4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Peter Zijlstra peterz@infradead.org
commit b5bc2231b8ad4387c9641f235ca0ad8cd300b6df upstream.
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: David Woodhouse dwmw2@infradead.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: David Woodhouse dwmw@amazon.co.uk Acked-by: Thomas Gleixner tglx@linutronix.de Acked-by: Josh 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: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- scripts/Makefile.build | 4 + tools/objtool/builtin-check.c | 3 - tools/objtool/builtin.h | 2 tools/objtool/check.c | 86 +++++++++++++++++++++++++++++++++++++++++- tools/objtool/check.h | 1 5 files changed, 93 insertions(+), 3 deletions(-)
--- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -269,6 +269,10 @@ 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) --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -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(), };
--- a/tools/objtool/builtin.h +++ b/tools/objtool/builtin.h @@ -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); --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -496,6 +496,7 @@ static int add_jump_destinations(struct * disguise, so convert them accordingly. */ insn->type = INSN_JUMP_DYNAMIC; + insn->retpoline_safe = true; continue; } else { /* sibling call */ @@ -547,7 +548,8 @@ static int add_call_destinations(struct 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; }
@@ -1107,6 +1109,54 @@ static int read_unwind_hints(struct objt 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; @@ -1145,6 +1195,10 @@ static int decode_sections(struct objtoo if (ret) return ret;
+ ret = read_retpoline_hints(file); + if (ret) + return ret; + return 0; }
@@ -1890,6 +1944,29 @@ static int validate_unwind_hints(struct 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 && @@ -2050,6 +2127,13 @@ 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; --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -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;