From 1e88e415ebccb9013b92b55e7512938040c53b61 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 10 Feb 2019 15:51:00 +0900 Subject: [PATCH] kbuild: Disable extra debugging info in .s output Modern gcc adds view assignments, reset assertion checking in .loc directives and a couple more additional debug markers, which clutters the asm output unnecessarily: For example: bsp_resume: .LFB3466: .loc 1 1868 1 is_stmt 1 view -0 .cfi_startproc .loc 1 1869 2 view .LVU73 # arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume) .loc 1 1869 14 is_stmt 0 view .LVU74 movq this_cpu(%rip), %rax # this_cpu, this_cpu movq 64(%rax), %rax # this_cpu.94_1->c_bsp_resume, _2 # arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume) .loc 1 1869 5 view .LVU75 testq %rax, %rax # _2 je .L8 #, .loc 1 1870 3 is_stmt 1 view .LVU76 movq $boot_cpu_data, %rdi #, jmp __x86_indirect_thunk_rax or .loc 2 57 9 view .LVU478 .loc 2 57 9 view .LVU479 .loc 2 57 9 view .LVU480 .loc 2 57 9 view .LVU481 .LBB1385: .LBB1383: .LBB1379: .LBB1377: .LBB1375: .loc 2 57 9 view .LVU482 .loc 2 57 9 view .LVU483 movl %edi, %edx # cpu, cpu .LVL87: .loc 2 57 9 is_stmt 0 view .LVU484 That MOV in there is drowned in debugging information and latter makes it hard to follow the asm. And that DWARF info is not really needed for asm output staring. Disable the debug information generation which clutters the asm output unnecessarily: bsp_resume: # arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume) movq this_cpu(%rip), %rax # this_cpu, this_cpu movq 64(%rax), %rax # this_cpu.94_1->c_bsp_resume, _2 # arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume) testq %rax, %rax # _2 je .L8 #, # arch/x86/kernel/cpu/common.c:1870: this_cpu->c_bsp_resume(&boot_cpu_data); movq $boot_cpu_data, %rdi #, jmp __x86_indirect_thunk_rax .L8: # arch/x86/kernel/cpu/common.c:1871: } rep ret .size bsp_resume, .-bsp_resume [ bp: write commit message. ] Signed-off-by: Masahiro Yamada Signed-off-by: Borislav Petkov --- Makefile | 13 ++++++++----- scripts/Makefile.build | 2 +- 2 files changed, 9 insertions(+), 6 deletions(-) diff --git a/Makefile b/Makefile index d487fca342c4..681bed05d104 100644 --- a/Makefile +++ b/Makefile @@ -732,25 +732,28 @@ KBUILD_CFLAGS += -fomit-frame-pointer endif endif -KBUILD_CFLAGS += $(call cc-option, -fno-var-tracking-assignments) +DEBUG_CFLAGS := $(call cc-option, -fno-var-tracking-assignments) ifdef CONFIG_DEBUG_INFO ifdef CONFIG_DEBUG_INFO_SPLIT -KBUILD_CFLAGS += $(call cc-option, -gsplit-dwarf, -g) +DEBUG_CFLAGS += $(call cc-option, -gsplit-dwarf, -g) else -KBUILD_CFLAGS += -g +DEBUG_CFLAGS += -g endif KBUILD_AFLAGS += -Wa,-gdwarf-2 endif ifdef CONFIG_DEBUG_INFO_DWARF4 -KBUILD_CFLAGS += $(call cc-option, -gdwarf-4,) +DEBUG_CFLAGS += $(call cc-option, -gdwarf-4,) endif ifdef CONFIG_DEBUG_INFO_REDUCED -KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \ +DEBUG_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \ $(call cc-option,-fno-var-tracking) endif +KBUILD_CFLAGS += $(DEBUG_CFLAGS) +export DEBUG_CFLAGS + ifdef CONFIG_FUNCTION_TRACER ifdef CONFIG_FTRACE_MCOUNT_RECORD # gcc 5 supports generating the mcount tables directly diff --git a/scripts/Makefile.build b/scripts/Makefile.build index f8e2794107ed..0a9d849d0fab 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -104,7 +104,7 @@ modkern_cflags = \ quiet_modtag = $(if $(part-of-module),[M], ) quiet_cmd_cc_s_c = CC $(quiet_modtag) $@ -cmd_cc_s_c = $(CC) $(c_flags) $(DISABLE_LTO) -fverbose-asm -S -o $@ $< + cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) $(DISABLE_LTO) -fverbose-asm -S -o $@ $< $(obj)/%.s: $(src)/%.c FORCE $(call if_changed_dep,cc_s_c) -- 2.30.2