Commit b5bc2231 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

objtool: Add retpoline validation



David requested a objtool validation pass for CONFIG_RETPOLINE=y enabled
builds, where it validates no unannotated indirect  jumps or calls are
left.

Add an additional .discard.retpoline_safe section to allow annotating
the few indirect sites that are required and safe.
Requested-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 43a4525f
......@@ -264,6 +264,10 @@ objtool_args += --no-unreachable
else
objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable)
endif
ifdef CONFIG_RETPOLINE
objtool_args += --retpoline
endif
ifdef CONFIG_MODVERSIONS
objtool_o = $(@D)/.tmp_$(@F)
......
......@@ -29,7 +29,7 @@
#include "builtin.h"
#include "check.h"
bool no_fp, no_unreachable;
bool no_fp, no_unreachable, retpoline;
static const char * const check_usage[] = {
"objtool check [<options>] file.o",
......@@ -39,6 +39,7 @@ static const char * const check_usage[] = {
const struct option check_options[] = {
OPT_BOOLEAN('f', "no-fp", &no_fp, "Skip frame pointer validation"),
OPT_BOOLEAN('u', "no-unreachable", &no_unreachable, "Skip 'unreachable instruction' warnings"),
OPT_BOOLEAN('r', "retpoline", &retpoline, "Validate retpoline assumptions"),
OPT_END(),
};
......
......@@ -20,7 +20,7 @@
#include <subcmd/parse-options.h>
extern const struct option check_options[];
extern bool no_fp, no_unreachable;
extern bool no_fp, no_unreachable, retpoline;
extern int cmd_check(int argc, const char **argv);
extern int cmd_orc(int argc, const char **argv);
......
......@@ -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;
}
......@@ -1108,6 +1110,54 @@ static int read_unwind_hints(struct objtool_file *file)
return 0;
}
static int read_retpoline_hints(struct objtool_file *file)
{
struct section *sec, *relasec;
struct instruction *insn;
struct rela *rela;
int i;
sec = find_section_by_name(file->elf, ".discard.retpoline_safe");
if (!sec)
return 0;
relasec = sec->rela;
if (!relasec) {
WARN("missing .rela.discard.retpoline_safe section");
return -1;
}
if (sec->len % sizeof(unsigned long)) {
WARN("retpoline_safe size mismatch: %d %ld", sec->len, sizeof(unsigned long));
return -1;
}
for (i = 0; i < sec->len / sizeof(unsigned long); i++) {
rela = find_rela_by_dest(sec, i * sizeof(unsigned long));
if (!rela) {
WARN("can't find rela for retpoline_safe[%d]", i);
return -1;
}
insn = find_insn(file, rela->sym->sec, rela->addend);
if (!insn) {
WARN("can't find insn for retpoline_safe[%d]", i);
return -1;
}
if (insn->type != INSN_JUMP_DYNAMIC &&
insn->type != INSN_CALL_DYNAMIC) {
WARN_FUNC("retpoline_safe hint not a 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;
......@@ -1146,6 +1196,10 @@ static int decode_sections(struct objtool_file *file)
if (ret)
return ret;
ret = read_retpoline_hints(file);
if (ret)
return ret;
return 0;
}
......@@ -1891,6 +1945,29 @@ 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;
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 &&
......@@ -2051,6 +2128,13 @@ int check(const char *_objname, 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;
......
......@@ -45,6 +45,7 @@ struct instruction {
unsigned char type;
unsigned long immediate;
bool alt_group, visited, dead_end, ignore, hint, save, restore, ignore_alts;
bool retpoline_safe;
struct symbol *call_dest;
struct instruction *jump_dest;
struct instruction *first_jump_src;
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment