg_controllen);
+ return err;
+}
+
+static int ____sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
+ struct msghdr *msg_sys, unsigned int flags,
+ struct used_address *used_address,
unsigned int allowed_msghdr_flags)
{
unsigned char ctl[sizeof(struct cmsghdr) + 20]
@@ -2549,6 +2590,8 @@ static int ____sys_sendmsg(struct socket *sock, struct msghdr *msg_sys,
ssize_t err;
err = -ENOBUFS;
+ if (static_branch_unlikely(&tx_copy_cmsg_to_user_key))
+ msg_sys->msg_control_copy_to_user = false;
if (msg_sys->msg_controllen > INT_MAX)
goto out;
@@ -2606,6 +2649,16 @@ static int ____sys_sendmsg(struct socket *sock, struct msghdr *msg_sys,
used_address->name_len);
}
+ if (static_branch_unlikely(&tx_copy_cmsg_to_user_key)) {
+ if (msg_sys->msg_control_copy_to_user && msg && err >= 0) {
+ ssize_t len = err;
+
+ err = sendmsg_copy_cmsg_to_user(msg_sys, msg);
+ if (!err)
+ err = len;
+ }
+ }
+
out_freectl:
if (ctl_buf != ctl)
sock_kfree_s(sock->sk, ctl_buf, ctl_len);
@@ -2648,8 +2701,8 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
if (err < 0)
return err;
- err = ____sys_sendmsg(sock, msg_sys, flags, used_address,
- allowed_msghdr_flags);
+ err = ____sys_sendmsg(sock, msg, msg_sys, flags, used_address,
+ allowed_msghdr_flags);
kfree(iov);
return err;
}
@@ -2660,7 +2713,7 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
long __sys_sendmsg_sock(struct socket *sock, struct msghdr *msg,
unsigned int flags)
{
- return ____sys_sendmsg(sock, msg, flags, NULL, 0);
+ return ____sys_sendmsg(sock, NULL, msg, flags, NULL, 0);
}
long __sys_sendmsg(int fd, struct user_msghdr __user *msg, unsigned int flags,
--
2.20.1
^ permalink raw reply related
* [PATCH net-next v8 0/3] net: A lightweight zero-copy notification mechanism for MSG_ZEROCOPY
From: zijianzhang @ 2024-07-30 18:41 UTC (permalink / raw)
To: netdev
Cc: linux-api, willemdebruijn.kernel, almasrymina, edumazet, davem,
kuba, pabeni, dsahern, axboe, shuah, linux-kselftest, cong.wang,
xiaochun.lu, Zijian Zhang
From: Zijian Zhang <zijianzhang@bytedance.com>
Original notification mechanism needs poll + recvmmsg which is not
easy for applcations to accommodate. And, it also incurs unignorable
overhead including extra system calls.
While making maximum reuse of the existing MSG_ZEROCOPY related code,
this patch set introduces a new zerocopy socket notification mechanism.
Users of sendmsg pass a control message as a placeholder for the incoming
notifications. Upon returning, kernel embeds notifications directly into
user arguments passed in. By doing so, we can reduce the complexity and
the overhead for managing notifications.
We also have the logic related to copying cmsg to the userspace in sendmsg
generic for any possible uses cases in the future. However, it introduces
ABI change of sendmsg.
Changelog:
v1 -> v2:
- Reuse errormsg queue in the new notification mechanism,
users can actually use these two mechanisms in hybrid way
if they want to do so.
- Update case SCM_ZC_NOTIFICATION in __sock_cmsg_send
1. Regardless of 32-bit, 64-bit program, we will always handle
u64 type user address.
2. The size of data to copy_to_user is precisely calculated
in case of kernel stack leak.
- fix (kbuild-bot)
1. Add SCM_ZC_NOTIFICATION to arch-specific header files.
2. header file types.h in include/uapi/linux/socket.h
v2 -> v3:
- 1. Users can now pass in the address of the zc_info_elem directly
with appropriate cmsg_len instead of the ugly user interface. Plus,
the handler is now compatible with MSG_CMSG_COMPAT and 32-bit
pointer.
- 2. Suggested by Willem, another strategy of getting zc info is
briefly taking the lock of sk_error_queue and move to a private
list, like net_rx_action. I thought sk_error_queue is protected by
sock_lock, so that it's impossible for the handling of zc info and
users recvmsg from the sk_error_queue at the same time.
However, sk_error_queue is protected by its own lock. I am afraid
that during the time it is handling the private list, users may
fail to get other error messages in the queue via recvmsg. Thus,
I don't implement the splice logic in this version. Any comments?
v3 -> v4:
- 1. Change SOCK_ZC_INFO_MAX to 64 to avoid large stack frame size.
- 2. Fix minor typos.
- 3. Change cfg_zerocopy from int to enum in msg_zerocopy.c
Initially, we expect users to pass the user address of the user array
as a data in cmsg, so that the kernel can copy_to_user to this address
directly.
As Willem commented,
> The main design issue with this series is this indirection, rather
> than passing the array of notifications as cmsg.
> This trick circumvents having to deal with compat issues and having to
> figure out copy_to_user in ____sys_sendmsg (as msg_control is an
> in-kernel copy).
> This is quite hacky, from an API design PoV.
> As is passing a pointer, but expecting msg_controllen to hold the
> length not of the pointer, but of the pointed to user buffer.
> I had also hoped for more significant savings. Especially with the
> higher syscall overhead due to meltdown and spectre mitigations vs
> when MSG_ZEROCOPY was introduced and I last tried this optimization.
We solve it by supporting put_cmsg to userspace in sendmsg path starting
from v5.
v4 -> v5:
- 1. Passing user address directly to kernel raises concerns about
ABI. In this version, we support put_cmsg to userspace in TX path
to solve this problem.
v5 -> v6:
- 1. Cleanly copy cmsg to user upon returning of ___sys_sendmsg
v6 -> v7:
- 1. Remove flag MSG_CMSG_COPY_TO_USER, use a member in msghdr instead
- 2. Pass msg to __sock_cmsg_send.
- 3. sendmsg_copy_cmsg_to_user should be put at the end of
____sys_sendmsg to make sure msg_sys->msg_control is a valid pointer.
- 4. Add struct zc_info to contain the array of zc_info_elem, so that
the kernel can update the zc_info->size. Another possible solution is
updating the cmsg_len directly, but it will break for_each_cmsghdr.
- 5. Update selftest to make cfg_notification_limit have the same
semantics in both methods for better comparison.
v7 -> v8:
- 1. Add a static_branch in ____sys_sendmsg to avoid overhead in the
hot path.
- 2. Add ZC_NOTIFICATION_MAX to limit the max size of zc_info->arr.
- 3. Minimize the code in SCM_ZC_NOTIFICATION handler by adding a local
sk_buff_head.
* Performance
We update selftests/net/msg_zerocopy.c to accommodate the new mechanism,
cfg_notification_limit has the same semantics for both methods. Test
results are as follows, we update skb_orphan_frags_rx to the same as
skb_orphan_frags to support zerocopy in the localhost test.
cfg_notification_limit = 1, both method get notifications after 1 calling
of sendmsg. In this case, the new method has around 17% cpu savings in TCP
and 23% cpu savings in UDP.
+----------------------+---------+---------+---------+---------+
| Test Type / Protocol | TCP v4 | TCP v6 | UDP v4 | UDP v6 |
+----------------------+---------+---------+---------+---------+
| ZCopy (MB) | 7523 | 7706 | 7489 | 7304 |
+----------------------+---------+---------+---------+---------+
| New ZCopy (MB) | 8834 | 8993 | 9053 | 9228 |
+----------------------+---------+---------+---------+---------+
| New ZCopy / ZCopy | 117.42% | 116.70% | 120.88% | 126.34% |
+----------------------+---------+---------+---------+---------+
cfg_notification_limit = 32, both get notifications after 32 calling of
sendmsg, which means more chances to coalesce notifications, and less
overhead of poll + recvmsg for the original method. In this case, the new
method has around 7% cpu savings in TCP and slightly better cpu usage in
UDP. In the env of selftest, notifications of TCP are more likely to be
out of order than UDP, it's easier to coalesce more notifications in UDP.
The original method can get one notification with range of 32 in a recvmsg
most of the time. In TCP, most notifications' range is around 2, so the
original method needs around 16 recvmsgs to get notified in one round.
That's the reason for the "New ZCopy / ZCopy" diff in TCP and UDP here.
+----------------------+---------+---------+---------+---------+
| Test Type / Protocol | TCP v4 | TCP v6 | UDP v4 | UDP v6 |
+----------------------+---------+---------+---------+---------+
| ZCopy (MB) | 8842 | 8735 | 10072 | 9380 |
+----------------------+---------+---------+---------+---------+
| New ZCopy (MB) | 9366 | 9477 | 10108 | 9385 |
+----------------------+---------+---------+---------+---------+
| New ZCopy / ZCopy | 106.00% | 108.28% | 100.31% | 100.01% |
+----------------------+---------+---------+---------+---------+
In conclusion, when notification interval is small or notifications are
hard to be coalesced, the new mechanism is highly recommended. Otherwise,
the performance gain from the new mechanism is very limited.
Zijian Zhang (3):
sock: support copying cmsgs to the user space in sendmsg
sock: add MSG_ZEROCOPY notification mechanism based on msg_control
selftests: add MSG_ZEROCOPY msg_control notification test
arch/alpha/include/uapi/asm/socket.h | 2 +
arch/mips/include/uapi/asm/socket.h | 2 +
arch/parisc/include/uapi/asm/socket.h | 2 +
arch/sparc/include/uapi/asm/socket.h | 2 +
include/linux/socket.h | 8 ++
include/net/sock.h | 2 +-
include/uapi/asm-generic/socket.h | 2 +
include/uapi/linux/socket.h | 23 +++++
net/core/sock.c | 72 +++++++++++++-
net/ipv4/ip_sockglue.c | 2 +-
net/ipv6/datagram.c | 2 +-
net/socket.c | 63 +++++++++++-
tools/testing/selftests/net/msg_zerocopy.c | 101 ++++++++++++++++++--
tools/testing/selftests/net/msg_zerocopy.sh | 1 +
14 files changed, 265 insertions(+), 19 deletions(-)
--
2.20.1
^ permalink raw reply
* Re: [PATCH 7/8] fs: add an ioctl to get the mnt ns id from nsfs
From: Dmitry V. Levin @ 2024-07-30 16:45 UTC (permalink / raw)
To: Josef Bacik; +Cc: Christian Brauner, linux-fsdevel, linux-api, kernel-team
In-Reply-To: <180449959d5a756af7306d6bda55f41b9d53e3cb.1719243756.git.josef@toxicpanda.com>
Hi,
On Mon, Jun 24, 2024 at 11:49:50AM -0400, Josef Bacik wrote:
> In order to utilize the listmount() and statmount() extensions that
> allow us to call them on different namespaces we need a way to get the
> mnt namespace id from user space. Add an ioctl to nsfs that will allow
> us to extract the mnt namespace id in order to make these new extensions
> usable.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
> fs/nsfs.c | 14 ++++++++++++++
> include/uapi/linux/nsfs.h | 2 ++
> 2 files changed, 16 insertions(+)
>
> diff --git a/fs/nsfs.c b/fs/nsfs.c
> index 07e22a15ef02..af352dadffe1 100644
> --- a/fs/nsfs.c
> +++ b/fs/nsfs.c
> @@ -12,6 +12,7 @@
> #include <linux/nsfs.h>
> #include <linux/uaccess.h>
>
> +#include "mount.h"
> #include "internal.h"
>
> static struct vfsmount *nsfs_mnt;
> @@ -143,6 +144,19 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
> argp = (uid_t __user *) arg;
> uid = from_kuid_munged(current_user_ns(), user_ns->owner);
> return put_user(uid, argp);
> + case NS_GET_MNTNS_ID: {
> + struct mnt_namespace *mnt_ns;
> + __u64 __user *idp;
> + __u64 id;
> +
> + if (ns->ops->type != CLONE_NEWNS)
> + return -EINVAL;
> +
> + mnt_ns = container_of(ns, struct mnt_namespace, ns);
> + idp = (__u64 __user *)arg;
> + id = mnt_ns->seq;
> + return put_user(id, idp);
> + }
> default:
> return -ENOTTY;
> }
> diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
> index a0c8552b64ee..56e8b1639b98 100644
> --- a/include/uapi/linux/nsfs.h
> +++ b/include/uapi/linux/nsfs.h
> @@ -15,5 +15,7 @@
> #define NS_GET_NSTYPE _IO(NSIO, 0x3)
> /* Get owner UID (in the caller's user namespace) for a user namespace */
> #define NS_GET_OWNER_UID _IO(NSIO, 0x4)
> +/* Get the id for a mount namespace */
> +#define NS_GET_MNTNS_ID _IO(NSIO, 0x5)
As the kernel is writing an object of type __u64,
this has to be defined to _IOR(NSIO, 0x5, __u64) instead,
see the corresponding comments in uapi/asm-generic/ioctl.h file.
--
ldv
^ permalink raw reply
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