[PATCH 47/48] perf annotate-data: Add stack canary type

[Namhyung Kim]

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@xxxxxxxxxx>
---
 tools/perf/util/annotate-data.c |  7 +++++++
 tools/perf/util/annotate-data.h |  1 +
 tools/perf/util/annotate.c      | 17 +++++++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index 677dc01432d3..68d7d207e2f7 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -37,6 +37,13 @@ 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),
+	},
+};
+
 /* Data type collection debug statistics */
 struct annotated_data_stat ann_data_stat;
 
diff --git a/tools/perf/util/annotate-data.h b/tools/perf/util/annotate-data.h
index 0bfef29fa52c..e293980eb11b 100644
--- a/tools/perf/util/annotate-data.h
+++ b/tools/perf/util/annotate-data.h
@@ -77,6 +77,7 @@ 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
diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index 414ae45b7c06..f343f90612d0 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -3720,6 +3720,17 @@ 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->offset == 40)
+			return true;
+	}
+
+	return false;
+}
+
 u64 annotate_calc_pcrel(struct map_symbol *ms, u64 ip, int offset,
 			struct disasm_line *dl)
 {
@@ -3889,6 +3900,12 @@ 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
-- 
2.42.0.655.g421f12c284-goog