Bug#469058: Linux doesn't follow x86/x86-64 ABI wrt direction flag
tag 469058 + patch
thanks
On Wed, Mar 05, 2008 at 10:53:28PM +0100, Aurelien Jarno wrote:
>
> So let's summarize:
> - linux 2.6 has to be fixed. A patch is available on the lkml [1] for
> 2.6.25-rc. It could be easily backported to 2.6.24
The patch for 2.6.25-rc went upstream. Please find a backported patch
for 2.6.24 below.
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.
This become 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>
---
arch/x86/ia32/ia32_signal.c | 4 ++--
arch/x86/kernel/signal_32.c | 4 ++--
arch/x86/kernel/signal_64.c | 2 +-
3 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 6ea19c2..4eaaf78 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -494,7 +494,7 @@ int ia32_setup_frame(int sig, struct k_sigaction *ka,
regs->ss = __USER32_DS;
set_fs(USER_DS);
- regs->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | 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->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
diff --git a/arch/x86/kernel/signal_32.c b/arch/x86/kernel/signal_32.c
index 9bdd830..20056db 100644
--- a/arch/x86/kernel/signal_32.c
+++ b/arch/x86/kernel/signal_32.c
@@ -396,7 +396,7 @@ static int setup_frame(int sig, struct k_sigaction *ka,
* The tracer may want to single-step inside the
* handler too.
*/
- regs->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
@@ -489,7 +489,7 @@ 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->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index ab086b0..62964c5 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -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->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
#ifdef DEBUG_SIG
--
.''`. Aurelien Jarno | GPG: 1024D/F1BCDB73
: :' : Debian developer | Electrical Engineer
`. `' aurel32@debian.org | aurelien@aurel32.net
`- people.debian.org/~aurel32 | www.aurel32.net
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