From: Andrea Righi andrea.righi@canonical.com
[ Upstream commit de979c83574abf6e78f3fa65b716515c91b2613d ]
With CONFIG_PREEMPTION disabled, arch/x86/entry/thunk_$(BITS).o becomes an empty object file.
With some old versions of binutils (i.e., 2.35.90.20210113-1ubuntu1) the GNU assembler doesn't generate a symbol table for empty object files and objtool fails with the following error when a valid symbol table cannot be found:
arch/x86/entry/thunk_64.o: warning: objtool: missing symbol table
To prevent this from happening, build thunk_$(BITS).o only if CONFIG_PREEMPTION is enabled.
BugLink: https://bugs.launchpad.net/bugs/1911359
Fixes: 320100a5ffe5 ("x86/entry: Remove the TRACE_IRQS cruft") Signed-off-by: Andrea Righi andrea.righi@canonical.com Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lore.kernel.org/r/Ys/Ke7EWjcX+ZlXO@arighi-desktop Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/entry/Makefile | 3 ++- arch/x86/entry/thunk_32.S | 2 -- arch/x86/entry/thunk_64.S | 4 ---- arch/x86/um/Makefile | 3 ++- 4 files changed, 4 insertions(+), 8 deletions(-)
diff --git a/arch/x86/entry/Makefile b/arch/x86/entry/Makefile index eeadbd7d92cc..ca2fe186994b 100644 --- a/arch/x86/entry/Makefile +++ b/arch/x86/entry/Makefile @@ -11,12 +11,13 @@ CFLAGS_REMOVE_common.o = $(CC_FLAGS_FTRACE)
CFLAGS_common.o += -fno-stack-protector
-obj-y := entry.o entry_$(BITS).o thunk_$(BITS).o syscall_$(BITS).o +obj-y := entry.o entry_$(BITS).o syscall_$(BITS).o obj-y += common.o
obj-y += vdso/ obj-y += vsyscall/
+obj-$(CONFIG_PREEMPTION) += thunk_$(BITS).o obj-$(CONFIG_IA32_EMULATION) += entry_64_compat.o syscall_32.o obj-$(CONFIG_X86_X32_ABI) += syscall_x32.o
diff --git a/arch/x86/entry/thunk_32.S b/arch/x86/entry/thunk_32.S index 7591bab060f7..ff6e7003da97 100644 --- a/arch/x86/entry/thunk_32.S +++ b/arch/x86/entry/thunk_32.S @@ -29,10 +29,8 @@ SYM_CODE_START_NOALIGN(\name) SYM_CODE_END(\name) .endm
-#ifdef CONFIG_PREEMPTION THUNK preempt_schedule_thunk, preempt_schedule THUNK preempt_schedule_notrace_thunk, preempt_schedule_notrace EXPORT_SYMBOL(preempt_schedule_thunk) EXPORT_SYMBOL(preempt_schedule_notrace_thunk) -#endif
diff --git a/arch/x86/entry/thunk_64.S b/arch/x86/entry/thunk_64.S index 505b488fcc65..f38b07d2768b 100644 --- a/arch/x86/entry/thunk_64.S +++ b/arch/x86/entry/thunk_64.S @@ -31,14 +31,11 @@ SYM_FUNC_END(\name) _ASM_NOKPROBE(\name) .endm
-#ifdef CONFIG_PREEMPTION THUNK preempt_schedule_thunk, preempt_schedule THUNK preempt_schedule_notrace_thunk, preempt_schedule_notrace EXPORT_SYMBOL(preempt_schedule_thunk) EXPORT_SYMBOL(preempt_schedule_notrace_thunk) -#endif
-#ifdef CONFIG_PREEMPTION SYM_CODE_START_LOCAL_NOALIGN(__thunk_restore) popq %r11 popq %r10 @@ -53,4 +50,3 @@ SYM_CODE_START_LOCAL_NOALIGN(__thunk_restore) RET _ASM_NOKPROBE(__thunk_restore) SYM_CODE_END(__thunk_restore) -#endif diff --git a/arch/x86/um/Makefile b/arch/x86/um/Makefile index 5ccb18290d71..a8591ec8ae68 100644 --- a/arch/x86/um/Makefile +++ b/arch/x86/um/Makefile @@ -28,7 +28,8 @@ else
obj-y += syscalls_64.o vdso/
-subarch-y = ../lib/csum-partial_64.o ../lib/memcpy_64.o ../entry/thunk_64.o +subarch-y = ../lib/csum-partial_64.o ../lib/memcpy_64.o +subarch-$(CONFIG_PREEMPTION) += ../entry/thunk_64.o
endif