[llvm-19] objtool warnings for drivers/gpu/drm/radeon/radeon.o

[cgzones]

When building v6.10.9 with LLVM 19 and LTO and CFI and UBSAN enabled the following warnings are shown:

drivers/gpu/drm/radeon/radeon.o: warning: objtool: .text.evergreen_irq_ack: unexpected end of section
drivers/gpu/drm/radeon/radeon.o: warning: objtool: .text.si_irq_ack: unexpected end of section

[nathanchance]

Does this happen without UBSAN?

[cgzones]

Disappears when disabling CONFIG_UBSAN_SIGNED_WRAP:

CONFIG_ARCH_HAS_UBSAN=y
CONFIG_UBSAN=y
# CONFIG_UBSAN_TRAP is not set
CONFIG_CC_HAS_UBSAN_ARRAY_BOUNDS=y
CONFIG_UBSAN_BOUNDS=y
CONFIG_UBSAN_ARRAY_BOUNDS=y
CONFIG_UBSAN_SHIFT=y
# CONFIG_UBSAN_SIGNED_WRAP is not set
CONFIG_UBSAN_BOOL=y
CONFIG_UBSAN_ENUM=y
# CONFIG_UBSAN_ALIGNMENT is not set
# CONFIG_TEST_UBSAN is not set

[nathanchance]

@kees @JustinStitt I wonder if this is a similar situation as what triggered commit e5d523f1ae8f ("ubsan: disable UBSAN_DIV_ZERO for clang")? If the sanitizer is not recoverable in the face of undefined behavior, I suspect optimizations could result in a wrecked control flow graph, which will make objtool unhappy. I wonder if the message changes if LTO is disabled (such that -ffunction-sections is not enabled)?