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: Namhyung 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: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/annotate-data.c

@@ -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

@@ -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

@@ -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 @@ retry:
 		}
 
 		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