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Date: Tue, 10 Jul 2018 19:28:13 +0530
From: Sandipan Das <sandipan@...ux.ibm.com>
To: acme@...nel.org
Cc: linux-kernel@...r.kernel.org, jolsa@...hat.com,
ravi.bangoria@...ux.vnet.ibm.com, naveen.n.rao@...ux.vnet.ibm.com,
sukadev@...ux.vnet.ibm.com, maynard@...ibm.com
Subject: [PATCH 1/5] perf powerpc: Fix callchain ip filtering
For powerpc64, redundant entries in the callchain are filtered out by
determining the state of the return address and the stack frame using
DWARF debug information. For making these filtering decisions we must
analyze the debug information for the location corresponding to the
program counter value, i.e. the first entry in the callchain, and not
the LR value; otherwise, perf may filter out either the second or the
third entry in the callchain incorrectly.
This can be observed on a powerpc64le system running Fedora 27 as shown
below.
Case 1 - Attaching a probe at inet_pton+0x8 (binary offset 0x15af28).
Return address is still in LR and a new stack frame is not yet
allocated. The LR value, i.e. the second entry, should not be
filtered out.
# objdump -d /usr/lib64/libc-2.26.so | less
...
000000000010eb10 <gaih_inet.constprop.7>:
...
10fa48: 78 bb e4 7e mr r4,r23
10fa4c: 0a 00 60 38 li r3,10
10fa50: d9 b4 04 48 bl 15af28 <inet_pton+0x8>
10fa54: 00 00 00 60 nop
10fa58: ac f4 ff 4b b 10ef04 <gaih_inet.constprop.7+0x3f4>
...
0000000000110450 <getaddrinfo>:
...
1105a8: 54 00 ff 38 addi r7,r31,84
1105ac: 58 00 df 38 addi r6,r31,88
1105b0: 69 e5 ff 4b bl 10eb18 <gaih_inet.constprop.7+0x8>
1105b4: 78 1b 71 7c mr r17,r3
1105b8: 50 01 7f e8 ld r3,336(r31)
...
000000000015af20 <inet_pton>:
15af20: 0b 00 4c 3c addis r2,r12,11
15af24: e0 c1 42 38 addi r2,r2,-15904
15af28: a6 02 08 7c mflr r0
15af2c: f0 ff c1 fb std r30,-16(r1)
15af30: f8 ff e1 fb std r31,-8(r1)
...
# perf probe -x /usr/lib64/libc-2.26.so -a inet_pton+0x8
# perf record -e probe_libc:inet_pton -g ping -6 -c 1 ::1
# perf script
Before:
ping 4507 [002] 514985.546540: probe_libc:inet_pton: (7fffa7dbaf28)
7fffa7dbaf28 __GI___inet_pton+0x8 (/usr/lib64/libc-2.26.so)
7fffa7d705b4 getaddrinfo+0x164 (/usr/lib64/libc-2.26.so)
13fb52d70 _init+0xbfc (/usr/bin/ping)
7fffa7c836a0 generic_start_main.isra.0+0x140 (/usr/lib64/libc-2.26.so)
7fffa7c83898 __libc_start_main+0xb8 (/usr/lib64/libc-2.26.so)
0 [unknown] ([unknown])
After:
ping 4507 [002] 514985.546540: probe_libc:inet_pton: (7fffa7dbaf28)
7fffa7dbaf28 __GI___inet_pton+0x8 (/usr/lib64/libc-2.26.so)
7fffa7d6fa54 gaih_inet.constprop.7+0xf44 (/usr/lib64/libc-2.26.so)
7fffa7d705b4 getaddrinfo+0x164 (/usr/lib64/libc-2.26.so)
13fb52d70 _init+0xbfc (/usr/bin/ping)
7fffa7c836a0 generic_start_main.isra.0+0x140 (/usr/lib64/libc-2.26.so)
7fffa7c83898 __libc_start_main+0xb8 (/usr/lib64/libc-2.26.so)
0 [unknown] ([unknown])
Case 2 - Attaching a probe at _int_malloc+0x180 (binary offset 0x9cf10).
Return address in still in LR and a new stack frame has already
been allocated but not used. The caller's caller, i.e. the third
entry, is invalid and should be filtered out and not the second
one.
# objdump -d /usr/lib64/libc-2.26.so | less
...
000000000009cd90 <_int_malloc>:
9cd90: 17 00 4c 3c addis r2,r12,23
9cd94: 70 a3 42 38 addi r2,r2,-23696
9cd98: 26 00 80 7d mfcr r12
9cd9c: f8 ff e1 fb std r31,-8(r1)
9cda0: 17 00 e4 3b addi r31,r4,23
9cda4: d8 ff 61 fb std r27,-40(r1)
9cda8: 78 23 9b 7c mr r27,r4
9cdac: 1f 00 bf 2b cmpldi cr7,r31,31
9cdb0: f0 ff c1 fb std r30,-16(r1)
9cdb4: b0 ff c1 fa std r22,-80(r1)
9cdb8: 78 1b 7e 7c mr r30,r3
9cdbc: 08 00 81 91 stw r12,8(r1)
9cdc0: 11 ff 21 f8 stdu r1,-240(r1)
9cdc4: 4c 01 9d 41 bgt cr7,9cf10 <_int_malloc+0x180>
9cdc8: 20 00 a4 2b cmpldi cr7,r4,32
...
9cf08: 00 00 00 60 nop
9cf0c: 00 00 42 60 ori r2,r2,0
9cf10: e4 06 ff 7b rldicr r31,r31,0,59
9cf14: 40 f8 a4 7f cmpld cr7,r4,r31
9cf18: 68 05 9d 41 bgt cr7,9d480 <_int_malloc+0x6f0>
...
000000000009e3c0 <tcache_init.part.4>:
...
9e420: 40 02 80 38 li r4,576
9e424: 78 fb e3 7f mr r3,r31
9e428: 71 e9 ff 4b bl 9cd98 <_int_malloc+0x8>
9e42c: 00 00 a3 2f cmpdi cr7,r3,0
9e430: 78 1b 7e 7c mr r30,r3
...
000000000009f7a0 <__libc_malloc>:
...
9f8f8: 00 00 89 2f cmpwi cr7,r9,0
9f8fc: 1c ff 9e 40 bne cr7,9f818 <__libc_malloc+0x78>
9f900: c9 ea ff 4b bl 9e3c8 <tcache_init.part.4+0x8>
9f904: 00 00 00 60 nop
9f908: e8 90 22 e9 ld r9,-28440(r2)
...
# perf probe -x /usr/lib64/libc-2.26.so -a _int_malloc+0x180
# perf record -e probe_libc:_int_malloc -g ./test-malloc
# perf script
Before:
test-malloc 6554 [009] 515975.797403: probe_libc:_int_malloc: (7fffa6e6cf10)
7fffa6e6cf10 _int_malloc+0x180 (/usr/lib64/libc-2.26.so)
7fffa6dd0000 [unknown] (/usr/lib64/libc-2.26.so)
7fffa6e6f904 malloc+0x164 (/usr/lib64/libc-2.26.so)
7fffa6e6f9fc malloc+0x25c (/usr/lib64/libc-2.26.so)
100006b4 main+0x38 (/home/testuser/test-malloc)
7fffa6df36a0 generic_start_main.isra.0+0x140 (/usr/lib64/libc-2.26.so)
7fffa6df3898 __libc_start_main+0xb8 (/usr/lib64/libc-2.26.so)
0 [unknown] ([unknown])
After:
test-malloc 6554 [009] 515975.797403: probe_libc:_int_malloc: (7fffa6e6cf10)
7fffa6e6cf10 _int_malloc+0x180 (/usr/lib64/libc-2.26.so)
7fffa6e6e42c tcache_init.part.4+0x6c (/usr/lib64/libc-2.26.so)
7fffa6e6f904 malloc+0x164 (/usr/lib64/libc-2.26.so)
7fffa6e6f9fc malloc+0x25c (/usr/lib64/libc-2.26.so)
100006b4 main+0x38 (/home/sandipan/test-malloc)
7fffa6df36a0 generic_start_main.isra.0+0x140 (/usr/lib64/libc-2.26.so)
7fffa6df3898 __libc_start_main+0xb8 (/usr/lib64/libc-2.26.so)
0 [unknown] ([unknown])
Fixes: a60335ba3298 ("perf tools powerpc: Adjust callchain based on DWARF debug info")
Signed-off-by: Sandipan Das <sandipan@...ux.ibm.com>
---
tools/perf/arch/powerpc/util/skip-callchain-idx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/arch/powerpc/util/skip-callchain-idx.c b/tools/perf/arch/powerpc/util/skip-callchain-idx.c
index ef5d59a5742e..264fc0158100 100644
--- a/tools/perf/arch/powerpc/util/skip-callchain-idx.c
+++ b/tools/perf/arch/powerpc/util/skip-callchain-idx.c
@@ -246,7 +246,7 @@ int arch_skip_callchain_idx(struct thread *thread, struct ip_callchain *chain)
if (!chain || chain->nr < 3)
return skip_slot;
- ip = chain->ips[2];
+ ip = chain->ips[1];
thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
--
2.14.4
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