[PATCH 4/6] perf annotate-data: Check memory access with two registers

From: Namhyung Kim
Date: Thu May 02 2024 - 02:00:48 EST


The following instruction pattern is used to access a global variable.

mov $0x231c0, %rax
movsql %edi, %rcx
mov -0x7dc94ae0(,%rcx,8), %rcx
cmpl $0x0, 0xa60(%rcx,%rax,1) <<<--- here

The first instruction set the address of the per-cpu variable (here, it
is 'runqueus' of struct rq). The second instruction seems like a cpu
number of the per-cpu base. The third instruction get the base offset
of per-cpu area for that cpu. The last instruction compares the value
of the per-cpu variable at the offset of 0xa60.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
tools/perf/util/annotate-data.c | 44 +++++++++++++++++++++++++++++----
1 file changed, 39 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index f1e52a531563..245e3ef3e2ff 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -1031,22 +1031,37 @@ static void update_insn_state_x86(struct type_state *state,
else if (has_reg_type(state, sreg) &&
state->regs[sreg].kind == TSR_KIND_PERCPU_BASE) {
u64 ip = dloc->ms->sym->start + dl->al.offset;
+ u64 var_addr = src->offset;
int offset;

+ if (src->multi_regs) {
+ int reg2 = (sreg == src->reg1) ? src->reg2 : src->reg1;
+
+ if (has_reg_type(state, reg2) && state->regs[reg2].ok &&
+ state->regs[reg2].kind == TSR_KIND_CONST)
+ var_addr += state->regs[reg2].imm_value;
+ }
+
/*
* In kernel, %gs points to a per-cpu region for the
* current CPU. Access with a constant offset should
* be treated as a global variable access.
*/
- if (get_global_var_type(cu_die, dloc, ip, src->offset,
+ if (get_global_var_type(cu_die, dloc, ip, var_addr,
&offset, &type_die) &&
die_get_member_type(&type_die, offset, &type_die)) {
tsr->type = type_die;
tsr->kind = TSR_KIND_TYPE;
tsr->ok = true;

- pr_debug_dtp("mov [%x] percpu %#x(reg%d) -> reg%d",
- insn_offset, src->offset, sreg, dst->reg1);
+ if (src->multi_regs) {
+ pr_debug_dtp("mov [%x] percpu %#x(reg%d,reg%d) -> reg%d",
+ insn_offset, src->offset, src->reg1,
+ src->reg2, dst->reg1);
+ } else {
+ pr_debug_dtp("mov [%x] percpu %#x(reg%d) -> reg%d",
+ insn_offset, src->offset, sreg, dst->reg1);
+ }
pr_debug_type_name(&tsr->type, tsr->kind);
} else {
tsr->ok = false;
@@ -1340,6 +1355,17 @@ static int check_matching_type(struct type_state *state,

pr_debug_dtp(" percpu var\n");

+ if (dloc->op->multi_regs) {
+ int reg2 = dloc->op->reg2;
+
+ if (dloc->op->reg2 == reg)
+ reg2 = dloc->op->reg1;
+
+ if (has_reg_type(state, reg2) && state->regs[reg2].ok &&
+ state->regs[reg2].kind == TSR_KIND_CONST)
+ var_addr += state->regs[reg2].imm_value;
+ }
+
if (get_global_var_type(cu_die, dloc, dloc->ip, var_addr,
&var_offset, type_die)) {
dloc->type_offset = var_offset;
@@ -1527,8 +1553,16 @@ static int find_data_type_block(struct data_loc_info *dloc, int reg,
found = find_data_type_insn(dloc, reg, &basic_blocks, var_types,
cu_die, type_die);
if (found > 0) {
- pr_debug_dtp("found by insn track: %#x(reg%d) type-offset=%#x\n",
- dloc->op->offset, reg, dloc->type_offset);
+ char buf[64];
+
+ if (dloc->op->multi_regs)
+ snprintf(buf, sizeof(buf), "reg%d, reg%d",
+ dloc->op->reg1, dloc->op->reg2);
+ else
+ snprintf(buf, sizeof(buf), "reg%d", dloc->op->reg1);
+
+ pr_debug_dtp("found by insn track: %#x(%s) type-offset=%#x\n",
+ dloc->op->offset, buf, dloc->type_offset);
pr_debug_type_name(type_die, TSR_KIND_TYPE);
ret = 0;
break;
--
2.45.0.rc1.225.g2a3ae87e7f-goog