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[PATCH 0/6] Use correct function address in dwarf assembler
- From: Yao Qi <yao at codesourcery dot com>
- To: <gdb-patches at sourceware dot org>
- Date: Sat, 25 Oct 2014 08:12:42 +0800
- Subject: [PATCH 0/6] Use correct function address in dwarf assembler
- Authentication-results: sourceware.org; auth=none
When we use dwarf assembler, it is common to generate DW_AT_low_pc and
DW_AT_high_pc attributes like this:
subprogram {
{name main}
{low_pc main addr}
{high_pc main+0x100 addr}
}
however, main is not resolved to function main's address on some
targets such as arm thumb mode and powerpc64. One approach is to
get function address by labels, like this:
asm ("func_start: .globl func_start");
static void func (void) {}
asm ("func_end: .globl func_end");
however, some compiler, such as clang, can't guarantee the order of
these labels and function, so it isn't portable.
In this patch series, we propose a new approach
1. get function start and end address correctly in a portable way,
2. don't affect too much on existing test cases.
In patch 2/6, a new proc function_range is added. In this proc, the
source file is compiled with debug info.
int main (void)
{
asm ("main_label: .globl main_label");
return 0;
}
we can get the offset of main_label in function main, and then compute
the start address of main via main_label - main_label_offset. This is
portable.
In order to avoid much changes to existing test cases, we have to use
function_range inside dwarf assembler. Then, I invent some attribute
macros which look like DW attributes, but can be expanded to one or
more standard attributes. The TAG_subprogram above will be simplified
with macro attribute used, it becomes:
subprogram {
{MACRO_AT_func { func ${srcdir}/${subdir}/${srcfile} }}
}
With this macro attribute, attributes name, low_pc and high_pc are
generated and set correctly. See more details in patch 2/6.
Patch 4/6 is to use dwarf assembler to generate .S file, which is
identical to .S current one we are using. Patch 3 and 5 is to use
macro attributes to get function start and end address correctly.
Patch 6 is remove labels and switch to use macro attribute to
get function start address to make clang happy.
I test the whole series by running tests under gdb.dwarf2/ on
powerpc-linux (both 32-bit and 64-bit), arm-none-eabi (arm mode
and thumb mode) and x86_64-linux.
Comments are very welcome!
*** BLURB HERE ***
Yao Qi (6):
New proc _handle_attribute
DW attribute macro MACRO_AT_func and MACRO_AT_range
Get start and end address of main in dwz.exp
Use Dwarf::assemble in implptr-optimized-out.exp
Fix implptr-optimized-out.exp fail
Fix dw2-ifort-parameter.exp fail with clang
gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter.c | 7 +-
gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter.exp | 8 +-
gdb/testsuite/gdb.dwarf2/dwz.exp | 60 +-------
gdb/testsuite/gdb.dwarf2/implptr-optimized-out.S | 166 ---------------------
gdb/testsuite/gdb.dwarf2/implptr-optimized-out.exp | 63 +++++++-
gdb/testsuite/gdb.dwarf2/main.c | 1 +
gdb/testsuite/lib/dwarf.exp | 143 ++++++++++++++++--
7 files changed, 201 insertions(+), 247 deletions(-)
delete mode 100644 gdb/testsuite/gdb.dwarf2/implptr-optimized-out.S
--
1.9.3