On 2/8/21 3:39 PM, James Clark wrote:
On 22/01/2021 18:18, Alexandre Truong wrote:
+}
+
+static int add_entry(struct unwind_entry *entry, void *arg)
+{
+ struct entries *entries = arg;
+
+ entries->stack[entries->i++] = entry->ip;
+ return 0;
+}
+
+u64 get_leaf_frame_caller_aarch64(struct perf_sample *sample, struct thread
*thread)
+{
+ u64 leaf_frame;
+ struct entries entries = {{0, 0}, 0};
+
+ if (get_leaf_frame_caller_enabled(sample))
+ return 0;
+
+ unwind__get_entries(add_entry, &entries, thread, sample, 2);
+ leaf_frame = callchain_param.order == ORDER_CALLER ?
+ entries.stack[0] : entries.stack[1];
+
+ if (leaf_frame + 1 == sample->user_regs.regs[PERF_REG_ARM64_LR])
+ return sample->user_regs.regs[PERF_REG_ARM64_LR];
Hi Alex,
From your other reply about your investigation it looks like the check against
PERF_REG_ARM64_LR isn't
required because libunwind won't return a value if it's not correct. Whether
it's equal to the LR or not.
And PERF_REG_ARM64_LR points to the instruction _after_ the call site. i.e.
where to return to,
not where the call was made from. So just leaf_frame rather than leaf_frame+1
would be more accurate.
I was also looking at unwind_entry in machine.c which is similar to your
add_entry function and saw that it
does some extra bits like this:
if (symbol_conf.hide_unresolved && entry->ms.sym == NULL)
return 0;
if (append_inlines(cursor, &entry->ms, entry->ip) == 0)
return 0;
/*
* Convert entry->ip from a virtual address to an offset in
* its corresponding binary.
*/
if (entry->ms.map)
addr = map__map_ip(entry->ms.map, entry->ip);
I have a feeling you will also need to do those on your values returned from
libunwind to make it 100%
equivalent.
James
Hi James,
Thanks for your reply.
The check against PERF_REG_ARM64_LR is indeed not required and I can
check if libunwind goes successfully.
I am going to follow up with a v2 of the patch applying these changes.
I think the bits you mentioned don't need to be added because this check
is already done in add_callchain_ip() called afterwards in machine.c :
if (symbol_conf.hide_unresolved && entry->ms.sym == NULL)
return 0;
For the second one, I don't think it needs to be added either because
append_inlines() appends ip on the cursor which is also already done by
add_callchain_ip().
For the last one, the conversion from a virtual address to a binary one
isn't required.
Also for the expansion to all platforms, it doesn't work on x86 so I'll
leave it just for arm for now.
Regards,
Alexandre
+ return 0;
+}
diff --git a/tools/perf/util/arm-frame-pointer-unwind-support.h
b/tools/perf/util/arm-frame-pointer-unwind-support.h
new file mode 100644
index 000000000000..16dc03fa9abe
--- /dev/null
+++ b/tools/perf/util/arm-frame-pointer-unwind-support.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H
+#define __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H
+
+u64 get_leaf_frame_caller_aarch64(struct perf_sample *sample, struct thread
*thread);
+
+#endif /* __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H */
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 40082d70eec1..bc6147e46c89 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -34,6 +34,7 @@
#include "bpf-event.h"
#include <internal/lib.h> // page_size
#include "cgroup.h"
+#include "arm-frame-pointer-unwind-support.h"
#include <linux/ctype.h>
#include <symbol/kallsyms.h>
@@ -2671,10 +2672,12 @@ static int find_prev_cpumode(struct ip_callchain
*chain, struct thread *thread,
return err;
}
-static u64 get_leaf_frame_caller(struct perf_sample *sample __maybe_unused,
- struct thread *thread __maybe_unused)
+static u64 get_leaf_frame_caller(struct perf_sample *sample, struct thread
*thread)
{
- return 0;
+ if (strncmp(thread->maps->machine->env->arch, "aarch64", 7) == 0)
+ return get_leaf_frame_caller_aarch64(sample, thread);
+ else
+ return 0;
}
static int thread__resolve_callchain_sample(struct thread *thread,
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