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authorJosh Poimboeuf <jpoimboe@redhat.com>2018-05-09 22:39:15 -0500
committerIngo Molnar <mingo@kernel.org>2018-05-14 10:20:53 +0200
commit13810435b9a7014fb92eb715f77da488f3b65b99 (patch)
tree4c5664dc44d3b63181134d176501484854e13640 /tools/objtool/elf.c
parent0afd0d9e0e7879d666c1df2fa1bea4d8716909fe (diff)
objtool: Support GCC 8's cold subfunctions
GCC 8 moves a lot of unlikely code out of line to "cold" subfunctions in .text.unlikely. Properly detect the new subfunctions and treat them as extensions of the original functions. This fixes a bunch of warnings like: kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags()+0x33: sibling call from callable instruction with modified stack frame kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x290: sibling call from callable instruction with modified stack frame kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable()+0x25b: sibling call from callable instruction with modified stack frame kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x325: sibling call from callable instruction with modified stack frame Reported-and-tested-by: damian <damian.tometzki@icloud.com> Reported-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: David Laight <David.Laight@ACULAB.COM> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/0965e7fcfc5f31a276f0c7f298ff770c19b68706.1525923412.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools/objtool/elf.c')
-rw-r--r--tools/objtool/elf.c42
1 files changed, 40 insertions, 2 deletions
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index c1c338661699..4e60e105583e 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -79,6 +79,19 @@ struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
return NULL;
}
+struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
+{
+ struct section *sec;
+ struct symbol *sym;
+
+ list_for_each_entry(sec, &elf->sections, list)
+ list_for_each_entry(sym, &sec->symbol_list, list)
+ if (!strcmp(sym->name, name))
+ return sym;
+
+ return NULL;
+}
+
struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
{
struct symbol *sym;
@@ -203,10 +216,11 @@ static int read_sections(struct elf *elf)
static int read_symbols(struct elf *elf)
{
- struct section *symtab;
- struct symbol *sym;
+ struct section *symtab, *sec;
+ struct symbol *sym, *pfunc;
struct list_head *entry, *tmp;
int symbols_nr, i;
+ char *coldstr;
symtab = find_section_by_name(elf, ".symtab");
if (!symtab) {
@@ -281,6 +295,30 @@ static int read_symbols(struct elf *elf)
hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
}
+ /* Create parent/child links for any cold subfunctions */
+ list_for_each_entry(sec, &elf->sections, list) {
+ list_for_each_entry(sym, &sec->symbol_list, list) {
+ if (sym->type != STT_FUNC)
+ continue;
+ sym->pfunc = sym->cfunc = sym;
+ coldstr = strstr(sym->name, ".cold.");
+ if (coldstr) {
+ coldstr[0] = '\0';
+ pfunc = find_symbol_by_name(elf, sym->name);
+ coldstr[0] = '.';
+
+ if (!pfunc) {
+ WARN("%s(): can't find parent function",
+ sym->name);
+ goto err;
+ }
+
+ sym->pfunc = pfunc;
+ pfunc->cfunc = sym;
+ }
+ }
+ }
+
return 0;
err: