perf probe: Support DW_OP_call_frame_cfa in debuginfo

When building kernel without CONFIG_FRAME_POINTER, gcc uses
CFA (canonical frame address) for frame base. With this patch,
perf probe just gets CFI (call frame information) from debuginfo
and search corresponding CFA from the CFI. IOW, this allows
perf probe works correctly on the kernel without CONFIG_FRAME_POINTER.

<Before>
 ./perf probe -fn sched_slice:12 lw.weight
  Fatal: DW_OP 156 is not supported.
              (^^^ DW_OP_call_frame_cfa)

<After>
./perf probe -fn sched_slice:12 lw.weight
Add new event:
  probe:sched_slice    (on sched_slice:12 with weight=lw.weight)

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100412171728.3790.98217.stgit@localhost6.localdomain6>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 12 insertions, 3 deletions

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index ab476736cbe7..1f4528555d42 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -398,7 +398,6 @@ static void convert_location(Dwarf_Op *op, struct probe_finder *pf)
         const char *regs;
         struct kprobe_trace_arg *tvar = pf->tvar;
 
-        /* TODO: support CFA */
         /* If this is based on frame buffer, set the offset */
         if (op->atom == DW_OP_fbreg) {
                 if (pf->fb_ops == NULL)
@@ -629,11 +628,17 @@ static void convert_probe_point(Dwarf_Die *sp_die, struct probe_finder *pf)
         /* Get the frame base attribute/ops */
         dwarf_attr(sp_die, DW_AT_frame_base, &fb_attr);
         ret = dwarf_getlocation_addr(&fb_attr, pf->addr, &pf->fb_ops, &nops, 1);
-        if (ret <= 0 || nops == 0)
+        if (ret <= 0 || nops == 0) {
                 pf->fb_ops = NULL;
+        } else if (nops == 1 && pf->fb_ops[0].atom == DW_OP_call_frame_cfa &&
+                   pf->cfi != NULL) {
+                Dwarf_Frame *frame;
+                ret = dwarf_cfi_addrframe(pf->cfi, pf->addr, &frame);
+                DIE_IF(ret != 0);
+                dwarf_frame_cfa(frame, &pf->fb_ops, &nops);
+        }
 
         /* Find each argument */
-        /* TODO: use dwarf_cfi_addrframe */
         tev->nargs = pf->pev->nargs;
         tev->args = xzalloc(sizeof(struct kprobe_trace_arg) * tev->nargs);
         for (i = 0; i < pf->pev->nargs; i++) {
@@ -842,6 +847,9 @@ int find_kprobe_trace_events(int fd, struct perf_probe_event *pev,
         if (!dbg)
                 return -ENOENT;
 
+        /* Get the call frame information from this dwarf */
+        pf.cfi = dwarf_getcfi(dbg);
+
         off = 0;
         line_list__init(&pf.lcache);
         /* Loop on CUs (Compilation Unit) */
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index 2a271321944f..310ce897229c 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -42,6 +42,7 @@ struct probe_finder {
         struct list_head        lcache;         /* Line cache for lazy match */
 
         /* For variable searching */
+        Dwarf_CFI               *cfi;           /* Call Frame Information */
         Dwarf_Op                *fb_ops;        /* Frame base attribute */
         struct perf_probe_arg   *pvar;          /* Current target variable */
         struct kprobe_trace_arg *tvar;          /* Current result variable */