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Created attachment 1885810[details]
Tarball showing the issue with -fpatchable-function-entry on aarch64
Description of problem:
When the -fpatchable-function-entry is used the debuginfo indicates that the function starts after the nop instructions inserted at the beginning of the function. This issue looks very similar to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103525
Version-Release number of selected component (if applicable):
gcc-11.2.1-9.4.el9.aarch64
How reproducible: every time
Steps to Reproduce:
1. Download the gcc_patchable.tar.gz in this bug
2. tar xvfz ./gcc_patchable.tar.gz
3. cd gcc_patchable
4. gcc -fpatchable-function-entry=8 -g -O2 -save-temps u32_test.c -o u32_test
5. llvm-dwarfdump --name="main" u32_test
6. nm u32_test |grep main
Actual results:
The nm states that the function starts at 0000000000400580, but the DW_AT_low_pc states it starts later at 0x00000000004005a0
Expected results:
The DW_AT_low_pc and start of the function reported by nm should match.
Additional info:
This issue was observed because the RHEL kernels are compiled with
CONFIG_DYNAMIC_FTRACE_WITH_REGS=y.
One of the comments, https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103525#c2 , mentions that a similar issue was addressed on x86_64.
I've updated PR103525 but it's been in NEW for 6 months, so I think this is not going to be fixed anytime soon. So it seems appropriate to track this upstream only.