[PATCH] musl: add debug information for mipsel syscalls

[Hauke Mehrtens]

On 6/25/20 1:14 AM, Daniel Santos wrote:
> This is split into two patches to ease reviewing, as it must be renamed
> to *.S in order to be preprocessed.
> 
> Co-Authored-By: Daniele Tamino <dtamino at irobot.com>
> Signed-off-by: Daniel Santos <daniel.santos at pobox.com>
> ---
>  ...ebug-information-to-__syscall_cp_asm.patch | 100 ++++++++++++++++++
>  .../221-mipsel-preprocess-syscall_cp.s.patch  |  18 ++++
>  2 files changed, 118 insertions(+)
>  create mode 100644 toolchain/musl/patches/220-mipsel-Add-debug-information-to-__syscall_cp_asm.patch
>  create mode 100644 toolchain/musl/patches/221-mipsel-preprocess-syscall_cp.s.patch
> 
> diff --git a/toolchain/musl/patches/220-mipsel-Add-debug-information-to-__syscall_cp_asm.patch b/toolchain/musl/patches/220-mipsel-Add-debug-information-to-__syscall_cp_asm.patch
> new file mode 100644
> index 0000000000..0aa9330bd4
> --- /dev/null
> +++ b/toolchain/musl/patches/220-mipsel-Add-debug-information-to-__syscall_cp_asm.patch
> @@ -0,0 +1,100 @@
> +From 6ce77039943af4ca51ebf1385fd6ed01ecce8159 Mon Sep 17 00:00:00 2001
> +From: Daniel Santos <daniel.santos at pobox.com>
> +Date: Wed, 24 Jun 2020 14:45:08 -0500
> +Subject: mipsel: Add debug information to __syscall_cp_asm
> +
> +This is the function called for interruptable / repeatable syscalls like
> +nanosleep.  Without this patch, attaching a debugger to a program making
> +such a syscall results in the debugger being completely unable to
> +perform a backtrace.
> +
> +Co-Authored-By: Daniele Tamino <dtamino at irobot.com>
> +Signed-off-by: Daniel Santos <daniel.santos at pobox.com>
> +---
> + src/thread/mips/syscall_cp.s | 41 +++++++++++++++++++++++++++++++++++-
> + 1 file changed, 40 insertions(+), 1 deletion(-)
> +
> +diff --git a/src/thread/mips/syscall_cp.s b/src/thread/mips/syscall_cp.s
> +index d2846264..d39bff59 100644
> +--- a/src/thread/mips/syscall_cp.s
> ++++ b/src/thread/mips/syscall_cp.s
> +@@ -1,4 +1,14 @@
> ++.section	.mdebug.abi32
> ++.previous
> + .set    noreorder
> ++.cfi_sections	.debug_frame
> ++.abicalls
> ++#ifdef __PIC__
> ++	.option	pic2
> ++#else
> ++	.option	pic0
> ++#endif
> ++.text
> + 
> + .global __cp_begin
> + .hidden __cp_begin
> +@@ -9,12 +19,32 @@
> + .global __cp_cancel
> + .hidden __cp_cancel
> + .type   __cp_cancel, at function
> +-.hidden __cancel
> ++.hidden __cancel	/* long __cancel() in src/thread/pthread_cancel.c */
> + .global __syscall_cp_asm
> + .hidden __syscall_cp_asm
> + .type   __syscall_cp_asm, at function
> ++
> ++/*
> ++long __syscall_cp_asm(
> ++	volatile int *cancel,
> ++	syscall_arg_t nr,
> ++	syscall_arg_t u,
> ++	syscall_arg_t v,
> ++	syscall_arg_t w,
> ++	syscall_arg_t x,
> ++	syscall_arg_t y,
> ++	syscall_arg_t z)
> ++*/
> ++
> ++	.ent	__syscall_cp_asm
> ++	.frame	$sp, 32, $ra
> ++	.mask	0x00000000, 0
> ++	.fmask	0x00000000, 0
> ++	.cfi_startproc
> ++	.cfi_return_column $ra
> + __syscall_cp_asm:
> + 	subu    $sp, $sp, 32
> ++	.cfi_adjust_cfa_offset 32
> + __cp_begin:
> + 	lw      $4, 0($4)
> + 	bne     $4, $0, __cp_cancel
> +@@ -35,14 +65,17 @@ __cp_begin:
> + __cp_end:
> + 	beq     $7, $0, 1f
> + 	addu    $sp, $sp, 32
> ++	.cfi_adjust_cfa_offset -32
> + 	subu    $2, $0, $2
> + 1:	jr      $ra
> + 	nop
> + 
> + __cp_cancel:
> + 	move    $2, $ra
> ++	.cfi_register $ra, $2
> + 	bal     1f
> + 	addu    $sp, $sp, 32
> ++	.cfi_adjust_cfa_offset -32
> + 	.gpword .
> + 	.gpword __cancel
> + 1:	lw      $3, ($ra)
> +@@ -51,3 +84,9 @@ __cp_cancel:
> + 	addu    $25, $25, $3
> + 	jr      $25
> + 	move    $ra, $2
> ++	.cfi_restore $ra
> ++#ifdef __ELF__
> ++	.size __syscall_cp_asm,.-__syscall_cp_asm
> ++#endif
> ++	.end	__syscall_cp_asm
> ++	.cfi_endproc
> +-- 
> +2.24.1
> +
> diff --git a/toolchain/musl/patches/221-mipsel-preprocess-syscall_cp.s.patch b/toolchain/musl/patches/221-mipsel-preprocess-syscall_cp.s.patch
> new file mode 100644
> index 0000000000..a4eb8fed51
> --- /dev/null
> +++ b/toolchain/musl/patches/221-mipsel-preprocess-syscall_cp.s.patch
> @@ -0,0 +1,18 @@
> +From 76cfae6e5a22bbbbdca17ff2ffa196b3ad2a3537 Mon Sep 17 00:00:00 2001
> +From: Daniel Santos <daniel.santos at pobox.com>
> +Date: Wed, 24 Jun 2020 14:46:15 -0500
> +Subject: mipsel: preprocess syscall_cp.s
> +
> +Signed-off-by: Daniel Santos <daniel.santos at pobox.com>
> +---
> + src/thread/mips/{syscall_cp.s => syscall_cp.S} | 0
> + 1 file changed, 0 insertions(+), 0 deletions(-)
> + rename src/thread/mips/{syscall_cp.s => syscall_cp.S} (100%)
> +
> +diff --git a/src/thread/mips/syscall_cp.s b/src/thread/mips/syscall_cp.S
> +similarity index 100%
> +rename from src/thread/mips/syscall_cp.s
> +rename to src/thread/mips/syscall_cp.S
> +-- 
> +2.24.1
> +

Hi,

Thank you for also sending this upstream. I will wait for a new version
which addresses the comments from Rich:
https://www.openwall.com/lists/musl/2020/06/25/1

Hauke

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