* [PATCH 1/2] x86/asm: Tidy up TSS limit code
2017-02-22 15:36 [PATCH 0/2] TSS incremental cleanups Andy Lutomirski
@ 2017-02-22 15:36 ` Andy Lutomirski
2017-02-22 15:36 ` [PATCH 2/2] selftests/x86: Add a basic selftest for ioperm Andy Lutomirski
1 sibling, 0 replies; 3+ messages in thread
From: Andy Lutomirski @ 2017-02-22 15:36 UTC (permalink / raw)
To: Paolo Bonzini, X86 ML
Cc: kvm list, linux-kernel@vger.kernel.org, Borislav Petkov,
Thomas Garnier, Jim Mattson, Andy Lutomirski
In an earlier version of the patch ("x86/kvm/vmx: Defer TR reload
after VM exit") that introduced TSS limit validity tracking, I
confused which helper was which. On reflection, the names I chose
sucked. Rename the helpers to make it more obvious what's going on
and add some comments.
While I'm at it, clear __tss_limit_invalid when force-reloading as
well as when contitionally reloading, since any TR reload fixes the
limit.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/include/asm/desc.h | 18 +++++++++++-------
arch/x86/kernel/ioport.c | 8 +++++++-
arch/x86/kernel/process.c | 6 +++---
3 files changed, 21 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index cb8f9149f6c8..1548ca92ad3f 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -205,6 +205,8 @@ static inline void native_load_tr_desc(void)
asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8));
}
+DECLARE_PER_CPU(bool, __tss_limit_invalid);
+
static inline void force_reload_TR(void)
{
struct desc_struct *d = get_cpu_gdt_table(smp_processor_id());
@@ -220,18 +222,20 @@ static inline void force_reload_TR(void)
write_gdt_entry(d, GDT_ENTRY_TSS, &tss, DESC_TSS);
load_TR_desc();
+ this_cpu_write(__tss_limit_invalid, false);
}
-DECLARE_PER_CPU(bool, need_tr_refresh);
-
-static inline void refresh_TR(void)
+/*
+ * Call this if you need the TSS limit to be correct, which should be the case
+ * if and only if you have TIF_IO_BITMAP set or you're switching to a task
+ * with TIF_IO_BITMAP set.
+ */
+static inline void refresh_tss_limit(void)
{
DEBUG_LOCKS_WARN_ON(preemptible());
- if (unlikely(this_cpu_read(need_tr_refresh))) {
+ if (unlikely(this_cpu_read(__tss_limit_invalid)))
force_reload_TR();
- this_cpu_write(need_tr_refresh, false);
- }
}
/*
@@ -250,7 +254,7 @@ static inline void invalidate_tss_limit(void)
if (unlikely(test_thread_flag(TIF_IO_BITMAP)))
force_reload_TR();
else
- this_cpu_write(need_tr_refresh, true);
+ this_cpu_write(__tss_limit_invalid, true);
}
static inline void native_load_gdt(const struct desc_ptr *dtr)
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index b01bc8517450..875d3d25dd6a 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -47,8 +47,14 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
t->io_bitmap_ptr = bitmap;
set_thread_flag(TIF_IO_BITMAP);
+ /*
+ * Now that we have an IO bitmap, we need our TSS limit to be
+ * correct. It's fine if we are preempted after doing this:
+ * with TIF_IO_BITMAP set, context switches will keep our TSS
+ * limit correct.
+ */
preempt_disable();
- refresh_TR();
+ refresh_tss_limit();
preempt_enable();
}
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 7780efa635b9..0b302591b51f 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -65,8 +65,8 @@ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
};
EXPORT_PER_CPU_SYMBOL(cpu_tss);
-DEFINE_PER_CPU(bool, need_tr_refresh);
-EXPORT_PER_CPU_SYMBOL_GPL(need_tr_refresh);
+DEFINE_PER_CPU(bool, __tss_limit_invalid);
+EXPORT_PER_CPU_SYMBOL_GPL(__tss_limit_invalid);
/*
* this gets called so that we can store lazy state into memory and copy the
@@ -218,7 +218,7 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
* Make sure that the TSS limit is correct for the CPU
* to notice the IO bitmap.
*/
- refresh_TR();
+ refresh_tss_limit();
} else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
/*
* Clear any possible leftover bits:
--
2.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH 2/2] selftests/x86: Add a basic selftest for ioperm
2017-02-22 15:36 [PATCH 0/2] TSS incremental cleanups Andy Lutomirski
2017-02-22 15:36 ` [PATCH 1/2] x86/asm: Tidy up TSS limit code Andy Lutomirski
@ 2017-02-22 15:36 ` Andy Lutomirski
1 sibling, 0 replies; 3+ messages in thread
From: Andy Lutomirski @ 2017-02-22 15:36 UTC (permalink / raw)
To: Paolo Bonzini, X86 ML
Cc: kvm list, linux-kernel@vger.kernel.org, Borislav Petkov,
Thomas Garnier, Jim Mattson, Andy Lutomirski
This doesn't fully exercise the interaction between KVM and ioperm(),
but it does test basic functionality.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
tools/testing/selftests/x86/Makefile | 2 +-
tools/testing/selftests/x86/ioperm.c | 171 +++++++++++++++++++++++++++++++++++
2 files changed, 172 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/x86/ioperm.c
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 8c1cb423cfe6..5743e2966adb 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -5,7 +5,7 @@ include ../lib.mk
.PHONY: all all_32 all_64 warn_32bit_failure clean
TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \
- check_initial_reg_state sigreturn ldt_gdt iopl \
+ check_initial_reg_state sigreturn ldt_gdt iopl ioperm \
protection_keys test_vdso
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
diff --git a/tools/testing/selftests/x86/ioperm.c b/tools/testing/selftests/x86/ioperm.c
new file mode 100644
index 000000000000..ddb97adcc321
--- /dev/null
+++ b/tools/testing/selftests/x86/ioperm.c
@@ -0,0 +1,171 @@
+/*
+ * ioperm.c - Test case for ioperm(2)
+ * Copyright (c) 2015 Andrew Lutomirski
+ */
+
+#define _GNU_SOURCE
+#include <err.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <signal.h>
+#include <setjmp.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdbool.h>
+#include <sched.h>
+#include <sys/io.h>
+
+static int nerrs = 0;
+
+static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
+ int flags)
+{
+ struct sigaction sa;
+ memset(&sa, 0, sizeof(sa));
+ sa.sa_sigaction = handler;
+ sa.sa_flags = SA_SIGINFO | flags;
+ sigemptyset(&sa.sa_mask);
+ if (sigaction(sig, &sa, 0))
+ err(1, "sigaction");
+
+}
+
+static void clearhandler(int sig)
+{
+ struct sigaction sa;
+ memset(&sa, 0, sizeof(sa));
+ sa.sa_handler = SIG_DFL;
+ sigemptyset(&sa.sa_mask);
+ if (sigaction(sig, &sa, 0))
+ err(1, "sigaction");
+}
+
+static jmp_buf jmpbuf;
+
+static void sigsegv(int sig, siginfo_t *si, void *ctx_void)
+{
+ siglongjmp(jmpbuf, 1);
+}
+
+static bool try_outb(unsigned short port)
+{
+ sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+ if (sigsetjmp(jmpbuf, 1) != 0) {
+ return false;
+ } else {
+ asm volatile ("outb %%al, %w[port]"
+ : : [port] "Nd" (port), "a" (0));
+ return true;
+ }
+ clearhandler(SIGSEGV);
+}
+
+static void expect_ok(unsigned short port)
+{
+ if (!try_outb(port)) {
+ printf("[FAIL]\toutb to 0x%02hx failed\n", port);
+ exit(1);
+ }
+
+ printf("[OK]\toutb to 0x%02hx worked\n", port);
+}
+
+static void expect_gp(unsigned short port)
+{
+ if (try_outb(port)) {
+ printf("[FAIL]\toutb to 0x%02hx worked\n", port);
+ exit(1);
+ }
+
+ printf("[OK]\toutb to 0x%02hx failed\n", port);
+}
+
+int main(void)
+{
+ cpu_set_t cpuset;
+ CPU_ZERO(&cpuset);
+ CPU_SET(0, &cpuset);
+ if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
+ err(1, "sched_setaffinity to CPU 0");
+
+ expect_gp(0x80);
+ expect_gp(0xed);
+
+ /*
+ * Probe for ioperm support. Note that clearing ioperm bits
+ * works even as nonroot.
+ */
+ printf("[RUN]\tenable 0x80\n");
+ if (ioperm(0x80, 1, 1) != 0) {
+ printf("[OK]\tioperm(0x80, 1, 1) failed (%d) -- try running as root\n",
+ errno);
+ return 0;
+ }
+ expect_ok(0x80);
+ expect_gp(0xed);
+
+ printf("[RUN]\tdisable 0x80\n");
+ if (ioperm(0x80, 1, 0) != 0) {
+ printf("[FAIL]\tioperm(0x80, 1, 0) failed (%d)", errno);
+ return 1;
+ }
+ expect_gp(0x80);
+ expect_gp(0xed);
+
+ /* Make sure that fork() preserves ioperm. */
+ if (ioperm(0x80, 1, 1) != 0) {
+ printf("[FAIL]\tioperm(0x80, 1, 0) failed (%d)", errno);
+ return 1;
+ }
+
+ pid_t child = fork();
+ if (child == -1)
+ err(1, "fork");
+
+ if (child == 0) {
+ printf("[RUN]\tchild: check that we inherited permissions\n");
+ expect_ok(0x80);
+ expect_gp(0xed);
+ return 0;
+ } else {
+ int status;
+ if (waitpid(child, &status, 0) != child ||
+ !WIFEXITED(status)) {
+ printf("[FAIL]\tChild died\n");
+ nerrs++;
+ } else if (WEXITSTATUS(status) != 0) {
+ printf("[FAIL]\tChild failed\n");
+ nerrs++;
+ } else {
+ printf("[OK]\tChild succeeded\n");
+ }
+ }
+
+ /* Test the capability checks. */
+
+ printf("\tDrop privileges\n");
+ if (setresuid(1, 1, 1) != 0) {
+ printf("[WARN]\tDropping privileges failed\n");
+ return 0;
+ }
+
+ printf("[RUN]\tdisable 0x80\n");
+ if (ioperm(0x80, 1, 0) != 0) {
+ printf("[FAIL]\tioperm(0x80, 1, 0) failed (%d)", errno);
+ return 1;
+ }
+ printf("[OK]\tit worked\n");
+
+ printf("[RUN]\tenable 0x80 again\n");
+ if (ioperm(0x80, 1, 1) == 0) {
+ printf("[FAIL]\tit succeeded but should have failed.\n");
+ return 1;
+ }
+ printf("[OK]\tit failed\n");
+ return 0;
+}
+
--
2.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread