https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109707
Bug ID: 109707
Summary: Skip __attribute__((naked)) functions for -pg and
-finstrument-functions
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: i at maskray dot me
Target Milestone: ---
The asm in a naked function may reasonably expect the argument registers and
the
return address register (if present) to be live.
When using -pg and -finstrument-functions, functions are instrumented by adding
a function call to mcount/__cyg_profile_func_enter, which will clobber these
registers.
If the return address register is clobbered, the function will be unable to
return to the caller, possibly causing an infinite loop.
% riscv64-linux-gnu-gcc a.c -finstrument-functions
-Wl,--dynamic-linker=/usr/riscv64-linux-gnu/lib/ld-linux-riscv64-lp64d.so.1
-Wl,-rpath=/usr/riscv64-linux-gnu/lib
% ./a.out # infinite loop
% riscv64-linux-gnu-gcc a.c -pg
-Wl,--dynamic-linker=/usr/riscv64-linux-gnu/lib/ld-linux-riscv64-lp64d.so.1
-Wl,-rpath=/usr/riscv64-linux-gnu/lib
% ./a.out # infinite loop
% arm-linux-gnueabihf-gcc a.c -finstrument-functions
-Wl,--dynamic-linker=/usr/arm-linux-gnueabihf/lib/ld-linux-armhf.so.3
-Wl,-rpath=/usr/arm-linux-gnueabihf/lib
% ./a.out # infinite loop
arm -pg uses `push {lr}; bl __gnu_mcount_nc`, so a naked function works with
-pg, but this appears to be a rare exception.
% arm-linux-gnueabihf-gcc a.c -pg
-Wl,--dynamic-linker=/usr/arm-linux-gnueabihf/lib/ld-linux-armhf.so.3
-Wl,-rpath=/usr/arm-linux-gnueabihf/lib
% ./a.out # good
