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Re: [PATCH] gdb/elfread.c: Enable ifunc support on ARM.
- From: Pedro Alves <palves at redhat dot com>
- To: Will Newton <will dot newton at linaro dot org>
- Cc: gdb-patches at sourceware dot org, Patch Tracking <patches at linaro dot org>
- Date: Thu, 06 Feb 2014 17:42:55 +0000
- Subject: Re: [PATCH] gdb/elfread.c: Enable ifunc support on ARM.
- Authentication-results: sourceware.org; auth=none
- References: <52AF4563 dot 2090304 at linaro dot org>
On 12/16/2013 06:24 PM, Will Newton wrote:
>
> There are two failures in the gnu-ifunc.exp test on ARM. These are
> due to the failure to resolve the correct target function when
> attempting to breakpoint a GNU ifunc resolved function:
>
> (gdb) break gnu_ifunc
> Breakpoint 4 at gnu-indirect-function resolver at 0x2aacb5a2
>
> when gnu_ifunc has been resolved this should actually be:
>
> (gdb) break gnu_ifunc
> Breakpoint 4 at 0x868c
>
> There are two reasons for this. The first is that ARM does not have a
> separate .got.plt section so looking this up will always fail. The second
> is that the Thumb bit needs to be stripped from the address to allow
> it to be reliably compared when inserting into the ifunc cache.
>
> Tested with no regressions on arm-linux-gnueabihf and
> x86_64-unknown-linux-gnu.
>
> gdb/ChangeLog:
>
> 2013-12-16 Will Newton <will.newton@linaro.org>
>
> * elfread.c (elf_rel_plt_read): Look for a .got section if
> looking up .got.plt fails.
> (elf_gnu_ifunc_resolve_by_got): Call gdbarch_addr_bits_remove
> on address passed to elf_gnu_ifunc_record_cache.
> (elf_gnu_ifunc_resolve_addr): Likewise.
> (elf_gnu_ifunc_resolver_return_stop): Likewise.
Couple notes:
- I think you can look at 'get_elf_backend_data (abfd)->want_got_plt'
to decide whether to look up ".got" vs ".got.plt".
- I'm also wondering whether got.plt in the symbol names
(#define SYMBOL_GOT_PLT_SUFFIX "@got.plt") won't be a little confusing,
and thus that prefix too should be decided on a want_got_plt basis,
similarly.
--
Pedro Alves