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x86: clear DF before calling signal handler 

The Linux kernel currently does not clear the direction flag before
calling a signal handler, whereas the x86/x86-64 ABI requires that.

Linux had this behavior/bug forever, but this becomes a real problem
with gcc version 4.3, which assumes that the direction flag is
correctly cleared at the entry of a function.

This patches changes the setup_frame() functions to clear the
direction before entering the signal handler.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Aurelien Jarno 2008-03-05 19:14:24 +01:00 committed by Ingo Molnar
parent ce4796d1e1
commit e40cd10ccf
3 changed files with 5 additions and 5 deletions
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4
arch/x86/ia32/ia32_signal.c
View File

@ -500,7 +500,7 @@ int ia32_setup_frame(int sig, struct k_sigaction *ka,
regs->ss = __USER32_DS;
set_fs(USER_DS);
regs->flags &= ~X86_EFLAGS_TF;
regs->flags &= ~(X86_EFLAGS_TF | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
@ -600,7 +600,7 @@ int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
regs->ss = __USER32_DS;
set_fs(USER_DS);
regs->flags &= ~X86_EFLAGS_TF;
regs->flags &= ~(X86_EFLAGS_TF | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);

4
arch/x86/kernel/signal_32.c
View File

@ -407,7 +407,7 @@ static int setup_frame(int sig, struct k_sigaction *ka,
* The tracer may want to single-step inside the
* handler too.
*/
regs->flags &= ~TF_MASK;
regs->flags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
@ -500,7 +500,7 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
* The tracer may want to single-step inside the
* handler too.
*/
regs->flags &= ~TF_MASK;
regs->flags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);

2
arch/x86/kernel/signal_64.c
View File

@ -295,7 +295,7 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
see include/asm-x86_64/uaccess.h for details. */
set_fs(USER_DS);
regs->flags &= ~X86_EFLAGS_TF;
regs->flags &= ~(X86_EFLAGS_TF | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
#ifdef DEBUG_SIG