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selftests/x86: Consolidate and fix get/set_eflags() helpers

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There are several copies of get_eflags() and set_eflags() and they all are
buggy.  Consolidate them and fix them.  The fixes are:

Add memory clobbers.  These are probably unnecessary but they make sure
that the compiler doesn't move something past one of these calls when it
shouldn't.

Respect the redzone on x86_64.  There has no failure been observed related
to this, but it's definitely a bug.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/982ce58ae8dea2f1e57093ee894760e35267e751.1593191971.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski
2020-06-26 10:21:16 -07:00
committed by Thomas Gleixner
parent a61fa2799e
commit cced0b24bb
7 changed files with 51 additions and 90 deletions
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15
tools/testing/selftests/x86/test_vsyscall.c
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@@ -20,6 +20,8 @@
#include <setjmp.h>
#include <sys/uio.h>
#include "helpers.h"
#ifdef __x86_64__
# define VSYS(x) (x)
#else
@@ -493,21 +495,8 @@ static int test_process_vm_readv(void)
}
#ifdef __x86_64__
#define X86_EFLAGS_TF (1UL << 8)
static volatile sig_atomic_t num_vsyscall_traps;
static unsigned long get_eflags(void)
{
unsigned long eflags;
asm volatile ("pushfq\n\tpopq %0" : "=rm" (eflags));
return eflags;
}
static void set_eflags(unsigned long eflags)
{
asm volatile ("pushq %0\n\tpopfq" : : "rm" (eflags) : "flags");
}
static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
{
ucontext_t *ctx = (ucontext_t *)ctx_void;