[PATCH 1/2] x86 signals: lift flags diddling code

[PATCH 1/2] x86 signals: lift flags diddling code

[Roland McGrath]

This lifts the code diddling the TF and DF bits for signal handler setup
out of the several places copying the same code into the one place that
calls them all.  There is no change in what it does.

I also separated the recently-added DF bit clearing from the TF diddling.
The compiler turns them back into one instruction anyway.  The tossing
in of DF to the same line of code with no new comments was a bit more
arcane than seems wise.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
 arch/x86/ia32/ia32_signal.c |    6 ------
 arch/x86/kernel/signal_32.c |   35 +++++++++++++++--------------------
 arch/x86/kernel/signal_64.c |   19 +++++++++++++++----
 3 files changed, 30 insertions(+), 30 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 05e155d..0866104 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -500,9 +500,6 @@ int ia32_setup_frame(int sig, struct k_sigaction *ka,
 	regs->ss = __USER32_DS;
 
 	set_fs(USER_DS);
-	regs->flags &= ~(X86_EFLAGS_TF | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
 
 #if DEBUG_SIG
 	printk(KERN_DEBUG "SIG deliver (%s:%d): sp=%p pc=%lx ra=%u\n",
@@ -600,9 +597,6 @@ 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 | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
 
 #if DEBUG_SIG
 	printk(KERN_DEBUG "SIG deliver (%s:%d): sp=%p pc=%lx ra=%u\n",
diff --git a/arch/x86/kernel/signal_32.c b/arch/x86/kernel/signal_32.c
index f1b1179..8e05e7f 100644
--- a/arch/x86/kernel/signal_32.c
+++ b/arch/x86/kernel/signal_32.c
@@ -413,16 +413,6 @@ setup_frame(int sig, struct k_sigaction *ka, sigset_t *set,
 	regs->ss = __USER_DS;
 	regs->cs = __USER_CS;
 
-	/*
-	 * Clear TF when entering the signal handler, but
-	 * notify any tracer that was single-stepping it.
-	 * The tracer may want to single-step inside the
-	 * handler too.
-	 */
-	regs->flags &= ~(X86_EFLAGS_TF | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
-
 	return 0;
 
 give_sigsegv:
@@ -501,16 +491,6 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 	regs->ss = __USER_DS;
 	regs->cs = __USER_CS;
 
-	/*
-	 * Clear TF when entering the signal handler, but
-	 * notify any tracer that was single-stepping it.
-	 * The tracer may want to single-step inside the
-	 * handler too.
-	 */
-	regs->flags &= ~(X86_EFLAGS_TF | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
-
 	return 0;
 
 give_sigsegv:
@@ -566,6 +546,21 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 	if (ret)
 		return ret;
 
+	/*
+	 * Clear the direction flag as per the ABI for function entry.
+	 */
+	regs->flags &= ~X86_EFLAGS_DF;
+
+	/*
+	 * Clear TF when entering the signal handler, but
+	 * notify any tracer that was single-stepping it.
+	 * The tracer may want to single-step inside the
+	 * handler too.
+	 */
+	regs->flags &= ~X86_EFLAGS_TF;
+	if (test_thread_flag(TIF_SINGLESTEP))
+		ptrace_notify(SIGTRAP);
+
 	spin_lock_irq(&current->sighand->siglock);
 	sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);
 	if (!(ka->sa.sa_flags & SA_NODEFER))
diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index 827179c..3a76702 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -289,10 +289,6 @@ 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 | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
-
 	return 0;
 
 give_sigsegv:
@@ -380,6 +376,21 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 	ret = setup_rt_frame(sig, ka, info, oldset, regs);
 
 	if (ret == 0) {
+		/*
+		 * Clear the direction flag as per the ABI for function entry.
+		 */
+		regs->flags &= ~X86_EFLAGS_DF;
+
+		/*
+		 * Clear TF when entering the signal handler, but
+		 * notify any tracer that was single-stepping it.
+		 * The tracer may want to single-step inside the
+		 * handler too.
+		 */
+		regs->flags &= ~X86_EFLAGS_TF;
+		if (test_thread_flag(TIF_SINGLESTEP))
+			ptrace_notify(SIGTRAP);
+
 		spin_lock_irq(&current->sighand->siglock);
 		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 		if (!(ka->sa.sa_flags & SA_NODEFER))

[PATCH 2/2] x86 signals: lift set_fs

[Roland McGrath]

This lifts the set_fs(USER_DS) call for signal handler setup out of the
three places copying the same code into the one place that calls them
all.  There is no change in what it does.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
 arch/x86/ia32/ia32_signal.c |    4 ----
 arch/x86/kernel/signal_64.c |   11 +++++++----
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 0866104..bbed3a2 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -499,8 +499,6 @@ int ia32_setup_frame(int sig, struct k_sigaction *ka,
 	regs->cs = __USER32_CS;
 	regs->ss = __USER32_DS;
 
-	set_fs(USER_DS);
-
 #if DEBUG_SIG
 	printk(KERN_DEBUG "SIG deliver (%s:%d): sp=%p pc=%lx ra=%u\n",
 	       current->comm, current->pid, frame, regs->ip, frame->pretcode);
@@ -596,8 +594,6 @@ int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 	regs->cs = __USER32_CS;
 	regs->ss = __USER32_DS;
 
-	set_fs(USER_DS);
-
 #if DEBUG_SIG
 	printk(KERN_DEBUG "SIG deliver (%s:%d): sp=%p pc=%lx ra=%u\n",
 	       current->comm, current->pid, frame, regs->ip, frame->pretcode);
diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index 3a76702..ccb2a45 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -285,10 +285,6 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 	   even if the handler happens to be interrupting 32-bit code. */
 	regs->cs = __USER_CS;
 
-	/* This, by contrast, has nothing to do with segment registers -
-	   see include/asm-x86_64/uaccess.h for details. */
-	set_fs(USER_DS);
-
 	return 0;
 
 give_sigsegv:
@@ -377,6 +373,13 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 
 	if (ret == 0) {
 		/*
+		 * This has nothing to do with segment registers,
+		 * despite the name.  This magic affects uaccess.h
+		 * macros' behavior.  Reset it to the normal setting.
+		 */
+		set_fs(USER_DS);
+
+		/*
 		 * Clear the direction flag as per the ABI for function entry.
 		 */
 		regs->flags &= ~X86_EFLAGS_DF;

Re: [PATCH 2/2] x86 signals: lift set_fs

[Ingo Molnar]

* Roland McGrath <roland@redhat.com> wrote:

> This lifts the set_fs(USER_DS) call for signal handler setup out of 
> the three places copying the same code into the one place that calls 
> them all.  There is no change in what it does.

thanks, applied.

	Ingo

Re: [PATCH 1/2] x86 signals: lift flags diddling code

[Ingo Molnar]

* Roland McGrath <roland@redhat.com> wrote:

> This lifts the code diddling the TF and DF bits for signal handler 
> setup out of the several places copying the same code into the one 
> place that calls them all.  There is no change in what it does.
> 
> I also separated the recently-added DF bit clearing from the TF 
> diddling. The compiler turns them back into one instruction anyway.  
> The tossing in of DF to the same line of code with no new comments was 
> a bit more arcane than seems wise.

thanks Roland, applied.

	Ingo

[PATCH 1/2] x86 signals: lift flags diddling code

[Roland McGrath]

This lifts the code diddling the TF and DF bits for signal handler setup
out of the several places copying the same code into the one place that
calls them all.  There is no change in what it does.

I also separated the recently-added DF bit clearing from the TF diddling.
The compiler turns them back into one instruction anyway.  The tossing
in of DF to the same line of code with no new comments was a bit more
arcane than seems wise.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
 arch/x86/ia32/ia32_signal.c |    6 ------
 arch/x86/kernel/signal_32.c |   35 +++++++++++++++--------------------
 arch/x86/kernel/signal_64.c |   18 +++++++++++++++---
 3 files changed, 30 insertions(+), 29 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 5e7771a..e5e4b00 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -500,9 +500,6 @@ int ia32_setup_frame(int sig, struct k_sigaction *ka,
 	regs->ss = __USER32_DS;
 
 	set_fs(USER_DS);
-	regs->flags &= ~(X86_EFLAGS_TF | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
 
 #if DEBUG_SIG
 	printk(KERN_DEBUG "SIG deliver (%s:%d): sp=%p pc=%lx ra=%u\n",
@@ -600,9 +597,6 @@ 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 | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
 
 #if DEBUG_SIG
 	printk(KERN_DEBUG "SIG deliver (%s:%d): sp=%p pc=%lx ra=%u\n",
diff --git a/arch/x86/kernel/signal_32.c b/arch/x86/kernel/signal_32.c
index 0157a6f..806b2d6 100644
--- a/arch/x86/kernel/signal_32.c
+++ b/arch/x86/kernel/signal_32.c
@@ -401,16 +401,6 @@ static int setup_frame(int sig, struct k_sigaction *ka,
 	regs->ss = __USER_DS;
 	regs->cs = __USER_CS;
 
-	/*
-	 * Clear TF when entering the signal handler, but
-	 * notify any tracer that was single-stepping it.
-	 * The tracer may want to single-step inside the
-	 * handler too.
-	 */
-	regs->flags &= ~(TF_MASK | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
-
 #if DEBUG_SIG
 	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
 		current->comm, current->pid, frame, regs->ip, frame->pretcode);
@@ -494,16 +484,6 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 	regs->ss = __USER_DS;
 	regs->cs = __USER_CS;
 
-	/*
-	 * Clear TF when entering the signal handler, but
-	 * notify any tracer that was single-stepping it.
-	 * The tracer may want to single-step inside the
-	 * handler too.
-	 */
-	regs->flags &= ~(TF_MASK | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
-
 #if DEBUG_SIG
 	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
 		current->comm, current->pid, frame, regs->ip, frame->pretcode);
@@ -562,6 +542,21 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 		ret = setup_frame(sig, ka, oldset, regs);
 
 	if (ret == 0) {
+		/*
+		 * Clear the direction flag as per the ABI for function entry.
+		 */
+		regs->flags &= ~X86_EFLAGS_DF;
+
+		/*
+		 * Clear TF when entering the signal handler, but
+		 * notify any tracer that was single-stepping it.
+		 * The tracer may want to single-step inside the
+		 * handler too.
+		 */
+		regs->flags &= ~X86_EFLAGS_TF;
+		if (test_thread_flag(TIF_SINGLESTEP))
+			ptrace_notify(SIGTRAP);
+
 		spin_lock_irq(&current->sighand->siglock);
 		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 		if (!(ka->sa.sa_flags & SA_NODEFER))
diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index 1c83e51..6c3f5f1 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -295,9 +295,6 @@ 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 | X86_EFLAGS_DF);
-	if (test_thread_flag(TIF_SINGLESTEP))
-		ptrace_notify(SIGTRAP);
 #ifdef DEBUG_SIG
 	printk("SIG deliver (%s:%d): sp=%p pc=%lx ra=%p\n",
 		current->comm, current->pid, frame, regs->ip, frame->pretcode);
@@ -396,6 +393,21 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 	ret = setup_rt_frame(sig, ka, info, oldset, regs);
 
 	if (ret == 0) {
+		/*
+		 * Clear the direction flag as per the ABI for function entry.
+		 */
+		regs->flags &= ~X86_EFLAGS_DF;
+
+		/*
+		 * Clear TF when entering the signal handler, but
+		 * notify any tracer that was single-stepping it.
+		 * The tracer may want to single-step inside the
+		 * handler too.
+		 */
+		regs->flags &= ~X86_EFLAGS_TF;
+		if (test_thread_flag(TIF_SINGLESTEP))
+			ptrace_notify(SIGTRAP);
+
 		spin_lock_irq(&current->sighand->siglock);
 		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 		if (!(ka->sa.sa_flags & SA_NODEFER))