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objtool: Add a pass for generating __mcount_loc

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Add the --mcount option for generating __mcount_loc sections
needed for dynamic ftrace. Using this pass requires the kernel to
be compiled with -mfentry and CC_USING_NOP_MCOUNT to be defined
in Makefile.

Link: https://lore.kernel.org/lkml/20200625200235.GQ4781@hirez.programming.kicks-ass.net/
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
[Sami: rebased, dropped config changes, fixed to actually use --mcount,
       and wrote a commit message.]
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Peter Zijlstra
2020-08-06 15:14:09 -07:00
committed by Kees Cook
parent 2b86895205
commit 99d0021569
6 changed files with 88 additions and 2 deletions
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3
tools/objtool/builtin-check.c
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@@ -18,7 +18,7 @@
#include "builtin.h"
#include "objtool.h"
bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux;
bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount;
static const char * const check_usage[] = {
"objtool check [<options>] file.o",
@@ -35,6 +35,7 @@ const struct option check_options[] = {
OPT_BOOLEAN('s', "stats", &stats, "print statistics"),
OPT_BOOLEAN('d', "duplicate", &validate_dup, "duplicate validation for vmlinux.o"),
OPT_BOOLEAN('l', "vmlinux", &vmlinux, "vmlinux.o validation"),
OPT_BOOLEAN('M', "mcount", &mcount, "generate __mcount_loc"),
OPT_END(),
};