From 1e88e415ebccb9013b92b55e7512938040c53b61 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <yamada.masahiro@socionext.com>
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 <yamada.masahiro@socionext.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
Makefile | 13 ++++++++-----
scripts/Makefile.build | 2 +-
2 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/Makefile b/Makefile
index d487fca342c49..681bed05d1042 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 f8e2794107ede..0a9d849d0fab2 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)
--
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