From fcb268b47a2f4a497fdb40ef24bb9e06488b7213 Mon Sep 17 00:00:00 2001 From: Alexandre Chartre Date: Fri, 21 Nov 2025 10:53:21 +0100 Subject: [PATCH] objtool: Trace instruction state changes during function validation During function validation, objtool maintains a per-instruction state, in particular to track call frame information. When tracing validation, print any instruction state changes. Signed-off-by: Alexandre Chartre Signed-off-by: Peter Zijlstra (Intel) Acked-by: Josh Poimboeuf Link: https://patch.msgid.link/20251121095340.464045-12-alexandre.chartre@oracle.com --- tools/objtool/check.c | 8 +- tools/objtool/include/objtool/trace.h | 10 ++ tools/objtool/trace.c | 132 ++++++++++++++++++++++++++ 3 files changed, 149 insertions(+), 1 deletion(-) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 409dec9efb494..a02f8db75827f 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -3677,6 +3677,8 @@ static int validate_insn(struct objtool_file *file, struct symbol *func, struct instruction *prev_insn, struct instruction *next_insn, bool *dead_end) { + /* prev_state is not used if there is no disassembly support */ + struct insn_state prev_state __maybe_unused; struct alternative *alt; u8 visited; int ret; @@ -3785,7 +3787,11 @@ static int validate_insn(struct objtool_file *file, struct symbol *func, if (skip_alt_group(insn)) return 0; - if (handle_insn_ops(insn, next_insn, statep)) + prev_state = *statep; + ret = handle_insn_ops(insn, next_insn, statep); + TRACE_INSN_STATE(insn, &prev_state, statep); + + if (ret) return 1; switch (insn->type) { diff --git a/tools/objtool/include/objtool/trace.h b/tools/objtool/include/objtool/trace.h index 3f3c830ed114e..33fe9c6acb4fd 100644 --- a/tools/objtool/include/objtool/trace.h +++ b/tools/objtool/include/objtool/trace.h @@ -30,6 +30,12 @@ extern int trace_depth; } \ }) +#define TRACE_INSN_STATE(insn, sprev, snext) \ +({ \ + if (trace) \ + trace_insn_state(insn, sprev, snext); \ +}) + static inline void trace_enable(void) { trace = true; @@ -53,10 +59,14 @@ static inline void trace_depth_dec(void) trace_depth--; } +void trace_insn_state(struct instruction *insn, struct insn_state *sprev, + struct insn_state *snext); + #else /* DISAS */ #define TRACE(fmt, ...) ({}) #define TRACE_INSN(insn, fmt, ...) ({}) +#define TRACE_INSN_STATE(insn, sprev, snext) ({}) static inline void trace_enable(void) {} static inline void trace_disable(void) {} diff --git a/tools/objtool/trace.c b/tools/objtool/trace.c index 134cc33ffe970..12bbad09d9c02 100644 --- a/tools/objtool/trace.c +++ b/tools/objtool/trace.c @@ -7,3 +7,135 @@ bool trace; int trace_depth; + +/* + * Macros to trace CFI state attributes changes. + */ + +#define TRACE_CFI_ATTR(attr, prev, next, fmt, ...) \ +({ \ + if ((prev)->attr != (next)->attr) \ + TRACE("%s=" fmt " ", #attr, __VA_ARGS__); \ +}) + +#define TRACE_CFI_ATTR_BOOL(attr, prev, next) \ + TRACE_CFI_ATTR(attr, prev, next, \ + "%s", (next)->attr ? "true" : "false") + +#define TRACE_CFI_ATTR_NUM(attr, prev, next, fmt) \ + TRACE_CFI_ATTR(attr, prev, next, fmt, (next)->attr) + +#define CFI_REG_NAME_MAXLEN 16 + +/* + * Return the name of a register. Note that the same static buffer + * is returned if the name is dynamically generated. + */ +static const char *cfi_reg_name(unsigned int reg) +{ + static char rname_buffer[CFI_REG_NAME_MAXLEN]; + + switch (reg) { + case CFI_UNDEFINED: + return ""; + case CFI_CFA: + return "cfa"; + case CFI_SP_INDIRECT: + return "(sp)"; + case CFI_BP_INDIRECT: + return "(bp)"; + } + + if (snprintf(rname_buffer, CFI_REG_NAME_MAXLEN, "r%d", reg) == -1) + return ""; + + return (const char *)rname_buffer; +} + +/* + * Functions and macros to trace CFI registers changes. + */ + +static void trace_cfi_reg(const char *prefix, int reg, const char *fmt, + int base_prev, int offset_prev, + int base_next, int offset_next) +{ + char *rname; + + if (base_prev == base_next && offset_prev == offset_next) + return; + + if (prefix) + TRACE("%s:", prefix); + + if (base_next == CFI_UNDEFINED) { + TRACE("%1$s= ", cfi_reg_name(reg)); + } else { + rname = strdup(cfi_reg_name(reg)); + TRACE(fmt, rname, cfi_reg_name(base_next), offset_next); + free(rname); + } +} + +static void trace_cfi_reg_val(const char *prefix, int reg, + int base_prev, int offset_prev, + int base_next, int offset_next) +{ + trace_cfi_reg(prefix, reg, "%1$s=%2$s%3$+d ", + base_prev, offset_prev, base_next, offset_next); +} + +static void trace_cfi_reg_ref(const char *prefix, int reg, + int base_prev, int offset_prev, + int base_next, int offset_next) +{ + trace_cfi_reg(prefix, reg, "%1$s=(%2$s%3$+d) ", + base_prev, offset_prev, base_next, offset_next); +} + +#define TRACE_CFI_REG_VAL(reg, prev, next) \ + trace_cfi_reg_val(NULL, reg, prev.base, prev.offset, \ + next.base, next.offset) + +#define TRACE_CFI_REG_REF(reg, prev, next) \ + trace_cfi_reg_ref(NULL, reg, prev.base, prev.offset, \ + next.base, next.offset) + +void trace_insn_state(struct instruction *insn, struct insn_state *sprev, + struct insn_state *snext) +{ + struct cfi_state *cprev, *cnext; + int i; + + if (!memcmp(sprev, snext, sizeof(struct insn_state))) + return; + + cprev = &sprev->cfi; + cnext = &snext->cfi; + + disas_print_insn(stderr, objtool_disas_ctx, insn, + trace_depth - 1, "state: "); + + /* print registers changes */ + TRACE_CFI_REG_VAL(CFI_CFA, cprev->cfa, cnext->cfa); + for (i = 0; i < CFI_NUM_REGS; i++) { + TRACE_CFI_REG_VAL(i, cprev->vals[i], cnext->vals[i]); + TRACE_CFI_REG_REF(i, cprev->regs[i], cnext->regs[i]); + } + + /* print attributes changes */ + TRACE_CFI_ATTR_NUM(stack_size, cprev, cnext, "%d"); + TRACE_CFI_ATTR_BOOL(drap, cprev, cnext); + if (cnext->drap) { + trace_cfi_reg_val("drap", cnext->drap_reg, + cprev->drap_reg, cprev->drap_offset, + cnext->drap_reg, cnext->drap_offset); + } + TRACE_CFI_ATTR_BOOL(bp_scratch, cprev, cnext); + TRACE_CFI_ATTR_NUM(instr, sprev, snext, "%d"); + TRACE_CFI_ATTR_NUM(uaccess_stack, sprev, snext, "%u"); + + TRACE("\n"); + + insn->trace = 1; +} -- 2.47.3