perf symbols: Accept symbols starting at address 0
That is the case of _text on s390, and we have some functions that return an
address, using address zero to report problems, oops.
This would lead the symbol loading routines to not use "_text" as the reference
relocation symbol, or the first symbol for the kernel, but use instead
"_stext", that is at the same address on x86_64 and others, but not on s390:
[acme@localhost perf-4.11.0-rc6]$ head -15 /proc/kallsyms
0000000000000000 T _text
0000000000000418 t iplstart
0000000000000800 T start
000000000000080a t .base
000000000000082e t .sk8x8
0000000000000834 t .gotr
0000000000000842 t .cmd
0000000000000846 t .parm
000000000000084a t .lowcase
0000000000010000 T startup
0000000000010010 T startup_kdump
0000000000010214 t startup_kdump_relocated
0000000000011000 T startup_continue
00000000000112a0 T _ehead
0000000000100000 T _stext
[acme@localhost perf-4.11.0-rc6]$
Which in turn would make 'perf test vmlinux' to fail because it wouldn't find
the symbols before "_stext" in kallsyms.
Fix it by using the return value only for errors and storing the
address, when the symbol is successfully found, in a provided pointer
arg.
Before this patch:
After:
[acme@localhost perf-4.11.0-rc6]$ tools/perf/perf test -v 1
1: vmlinux symtab matches kallsyms :
--- start ---
test child forked, pid 40693
Looking at the vmlinux_path (8 entries long)
Using /usr/lib/debug/lib/modules/3.10.0-654.el7.s390x/vmlinux for symbols
ERR : 0: _text not on kallsyms
ERR : 0x418: iplstart not on kallsyms
ERR : 0x800: start not on kallsyms
ERR : 0x80a: .base not on kallsyms
ERR : 0x82e: .sk8x8 not on kallsyms
ERR : 0x834: .gotr not on kallsyms
ERR : 0x842: .cmd not on kallsyms
ERR : 0x846: .parm not on kallsyms
ERR : 0x84a: .lowcase not on kallsyms
ERR : 0x10000: startup not on kallsyms
ERR : 0x10010: startup_kdump not on kallsyms
ERR : 0x10214: startup_kdump_relocated not on kallsyms
ERR : 0x11000: startup_continue not on kallsyms
ERR : 0x112a0: _ehead not on kallsyms
<SNIP warnings>
test child finished with -1
---- end ----
vmlinux symtab matches kallsyms: FAILED!
[acme@localhost perf-4.11.0-rc6]$
After:
[acme@localhost perf-4.11.0-rc6]$ tools/perf/perf test -v 1
1: vmlinux symtab matches kallsyms :
--- start ---
test child forked, pid 47160
<SNIP warnings>
test child finished with 0
---- end ----
vmlinux symtab matches kallsyms: Ok
[acme@localhost perf-4.11.0-rc6]$
Reported-by: Michael Petlan <mpetlan@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-9x9bwgd3btwdk1u51xie93fz@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 7a47f52..d97e014 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -796,11 +796,11 @@ const char *ref_reloc_sym_names[] = {"_text", "_stext", NULL};
* Returns the name of the start symbol in *symbol_name. Pass in NULL as
* symbol_name if it's not that important.
*/
-static u64 machine__get_running_kernel_start(struct machine *machine,
- const char **symbol_name)
+static int machine__get_running_kernel_start(struct machine *machine,
+ const char **symbol_name, u64 *start)
{
char filename[PATH_MAX];
- int i;
+ int i, err = -1;
const char *name;
u64 addr = 0;
@@ -810,21 +810,28 @@ static u64 machine__get_running_kernel_start(struct machine *machine,
return 0;
for (i = 0; (name = ref_reloc_sym_names[i]) != NULL; i++) {
- addr = kallsyms__get_function_start(filename, name);
- if (addr)
+ err = kallsyms__get_function_start(filename, name, &addr);
+ if (!err)
break;
}
+ if (err)
+ return -1;
+
if (symbol_name)
*symbol_name = name;
- return addr;
+ *start = addr;
+ return 0;
}
int __machine__create_kernel_maps(struct machine *machine, struct dso *kernel)
{
int type;
- u64 start = machine__get_running_kernel_start(machine, NULL);
+ u64 start = 0;
+
+ if (machine__get_running_kernel_start(machine, NULL, &start))
+ return -1;
/* In case of renewal the kernel map, destroy previous one */
machine__destroy_kernel_maps(machine);
@@ -1185,8 +1192,8 @@ static int machine__create_modules(struct machine *machine)
int machine__create_kernel_maps(struct machine *machine)
{
struct dso *kernel = machine__get_kernel(machine);
- const char *name;
- u64 addr;
+ const char *name = NULL;
+ u64 addr = 0;
int ret;
if (kernel == NULL)
@@ -1211,8 +1218,7 @@ int machine__create_kernel_maps(struct machine *machine)
*/
map_groups__fixup_end(&machine->kmaps);
- addr = machine__get_running_kernel_start(machine, &name);
- if (!addr) {
+ if (machine__get_running_kernel_start(machine, &name, &addr)) {
} else if (maps__set_kallsyms_ref_reloc_sym(machine->vmlinux_maps, name, addr)) {
machine__destroy_kernel_maps(machine);
return -1;