* [PATCHv3] x86/selftests: add clobbers for int80 on x86_64
@ 2017-02-13 10:13 Dmitry Safonov
2017-02-13 19:06 ` Andy Lutomirski
2017-03-01 9:47 ` [tip:x86/urgent] x86/selftests: Add " tip-bot for Dmitry Safonov
0 siblings, 2 replies; 6+ messages in thread
From: Dmitry Safonov @ 2017-02-13 10:13 UTC (permalink / raw)
To: linux-kernel
Cc: 0x7f454c46, Dmitry Safonov, Shuah Khan, Thomas Gleixner,
Ingo Molnar, H. Peter Anvin, Andy Lutomirski, Borislav Petkov,
x86, linux-kselftest
Kernel erases R8..R11 registers prior returning to userspace
from int80: https://lkml.org/lkml/2009/10/1/164
GCC can reuse this registers and doesn't expect them to change
during syscall invocation. I met this kind of bug in CRIU once
gcc 6.1 and clang stored local variables in those registers
and the kernel zerofied them during syscall:
https://github.com/xemul/criu/commit/990d33f1a1cdd17bca6c2eb059ab3be2564f7fa2
By that reason I suggest to add those registers to clobbers
in selftests. Also, as notted by Andy - removed unneeded clobber
for flags in int 0x80 inline asm.
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: x86@kernel.org
Cc: linux-kselftest@vger.kernel.org
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
---
v3: Remove not needed clobber for "flags" (Andy)
v2: Don't touch iopl test: it doesn't do int 0x80
tools/testing/selftests/x86/fsgsbase.c | 2 +-
tools/testing/selftests/x86/ldt_gdt.c | 16 +++++++++++-----
tools/testing/selftests/x86/ptrace_syscall.c | 3 ++-
tools/testing/selftests/x86/single_step_syscall.c | 5 ++++-
4 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/tools/testing/selftests/x86/fsgsbase.c b/tools/testing/selftests/x86/fsgsbase.c
index 5b2b4b3c634c..b4967d875236 100644
--- a/tools/testing/selftests/x86/fsgsbase.c
+++ b/tools/testing/selftests/x86/fsgsbase.c
@@ -245,7 +245,7 @@ void do_unexpected_base(void)
long ret;
asm volatile ("int $0x80"
: "=a" (ret) : "a" (243), "b" (low_desc)
- : "flags");
+ : "r8", "r9", "r10", "r11");
memcpy(&desc, low_desc, sizeof(desc));
munmap(low_desc, sizeof(desc));
diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c
index 4af47079cf04..f6121612e769 100644
--- a/tools/testing/selftests/x86/ldt_gdt.c
+++ b/tools/testing/selftests/x86/ldt_gdt.c
@@ -45,6 +45,12 @@
#define AR_DB (1 << 22)
#define AR_G (1 << 23)
+#ifdef __x86_64__
+# define INT80_CLOBBERS "r8", "r9", "r10", "r11"
+#else
+# define INT80_CLOBBERS
+#endif
+
static int nerrs;
/* Points to an array of 1024 ints, each holding its own index. */
@@ -588,7 +594,7 @@ static int invoke_set_thread_area(void)
asm volatile ("int $0x80"
: "=a" (ret), "+m" (low_user_desc) :
"a" (243), "b" (low_user_desc)
- : "flags");
+ : INT80_CLOBBERS);
return ret;
}
@@ -657,7 +663,7 @@ static void test_gdt_invalidation(void)
"+a" (eax)
: "m" (low_user_desc_clear),
[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
- : "flags");
+ : INT80_CLOBBERS);
if (sel != 0) {
result = "FAIL";
@@ -688,7 +694,7 @@ static void test_gdt_invalidation(void)
"+a" (eax)
: "m" (low_user_desc_clear),
[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
- : "flags");
+ : INT80_CLOBBERS);
if (sel != 0) {
result = "FAIL";
@@ -721,7 +727,7 @@ static void test_gdt_invalidation(void)
"+a" (eax)
: "m" (low_user_desc_clear),
[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
- : "flags");
+ : INT80_CLOBBERS);
#ifdef __x86_64__
syscall(SYS_arch_prctl, ARCH_GET_FS, &new_base);
@@ -774,7 +780,7 @@ static void test_gdt_invalidation(void)
"+a" (eax)
: "m" (low_user_desc_clear),
[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
- : "flags");
+ : INT80_CLOBBERS);
#ifdef __x86_64__
syscall(SYS_arch_prctl, ARCH_GET_GS, &new_base);
diff --git a/tools/testing/selftests/x86/ptrace_syscall.c b/tools/testing/selftests/x86/ptrace_syscall.c
index b037ce9cf116..eaea92439708 100644
--- a/tools/testing/selftests/x86/ptrace_syscall.c
+++ b/tools/testing/selftests/x86/ptrace_syscall.c
@@ -58,7 +58,8 @@ static void do_full_int80(struct syscall_args32 *args)
asm volatile ("int $0x80"
: "+a" (args->nr),
"+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2),
- "+S" (args->arg3), "+D" (args->arg4), "+r" (bp));
+ "+S" (args->arg3), "+D" (args->arg4), "+r" (bp)
+ : : "r8", "r9", "r10", "r11");
args->arg5 = bp;
#else
sys32_helper(args, int80_and_ret);
diff --git a/tools/testing/selftests/x86/single_step_syscall.c b/tools/testing/selftests/x86/single_step_syscall.c
index 50c26358e8b7..a48da95c18fd 100644
--- a/tools/testing/selftests/x86/single_step_syscall.c
+++ b/tools/testing/selftests/x86/single_step_syscall.c
@@ -56,9 +56,11 @@ static volatile sig_atomic_t sig_traps;
#ifdef __x86_64__
# define REG_IP REG_RIP
# define WIDTH "q"
+# define INT80_CLOBBERS "r8", "r9", "r10", "r11"
#else
# define REG_IP REG_EIP
# define WIDTH "l"
+# define INT80_CLOBBERS
#endif
static unsigned long get_eflags(void)
@@ -140,7 +142,8 @@ int main()
printf("[RUN]\tSet TF and check int80\n");
set_eflags(get_eflags() | X86_EFLAGS_TF);
- asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid));
+ asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid)
+ : INT80_CLOBBERS);
check_result();
/*
--
2.11.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCHv3] x86/selftests: add clobbers for int80 on x86_64
2017-02-13 10:13 [PATCHv3] x86/selftests: add clobbers for int80 on x86_64 Dmitry Safonov
@ 2017-02-13 19:06 ` Andy Lutomirski
2017-02-13 19:30 ` Ingo Molnar
2017-02-13 22:18 ` hpa
2017-03-01 9:47 ` [tip:x86/urgent] x86/selftests: Add " tip-bot for Dmitry Safonov
1 sibling, 2 replies; 6+ messages in thread
From: Andy Lutomirski @ 2017-02-13 19:06 UTC (permalink / raw)
To: Dmitry Safonov
Cc: linux-kernel@vger.kernel.org, Dmitry Safonov, Shuah Khan,
Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Andy Lutomirski,
Borislav Petkov, X86 ML, open list:KERNEL SELFTEST FRAMEWORK
On Mon, Feb 13, 2017 at 2:13 AM, Dmitry Safonov <dsafonov@virtuozzo.com> wrote:
> Kernel erases R8..R11 registers prior returning to userspace
> from int80: https://lkml.org/lkml/2009/10/1/164
>
> GCC can reuse this registers and doesn't expect them to change
> during syscall invocation. I met this kind of bug in CRIU once
> gcc 6.1 and clang stored local variables in those registers
> and the kernel zerofied them during syscall:
> https://github.com/xemul/criu/commit/990d33f1a1cdd17bca6c2eb059ab3be2564f7fa2
>
> By that reason I suggest to add those registers to clobbers
> in selftests. Also, as notted by Andy - removed unneeded clobber
> for flags in int 0x80 inline asm.
Acked-by: Andy Lutomirski <luto@kernel.org>
Although these days we could preserve these regs in the kernel at the
cost of (I think) 4 bytes of text and zero runtime overhead.
--Andy
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCHv3] x86/selftests: add clobbers for int80 on x86_64
2017-02-13 19:06 ` Andy Lutomirski
@ 2017-02-13 19:30 ` Ingo Molnar
2017-02-13 22:18 ` hpa
1 sibling, 0 replies; 6+ messages in thread
From: Ingo Molnar @ 2017-02-13 19:30 UTC (permalink / raw)
To: Andy Lutomirski
Cc: Dmitry Safonov, linux-kernel@vger.kernel.org, Dmitry Safonov,
Shuah Khan, Thomas Gleixner, Ingo Molnar, H. Peter Anvin,
Andy Lutomirski, Borislav Petkov, X86 ML,
open list:KERNEL SELFTEST FRAMEWORK
* Andy Lutomirski <luto@amacapital.net> wrote:
> On Mon, Feb 13, 2017 at 2:13 AM, Dmitry Safonov <dsafonov@virtuozzo.com> wrote:
> > Kernel erases R8..R11 registers prior returning to userspace
> > from int80: https://lkml.org/lkml/2009/10/1/164
> >
> > GCC can reuse this registers and doesn't expect them to change
> > during syscall invocation. I met this kind of bug in CRIU once
> > gcc 6.1 and clang stored local variables in those registers
> > and the kernel zerofied them during syscall:
> > https://github.com/xemul/criu/commit/990d33f1a1cdd17bca6c2eb059ab3be2564f7fa2
> >
> > By that reason I suggest to add those registers to clobbers
> > in selftests. Also, as notted by Andy - removed unneeded clobber
> > for flags in int 0x80 inline asm.
>
> Acked-by: Andy Lutomirski <luto@kernel.org>
>
> Although these days we could preserve these regs in the kernel at the cost of (I
> think) 4 bytes of text and zero runtime overhead.
I think we should try that...
Thanks,
Ingo
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCHv3] x86/selftests: add clobbers for int80 on x86_64
2017-02-13 19:06 ` Andy Lutomirski
2017-02-13 19:30 ` Ingo Molnar
@ 2017-02-13 22:18 ` hpa
2017-02-17 17:03 ` Andy Lutomirski
1 sibling, 1 reply; 6+ messages in thread
From: hpa @ 2017-02-13 22:18 UTC (permalink / raw)
To: Andy Lutomirski, Dmitry Safonov
Cc: linux-kernel@vger.kernel.org, Dmitry Safonov, Shuah Khan,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, Borislav Petkov,
X86 ML, open list:KERNEL SELFTEST FRAMEWORK
On February 13, 2017 11:06:04 AM PST, Andy Lutomirski <luto@amacapital.net> wrote:
>On Mon, Feb 13, 2017 at 2:13 AM, Dmitry Safonov
><dsafonov@virtuozzo.com> wrote:
>> Kernel erases R8..R11 registers prior returning to userspace
>> from int80: https://lkml.org/lkml/2009/10/1/164
>>
>> GCC can reuse this registers and doesn't expect them to change
>> during syscall invocation. I met this kind of bug in CRIU once
>> gcc 6.1 and clang stored local variables in those registers
>> and the kernel zerofied them during syscall:
>>
>https://github.com/xemul/criu/commit/990d33f1a1cdd17bca6c2eb059ab3be2564f7fa2
>>
>> By that reason I suggest to add those registers to clobbers
>> in selftests. Also, as notted by Andy - removed unneeded clobber
>> for flags in int 0x80 inline asm.
>
>Acked-by: Andy Lutomirski <luto@kernel.org>
>
>Although these days we could preserve these regs in the kernel at the
>cost of (I think) 4 bytes of text and zero runtime overhead.
>
>--Andy
If we can do so that cheaply I think we should.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCHv3] x86/selftests: add clobbers for int80 on x86_64
2017-02-13 22:18 ` hpa
@ 2017-02-17 17:03 ` Andy Lutomirski
0 siblings, 0 replies; 6+ messages in thread
From: Andy Lutomirski @ 2017-02-17 17:03 UTC (permalink / raw)
To: H. Peter Anvin
Cc: Dmitry Safonov, linux-kernel@vger.kernel.org, Dmitry Safonov,
Shuah Khan, Thomas Gleixner, Ingo Molnar, Andy Lutomirski,
Borislav Petkov, X86 ML, open list:KERNEL SELFTEST FRAMEWORK
On Mon, Feb 13, 2017 at 2:18 PM, <hpa@zytor.com> wrote:
> On February 13, 2017 11:06:04 AM PST, Andy Lutomirski <luto@amacapital.net> wrote:
>>On Mon, Feb 13, 2017 at 2:13 AM, Dmitry Safonov
>><dsafonov@virtuozzo.com> wrote:
>>> Kernel erases R8..R11 registers prior returning to userspace
>>> from int80: https://lkml.org/lkml/2009/10/1/164
>>>
>>> GCC can reuse this registers and doesn't expect them to change
>>> during syscall invocation. I met this kind of bug in CRIU once
>>> gcc 6.1 and clang stored local variables in those registers
>>> and the kernel zerofied them during syscall:
>>>
>>https://github.com/xemul/criu/commit/990d33f1a1cdd17bca6c2eb059ab3be2564f7fa2
>>>
>>> By that reason I suggest to add those registers to clobbers
>>> in selftests. Also, as notted by Andy - removed unneeded clobber
>>> for flags in int 0x80 inline asm.
>>
>>Acked-by: Andy Lutomirski <luto@kernel.org>
>>
>>Although these days we could preserve these regs in the kernel at the
>>cost of (I think) 4 bytes of text and zero runtime overhead.
>>
>>--Andy
>
> If we can do so that cheaply I think we should.
Sure, but we should still apply Dmitry's patches first.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [tip:x86/urgent] x86/selftests: Add clobbers for int80 on x86_64
2017-02-13 10:13 [PATCHv3] x86/selftests: add clobbers for int80 on x86_64 Dmitry Safonov
2017-02-13 19:06 ` Andy Lutomirski
@ 2017-03-01 9:47 ` tip-bot for Dmitry Safonov
1 sibling, 0 replies; 6+ messages in thread
From: tip-bot for Dmitry Safonov @ 2017-03-01 9:47 UTC (permalink / raw)
To: linux-tip-commits
Cc: hpa, torvalds, dsafonov, luto, brgerst, jpoimboe, shuah, bp,
linux-kernel, peterz, dvlasenk, bp, tglx, mingo
Commit-ID: 2a4d0c627f5374f365a873dea4e10ae0bb437680
Gitweb: http://git.kernel.org/tip/2a4d0c627f5374f365a873dea4e10ae0bb437680
Author: Dmitry Safonov <dsafonov@virtuozzo.com>
AuthorDate: Mon, 13 Feb 2017 13:13:36 +0300
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 1 Mar 2017 10:24:56 +0100
x86/selftests: Add clobbers for int80 on x86_64
Kernel erases R8..R11 registers prior returning to userspace
from int80:
https://lkml.org/lkml/2009/10/1/164
GCC can reuse these registers and doesn't expect them to change
during syscall invocation. I met this kind of bug in CRIU once
GCC 6.1 and CLANG stored local variables in those registers
and the kernel zerofied them during syscall:
https://github.com/xemul/criu/commit/990d33f1a1cdd17bca6c2eb059ab3be2564f7fa2
By that reason I suggest to add those registers to clobbers
in selftests. Also, as noted by Andy - removed unneeded clobber
for flags in INT $0x80 inline asm.
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: 0x7f454c46@gmail.com
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kselftest@vger.kernel.org
Link: http://lkml.kernel.org/r/20170213101336.20486-1-dsafonov@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
tools/testing/selftests/x86/fsgsbase.c | 2 +-
tools/testing/selftests/x86/ldt_gdt.c | 16 +++++++++++-----
tools/testing/selftests/x86/ptrace_syscall.c | 3 ++-
tools/testing/selftests/x86/single_step_syscall.c | 5 ++++-
4 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/tools/testing/selftests/x86/fsgsbase.c b/tools/testing/selftests/x86/fsgsbase.c
index 5b2b4b3..b4967d8 100644
--- a/tools/testing/selftests/x86/fsgsbase.c
+++ b/tools/testing/selftests/x86/fsgsbase.c
@@ -245,7 +245,7 @@ void do_unexpected_base(void)
long ret;
asm volatile ("int $0x80"
: "=a" (ret) : "a" (243), "b" (low_desc)
- : "flags");
+ : "r8", "r9", "r10", "r11");
memcpy(&desc, low_desc, sizeof(desc));
munmap(low_desc, sizeof(desc));
diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c
index 4af4707..f612161 100644
--- a/tools/testing/selftests/x86/ldt_gdt.c
+++ b/tools/testing/selftests/x86/ldt_gdt.c
@@ -45,6 +45,12 @@
#define AR_DB (1 << 22)
#define AR_G (1 << 23)
+#ifdef __x86_64__
+# define INT80_CLOBBERS "r8", "r9", "r10", "r11"
+#else
+# define INT80_CLOBBERS
+#endif
+
static int nerrs;
/* Points to an array of 1024 ints, each holding its own index. */
@@ -588,7 +594,7 @@ static int invoke_set_thread_area(void)
asm volatile ("int $0x80"
: "=a" (ret), "+m" (low_user_desc) :
"a" (243), "b" (low_user_desc)
- : "flags");
+ : INT80_CLOBBERS);
return ret;
}
@@ -657,7 +663,7 @@ static void test_gdt_invalidation(void)
"+a" (eax)
: "m" (low_user_desc_clear),
[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
- : "flags");
+ : INT80_CLOBBERS);
if (sel != 0) {
result = "FAIL";
@@ -688,7 +694,7 @@ static void test_gdt_invalidation(void)
"+a" (eax)
: "m" (low_user_desc_clear),
[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
- : "flags");
+ : INT80_CLOBBERS);
if (sel != 0) {
result = "FAIL";
@@ -721,7 +727,7 @@ static void test_gdt_invalidation(void)
"+a" (eax)
: "m" (low_user_desc_clear),
[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
- : "flags");
+ : INT80_CLOBBERS);
#ifdef __x86_64__
syscall(SYS_arch_prctl, ARCH_GET_FS, &new_base);
@@ -774,7 +780,7 @@ static void test_gdt_invalidation(void)
"+a" (eax)
: "m" (low_user_desc_clear),
[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
- : "flags");
+ : INT80_CLOBBERS);
#ifdef __x86_64__
syscall(SYS_arch_prctl, ARCH_GET_GS, &new_base);
diff --git a/tools/testing/selftests/x86/ptrace_syscall.c b/tools/testing/selftests/x86/ptrace_syscall.c
index b037ce9c..eaea924 100644
--- a/tools/testing/selftests/x86/ptrace_syscall.c
+++ b/tools/testing/selftests/x86/ptrace_syscall.c
@@ -58,7 +58,8 @@ static void do_full_int80(struct syscall_args32 *args)
asm volatile ("int $0x80"
: "+a" (args->nr),
"+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2),
- "+S" (args->arg3), "+D" (args->arg4), "+r" (bp));
+ "+S" (args->arg3), "+D" (args->arg4), "+r" (bp)
+ : : "r8", "r9", "r10", "r11");
args->arg5 = bp;
#else
sys32_helper(args, int80_and_ret);
diff --git a/tools/testing/selftests/x86/single_step_syscall.c b/tools/testing/selftests/x86/single_step_syscall.c
index 50c2635..a48da95 100644
--- a/tools/testing/selftests/x86/single_step_syscall.c
+++ b/tools/testing/selftests/x86/single_step_syscall.c
@@ -56,9 +56,11 @@ static volatile sig_atomic_t sig_traps;
#ifdef __x86_64__
# define REG_IP REG_RIP
# define WIDTH "q"
+# define INT80_CLOBBERS "r8", "r9", "r10", "r11"
#else
# define REG_IP REG_EIP
# define WIDTH "l"
+# define INT80_CLOBBERS
#endif
static unsigned long get_eflags(void)
@@ -140,7 +142,8 @@ int main()
printf("[RUN]\tSet TF and check int80\n");
set_eflags(get_eflags() | X86_EFLAGS_TF);
- asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid));
+ asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid)
+ : INT80_CLOBBERS);
check_result();
/*
^ permalink raw reply related [flat|nested] 6+ messages in thread
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Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2017-02-13 10:13 [PATCHv3] x86/selftests: add clobbers for int80 on x86_64 Dmitry Safonov
2017-02-13 19:06 ` Andy Lutomirski
2017-02-13 19:30 ` Ingo Molnar
2017-02-13 22:18 ` hpa
2017-02-17 17:03 ` Andy Lutomirski
2017-03-01 9:47 ` [tip:x86/urgent] x86/selftests: Add " tip-bot for Dmitry Safonov
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