From a4f1599672e7bf494d79928a38fd6aa873e2e50c Mon Sep 17 00:00:00 2001 From: Alexandre Chartre Date: Fri, 21 Nov 2025 10:53:30 +0100 Subject: [PATCH] objtool: Disassemble group alternatives When using the --disas option, disassemble all group alternatives. Jump tables and exception tables (which are handled as alternatives) are not disassembled at the moment. Signed-off-by: Alexandre Chartre Signed-off-by: Peter Zijlstra (Intel) Acked-by: Josh Poimboeuf Link: https://patch.msgid.link/20251121095340.464045-21-alexandre.chartre@oracle.com --- tools/objtool/disas.c | 166 +++++++++++++++++++++++++++++++++++++----- 1 file changed, 149 insertions(+), 17 deletions(-) diff --git a/tools/objtool/disas.c b/tools/objtool/disas.c index f9b13d56acab7..ae69bef2eb37e 100644 --- a/tools/objtool/disas.c +++ b/tools/objtool/disas.c @@ -47,8 +47,14 @@ struct disas_alt { struct alternative *alt; /* alternative or NULL if default code */ char *name; /* name for this alternative */ int width; /* formatting width */ + char *insn[DISAS_ALT_INSN_MAX]; /* alternative instructions */ }; +#define DALT_DEFAULT(dalt) (!(dalt)->alt) +#define DALT_INSN(dalt) (DALT_DEFAULT(dalt) ? (dalt)->orig_insn : (dalt)->alt->insn) +#define DALT_GROUP(dalt) (DALT_INSN(dalt)->alt_group) +#define DALT_ALTID(dalt) ((dalt)->orig_insn->offset) + /* * Wrapper around asprintf() to allocate and format a string. * Return the allocated string or NULL on error. @@ -506,6 +512,21 @@ size_t disas_insn(struct disas_context *dctx, struct instruction *insn) return disasm(insn->offset, &dctx->info); } +static struct instruction *next_insn_same_alt(struct objtool_file *file, + struct alt_group *alt_grp, + struct instruction *insn) +{ + if (alt_grp->last_insn == insn || alt_grp->nop == insn) + return NULL; + + return next_insn_same_sec(file, insn); +} + +#define alt_for_each_insn(file, alt_grp, insn) \ + for (insn = alt_grp->first_insn; \ + insn; \ + insn = next_insn_same_alt(file, alt_grp, insn)) + /* * Provide a name for the type of alternatives present at the * specified instruction. @@ -594,23 +615,107 @@ static int disas_alt_init(struct disas_alt *dalt, return 0; } +static int disas_alt_add_insn(struct disas_alt *dalt, int index, char *insn_str) +{ + int len; + + if (index >= DISAS_ALT_INSN_MAX) { + WARN("Alternative %lx.%s has more instructions than supported", + DALT_ALTID(dalt), dalt->name); + return -1; + } + + len = strlen(insn_str); + dalt->insn[index] = insn_str; + if (len > dalt->width) + dalt->width = len; + + return 0; +} + +/* + * Disassemble an alternative and store instructions in the disas_alt + * structure. Return the number of instructions in the alternative. + */ +static int disas_alt_group(struct disas_context *dctx, struct disas_alt *dalt) +{ + struct objtool_file *file; + struct instruction *insn; + char *str; + int count; + int err; + + file = dctx->file; + count = 0; + + alt_for_each_insn(file, DALT_GROUP(dalt), insn) { + + disas_insn(dctx, insn); + str = strdup(disas_result(dctx)); + if (!str) + return -1; + + err = disas_alt_add_insn(dalt, count, str); + if (err) + break; + count++; + } + + return count; +} + +/* + * Disassemble the default alternative. + */ +static int disas_alt_default(struct disas_context *dctx, struct disas_alt *dalt) +{ + char *str; + int err; + + if (DALT_GROUP(dalt)) + return disas_alt_group(dctx, dalt); + + /* + * Default alternative with no alt_group: this is the default + * code associated with either a jump table or an exception + * table and no other instruction alternatives. In that case + * the default alternative is made of a single instruction. + */ + disas_insn(dctx, dalt->orig_insn); + str = strdup(disas_result(dctx)); + if (!str) + return -1; + err = disas_alt_add_insn(dalt, 0, str); + if (err) + return -1; + + return 1; +} + /* * Print all alternatives one above the other. */ static void disas_alt_print_compact(char *alt_name, struct disas_alt *dalts, - int alt_count) + int alt_count, int insn_count) { struct instruction *orig_insn; + int i, j; int len; - int i; orig_insn = dalts[0].orig_insn; len = disas_print(stdout, orig_insn->sec, orig_insn->offset, 0, NULL); printf("%s\n", alt_name); - for (i = 0; i < alt_count; i++) + for (i = 0; i < alt_count; i++) { printf("%*s= %s\n", len, "", dalts[i].name); + for (j = 0; j < insn_count; j++) { + if (!dalts[i].insn[j]) + break; + printf("%*s| %s\n", len, "", dalts[i].insn[j]); + } + printf("%*s|\n", len, ""); + } } /* @@ -624,11 +729,15 @@ static void *disas_alt(struct disas_context *dctx, struct instruction *orig_insn) { struct disas_alt dalts[DISAS_ALT_MAX] = { 0 }; + struct instruction *last_insn = NULL; struct alternative *alt; + struct disas_alt *dalt; + int insn_count = 0; int alt_count = 0; char *alt_name; + int count; + int i, j; int err; - int i; alt_name = strfmt("<%s.%lx>", disas_alt_type_name(orig_insn), orig_insn->offset); @@ -639,7 +748,7 @@ static void *disas_alt(struct disas_context *dctx, } /* - * Initialize the default alternative. + * Initialize and disassemble the default alternative. */ err = disas_alt_init(&dalts[0], orig_insn, NULL); if (err) { @@ -647,8 +756,14 @@ static void *disas_alt(struct disas_context *dctx, goto done; } + insn_count = disas_alt_default(dctx, &dalts[0]); + if (insn_count < 0) { + WARN("%s: failed to disassemble default alternative", alt_name); + goto done; + } + /* - * Initialize all other alternatives. + * Initialize and disassemble all other alternatives. */ i = 1; for (alt = orig_insn->alts; alt; alt = alt->next) { @@ -656,35 +771,52 @@ static void *disas_alt(struct disas_context *dctx, WARN("%s has more alternatives than supported", alt_name); break; } - err = disas_alt_init(&dalts[i], orig_insn, alt); + dalt = &dalts[i]; + err = disas_alt_init(dalt, orig_insn, alt); if (err) { WARN("%s: failed to disassemble alternative", alt_name); goto done; } + /* + * Only group alternatives are supported at the moment. + */ + switch (dalt->alt->type) { + case ALT_TYPE_INSTRUCTIONS: + count = disas_alt_group(dctx, dalt); + break; + default: + count = 0; + } + if (count < 0) { + WARN("%s: failed to disassemble alternative %s", + alt_name, dalt->name); + goto done; + } + + insn_count = count > insn_count ? count : insn_count; i++; } alt_count = i; /* * Print default and non-default alternatives. - * - * At the moment, this just prints an header for each alternative. */ - disas_alt_print_compact(alt_name, dalts, alt_count); + disas_alt_print_compact(alt_name, dalts, alt_count, insn_count); + + last_insn = orig_insn->alt_group ? orig_insn->alt_group->last_insn : + orig_insn; done: - for (i = 0; i < alt_count; i++) + for (i = 0; i < alt_count; i++) { free(dalts[i].name); + for (j = 0; j < insn_count; j++) + free(dalts[i].insn[j]); + } free(alt_name); - /* - * Currently we are not disassembling any alternative but just - * printing alternative names. Return NULL to have disas_func() - * resume the disassembly with the default alternative. - */ - return NULL; + return last_insn; } /* -- 2.47.3