Patchwork [RFC] Demultiplexing SIGTRAP signal

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Submitter Srinivasa Ds
Date Sept. 22, 2008, 10:32 a.m.
Message ID <200809221602.32616.srinivasa@in.ibm.com>
Download mbox | patch
Permalink /patch/835/
State RFC, archived
Headers show

Comments

Srinivasa Ds - Sept. 22, 2008, 10:32 a.m.
Currently a SIGTRAP signal can denote any one of below reasons.
	- Breakpoint hit
	- H/W debug register hit
	- Single step
	- SIGTRAP signal sent through kill() or rasie()

Architectures like powerpc/parisc provides infrastructure to demultiplex
SIGTRAP signal by passing down the information for receiving SIGTRAP through
si_code of siginfot_t structure. Here is an attempt is generalise this 
infrastructure by extending it to x86 and x86_64 archs. 

Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com>



---
 arch/ia64/include/asm/siginfo.h    |    5 -----
 arch/powerpc/include/asm/siginfo.h |    5 -----
 arch/x86/kernel/traps_32.c         |   19 +++++++++++++++++--
 arch/x86/kernel/traps_64.c         |    7 ++++++-
 include/asm-generic/siginfo.h      |    2 ++
 include/asm-parisc/siginfo.h       |    5 -----
 6 files changed, 25 insertions(+), 18 deletions(-)
Ingo Molnar - Sept. 22, 2008, 10:42 a.m.
* Srinivasa Ds <srinivasa@in.ibm.com> wrote:

> Currently a SIGTRAP signal can denote any one of below reasons.
> 	- Breakpoint hit
> 	- H/W debug register hit
> 	- Single step
> 	- SIGTRAP signal sent through kill() or rasie()
> 
> Architectures like powerpc/parisc provides infrastructure to 
> demultiplex SIGTRAP signal by passing down the information for 
> receiving SIGTRAP through si_code of siginfot_t structure. Here is an 
> attempt is generalise this infrastructure by extending it to x86 and 
> x86_64 archs.

no fundamental objections - assuming existing x86 apps have not grown an 
ABI dependency on the existing send_sigtrap() semantics. (Debuggers and 
JITs would be a candidate for such dependencies.)

a small implementational detail, this bit:

> @@ -935,8 +936,22 @@ void __kprobes do_debug(struct pt_regs *
>  			goto clear_TF_reenable;
>  	}
>  
> -	/* Ok, finally something we can handle */
> -	send_sigtrap(tsk, regs, error_code);
> +	tsk->thread.trap_no = 1;
> +	tsk->thread.error_code = error_code;
> +
> +	memset(&info, 0, sizeof(info));
> +	info.si_signo = SIGTRAP;
> +	if (condition & DR_STEP)
> +		info.si_code = TRAP_TRACE;
> +	else if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3))
> +		info.si_code = TRAP_HWBKPT;
> +	else
> +		info.si_code = TRAP_BRKPT;
> +	/* User-mode ip? */
> +	info.si_addr = user_mode_vm(regs) ? (void __user *) regs->ip : NULL;
> +
> +	/* Send us the fake SIGTRAP */
> +	force_sig_info(SIGTRAP, &info, tsk);

should be pushed into [a sufficiently extended] send_sigtrap() instead.

and this bit:

> -	info.si_code = TRAP_BRKPT;
> +	if (condition & DR_STEP)
> +		info.si_code = TRAP_TRACE;
> +	else if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3))
> +		info.si_code = TRAP_HWBKPT;
> +	else
> +		info.si_code = TRAP_BRKPT;

should be separated into a helper function as well i guess.

Roland, any objections to the core idea (or to the implementation)?

	Ingo

Patch

Index: linux-2.6.27-rc7/arch/ia64/include/asm/siginfo.h
===================================================================
--- linux-2.6.27-rc7.orig/arch/ia64/include/asm/siginfo.h
+++ linux-2.6.27-rc7/arch/ia64/include/asm/siginfo.h
@@ -113,11 +113,6 @@  typedef struct siginfo {
 #undef NSIGSEGV
 #define NSIGSEGV	3
 
-/*
- * SIGTRAP si_codes
- */
-#define TRAP_BRANCH	(__SI_FAULT|3)	/* process taken branch trap */
-#define TRAP_HWBKPT	(__SI_FAULT|4)	/* hardware breakpoint or watchpoint */
 #undef NSIGTRAP
 #define NSIGTRAP	4
 
Index: linux-2.6.27-rc7/arch/powerpc/include/asm/siginfo.h
===================================================================
--- linux-2.6.27-rc7.orig/arch/powerpc/include/asm/siginfo.h
+++ linux-2.6.27-rc7/arch/powerpc/include/asm/siginfo.h
@@ -15,11 +15,6 @@ 
 
 #include <asm-generic/siginfo.h>
 
-/*
- * SIGTRAP si_codes
- */
-#define TRAP_BRANCH	(__SI_FAULT|3)	/* process taken branch trap */
-#define TRAP_HWBKPT	(__SI_FAULT|4)	/* hardware breakpoint or watchpoint */
 #undef NSIGTRAP
 #define NSIGTRAP	4
 
Index: linux-2.6.27-rc7/arch/x86/kernel/traps_32.c
===================================================================
--- linux-2.6.27-rc7.orig/arch/x86/kernel/traps_32.c
+++ linux-2.6.27-rc7/arch/x86/kernel/traps_32.c
@@ -890,6 +890,7 @@  void __kprobes do_int3(struct pt_regs *r
 void __kprobes do_debug(struct pt_regs *regs, long error_code)
 {
 	struct task_struct *tsk = current;
+	struct siginfo info;
 	unsigned int condition;
 
 	trace_hardirqs_fixup();
@@ -935,8 +936,22 @@  void __kprobes do_debug(struct pt_regs *
 			goto clear_TF_reenable;
 	}
 
-	/* Ok, finally something we can handle */
-	send_sigtrap(tsk, regs, error_code);
+	tsk->thread.trap_no = 1;
+	tsk->thread.error_code = error_code;
+
+	memset(&info, 0, sizeof(info));
+	info.si_signo = SIGTRAP;
+	if (condition & DR_STEP)
+		info.si_code = TRAP_TRACE;
+	else if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3))
+		info.si_code = TRAP_HWBKPT;
+	else
+		info.si_code = TRAP_BRKPT;
+	/* User-mode ip? */
+	info.si_addr = user_mode_vm(regs) ? (void __user *) regs->ip : NULL;
+
+	/* Send us the fake SIGTRAP */
+	force_sig_info(SIGTRAP, &info, tsk);
 
 	/*
 	 * Disable additional traps. They'll be re-enabled when
Index: linux-2.6.27-rc7/arch/x86/kernel/traps_64.c
===================================================================
--- linux-2.6.27-rc7.orig/arch/x86/kernel/traps_64.c
+++ linux-2.6.27-rc7/arch/x86/kernel/traps_64.c
@@ -936,7 +936,12 @@  asmlinkage void __kprobes do_debug(struc
 	tsk->thread.error_code = error_code;
 	info.si_signo = SIGTRAP;
 	info.si_errno = 0;
-	info.si_code = TRAP_BRKPT;
+	if (condition & DR_STEP)
+		info.si_code = TRAP_TRACE;
+	else if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3))
+		info.si_code = TRAP_HWBKPT;
+	else
+		info.si_code = TRAP_BRKPT;
 	info.si_addr = user_mode(regs) ? (void __user *)regs->ip : NULL;
 	force_sig_info(SIGTRAP, &info, tsk);
 
Index: linux-2.6.27-rc7/include/asm-generic/siginfo.h
===================================================================
--- linux-2.6.27-rc7.orig/include/asm-generic/siginfo.h
+++ linux-2.6.27-rc7/include/asm-generic/siginfo.h
@@ -199,6 +199,8 @@  typedef struct siginfo {
  */
 #define TRAP_BRKPT	(__SI_FAULT|1)	/* process breakpoint */
 #define TRAP_TRACE	(__SI_FAULT|2)	/* process trace trap */
+#define TRAP_BRANCH     (__SI_FAULT|3)  /* process taken branch trap */
+#define TRAP_HWBKPT     (__SI_FAULT|4)  /* hardware breakpoint or watchpoint 
*/
 #define NSIGTRAP	2
 
 /*
Index: linux-2.6.27-rc7/include/asm-parisc/siginfo.h
===================================================================
--- linux-2.6.27-rc7.orig/include/asm-parisc/siginfo.h
+++ linux-2.6.27-rc7/include/asm-parisc/siginfo.h
@@ -3,11 +3,6 @@ 
 
 #include <asm-generic/siginfo.h>
 
-/*
- * SIGTRAP si_codes
- */
-#define TRAP_BRANCH	(__SI_FAULT|3)	/* process taken branch trap */
-#define TRAP_HWBKPT	(__SI_FAULT|4)	/* hardware breakpoint or watchpoint */
 #undef NSIGTRAP
 #define NSIGTRAP	4