linux-kernel - [PATCH 3/6] perf annotate-data: Handle direct global variable access

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Message-ID: <20240502060011.1838090-4-namhyung@kernel.org>
Date: Wed,  1 May 2024 23:00:08 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Kan Liang <kan.liang@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org
Subject: [PATCH 3/6] perf annotate-data: Handle direct global variable access

Like per-cpu base offset array, sometimes it accesses the global
variable directly using the offset.  Allow this type of instructions as
long as it finds a global variable for the address.

  movslq  %edi, %rcx
  mov     -0x7dc94ae0(,%rcx,8), %rcx   <<<--- here

As %rcx has a valid type (i.e. array index) from the first instruction,
it will be checked by the first case in check_matching_type().  But as
it's not a pointer type, the match will fail.  But in this case, it
should check if it accesses the kernel global array variable.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/annotate-data.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index 4dd0911904f2..f1e52a531563 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -1256,14 +1256,19 @@ static int check_matching_type(struct type_state *state,
 	if (state->regs[reg].ok && state->regs[reg].kind == TSR_KIND_TYPE) {
 		int tag = dwarf_tag(&state->regs[reg].type);
 
-		pr_debug_dtp("\n");
-
 		/*
 		 * Normal registers should hold a pointer (or array) to
 		 * dereference a memory location.
 		 */
-		if (tag != DW_TAG_pointer_type && tag != DW_TAG_array_type)
+		if (tag != DW_TAG_pointer_type && tag != DW_TAG_array_type) {
+			if (dloc->op->offset < 0 && reg != state->stack_reg)
+				goto check_kernel;
+
+			pr_debug_dtp("\n");
 			return -1;
+		}
+
+		pr_debug_dtp("\n");
 
 		/* Remove the pointer and get the target type */
 		if (die_get_real_type(&state->regs[reg].type, type_die) == NULL)
@@ -1376,12 +1381,14 @@ static int check_matching_type(struct type_state *state,
 		return -1;
 	}
 
-	if (map__dso(dloc->ms->map)->kernel && arch__is(dloc->arch, "x86")) {
+check_kernel:
+	if (map__dso(dloc->ms->map)->kernel) {
 		u64 addr;
 		int offset;
 
 		/* Direct this-cpu access like "%gs:0x34740" */
-		if (dloc->op->segment == INSN_SEG_X86_GS && dloc->op->imm) {
+		if (dloc->op->segment == INSN_SEG_X86_GS && dloc->op->imm &&
+		    arch__is(dloc->arch, "x86")) {
 			pr_debug_dtp(" this-cpu var\n");
 
 			addr = dloc->op->offset;
@@ -1394,17 +1401,13 @@ static int check_matching_type(struct type_state *state,
 			return -1;
 		}
 
-		/* Access to per-cpu base like "-0x7dcf0500(,%rdx,8)" */
+		/* Access to global variable like "-0x7dcf0500(,%rdx,8)" */
 		if (dloc->op->offset < 0 && reg != state->stack_reg) {
-			const char *var_name = NULL;
-
 			addr = (s64) dloc->op->offset;
 
-			if (get_global_var_info(dloc, addr, &var_name, &offset) &&
-			    !strcmp(var_name, "__per_cpu_offset") && offset == 0 &&
-			    get_global_var_type(cu_die, dloc, dloc->ip, addr,
+			if (get_global_var_type(cu_die, dloc, dloc->ip, addr,
 						&offset, type_die)) {
-				pr_debug_dtp(" percpu base\n");
+				pr_debug_dtp(" global var\n");
 
 				dloc->type_offset = offset;
 				return 1;
-- 
2.45.0.rc1.225.g2a3ae87e7f-goog