[gdb/tdep] Fix gdb.base/msym-bp-shl.exp for ppc64le

  With test-case gdb.base/msym-bp-shl.exp on powerpc64le-linux, I run into:
...
(gdb) PASS: gdb.base/msym-bp-shl.exp: debug=0: before run: break foo
info breakpoint^M
Num     Type           Disp Enb Address            What^M
1       breakpoint     keep y   <MULTIPLE>         ^M
1.1                         y   0x00000000000008d4 <foo+12>^M
1.2                         y   0x0000000000000a34 crti.S:88^M
(gdb) FAIL: gdb.base/msym-bp-shl.exp: debug=0: before run: info breakpoint
...

The problem is that the prologue skipper walks from foo@plt at 0xa28 to 0xa34:
...
0000000000000a28 <foo@plt>:
 a28:   c0 ff ff 4b     b       9e8 <__glink_PLTresolve>

Disassembly of section .fini:

0000000000000a2c <_fini>:
 a2c:   02 00 4c 3c     addis   r2,r12,2
 a30:   d4 74 42 38     addi    r2,r2,29908
 a34:   a6 02 08 7c     mflr    r0
...

This is caused by ppc_elfv2_elf_make_msymbol_special which marks foo@plt as
having a local entry point, due incorrectly accessing an asymbol struct using
a (larger) elf_symbol_type.

Fix this by simply ignoring artificial symbols in
ppc_elfv2_elf_make_msymbol_special.

Tested on powerpc64le.

Approved-By: Ulrich Weigand <uweigand@de.ibm.com>
Reviewed-By: Carl Love <cel@us.ibm.com>
Tested-By: Carl Love <cel@us.ibm.com>
PR tdep/29814
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29814
---
 gdb/ppc-linux-tdep.c | 5 +++++
 1 file changed, 5 insertions(+)


base-commit: 8ee52bcf39e95abbc9cfffbb0afbb55be67e8c3d
  

On 11/24/22 13:45, Tom de Vries via Gdb-patches wrote:
> With test-case gdb.base/msym-bp-shl.exp on powerpc64le-linux, I run into:
> ...
> (gdb) PASS: gdb.base/msym-bp-shl.exp: debug=0: before run: break foo
> info breakpoint^M
> Num     Type           Disp Enb Address            What^M
> 1       breakpoint     keep y   <MULTIPLE>         ^M
> 1.1                         y   0x00000000000008d4 <foo+12>^M
> 1.2                         y   0x0000000000000a34 crti.S:88^M
> (gdb) FAIL: gdb.base/msym-bp-shl.exp: debug=0: before run: info breakpoint
> ...
> 
> The problem is that the prologue skipper walks from foo@plt at 0xa28 to 0xa34:
> ...
> 0000000000000a28 <foo@plt>:
>   a28:   c0 ff ff 4b     b       9e8 <__glink_PLTresolve>
> 
> Disassembly of section .fini:
> 
> 0000000000000a2c <_fini>:
>   a2c:   02 00 4c 3c     addis   r2,r12,2
>   a30:   d4 74 42 38     addi    r2,r2,29908
>   a34:   a6 02 08 7c     mflr    r0
> ...
> 
> This is caused by ppc_elfv2_elf_make_msymbol_special which marks foo@plt as
> having a local entry point, due incorrectly accessing an asymbol struct using
> a (larger) elf_symbol_type.
> 
> Fix this by simply ignoring artificial symbols in
> ppc_elfv2_elf_make_msymbol_special.
> 
> Tested on powerpc64le.
> 

No further comments, so committed.

Thanks,
- Tom

> Approved-By: Ulrich Weigand <uweigand@de.ibm.com>
> Reviewed-By: Carl Love <cel@us.ibm.com>
> Tested-By: Carl Love <cel@us.ibm.com>
> PR tdep/29814
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29814
> ---
>   gdb/ppc-linux-tdep.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/gdb/ppc-linux-tdep.c b/gdb/ppc-linux-tdep.c
> index cc5a26431ba..39d692b2764 100644
> --- a/gdb/ppc-linux-tdep.c
> +++ b/gdb/ppc-linux-tdep.c
> @@ -1632,6 +1632,11 @@ ppc_linux_core_read_description (struct gdbarch *gdbarch,
>   static void
>   ppc_elfv2_elf_make_msymbol_special (asymbol *sym, struct minimal_symbol *msym)
>   {
> +  if ((sym->flags & BSF_SYNTHETIC) != 0)
> +    /* ELFv2 synthetic symbols (the PLT stubs and the __glink_PLTresolve
> +       trampoline) do not have a local entry point.  */
> +    return;
> +
>     elf_symbol_type *elf_sym = (elf_symbol_type *)sym;
>   
>     /* If the symbol is marked as having a local entry point, set a target
> 
> base-commit: 8ee52bcf39e95abbc9cfffbb0afbb55be67e8c3d