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Subject[PATCH -tip 5/6] perf probe: Support DW_OP_plus_uconst in DW_AT_data_member_location
Date
DW_OP_plus_uconst can be used for DW_AT_data_member_location.
This patch adds DW_OP_plus_uconst support when getting
structure member offset.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
---
tools/perf/util/probe-finder.c | 37 ++++++++++++++++++++++++++++++++-----
1 files changed, 32 insertions(+), 5 deletions(-)
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index b4c9365..4f83121 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -249,6 +249,33 @@ static int die_get_byte_size(Dwarf_Die *tp_die)
return (int)ret;
}

+/* Get data_member_location offset */
+static int die_get_data_member_location(Dwarf_Die *mb_die, Dwarf_Word *offs)
+{
+ Dwarf_Attribute attr;
+ Dwarf_Op *expr;
+ size_t nexpr;
+ int ret;
+
+ if (dwarf_attr(mb_die, DW_AT_data_member_location, &attr) == NULL)
+ return -ENOENT;
+
+ if (dwarf_formudata(&attr, offs) != 0) {
+ /* DW_AT_data_member_location should be DW_OP_plus_uconst */
+ ret = dwarf_getlocation(&attr, &expr, &nexpr);
+ if (ret < 0 || nexpr == 0)
+ return -ENOENT;
+
+ if (expr[0].atom != DW_OP_plus_uconst || nexpr != 1) {
+ pr_debug("Unable to get offset:Unexpected OP %x (%d)\n",
+ expr[0].atom, nexpr);
+ return -ENOTSUP;
+ }
+ *offs = (Dwarf_Word)expr[0].number;
+ }
+ return 0;
+}
+
/* Return values for die_find callbacks */
enum {
DIE_FIND_CB_FOUND = 0, /* End of Search */
@@ -482,9 +509,9 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
Dwarf_Die *die_mem)
{
struct kprobe_trace_arg_ref *ref = *ref_ptr;
- Dwarf_Attribute attr;
Dwarf_Die type;
Dwarf_Word offs;
+ int ret;

pr_debug("converting %s in %s\n", field->name, varname);
if (die_get_real_type(vr_die, &type) == NULL) {
@@ -542,17 +569,17 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
}

/* Get the offset of the field */
- if (dwarf_attr(die_mem, DW_AT_data_member_location, &attr) == NULL ||
- dwarf_formudata(&attr, &offs) != 0) {
+ ret = die_get_data_member_location(die_mem, &offs);
+ if (ret < 0) {
pr_warning("Failed to get the offset of %s.\n", field->name);
- return -ENOENT;
+ return ret;
}
ref->offset += (long)offs;

/* Converting next field */
if (field->next)
return convert_variable_fields(die_mem, field->name,
- field->next, &ref, die_mem);
+ field->next, &ref, die_mem);
else
return 0;
}

--
Masami Hiramatsu
e-mail: mhiramat@redhat.com


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