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Re: [PATCH v2] ARM: Add SystemTap probes to longjmp and setjmp.

From: "Carlos O'Donell" <carlos at redhat dot com>
To: Will Newton <will dot newton at linaro dot org>, libc-ports at sourceware dot org
Cc: patches at linaro dot org
Date: Thu, 06 Feb 2014 11:26:40 -0500
Subject: Re: [PATCH v2] ARM: Add SystemTap probes to longjmp and setjmp.
Authentication-results: sourceware.org; auth=none
References: <1391594162-22269-1-git-send-email-will dot newton at linaro dot org>

On 02/05/2014 04:56 AM, Will Newton wrote:
> Now the ARM port implements pointer encryption for jmpbufs, gdb needs
> a SystemTap probe point in longjmp to determine the target PC of
> a call to longjmp. This patch implements the probe points in longjmp
> and a similar probe point in setjmp.
> 
> In order to have all the appropriate registers available to pass to the
> probe this reorders the layout of jmpbuf, putting the sp and lr registers
> at the start rather than the end.
> 
> Tested on armv7, no new failures in the glibc testsuite and confirmed
> that this fixes the gdb.base/longjmp.exp failures in the gdb testsuite.

This looks good to me.

If it's considered a bug, please check this in immediately and CC Allan
to keep him in the loop for these last minute bug fixes.

We are about to freeze so the 2.19 branch can be cut. If there is anything
else like this please bring it to his attention immediately.
 
> ports/ChangeLog.arm:
> 
> 2014-01-27  Will Newton  <will.newton@linaro.org>
> 
> 	* sysdeps/arm/__longjmp.S: Include stap-probe.h.
> 	(__longjmp): Restore sp and lr before restoring callee
> 	saved registers.  Add longjmp and longjmp_target
> 	SystemTap probe point.
> 	* sysdeps/arm/include/bits/setjmp.h (__JMP_BUF_SP):
> 	Define to zero to match jmpbuf layout.
> 	* sysdeps/arm/setjmp.S: Include stap-probe.h.
> 	(__sigsetjmp): Save sp and lr before saving callee
> 	saved registers.  Add setjmp SystemTap probe point.
> ---
>  ports/sysdeps/arm/__longjmp.S           | 61 ++++++++++++++++++++-------------
>  ports/sysdeps/arm/include/bits/setjmp.h |  2 +-
>  ports/sysdeps/arm/setjmp.S              | 12 +++++--
>  3 files changed, 47 insertions(+), 28 deletions(-)
> 
> Changes in v2:
>  - Add longjmp_target probe
>  - Move longjmp probe up to point before restore of sp/lr
> 
> diff --git a/ports/sysdeps/arm/__longjmp.S b/ports/sysdeps/arm/__longjmp.S
> index 27c57a1..08521e5 100644
> --- a/ports/sysdeps/arm/__longjmp.S
> +++ b/ports/sysdeps/arm/__longjmp.S
> @@ -17,6 +17,7 @@
>     <http://www.gnu.org/licenses/>.  */
>  
>  #include <sysdep.h>
> +#include <stap-probe.h>
>  #include <bits/setjmp.h>
>  #include <rtld-global-offsets.h>
>  #include <arm-features.h>
> @@ -25,31 +26,35 @@
>  
>  ENTRY (__longjmp)
>  	mov	ip, r0
> -	movs	r0, r1		/* get the return value in place */
> -	it	eq
> -	moveq	r0, #1		/* can't let setjmp() return zero! */
>  
>  #ifdef CHECK_SP
>  	sfi_breg ip, \
> -	ldr	r4, [\B, #32]	/* jmpbuf's sp */
> +	ldr	r4, [\B]	/* jmpbuf's sp */
>  	cfi_undefined (r4)
>  #ifdef PTR_DEMANGLE
>  	PTR_DEMANGLE (r4, r4, a3, a4)
>  #endif
>  	CHECK_SP (r4)
>  #endif
> -	sfi_sp sfi_breg ip, \
> -	ldmia	\B!, JMP_BUF_REGLIST
> +
>  #ifdef PTR_DEMANGLE
>  	ldr	a4, [ip], #4
> -	PTR_DEMANGLE (a4, a4, a3, a2)
> -	mov	sp, a4
> -	ldr	a4, [ip], #4
> -	PTR_DEMANGLE2 (lr, a4, a3)
> +	PTR_DEMANGLE (a4, a4, a3, r4)
> +	cfi_undefined (r4)
> +	ldr	r4, [ip], #4
> +	PTR_DEMANGLE2 (r4, r4, a3)
>  #else
> -	ldr	sp, [ip], #4
> -	ldr	lr, [ip], #4
> +	ldr	a4, [ip], #4
> +	ldr	r4, [ip], #4
> +	cfi_undefined (r4)
>  #endif
> +	/* longjmp probe expects longjmp first argument (4@r0), second
> +	   argument (-4@r1), and target address (4@r4), respectively.  */
> +	LIBC_PROBE (longjmp, 3, 4@r0, -4@r1, 4@r4)
> +	mov	sp, a4
> +	mov	lr, r4
> +	sfi_sp sfi_breg ip, \
> +	ldmia	\B!, JMP_BUF_REGLIST
>  	cfi_restore (v1)
>  	cfi_restore (v2)
>  	cfi_restore (v3)
> @@ -67,27 +72,27 @@ ENTRY (__longjmp)
>  
>  #ifdef NEED_HWCAP
>  # ifdef IS_IN_rtld
> -	ldr	a2, 1f
> +	ldr	a4, 1f
>  	ldr	a3, .Lrtld_local_ro
> -0:	add	a2, pc, a2
> -	add	a2, a2, a3
> -	ldr	a2, [a2, #RTLD_GLOBAL_RO_DL_HWCAP_OFFSET]
> +0:	add	a4, pc, a4
> +	add	a4, a4, a3
> +	ldr	a4, [a4, #RTLD_GLOBAL_RO_DL_HWCAP_OFFSET]
>  # else
>  #  ifdef PIC
> -	ldr	a2, 1f
> +	ldr	a4, 1f
>  	ldr	a3, .Lrtld_global_ro
> -0:	add	a2, pc, a2
> -	ldr	a2, [a2, a3]
> -	ldr	a2, [a2, #RTLD_GLOBAL_RO_DL_HWCAP_OFFSET]
> +0:	add	a4, pc, a4
> +	ldr	a4, [a4, a3]
> +	ldr	a4, [a4, #RTLD_GLOBAL_RO_DL_HWCAP_OFFSET]
>  #  else
> -	ldr	a2, .Lhwcap
> -	ldr	a2, [a2, #0]
> +	ldr	a4, .Lhwcap
> +	ldr	a4, [a4, #0]
>  #  endif
>  # endif
>  #endif
>  
>  #ifdef __SOFTFP__
> -	tst	a2, #HWCAP_ARM_VFP
> +	tst	a4, #HWCAP_ARM_VFP
>  	beq	.Lno_vfp
>  #endif
>  
> @@ -98,7 +103,7 @@ ENTRY (__longjmp)
>  .Lno_vfp:
>  
>  #ifndef ARM_ASSUME_NO_IWMMXT
> -	tst	a2, #HWCAP_ARM_IWMMXT
> +	tst	a4, #HWCAP_ARM_IWMMXT
>  	beq	.Lno_iwmmxt
>  
>  	/* Restore the call-preserved iWMMXt registers.  */
> @@ -118,6 +123,14 @@ ENTRY (__longjmp)
>  .Lno_iwmmxt:
>  #endif
>  
> +	/* longjmp_target probe expects longjmp first argument (4@r0), second
> +	   argument (-4@r1), and target address (4@r14), respectively.  */
> +	LIBC_PROBE (longjmp_target, 3, 4@r0, -4@r1, 4@r14)
> +
> +	movs	r0, r1		/* get the return value in place */
> +	it	eq
> +	moveq	r0, #1		/* can't let setjmp() return zero! */
> +
>  	DO_RET(lr)
>  
>  #ifdef NEED_HWCAP
> diff --git a/ports/sysdeps/arm/include/bits/setjmp.h b/ports/sysdeps/arm/include/bits/setjmp.h
> index 220dfe8..5877c1f 100644
> --- a/ports/sysdeps/arm/include/bits/setjmp.h
> +++ b/ports/sysdeps/arm/include/bits/setjmp.h
> @@ -30,7 +30,7 @@
>  # define JMP_BUF_REGLIST	{v1-v6, sl, fp}
>  
>  /* Index of __jmp_buf where the sp register resides.  */
> -# define __JMP_BUF_SP		8
> +# define __JMP_BUF_SP		0
>  #endif
>  
>  #endif  /* include/bits/setjmp.h */
> diff --git a/ports/sysdeps/arm/setjmp.S b/ports/sysdeps/arm/setjmp.S
> index b0b45ed..5e55ca5 100644
> --- a/ports/sysdeps/arm/setjmp.S
> +++ b/ports/sysdeps/arm/setjmp.S
> @@ -17,6 +17,7 @@
>     <http://www.gnu.org/licenses/>.  */
>  
>  #include <sysdep.h>
> +#include <stap-probe.h>
>  #include <bits/setjmp.h>
>  #include <rtld-global-offsets.h>
>  #include <arm-features.h>
> @@ -27,9 +28,11 @@ ENTRY (__sigsetjmp)
>  #endif
>  	mov	ip, r0
>  
> -	/* Save registers */
> -	sfi_breg ip, \
> -	stmia	\B!, JMP_BUF_REGLIST
> +	/* setjmp probe expects sigsetjmp first argument (4@r0), second
> +	   argument (-4@r1), and target address (4@r14), respectively.  */
> +	LIBC_PROBE (setjmp, 3, 4@r0, -4@r1, 4@r14)
> +
> +	/* Save sp and lr */
>  #ifdef PTR_MANGLE
>  	mov	a4, sp
>  	PTR_MANGLE2 (a4, a4, a3)
> @@ -40,6 +43,9 @@ ENTRY (__sigsetjmp)
>  	str	sp, [ip], #4
>  	str	lr, [ip], #4
>  #endif
> +	/* Save registers */
> +	sfi_breg ip, \
> +	stmia	\B!, JMP_BUF_REGLIST
>  
>  #if !defined ARM_ASSUME_NO_IWMMXT || defined __SOFTFP__
>  # define NEED_HWCAP 1
>

Follow-Ups:
- Re: [PATCH v2] ARM: Add SystemTap probes to longjmp and setjmp.
  - From: Joseph S. Myers
- Re: [PATCH v2] ARM: Add SystemTap probes to longjmp and setjmp.
  - From: Will Newton

References:
- [PATCH v2] ARM: Add SystemTap probes to longjmp and setjmp.
  - From: Will Newton

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