summaryrefslogtreecommitdiffstats
path: root/tools/objtool/check.c
diff options
context:
space:
mode:
Diffstat (limited to 'tools/objtool/check.c')
-rw-r--r--tools/objtool/check.c146
1 files changed, 136 insertions, 10 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index b00b1896547e..92b6a2c21631 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -18,6 +18,7 @@
#include <string.h>
#include <stdlib.h>
+#include "builtin.h"
#include "check.h"
#include "elf.h"
#include "special.h"
@@ -33,7 +34,6 @@ struct alternative {
};
const char *objname;
-static bool no_fp;
struct cfi_state initial_func_cfi;
struct instruction *find_insn(struct objtool_file *file,
@@ -497,6 +497,7 @@ static int add_jump_destinations(struct objtool_file *file)
* disguise, so convert them accordingly.
*/
insn->type = INSN_JUMP_DYNAMIC;
+ insn->retpoline_safe = true;
continue;
} else {
/* sibling call */
@@ -548,7 +549,8 @@ static int add_call_destinations(struct objtool_file *file)
if (!insn->call_dest && !insn->ignore) {
WARN_FUNC("unsupported intra-function call",
insn->sec, insn->offset);
- WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
+ if (retpoline)
+ WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
return -1;
}
@@ -852,8 +854,14 @@ static int add_switch_table(struct objtool_file *file, struct symbol *func,
* This is a fairly uncommon pattern which is new for GCC 6. As of this
* writing, there are 11 occurrences of it in the allmodconfig kernel.
*
+ * As of GCC 7 there are quite a few more of these and the 'in between' code
+ * is significant. Esp. with KASAN enabled some of the code between the mov
+ * and jmpq uses .rodata itself, which can confuse things.
+ *
* TODO: Once we have DWARF CFI and smarter instruction decoding logic,
* ensure the same register is used in the mov and jump instructions.
+ *
+ * NOTE: RETPOLINE made it harder still to decode dynamic jumps.
*/
static struct rela *find_switch_table(struct objtool_file *file,
struct symbol *func,
@@ -875,12 +883,25 @@ static struct rela *find_switch_table(struct objtool_file *file,
text_rela->addend + 4);
if (!rodata_rela)
return NULL;
+
file->ignore_unreachables = true;
return rodata_rela;
}
/* case 3 */
- func_for_each_insn_continue_reverse(file, func, insn) {
+ /*
+ * Backward search using the @first_jump_src links, these help avoid
+ * much of the 'in between' code. Which avoids us getting confused by
+ * it.
+ */
+ for (insn = list_prev_entry(insn, list);
+
+ &insn->list != &file->insn_list &&
+ insn->sec == func->sec &&
+ insn->offset >= func->offset;
+
+ insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
+
if (insn->type == INSN_JUMP_DYNAMIC)
break;
@@ -904,20 +925,42 @@ static struct rela *find_switch_table(struct objtool_file *file,
if (find_symbol_containing(file->rodata, text_rela->addend))
continue;
- return find_rela_by_dest(file->rodata, text_rela->addend);
+ rodata_rela = find_rela_by_dest(file->rodata, text_rela->addend);
+ if (!rodata_rela)
+ continue;
+
+ return rodata_rela;
}
return NULL;
}
+
static int add_func_switch_tables(struct objtool_file *file,
struct symbol *func)
{
- struct instruction *insn, *prev_jump = NULL;
+ struct instruction *insn, *last = NULL, *prev_jump = NULL;
struct rela *rela, *prev_rela = NULL;
int ret;
func_for_each_insn(file, func, insn) {
+ if (!last)
+ last = insn;
+
+ /*
+ * Store back-pointers for unconditional forward jumps such
+ * that find_switch_table() can back-track using those and
+ * avoid some potentially confusing code.
+ */
+ if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
+ insn->offset > last->offset &&
+ insn->jump_dest->offset > insn->offset &&
+ !insn->jump_dest->first_jump_src) {
+
+ insn->jump_dest->first_jump_src = insn;
+ last = insn->jump_dest;
+ }
+
if (insn->type != INSN_JUMP_DYNAMIC)
continue;
@@ -1071,6 +1114,41 @@ static int read_unwind_hints(struct objtool_file *file)
return 0;
}
+static int read_retpoline_hints(struct objtool_file *file)
+{
+ struct section *sec;
+ struct instruction *insn;
+ struct rela *rela;
+
+ sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
+ if (!sec)
+ return 0;
+
+ list_for_each_entry(rela, &sec->rela_list, list) {
+ if (rela->sym->type != STT_SECTION) {
+ WARN("unexpected relocation symbol type in %s", sec->name);
+ return -1;
+ }
+
+ insn = find_insn(file, rela->sym->sec, rela->addend);
+ if (!insn) {
+ WARN("bad .discard.retpoline_safe entry");
+ return -1;
+ }
+
+ if (insn->type != INSN_JUMP_DYNAMIC &&
+ insn->type != INSN_CALL_DYNAMIC) {
+ WARN_FUNC("retpoline_safe hint not an indirect jump/call",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ insn->retpoline_safe = true;
+ }
+
+ return 0;
+}
+
static int decode_sections(struct objtool_file *file)
{
int ret;
@@ -1109,6 +1187,10 @@ static int decode_sections(struct objtool_file *file)
if (ret)
return ret;
+ ret = read_retpoline_hints(file);
+ if (ret)
+ return ret;
+
return 0;
}
@@ -1854,6 +1936,38 @@ static int validate_unwind_hints(struct objtool_file *file)
return warnings;
}
+static int validate_retpoline(struct objtool_file *file)
+{
+ struct instruction *insn;
+ int warnings = 0;
+
+ for_each_insn(file, insn) {
+ if (insn->type != INSN_JUMP_DYNAMIC &&
+ insn->type != INSN_CALL_DYNAMIC)
+ continue;
+
+ if (insn->retpoline_safe)
+ continue;
+
+ /*
+ * .init.text code is ran before userspace and thus doesn't
+ * strictly need retpolines, except for modules which are
+ * loaded late, they very much do need retpoline in their
+ * .init.text
+ */
+ if (!strcmp(insn->sec->name, ".init.text") && !module)
+ continue;
+
+ WARN_FUNC("indirect %s found in RETPOLINE build",
+ insn->sec, insn->offset,
+ insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
+
+ warnings++;
+ }
+
+ return warnings;
+}
+
static bool is_kasan_insn(struct instruction *insn)
{
return (insn->type == INSN_CALL &&
@@ -1899,13 +2013,19 @@ static bool ignore_unreachable_insn(struct instruction *insn)
if (is_kasan_insn(insn) || is_ubsan_insn(insn))
return true;
- if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
- insn = insn->jump_dest;
- continue;
+ if (insn->type == INSN_JUMP_UNCONDITIONAL) {
+ if (insn->jump_dest &&
+ insn->jump_dest->func == insn->func) {
+ insn = insn->jump_dest;
+ continue;
+ }
+
+ break;
}
if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
break;
+
insn = list_next_entry(insn, list);
}
@@ -1979,13 +2099,12 @@ static void cleanup(struct objtool_file *file)
elf_close(file->elf);
}
-int check(const char *_objname, bool _no_fp, bool no_unreachable, bool orc)
+int check(const char *_objname, bool orc)
{
struct objtool_file file;
int ret, warnings = 0;
objname = _objname;
- no_fp = _no_fp;
file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY);
if (!file.elf)
@@ -2009,6 +2128,13 @@ int check(const char *_objname, bool _no_fp, bool no_unreachable, bool orc)
if (list_empty(&file.insn_list))
goto out;
+ if (retpoline) {
+ ret = validate_retpoline(&file);
+ if (ret < 0)
+ return ret;
+ warnings += ret;
+ }
+
ret = validate_functions(&file);
if (ret < 0)
goto out;