Commit eba1f853 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
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perf annotate-data: Check memory access with two registers 



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 'runqueues' of type '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: 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: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240502060011.1838090-5-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 4449c904

tools/perf/util/annotate-data.c

+39 −5
Original line number Diff line number Diff line
@@ -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;



				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;