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Message-ID: <20240816235840.2754937-9-namhyung@kernel.org>
Date: Fri, 16 Aug 2024 16:58:38 -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,
Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
Subject: [PATCH 8/9] 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: Namhyung Kim <namhyung@...nel.org>
---
tools/perf/util/annotate-data.c | 44 ++++++++++++++++++++-------------
1 file changed, 27 insertions(+), 17 deletions(-)
diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index 916d26bfb9eb..e86f40fed323 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -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);
+ 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++;
}
--
2.46.0.184.g6999bdac58-goog
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