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Re: [PATCH] Remove some obfuscation from ${arch}_skip_prologue functions
- From: Yao Qi <yao at codesourcery dot com>
- To: Doug Evans <dje at google dot com>
- Cc: <gdb-patches at sourceware dot org>, <macro at codesourcery dot com>, <green at moxielogic dot com>
- Date: Thu, 4 Sep 2014 16:54:52 +0800
- Subject: Re: [PATCH] Remove some obfuscation from ${arch}_skip_prologue functions
- Authentication-results: sourceware.org; auth=none
- References: <yjt2y4u1pokj dot fsf at ruffy dot mtv dot corp dot google dot com>
Doug Evans <dje@google.com> writes:
> 1) There's no need to call find_pc_partial_function before
> calling skip_prologue_using_sal: The first thing skip_prologue_using_sal
> does is call find_pc_partial_function!
Nowadays we have:
if (find_pc_partial_function (pc, NULL, &func_addr, NULL))
{
CORE_ADDR post_prologue_pc
= skip_prologue_using_sal (gdbarch, func_addr);
if (post_prologue_pc != 0)
return max (pc, post_prologue_pc);
}
so your statement is valid if PC equals to FUNC_ADDR. I don't have a
case that PC and FUNC_ADDR are different, but I'd like to add an assert
to check this, in each target's implementation of skip_prologue hook, or
in the callers of gdbarch_skip_prologue, something like:
if (find_pc_partial_function (pc, NULL, &func_addr, NULL))
gdb_assert (pc == func_addr);
Note that this assert is triggered on arm in
gdb.cp/re-set-overloaded.exp, that is PC is [1] but FUNC_ADDR is [2].
(gdb) disassemble _ZN1CC1Ei
Dump of assembler code for function _ZN1CC1Ev:
0x0000090c <+0>: ldr r12, [pc, #4] ; 0x918 <_ZN1CC1Ev+12> <- [2]
0x00000910 <+4>: add r12, r12, pc
0x00000914 <+8>: bx r12
0x00000918 <+12>: ; <UNDEFINED> instruction: 0xffffffc5
0x0000091c <+0>: ldr r12, [pc, #4] ; 0x928 <_ZN1CC1Ei+12> <- [1]
0x00000920 <+4>: add r12, r12, pc
AFAICS, PC is still the function address but find_pc_partial_function
computes the FUNC_ADDR incorrectly and it is nothing wrong about your
patch.
> nios2: yao@codesourcery.com
I tested your patch on nios2-linux, and no regression is found.
> tic6x:yao@codesourcery.com
My c6x board is dead in data center, so I can't test this patch for it.
--
Yao (éå)