Commit de979c83 authored by Andrea Righi's avatar Andrea Righi Committed by Ingo Molnar
Browse files

x86/entry: Build thunk_$(BITS) only if CONFIG_PREEMPTION=y 

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: 320100a5 ("x86/entry: Remove the TRACE_IRQS cruft")
Signed-off-by: default avatarAndrea Righi <andrea.righi@canonical.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/Ys/Ke7EWjcX+ZlXO@arighi-desktop
parent 625395c4

arch/x86/entry/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -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

arch/x86/entry/thunk_32.S

+0 −2
Original line number Diff line number Diff line
@@ -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

arch/x86/entry/thunk_64.S

+0 −4
Original line number Diff line number Diff line
@@ -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

arch/x86/um/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -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