Commit ba883370 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
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perf annotate-data: Check variables in every scope 



Sometimes it matches a variable in the inner scope but it fails because
the actual access can be on a different type.  Let's try variables in
every scope and choose the best one using is_better_type().

I have an example with update_blocked_averages(), at first it found a
variable (__mptr) but it's a void pointer.  So it moved on to the upper
scope and found another variable (cfs_rq).

  $ perf --debug type-profile annotate --data-type --stdio
  ...
  -----------------------------------------------------------
  find data type for 0x140(reg14) at update_blocked_averages+0x2db
  CU for kernel/sched/fair.c (die:0x12dd892)
  frame base: cfa=1 fbreg=7
  found "__mptr" (die: 0x13022f1) in scope=4/4 (die: 0x13022e8) failed: no/void pointer
   variable location: base=reg14, offset=0x140
   type='void*' size=0x8 (die:0x12dd8f9)
  found "cfs_rq" (die: 0x1301721) in scope=3/4 (die: 0x130171c) type_offset=0x140
   variable location: reg14
   type='struct cfs_rq' size=0x1c0 (die:0x12e37e5)
  final type: type='struct cfs_rq' size=0x1c0 (die:0x12e37e5)

IIUC the scope is like below:
  1: update_blocked_averages
  2:   __update_blocked_fair
  3:     for_each_leaf_cfs_rq_safe
  4:       list_entry -> (container_of)

The container_of is implemented like:

  #define container_of(ptr, type, member) ({				\
  	void *__mptr = (void *)(ptr);					\
  	static_assert(__same_type(*(ptr), ((type *)0)->member) ||	\
  		      __same_type(*(ptr), void),			\
  		      "pointer type mismatch in container_of()");	\
  	((type *)(__mptr - offsetof(type, member))); })

That's why we see the __mptr variable first but it failed since it has
no type information.

Then for_each_leaf_cfs_rq_safe() is defined as

  #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)			\
  	list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list,	\
  				 leaf_cfs_rq_list)

Note that the access was 0x140(r14).  And the cfs_rq has
leaf_cfs_rq_list at the 0x140.  So it converts the list_head pointer to
a pointer to struct cfs_rq here.

  $ pahole --hex -C cfs_rq vmlinux | grep 140
  struct cfs_rq 	struct list_head           leaf_cfs_rq_list;     /* 0x140  0x10 */

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.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/20240816235840.2754937-9-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent c663451f

tools/perf/util/annotate-data.c

+27 −17
Original line number Diff line number Diff line
@@ -1244,7 +1244,6 @@ static enum type_match_result find_data_type_block(struct data_loc_info *dloc, 


			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);

			break;

		}
@@ -1273,6 +1272,7 @@ static int find_data_type_die(struct data_loc_info *dloc, Dwarf_Die *type_die) 
	int fbreg = -1;

	int fb_offset = 0;

	bool is_fbreg = false;

	bool found = false;

	u64 pc;

	char buf[64];

	enum type_match_result result;
@@ -1358,14 +1358,17 @@ static int find_data_type_die(struct data_loc_info *dloc, Dwarf_Die *type_die) 


	/* Search from the inner-most scope to the outer */

	for (i = nr_scopes - 1; i >= 0; i--) {

		Dwarf_Die mem_die;

		int type_offset = offset;



		if (reg == DWARF_REG_PC) {

			if (!die_find_variable_by_addr(&scopes[i], dloc->var_addr,

						       &var_die, &offset))

						       &var_die, &type_offset))

				continue;

		} else {

			/* Look up variables/parameters in this scope */

			if (!die_find_variable_by_reg(&scopes[i], pc, reg,

						      &offset, is_fbreg, &var_die))

						      &type_offset, is_fbreg, &var_die))

				continue;

		}
@@ -1374,43 +1377,50 @@ static int find_data_type_die(struct data_loc_info *dloc, Dwarf_Die *type_die) 
			     i+1, nr_scopes, (long)dwarf_dieoffset(&scopes[i]));



		/* Found a variable, see if it's correct */

		result = check_variable(dloc, &var_die, type_die, reg, offset, is_fbreg);

		result = check_variable(dloc, &var_die, &mem_die, reg, type_offset, is_fbreg);

		if (result == PERF_TMR_OK) {

			if (reg == DWARF_REG_PC) {

				pr_debug_dtp("addr=%#"PRIx64" type_offset=%#x\n",

					     dloc->var_addr, offset);

					     dloc->var_addr, type_offset);

			} else if (reg == DWARF_REG_FB || is_fbreg) {

				pr_debug_dtp("stack_offset=%#x type_offset=%#x\n",

					     fb_offset, offset);

					     fb_offset, type_offset);

			} else {

				pr_debug_dtp("type_offset=%#x\n", offset);

				pr_debug_dtp("type_offset=%#x\n", type_offset);

			}



			if (!found || is_better_type(type_die, &mem_die)) {

				*type_die = mem_die;

				dloc->type_offset = type_offset;

				found = true;

			}

			ret = 0;

		} else {

			pr_debug_dtp("failed: %s\n", match_result_str(result));

			ret = -1;

		}



		pr_debug_location(&var_die, pc, reg);

		pr_debug_type_name(type_die, TSR_KIND_TYPE);

		dloc->type_offset = offset;

		goto out;

		pr_debug_type_name(&mem_die, TSR_KIND_TYPE);

	}



	if (loc->multi_regs && reg == loc->reg1 && loc->reg1 != loc->reg2) {

	if (!found && loc->multi_regs && reg == loc->reg1 && loc->reg1 != loc->reg2) {

		reg = loc->reg2;

		goto retry;

	}



	if (reg != DWARF_REG_PC) {

	if (!found && reg != DWARF_REG_PC) {

		result = find_data_type_block(dloc, &cu_die, scopes,

					      nr_scopes, type_die);

		if (result == PERF_TMR_OK) {

			ann_data_stat.insn_track++;

			ret = 0;

			found = true;

		}

	}



	if (ret < 0) {

	if (found) {

		pr_debug_dtp("final type:");

		pr_debug_type_name(type_die, TSR_KIND_TYPE);

		ret = 0;

	} else {

		pr_debug_dtp("no variable found\n");

		ann_data_stat.no_var++;

	}