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objtool, modules: Discard objtool annotation sections for modules

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commit e390f9a9689a42f477a6073e2e7df530a4c1b740 upstream.

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: d1091c7fa3d5 ("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>
[dwmw2: Remove the unreachable part in backporting since it's not here yet]
Signed-off-by: David Woodhouse <dwmw@amazon.co.ku>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josh Poimboeuf 2017-03-01 12:04:44 -06:00 • committed by Greg Kroah-Hartman
commit 35aee626fa
4 changed files with 7 additions and 3 deletions
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2
include/linux/frame.h
View file

@ -11,7 +11,7 @@
* For more information, see tools/objtool/Documentation/stack-validation.txt.
*/
#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
#else /* !CONFIG_STACK_VALIDATION */

1
scripts/mod/modpost.c
View file

@ -838,6 +838,7 @@ static const char *const section_white_list[] =
".cmem*", /* EZchip */
".fmt_slot*", /* EZchip */
".gnu.lto*",
".discard.*",
NULL
};

5
scripts/module-common.lds
View file

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

2
tools/objtool/builtin-check.c
View file

@ -1229,7 +1229,7 @@ int cmd_check(int argc, const char **argv)
INIT_LIST_HEAD(&file.insn_list);
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.ignore_unreachables = false;
file.c_file = find_section_by_name(file.elf, ".comment");