From: Josh Poimboeuf jpoimboe@kernel.org
[ Upstream commit 6b023c7842048c4bbeede802f3cf36b96c7a8b25 ]
In the past there were issues with KCOV triggering unreachable instruction warnings, which is why unreachable warnings are now disabled with CONFIG_KCOV.
Now some new KCOV warnings are showing up with GCC 14:
vmlinux.o: warning: objtool: cpuset_write_resmask() falls through to next function cpuset_update_active_cpus.cold() drivers/usb/core/driver.o: error: objtool: usb_deregister() falls through to next function usb_match_device() sound/soc/codecs/snd-soc-wcd934x.o: warning: objtool: .text.wcd934x_slim_irq_handler: unexpected end of section
All are caused by GCC KCOV not finishing an optimization, leaving behind a never-taken conditional branch to a basic block which falls through to the next function (or end of section).
At a high level this is similar to the unreachable warnings mentioned above, in that KCOV isn't fully removing dead code. Treat it the same way by adding these to the list of warnings to ignore with CONFIG_KCOV.
Reported-by: Ingo Molnar mingo@kernel.org Reported-by: kernel test robot lkp@intel.com Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Link: https://lore.kernel.org/r/66a61a0b65d74e072d3dc02384e395edb2adc3c5.174285284... Closes: https://lore.kernel.org/Z9iTsI09AEBlxlHC@gmail.com Closes: https://lore.kernel.org/oe-kbuild-all/202503180044.oH9gyPeg-lkp@intel.com/ Signed-off-by: Sasha Levin sashal@kernel.org --- tools/objtool/check.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 6f3f408d0a019..5b0ff4b9221d7 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -3633,6 +3633,9 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, !strncmp(func->name, "__pfx_", 6)) return 0;
+ if (file->ignore_unreachables) + return 0; + WARN("%s() falls through to next function %s()", func->name, insn_func(insn)->name); return 1; @@ -3852,6 +3855,9 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, if (!next_insn) { if (state.cfi.cfa.base == CFI_UNDEFINED) return 0; + if (file->ignore_unreachables) + return 0; + WARN("%s: unexpected end of section", sec->name); return 1; }