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objtool: Trace instruction state changes during function validation

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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 <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-12-alexandre.chartre@oracle.com
This commit is contained in:
Alexandre Chartre
2025-11-21 10:53:21 +01:00
committed by Peter Zijlstra
parent 70589843b3
commit fcb268b47a
3 changed files with 149 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
tools/objtool/check.c
View File

@@ -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) {

10
tools/objtool/include/objtool/trace.h
View File

@@ -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) {}

132
tools/objtool/trace.c
View File

@@ -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 "<undefined>";
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 "<error>";
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$s=<undef> ", cfi_reg_name(reg));
} else {
rname = strdup(cfi_reg_name(reg));
TRACE(fmt, rname, cfi_reg_name(base_next), offset_next);
free(rname);
}
}
static void trace_cfi_reg_val(const char *prefix, int reg,
int base_prev, int offset_prev,
int base_next, int offset_next)
{
trace_cfi_reg(prefix, reg, "%1$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;
}