perf tools: Handle relocatable kernels
DSOs don't have this problem because the kernel emits a
PERF_MMAP for each new executable mapping it performs on
monitored threads.
To fix the kernel case we simulate the same behaviour, by having
'perf record' to synthesize a PERF_MMAP for the kernel, encoded
like this:
[root@doppio ~]# perf record -a -f sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.344 MB perf.data (~15038 samples) ]
[root@doppio ~]# perf report -D | head -10
0xd0 [0x40]: event: 1
.
. ... raw event: size 64 bytes
. 0000: 01 00 00 00 00 00 40 00 00 00 00 00 00 00 00 00 ......@........
. 0010: 00 00 00 81 ff ff ff ff 00 00 00 00 00 00 00 00 ...............
. 0020: 00 00 00 00 00 00 00 00 5b 6b 65 72 6e 65 6c 2e ........ [kernel
. 0030: 6b 61 6c 6c 73 79 6d 73 2e 5f 74 65 78 74 5d 00 kallsyms._text]
. 0xd0
[0x40]: PERF_RECORD_MMAP 0/0: [0xffffffff81000000((nil)) @ (nil)]: [kernel.kallsyms._text]
I.e. we identify such event as having:
.pid = 0
.filename = [kernel.kallsyms.REFNAME]
.start = REFNAME addr in /proc/kallsyms at 'perf record' time
and use now a hardcoded value of '.text' for REFNAME.
Then, later, in 'perf report', if there are any kernel hits and
thus we need to resolve kernel symbols, we search for REFNAME
and if its address changed, relocation happened and we thus must
change the kernel mapping routines to one that uses .pgoff as
the relocation to apply.
This way we use the same mechanism used for the other DSOs and
don't have to do a two pass in all the kernel symbols.
Reported-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
LKML-Reference: <1262717431-1246-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 7f0537d..e0e6a07 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -401,3 +401,49 @@
return true;
}
+
+int perf_session__set_kallsyms_ref_reloc_sym(struct perf_session *self,
+ const char *symbol_name,
+ u64 addr)
+{
+ char *bracket;
+
+ self->ref_reloc_sym.name = strdup(symbol_name);
+ if (self->ref_reloc_sym.name == NULL)
+ return -ENOMEM;
+
+ bracket = strchr(self->ref_reloc_sym.name, ']');
+ if (bracket)
+ *bracket = '\0';
+
+ self->ref_reloc_sym.addr = addr;
+ return 0;
+}
+
+static u64 map__reloc_map_ip(struct map *map, u64 ip)
+{
+ return ip + (s64)map->pgoff;
+}
+
+static u64 map__reloc_unmap_ip(struct map *map, u64 ip)
+{
+ return ip - (s64)map->pgoff;
+}
+
+void perf_session__reloc_vmlinux_maps(struct perf_session *self,
+ u64 unrelocated_addr)
+{
+ enum map_type type;
+ s64 reloc = unrelocated_addr - self->ref_reloc_sym.addr;
+
+ if (!reloc)
+ return;
+
+ for (type = 0; type < MAP__NR_TYPES; ++type) {
+ struct map *map = self->vmlinux_maps[type];
+
+ map->map_ip = map__reloc_map_ip;
+ map->unmap_ip = map__reloc_unmap_ip;
+ map->pgoff = reloc;
+ }
+}