GSoC'11: DWARF2 call frame information

[Chagin Dmitry]

On Mon, Mar 21, 2011 at 05:36:13PM +0800, Xingxing Pan wrote:
> 2011/3/21 Chagin Dmitry <dchagin at freebsd.org>:
> >> powerfull script.
> >>
> >> Xingxing Pan
> >
> > hmm, which script? I think enough amd64, i386 and amd64/ia32.
> >
> > I suggest to write a example before continuing the conversation
> > about the GSoC. For example (bcopy || bzero) && cpu_switch.
> > Is it ok for you?
> >
> > --
> > Have fun!
> > chd
> >
> 
> Hi Chargin,
> 
> Thank you for your reply.
> The followings shows how I try to add DWARF for bcopy.
> 
> --- ../8.2.0/sys/i386/include/asm.h     2011-03-21 14:35:56.111973722 +0800
> +++ asm.h       2011-03-21 15:25:31.564636162 +0800
> @@ -71,7 +71,7 @@
> 
>  #define _ENTRY(x)      _START_ENTRY; \
>                         .globl CNAME(x); .type CNAME(x), at function; CNAME(x):
> -#define        END(x)          .size x, . - x
> +#define        END(x)          .cfi_endproc; .size x, . - x
> 
>  #ifdef PROF
>  #define        ALTENTRY(x)     _ENTRY(x); \
> @@ -80,9 +80,10 @@
>                         popl %ebp; \
>                         jmp 9f
>  #define        ENTRY(x)        _ENTRY(x); \
> -                       pushl %ebp; movl %esp,%ebp; \
> +                       .cfi_startproc; \
> +                       pushl %ebp; .cfi_adjust_cfa_offset 4; movl
> %esp,%ebp; .cfi_def_cfa_register %ebp; \
>                         call PIC_PLT(HIDENAME(mcount)); \
> -                       popl %ebp; \
> +                       popl %ebp; .cfi_def_cfa %esp, 4; \
> 
> --- bcopy.S     2011-03-21 15:51:26.804203809 +0800
> +++ ../8.2.0/lib/libc/i386/string/bcopy.S       2011-03-21
> 14:28:15.023069890 +0800
> @@ -51,9 +51,7 @@ ENTRY(bcopy)
>  #endif
>  #endif
>         pushl   %esi
> -       .cfi_adjust_cfa_offset 4;
>         pushl   %edi
> -       .cfi_adjust_cfa_offset 4;
>  #if defined(MEMCOPY) || defined(MEMMOVE)
>         movl    12(%esp),%edi
>         movl    16(%esp),%esi
> @@ -77,9 +75,7 @@ ENTRY(bcopy)
>         rep
>         movsb
>         popl    %edi
> -       .cfi_adjust_cfa_offset -4;
>         popl    %esi
> -       .cfi_adjust_cfa_offset -4;
>         ret
>  1:
>         addl    %ecx,%edi       /* copy backwards. */
> @@ -98,9 +94,7 @@ ENTRY(bcopy)
>         rep
>         movsl
>         popl    %edi
> -       .cfi_adjust_cfa_offset -4;
>         popl    %esi
> -       .cfi_adjust_cfa_offset -4;
>         cld
>         ret
>  #ifdef MEMCOPY
> 
> But I don't know how to add DWARF for cpu_switch, because I have no
> idea about the circumstance when we need to backtrace through this
> function. Suppose there's a cpu switch like this,
> threadA->kernel->threadB. Then should the expected backtrace has the
> following result?
> 
> threadB's stack
> kernel's stack
> threadA's stack


hmm, ok. good, avoid cpu_switch.
First of all, please, read style(9) man page.
In the second, evaluate the proposed plan (discussed with kib@):

1) Annotate libc, msun, rtld, libthr (you)
2) vdso (I'm)
3) Annotate signal trampolines (you, after vdso)

And i'm going to understand what I need to do to start GSoC for you.
Thanks!


-- 
Have fun!
chd
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