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objtool, modules: Discard objtool annotation sections for modules

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The '__unreachable' and '__func_stack_frame_non_standard' sections are
only used at compile time.  They're discarded for vmlinux but they
should also be discarded for modules.

Since this is a recurring pattern, prefix the section names with
".discard.".  It's a nice convention and vmlinux.lds.h already discards
such sections.

Also remove the 'a' (allocatable) flag from the __unreachable section
since it doesn't make sense for a discarded section.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jessica Yu <jeyu@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: d1091c7fa3 ("objtool: Improve detection of BUG() and other dead ends")
Link: http://lkml.kernel.org/r/20170301180444.lhd53c5tibc4ns77@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2017-03-01 12:04:44 -06:00 • committed by Ingo Molnar
parent 55149d0653
commit e390f9a968
6 changed files with 10 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

2
arch/x86/kernel/vmlinux.lds.S
View file

@ -345,8 +345,6 @@ SECTIONS
DISCARDS DISCARDS
/DISCARD/ : { /DISCARD/ : {
*(.eh_frame) *(.eh_frame)
*(__func_stack_frame_non_standard)
*(__unreachable)
} }
} }

2
include/linux/compiler-gcc.h
View file

@ -200,7 +200,7 @@
#ifdef CONFIG_STACK_VALIDATION #ifdef CONFIG_STACK_VALIDATION
#define annotate_unreachable() ({ \ #define annotate_unreachable() ({ \
asm("%c0:\t\n" \ asm("%c0:\t\n" \
".pushsection __unreachable, \"a\"\t\n" \ ".pushsection .discard.unreachable\t\n" \
".long %c0b - .\t\n" \ ".long %c0b - .\t\n" \
".popsection\t\n" : : "i" (__LINE__)); \ ".popsection\t\n" : : "i" (__LINE__)); \
}) })

2
include/linux/frame.h
View file

@ -11,7 +11,7 @@
* For more information, see tools/objtool/Documentation/stack-validation.txt. * For more information, see tools/objtool/Documentation/stack-validation.txt.
*/ */
#define STACK_FRAME_NON_STANDARD(func) \ #define STACK_FRAME_NON_STANDARD(func) \
static void __used __section(__func_stack_frame_non_standard) \ static void __used __section(.discard.func_stack_frame_non_standard) \
*__func_stack_frame_non_standard_##func = func *__func_stack_frame_non_standard_##func = func
#else /* !CONFIG_STACK_VALIDATION */ #else /* !CONFIG_STACK_VALIDATION */

1
scripts/mod/modpost.c
View file

@ -854,6 +854,7 @@ static const char *const section_white_list[] =
".cmem*", /* EZchip */ ".cmem*", /* EZchip */
".fmt_slot*", /* EZchip */ ".fmt_slot*", /* EZchip */
".gnu.lto*", ".gnu.lto*",
".discard.*",
NULL NULL
}; };

5
scripts/module-common.lds
View file

@ -4,7 +4,10 @@
* combine them automatically. * combine them automatically.
*/ */
SECTIONS { SECTIONS {
/DISCARD/ : { *(.discard) } /DISCARD/ : {
*(.discard)
*(.discard.*)
}
__ksymtab 0 : { *(SORT(___ksymtab+*)) } __ksymtab 0 : { *(SORT(___ksymtab+*)) }
__ksymtab_gpl 0 : { *(SORT(___ksymtab_gpl+*)) } __ksymtab_gpl 0 : { *(SORT(___ksymtab_gpl+*)) }

6
tools/objtool/builtin-check.c
View file

@ -339,13 +339,13 @@ static int add_dead_ends(struct objtool_file *file)
struct instruction *insn; struct instruction *insn;
bool found; bool found;
sec = find_section_by_name(file->elf, ".rela__unreachable"); sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
if (!sec) if (!sec)
return 0; return 0;
list_for_each_entry(rela, &sec->rela_list, list) { list_for_each_entry(rela, &sec->rela_list, list) {
if (rela->sym->type != STT_SECTION) { if (rela->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in .rela__unreachable"); WARN("unexpected relocation symbol type in %s", sec->name);
return -1; return -1;
} }
insn = find_insn(file, rela->sym->sec, rela->addend); insn = find_insn(file, rela->sym->sec, rela->addend);
@ -1272,7 +1272,7 @@ int cmd_check(int argc, const char **argv)
INIT_LIST_HEAD(&file.insn_list); INIT_LIST_HEAD(&file.insn_list);
hash_init(file.insn_hash); hash_init(file.insn_hash);
file.whitelist = find_section_by_name(file.elf, "__func_stack_frame_non_standard"); file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
file.rodata = find_section_by_name(file.elf, ".rodata"); file.rodata = find_section_by_name(file.elf, ".rodata");
file.ignore_unreachables = false; file.ignore_unreachables = false;
file.c_file = find_section_by_name(file.elf, ".comment"); file.c_file = find_section_by_name(file.elf, ".comment");