Commit fcb268b4 authored by Alexandre Chartre's avatar Alexandre Chartre Committed by Peter Zijlstra
Browse files

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: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-12-alexandre.chartre@oracle.com
parent 70589843

tools/objtool/check.c

+7 −1
Original line number Diff line number Diff line
@@ -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) {

tools/objtool/include/objtool/trace.h

+10 −0
Original line number Diff line number Diff line
@@ -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) {}

tools/objtool/trace.c

+132 −0
Original line number Diff line number Diff line
@@ -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;

}