On Thu, Jan 31, 2019 at 8:58 PM Borislav Petkov <bp@xxxxxxxxx> wrote: > > Ping? > > On Mon, Jan 21, 2019 at 10:53:38AM +0100, Borislav Petkov wrote: > > From: Borislav Petkov <bp@xxxxxxx> > > > > 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: > > .LFB3466: > > .loc 1 1868 1 > > # arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume) > > .loc 1 1869 14 > > 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 > > testq %rax, %rax # _2 > > je .L8 #, > > # arch/x86/kernel/cpu/common.c:1870: this_cpu->c_bsp_resume(&boot_cpu_data); > > .loc 1 1870 3 > > movq $boot_cpu_data, %rdi #, > > jmp __x86_indirect_thunk_rax > > > > Signed-off-by: Borislav Petkov <bp@xxxxxxx> > > Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > > Cc: Michal Marek <michal.lkml@xxxxxxxxxxx> > > Cc: linux-kbuild@xxxxxxxxxxxxxxx > > --- > > scripts/Makefile.build | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build > > index fd03d60f6c5a..4f33fdab89d2 100644 > > --- a/scripts/Makefile.build > > +++ b/scripts/Makefile.build > > @@ -103,8 +103,12 @@ modkern_cflags = \ > > $(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL)) > > quiet_modtag = $(if $(part-of-module),[M], ) > > > > +disable_extra_cc_dbg := $(call cc-option,-gno-as-locview-support) > > +disable_extra_cc_dbg += $(call cc-option,-fno-dwarf2-cfi-asm) > > +disable_extra_cc_dbg += $(call cc-option,-feliminate-unused-debug-symbols) > > +disable_extra_cc_dbg += $(call cc-option,-gno-statement-frontiers) This would make the build speed slower because the compiler is invoked to check those flags in every directory. I tested this patch with x86_64_defconfig and GCC 8.2 (on ubuntu 18.10 in docker) but I saw no effect of this patch. CONFIG_DEBUG_INFO adds dwarf info, and clutters asm output. Did you enable CONFIG_DEBUG_INFO when you were debugging asm files? -- Best Regards Masahiro Yamada
