Commit b3c95109 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
Browse files

perf annotate-data: Add stack canary type 



When the stack protector is enabled, compiler would generate code to
check stack overflow with a special value called 'stack carary' at
runtime.  On x86_64, GCC hard-codes the stack canary as %gs:40.

While there's a definition of fixed_percpu_data in asm/processor.h,
it seems that the header is not included everywhere and many places
it cannot find the type info.  As it's in the well-known location (at
%gs:40), let's add a pseudo stack canary type to handle it specially.

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20240319055115.4063940-22-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent eb9190af

tools/perf/util/annotate-data.c

+46 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ enum type_state_kind { 
	TSR_KIND_PERCPU_BASE,

	TSR_KIND_CONST,

	TSR_KIND_POINTER,

	TSR_KIND_CANARY,

};



#define pr_debug_dtp(fmt, ...)					\
@@ -62,6 +63,9 @@ static void pr_debug_type_name(Dwarf_Die *die, enum type_state_kind kind) 
		pr_info(" pointer");

		/* it also prints the type info */

		break;

	case TSR_KIND_CANARY:

		pr_info(" stack canary\n");

		return;

	case TSR_KIND_TYPE:

	default:

		break;
@@ -676,6 +680,15 @@ static void update_insn_state_x86(struct type_state *state, 
			 */

			var_addr = src->offset;



			if (var_addr == 40) {

				tsr->kind = TSR_KIND_CANARY;

				tsr->ok = true;



				pr_debug_dtp("mov [%x] stack canary -> reg%d\n",

					     insn_offset, dst->reg1);

				return;

			}



			if (!get_global_var_type(cu_die, dloc, ip, var_addr,

						 &offset, &type_die) ||

			    !die_get_member_type(&type_die, offset, &type_die)) {
@@ -991,6 +1004,16 @@ static void delete_var_types(struct die_var_type *var_types) 
	}

}



/* should match to is_stack_canary() in util/annotate.c */

static void setup_stack_canary(struct data_loc_info *dloc)

{

	if (arch__is(dloc->arch, "x86")) {

		dloc->op->segment = INSN_SEG_X86_GS;

		dloc->op->imm = true;

		dloc->op->offset = 40;

	}

}



/* It's at the target address, check if it has a matching type */

static bool check_matching_type(struct type_state *state,

				struct data_loc_info *dloc, int reg,
@@ -1038,6 +1061,11 @@ static bool check_matching_type(struct type_state *state, 
		if (stack == NULL)

			return false;



		if (stack->kind == TSR_KIND_CANARY) {

			setup_stack_canary(dloc);

			return false;

		}



		*type_die = stack->type;

		/* Update the type offset from the start of slot */

		dloc->type_offset -= stack->offset;
@@ -1062,6 +1090,11 @@ static bool check_matching_type(struct type_state *state, 
		if (stack == NULL)

			return false;



		if (stack->kind == TSR_KIND_CANARY) {

			setup_stack_canary(dloc);

			return false;

		}



		*type_die = stack->type;

		/* Update the type offset from the start of slot */

		dloc->type_offset -= fboff + stack->offset;
@@ -1102,6 +1135,19 @@ static bool check_matching_type(struct type_state *state, 
		return true;

	}



	if (state->regs[reg].ok && state->regs[reg].kind == TSR_KIND_CANARY) {

		pr_debug_dtp(" stack canary\n");



		/*

		 * This is a saved value of the stack canary which will be handled

		 * in the outer logic when it returns failure here.  Pretend it's

		 * from the stack canary directly.

		 */

		setup_stack_canary(dloc);



		return false;

	}



	if (map__dso(dloc->ms->map)->kernel && arch__is(dloc->arch, "x86")) {

		u64 addr;

		int offset;

tools/perf/util/annotate-data.h

+1 −0
Original line number Diff line number Diff line
@@ -73,6 +73,7 @@ struct annotated_data_type { 


extern struct annotated_data_type unknown_type;

extern struct annotated_data_type stackop_type;

extern struct annotated_data_type canary_type;



/**

 * struct data_loc_info - Data location information

tools/perf/util/annotate.c

+25 −0
Original line number Diff line number Diff line
@@ -118,6 +118,13 @@ struct annotated_data_type stackop_type = { 
	},

};



struct annotated_data_type canary_type = {

	.self = {

		.type_name = (char *)"(stack canary)",

		.children = LIST_HEAD_INIT(canary_type.self.children),

	},

};



static int arch__grow_instructions(struct arch *arch)

{

	struct ins *new_instructions;
@@ -3803,6 +3810,18 @@ static bool is_stack_operation(struct arch *arch, struct disasm_line *dl) 
	return false;

}



static bool is_stack_canary(struct arch *arch, struct annotated_op_loc *loc)

{

	/* On x86_64, %gs:40 is used for stack canary */

	if (arch__is(arch, "x86")) {

		if (loc->segment == INSN_SEG_X86_GS && loc->imm &&

		    loc->offset == 40)

			return true;

	}



	return false;

}



u64 annotate_calc_pcrel(struct map_symbol *ms, u64 ip, int offset,

			struct disasm_line *dl)

{
@@ -3929,6 +3948,12 @@ struct annotated_data_type *hist_entry__get_data_type(struct hist_entry *he) 
		}



		mem_type = find_data_type(&dloc);



		if (mem_type == NULL && is_stack_canary(arch, op_loc)) {

			mem_type = &canary_type;

			dloc.type_offset = 0;

		}



		if (mem_type)

			istat->good++;

		else