[BZ,#19490] Add unwind descriptors for x86_64 _mcount and __fentry__
Commit Message
On Thu, Mar 3, 2016 at 12:30 AM, Andreas Schwab <schwab@suse.de> wrote:
> Paul Pluzhnikov <ppluzhnikov@google.com> writes:
>
>> Using CALL_MCOUNT in implementation of _mcount isn't going to end well.
>
> _mcount needs to be arranged to be compiled without PROF, like the
> noprof routines in gmon/Makefile.
Done by HJ in commit 87a07a437656aede6f303688b55ae1834962bee2.
Updated patch attached. Tested on Linux/x86_64.
Thanks,
2016-03-03 Paul Pluzhnikov <ppluzhnikov@google.com>
[BZ #19490]
* sysdeps/x86_64/_mcount.S (_mcount): Add unwind descriptor.
(__fentry__): Likewise
Comments
On Thu, Mar 3, 2016 at 9:01 AM, Paul Pluzhnikov <ppluzhnikov@google.com> wrote:
> On Thu, Mar 3, 2016 at 12:30 AM, Andreas Schwab <schwab@suse.de> wrote:
>> Paul Pluzhnikov <ppluzhnikov@google.com> writes:
>>
>>> Using CALL_MCOUNT in implementation of _mcount isn't going to end well.
>>
>> _mcount needs to be arranged to be compiled without PROF, like the
>> noprof routines in gmon/Makefile.
>
> Done by HJ in commit 87a07a437656aede6f303688b55ae1834962bee2.
>
> Updated patch attached. Tested on Linux/x86_64.
>
> Thanks,
>
> 2016-03-03 Paul Pluzhnikov <ppluzhnikov@google.com>
>
> [BZ #19490]
> * sysdeps/x86_64/_mcount.S (_mcount): Add unwind descriptor.
> (__fentry__): Likewise
>
Hi Andi,
Why do we need __fentry__ different from _mcount in glibc? Can we
make __fentry__ an alias of _mcount?
On Thu, Mar 3, 2016 at 9:30 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> Why do we need __fentry__ different from _mcount in glibc? Can we
> make __fentry__ an alias of _mcount?
For one thing, they have different stack alignment requirements, as I
already said on this thread:
https://sourceware.org/ml/libc-alpha/2016-02/msg00823.html
On Thu, Mar 3, 2016 at 9:35 AM, Paul Pluzhnikov <ppluzhnikov@google.com> wrote:
> On Thu, Mar 3, 2016 at 9:30 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>
>> Why do we need __fentry__ different from _mcount in glibc? Can we
>> make __fentry__ an alias of _mcount?
>
> For one thing, they have different stack alignment requirements, as I
> already said on this thread:
> https://sourceware.org/ml/libc-alpha/2016-02/msg00823.html
Please update _mcount.S with your comments above. OK with
that change.
Thanks for your patience.
On Thu, Mar 3, 2016 at 9:41 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> Please update _mcount.S with your comments above. OK with
> that change.
Done and committed.
Thanks!
> Why do we need __fentry__ different from _mcount in glibc? Can we
> make __fentry__ an alias of _mcount?
The stack frame is different, and mcount needs to look at the
stack frame. mcount is after the frame pointer, __fentry__ before.
-Andi
@@ -24,19 +24,24 @@
#include <sysdep.h>
- .globl C_SYMBOL_NAME(_mcount)
- .type C_SYMBOL_NAME(_mcount), @function
- .align ALIGNARG(4)
-C_LABEL(_mcount)
+ENTRY(_mcount)
/* Allocate space for 7 registers. */
subq $56,%rsp
+ cfi_adjust_cfa_offset (56)
movq %rax,(%rsp)
+ cfi_rel_offset (rax, 0)
movq %rcx,8(%rsp)
+ cfi_rel_offset (rcx, 8)
movq %rdx,16(%rsp)
+ cfi_rel_offset (rdx, 16)
movq %rsi,24(%rsp)
+ cfi_rel_offset (rsi, 24)
movq %rdi,32(%rsp)
+ cfi_rel_offset (rdi, 32)
movq %r8,40(%rsp)
+ cfi_rel_offset (r8, 40)
movq %r9,48(%rsp)
+ cfi_rel_offset (r9, 48)
/* Setup parameter for __mcount_internal. */
/* selfpc is the return address on the stack. */
@@ -47,33 +52,46 @@ C_LABEL(_mcount)
/* Pop the saved registers. Please note that `mcount' has no
return value. */
movq 48(%rsp),%r9
+ cfi_restore (r9)
movq 40(%rsp),%r8
+ cfi_restore (r8)
movq 32(%rsp),%rdi
+ cfi_restore (rdi)
movq 24(%rsp),%rsi
+ cfi_restore (rsi)
movq 16(%rsp),%rdx
+ cfi_restore (rdx)
movq 8(%rsp),%rcx
+ cfi_restore (rcx)
movq (%rsp),%rax
+ cfi_restore (rax)
addq $56,%rsp
+ cfi_adjust_cfa_offset (-56)
ret
-
- ASM_SIZE_DIRECTIVE(C_SYMBOL_NAME(_mcount))
+END(_mcount)
#undef mcount
weak_alias (_mcount, mcount)
- .globl C_SYMBOL_NAME(__fentry__)
- .type C_SYMBOL_NAME(__fentry__), @function
- .align ALIGNARG(4)
-C_LABEL(__fentry__)
- /* Allocate space for 7 registers. */
+ENTRY(__fentry__)
+ /* Allocate space for 7 registers
+ (+8 bytes for proper stack alignment). */
subq $64,%rsp
+ cfi_adjust_cfa_offset (64)
movq %rax,(%rsp)
+ cfi_rel_offset (rax, 0)
movq %rcx,8(%rsp)
+ cfi_rel_offset (rcx, 8)
movq %rdx,16(%rsp)
+ cfi_rel_offset (rdx, 16)
movq %rsi,24(%rsp)
+ cfi_rel_offset (rsi, 24)
movq %rdi,32(%rsp)
+ cfi_rel_offset (rdi, 32)
movq %r8,40(%rsp)
+ cfi_rel_offset (r8, 40)
movq %r9,48(%rsp)
+ cfi_rel_offset (r9, 48)
/* Setup parameter for __mcount_internal. */
/* selfpc is the return address on the stack. */
@@ -84,13 +102,20 @@ C_LABEL(__fentry__)
/* Pop the saved registers. Please note that `__fentry__' has no
return value. */
movq 48(%rsp),%r9
+ cfi_restore (r9)
movq 40(%rsp),%r8
+ cfi_restore (r8)
movq 32(%rsp),%rdi
+ cfi_restore (rdi)
movq 24(%rsp),%rsi
+ cfi_restore (rsi)
movq 16(%rsp),%rdx
+ cfi_restore (rdx)
movq 8(%rsp),%rcx
+ cfi_restore (rcx)
movq (%rsp),%rax
+ cfi_restore (rax)
addq $64,%rsp
+ cfi_adjust_cfa_offset (-64)
ret
-
- ASM_SIZE_DIRECTIVE(C_SYMBOL_NAME(__fentry__))
+END(__fentry__)