[RFC,4/5] x86: Add SFrame support for x86 architecture
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Commit Message
From: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
The SFrame is well supported by x86 architecture since binutils 2.41.
Enable it to be used as default frame tracer.
Signed-off-by: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
---
sysdeps/unix/sysv/linux/x86/uw-sigframe.h | 99 +++++++++++++++++++++++
sysdeps/x86/bits/dl_find_object.h | 2 +
2 files changed, 101 insertions(+)
create mode 100644 sysdeps/unix/sysv/linux/x86/uw-sigframe.h
Comments
On 18.03.2025 14:03, claudiu.zissulescu-ianculescu@oracle.com wrote:
> From: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
>
> The SFrame is well supported by x86 architecture since binutils 2.41.
> Enable it to be used as default frame tracer.
>
> Signed-off-by: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
> diff --git a/sysdeps/unix/sysv/linux/x86/uw-sigframe.h b/sysdeps/unix/sysv/linux/x86/uw-sigframe.h
> +#else /* ifdef __x86_64__ */
Maybe the following is less confusing:
#else /* !__x86_64__ */
> +
> +#define MD_DECODE_SIGNAL_FRAME x86_decode_signal_frame
> +
> +static _Unwind_Reason_Code
> +x86_fallback_frame_state (frame *frame)
I could not find any further reference to x86_fallback_frame_state.
> +{
Regards,
Jens
On 3/19/25 6:05 PM, Jens Remus wrote:
> On 18.03.2025 14:03, claudiu.zissulescu-ianculescu@oracle.com wrote:
>> From: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
>>
>> The SFrame is well supported by x86 architecture since binutils 2.41.
>> Enable it to be used as default frame tracer.
>>
>> Signed-off-by: Claudiu Zissulescu <claudiu.zissulescu-
>> ianculescu@oracle.com>
>
>> diff --git a/sysdeps/unix/sysv/linux/x86/uw-sigframe.h b/sysdeps/unix/
>> sysv/linux/x86/uw-sigframe.h
>
>> +#else /* ifdef __x86_64__ */
>
> Maybe the following is less confusing:
>
> #else /* !__x86_64__ */
>
>> +
>> +#define MD_DECODE_SIGNAL_FRAME x86_decode_signal_frame
>> +
>> +static _Unwind_Reason_Code
>> +x86_fallback_frame_state (frame *frame)
>
> I could not find any further reference to x86_fallback_frame_state.
>
Ups :) my fault :)
Thank you Jens for your feedback! I'll address it on my second round,
Claudiu
new file mode 100644
@@ -0,0 +1,99 @@
+/* Signal frame backtracing support for SFrame on AMD, x86-64 and x86.
+ Copyright (C) 2025 Free Software Foundation, Inc.
+
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public License
+ as published by the Free Software Foundation; either version 2.1 of
+ the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be
+ useful, but WITHOUT ANY WARRANTY; without even the implied warranty
+ of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* This code is inspired from libgcc's MD_FALLBACK_FRAME_STATE_FOR
+ implementation. See libgcc/config/i386/gnu-unwind.h */
+
+#include <signal.h>
+#include <sys/ucontext.h>
+
+#ifdef __x86_64__
+
+#define MD_DECODE_SIGNAL_FRAME x86_64_decode_signal_frame
+
+static _Unwind_Reason_Code
+x86_64_decode_signal_frame (frame *frame)
+{
+ unsigned char *pc = (unsigned char *) frame->pc;
+ struct sigcontext *sc;
+
+ /* movq $__NR_rt_sigreturn, %rax ; syscall. */
+#ifdef __LP64__
+#define RT_SIGRETURN_SYSCALL 0x050f0000000fc0c7ULL
+#else
+#define RT_SIGRETURN_SYSCALL 0x050f40000201c0c7ULL
+#endif
+ if (*(unsigned char *)(pc+0) == 0x48
+ && *(unsigned long long *)(pc+1) == RT_SIGRETURN_SYSCALL)
+ {
+ ucontext_t *uc_ = (ucontext_t *)frame->sp;
+ /* The void * cast is necessary to avoid an aliasing warning.
+ The aliasing warning is correct, but should not be a problem
+ because it does not alias anything. */
+ sc = (struct sigcontext *) (void *) &uc_->uc_mcontext;
+ }
+ else
+ return _URC_END_OF_STACK;
+
+ frame->pc = (_Unwind_Ptr) sc->rip;
+ frame->sp = (_Unwind_Ptr) sc->rsp;
+ frame->fp = (_Unwind_Ptr) sc->rbp;
+ return _URC_NO_REASON;
+}
+#else /* ifdef __x86_64__ */
+
+#define MD_DECODE_SIGNAL_FRAME x86_decode_signal_frame
+
+static _Unwind_Reason_Code
+x86_fallback_frame_state (frame *frame)
+{
+ unsigned char *pc = (unsigned char *) frame->pc;
+ struct sigcontext *sc;
+
+ /* popl %eax ; movl $__NR_sigreturn,%eax ; int $0x80 */
+ if (*(unsigned short *)(pc+0) == 0xb858
+ && *(unsigned int *)(pc+2) == 119
+ && *(unsigned short *)(pc+6) == 0x80cd)
+ sc = context->cfa + 4;
+ /* movl $__NR_rt_sigreturn,%eax ; int $0x80 */
+ else if (*(unsigned char *)(pc+0) == 0xb8
+ && *(unsigned int *)(pc+1) == 173
+ && *(unsigned short *)(pc+5) == 0x80cd)
+ {
+ struct rt_sigframe {
+ int sig;
+ siginfo_t *pinfo;
+ void *puc;
+ siginfo_t info;
+ ucontext_t uc;
+ } *rt_ = context->cfa;
+ /* The void * cast is necessary to avoid an aliasing warning.
+ The aliasing warning is correct, but should not be a problem
+ because it does not alias anything. */
+ sc = (struct sigcontext *) (void *) &rt_->uc.uc_mcontext;
+ }
+ else
+ return _URC_END_OF_STACK;
+
+ frame->pc = (_Unwind_Ptr) sc->eip;
+ frame->sp = (_Unwind_Ptr) sc->esp;
+ frame->fp = (_Unwind_Ptr) sc->ebp;
+ return _URC_NO_REASON;
+}
+#endif /* ifdef __x86_64__ */
@@ -27,3 +27,5 @@
#endif
#define DLFO_STRUCT_HAS_EH_COUNT 0
#define DLFO_EH_SEGMENT_TYPE PT_GNU_EH_FRAME
+#define DLFO_SFRAME_SEGMENT_TYPE PT_GNU_SFRAME
+#define DLFO_STRUCT_HAS_SFRAME 1