objtool, modules: Discard objtool annotation sections for modules

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>

diff --git a/include/linux/frame.h b/include/linux/frame.h
index e6baaba..d772c61 100644 (file)
--- a/include/linux/frame.h
+++ b/include/linux/frame.h
@@ -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 */

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index bd83497..845eb9b 100644 (file)
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -838,6 +838,7 @@ static const char *const section_white_list[] =
        ".cmem*",                       /* EZchip */
        ".fmt_slot*",                   /* EZchip */
        ".gnu.lto*",
+       ".discard.*",
        NULL
 };
 

diff --git a/scripts/module-common.lds b/scripts/module-common.lds
index 53234e8..9b6e246 100644 (file)
--- a/scripts/module-common.lds
+++ b/scripts/module-common.lds
@@ -4,7 +4,10 @@
  * combine them automatically.
  */
 SECTIONS {
-       /DISCARD/ : { *(.discard) }
+       /DISCARD/ : {
+               *(.discard)
+               *(.discard.*)
+       }
 
        __ksymtab               0 : { *(SORT(___ksymtab+*)) }
        __ksymtab_gpl           0 : { *(SORT(___ksymtab_gpl+*)) }

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index b8dadb0..f8b6cf5 100644 (file)
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -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");