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authorJosh Poimboeuf <jpoimboe@redhat.com>2016-03-09 00:06:58 -0600
committerIngo Molnar <mingo@kernel.org>2016-03-09 10:48:09 +0100
commit8133fbb4240ae2918d993defa0f6824864412f56 (patch)
tree82df4917d216aaf1a5fb7594f8adbb2d0667a119
parenta196e17198224cacd2d992f12cb6d81d354de82f (diff)
objtool: Fix false positive warnings for functions with multiple switch statements
Ingo reported [1] some false positive objtool warnings: drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch ... And so did the 0-day bot [2]: drivers/gpu/drm/radeon/cik.o: warning: objtool: cik_tiling_mode_table_init()+0x6ce: call without frame pointer save/setup drivers/gpu/drm/radeon/cik.o: warning: objtool: cik_tiling_mode_table_init()+0x72b: call without frame pointer save/setup ... Both sets of warnings involve functions which have multiple switch statements. When there's more than one switch statement in a function, objtool interprets all the switch jump tables as a single table. If the targets of one jump table assume a stack frame and the targets of another one don't, it prints false positive warnings. Fix the bug by detecting the size of each switch jump table. For multiple tables, each one ends where the next one begins. [1] https://lkml.kernel.org/r/20160308103716.GA9618@gmail.com [2] https://lists.01.org/pipermail/kbuild-all/2016-March/018124.html Reported-by: Ingo Molnar <mingo@kernel.org> Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris J Arges <chris.j.arges@canonical.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Namhyung Kim <namhyung@gmail.com> Cc: Pedro Alves <palves@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/2d7eecc6bc52d301f494b80f5fd62c2b6c895658.1457502970.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--tools/objtool/builtin-check.c145
1 files changed, 100 insertions, 45 deletions
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index cdbdd7d9333a..cf1e48dbfa97 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -61,6 +61,7 @@ struct alternative {
struct objtool_file {
struct elf *elf;
struct list_head insn_list;
+ struct section *rodata;
};
const char *objname;
@@ -599,73 +600,125 @@ out:
return ret;
}
-/*
- * For some switch statements, gcc generates a jump table in the .rodata
- * section which contains a list of addresses within the function to jump to.
- * This finds these jump tables and adds them to the insn->alts lists.
- */
-static int add_switch_table_alts(struct objtool_file *file)
+static int add_switch_table(struct objtool_file *file, struct symbol *func,
+ struct instruction *insn, struct rela *table,
+ struct rela *next_table)
{
- struct instruction *insn, *alt_insn;
- struct rela *rodata_rela, *text_rela;
- struct section *rodata;
- struct symbol *func;
+ struct rela *rela = table;
+ struct instruction *alt_insn;
struct alternative *alt;
- for_each_insn(file, insn) {
+ list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
+ if (rela == next_table)
+ break;
+
+ if (rela->sym->sec != insn->sec ||
+ rela->addend <= func->offset ||
+ rela->addend >= func->offset + func->len)
+ break;
+
+ alt_insn = find_insn(file, insn->sec, rela->addend);
+ if (!alt_insn) {
+ WARN("%s: can't find instruction at %s+0x%x",
+ file->rodata->rela->name, insn->sec->name,
+ rela->addend);
+ return -1;
+ }
+
+ alt = malloc(sizeof(*alt));
+ if (!alt) {
+ WARN("malloc failed");
+ return -1;
+ }
+
+ alt->insn = alt_insn;
+ list_add_tail(&alt->list, &insn->alts);
+ }
+
+ return 0;
+}
+
+static int add_func_switch_tables(struct objtool_file *file,
+ struct symbol *func)
+{
+ struct instruction *insn, *prev_jump;
+ struct rela *text_rela, *rodata_rela, *prev_rela;
+ int ret;
+
+ prev_jump = NULL;
+
+ func_for_each_insn(file, func, insn) {
if (insn->type != INSN_JUMP_DYNAMIC)
continue;
text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
insn->len);
- if (!text_rela || strcmp(text_rela->sym->name, ".rodata"))
- continue;
-
- rodata = find_section_by_name(file->elf, ".rodata");
- if (!rodata || !rodata->rela)
+ if (!text_rela || text_rela->sym != file->rodata->sym)
continue;
/* common case: jmpq *[addr](,%rax,8) */
- rodata_rela = find_rela_by_dest(rodata, text_rela->addend);
+ rodata_rela = find_rela_by_dest(file->rodata,
+ text_rela->addend);
- /* rare case: jmpq *[addr](%rip) */
+ /*
+ * TODO: Document where this is needed, or get rid of it.
+ *
+ * rare case: jmpq *[addr](%rip)
+ */
if (!rodata_rela)
- rodata_rela = find_rela_by_dest(rodata,
+ rodata_rela = find_rela_by_dest(file->rodata,
text_rela->addend + 4);
+
if (!rodata_rela)
continue;
- func = find_containing_func(insn->sec, insn->offset);
- if (!func) {
- WARN_FUNC("can't find containing func",
- insn->sec, insn->offset);
- return -1;
+ /*
+ * We found a switch table, but we don't know yet how big it
+ * is. Don't add it until we reach the end of the function or
+ * the beginning of another switch table in the same function.
+ */
+ if (prev_jump) {
+ ret = add_switch_table(file, func, prev_jump, prev_rela,
+ rodata_rela);
+ if (ret)
+ return ret;
}
- list_for_each_entry_from(rodata_rela, &rodata->rela->rela_list,
- list) {
- if (rodata_rela->sym->sec != insn->sec ||
- rodata_rela->addend <= func->offset ||
- rodata_rela->addend >= func->offset + func->len)
- break;
+ prev_jump = insn;
+ prev_rela = rodata_rela;
+ }
- alt_insn = find_insn(file, insn->sec,
- rodata_rela->addend);
- if (!alt_insn) {
- WARN("%s: can't find instruction at %s+0x%x",
- rodata->rela->name, insn->sec->name,
- rodata_rela->addend);
- return -1;
- }
+ if (prev_jump) {
+ ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
+ if (ret)
+ return ret;
+ }
- alt = malloc(sizeof(*alt));
- if (!alt) {
- WARN("malloc failed");
- return -1;
- }
+ return 0;
+}
- alt->insn = alt_insn;
- list_add_tail(&alt->list, &insn->alts);
+/*
+ * For some switch statements, gcc generates a jump table in the .rodata
+ * section which contains a list of addresses within the function to jump to.
+ * This finds these jump tables and adds them to the insn->alts lists.
+ */
+static int add_switch_table_alts(struct objtool_file *file)
+{
+ struct section *sec;
+ struct symbol *func;
+ int ret;
+
+ if (!file->rodata || !file->rodata->rela)
+ return 0;
+
+ list_for_each_entry(sec, &file->elf->sections, list) {
+ list_for_each_entry(func, &sec->symbol_list, list) {
+ if (func->type != STT_FUNC)
+ continue;
+
+ ret = add_func_switch_tables(file, func);
+ if (ret)
+ return ret;
}
}
@@ -676,6 +729,8 @@ static int decode_sections(struct objtool_file *file)
{
int ret;
+ file->rodata = find_section_by_name(file->elf, ".rodata");
+
ret = decode_instructions(file);
if (ret)
return ret;