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Date: Wed, 1 Mar 2017 01:47:41 -0800
From: tip-bot for Dmitry Safonov <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: hpa@...or.com, torvalds@...ux-foundation.org,
dsafonov@...tuozzo.com, luto@...nel.org, brgerst@...il.com,
jpoimboe@...hat.com, shuah@...nel.org, bp@...en8.de,
linux-kernel@...r.kernel.org, peterz@...radead.org,
dvlasenk@...hat.com, bp@...e.de, tglx@...utronix.de,
mingo@...nel.org
Subject: [tip:x86/urgent] x86/selftests: Add clobbers for int80 on x86_64
Commit-ID: 2a4d0c627f5374f365a873dea4e10ae0bb437680
Gitweb: http://git.kernel.org/tip/2a4d0c627f5374f365a873dea4e10ae0bb437680
Author: Dmitry Safonov <dsafonov@...tuozzo.com>
AuthorDate: Mon, 13 Feb 2017 13:13:36 +0300
Committer: Ingo Molnar <mingo@...nel.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@...tuozzo.com>
Acked-by: Andy Lutomirski <luto@...nel.org>
Cc: 0x7f454c46@...il.com
Cc: Borislav Petkov <bp@...en8.de>
Cc: Borislav Petkov <bp@...e.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Shuah Khan <shuah@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kselftest@...r.kernel.org
Link: http://lkml.kernel.org/r/20170213101336.20486-1-dsafonov@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@...nel.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();
/*
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