[tip:perf/urgent] perf symbols: Accept symbols starting at address 0

From: tip-bot for Arnaldo Carvalho de Melo
Date: Wed May 03 2017 - 13:40:17 EST

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Commit-ID: b843f62ad942f3879c2d7acd27b44f931c609685
Gitweb: http://git.kernel.org/tip/b843f62ad942f3879c2d7acd27b44f931c609685
Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Thu, 27 Apr 2017 21:21:09 -0300
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 2 May 2017 18:23:04 -0300

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@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-9x9bwgd3btwdk1u51xie93fz@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/builtin-buildid-cache.c | 13 ++++++++-----
tools/perf/util/event.c | 9 +++++----
tools/perf/util/event.h | 4 ++--
tools/perf/util/machine.c | 28 +++++++++++++++++-----------
tools/perf/util/symbol.c | 11 +++++------
5 files changed, 37 insertions(+), 28 deletions(-)

diff --git a/tools/perf/builtin-buildid-cache.c b/tools/perf/builtin-buildid-cache.c
index 64b44e8..9eba7f1 100644
--- a/tools/perf/builtin-buildid-cache.c
+++ b/tools/perf/builtin-buildid-cache.c
@@ -49,19 +49,22 @@ static bool same_kallsyms_reloc(const char *from_dir, char *to_dir)
char to[PATH_MAX];
const char *name;
u64 addr1 = 0, addr2 = 0;
- int i;
+ int i, err = -1;

scnprintf(from, sizeof(from), "%s/kallsyms", from_dir);
scnprintf(to, sizeof(to), "%s/kallsyms", to_dir);

for (i = 0; (name = ref_reloc_sym_names[i]) != NULL; i++) {
- addr1 = kallsyms__get_function_start(from, name);
- if (addr1)
+ err = kallsyms__get_function_start(from, name, &addr1);
+ if (!err)
break;
}

- if (name)
- addr2 = kallsyms__get_function_start(to, name);
+ if (err)
+ return false;
+
+ if (kallsyms__get_function_start(to, name, &addr2))
+ return false;

return addr1 == addr2;
}
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 437194f..dc5c3bb 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -768,15 +768,16 @@ static int find_symbol_cb(void *arg, const char *name, char type,
return 1;
}

-u64 kallsyms__get_function_start(const char *kallsyms_filename,
- const char *symbol_name)
+int kallsyms__get_function_start(const char *kallsyms_filename,
+ const char *symbol_name, u64 *addr)
{
struct process_symbol_args args = { .name = symbol_name, };

if (kallsyms__parse(kallsyms_filename, &args, find_symbol_cb) <= 0)
- return 0;
+ return -1;

- return args.start;
+ *addr = args.start;
+ return 0;
}

int perf_event__synthesize_kernel_mmap(struct perf_tool *tool,
diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index cfbe32b..27ac047 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -675,8 +675,8 @@ size_t perf_event__fprintf_cpu_map(union perf_event *event, FILE *fp);
size_t perf_event__fprintf_namespaces(union perf_event *event, FILE *fp);
size_t perf_event__fprintf(union perf_event *event, FILE *fp);

-u64 kallsyms__get_function_start(const char *kallsyms_filename,
- const char *symbol_name);
+int kallsyms__get_function_start(const char *kallsyms_filename,
+ const char *symbol_name, u64 *addr);

void *cpu_map_data__alloc(struct cpu_map *map, size_t *size, u16 *type, int *max);
void cpu_map_data__synthesize(struct cpu_map_data *data, struct cpu_map *map,
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;
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 2cb7665..b349e8e 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -466,7 +466,7 @@ void dso__insert_symbol(struct dso *dso, enum map_type type, struct symbol *sym)
struct symbol *dso__find_symbol(struct dso *dso,
enum map_type type, u64 addr)
{
- if (dso->last_find_result[type].addr != addr) {
+ if (dso->last_find_result[type].addr != addr || dso->last_find_result[type].symbol == NULL) {
dso->last_find_result[type].addr = addr;
dso->last_find_result[type].symbol = symbols__find(&dso->symbols[type], addr);
}
@@ -1075,8 +1075,9 @@ static int validate_kcore_addresses(const char *kallsyms_filename,
if (kmap->ref_reloc_sym && kmap->ref_reloc_sym->name) {
u64 start;

- start = kallsyms__get_function_start(kallsyms_filename,
- kmap->ref_reloc_sym->name);
+ if (kallsyms__get_function_start(kallsyms_filename,
+ kmap->ref_reloc_sym->name, &start))
+ return -ENOENT;
if (start != kmap->ref_reloc_sym->addr)
return -EINVAL;
}
@@ -1248,9 +1249,7 @@ static int kallsyms__delta(struct map *map, const char *filename, u64 *delta)
if (!kmap->ref_reloc_sym || !kmap->ref_reloc_sym->name)
return 0;

- addr = kallsyms__get_function_start(filename,
- kmap->ref_reloc_sym->name);
- if (!addr)
+ if (kallsyms__get_function_start(filename, kmap->ref_reloc_sym->name, &addr))
return -1;

*delta = addr - kmap->ref_reloc_sym->addr;

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Previous message: tip-bot for Arnaldo Carvalho de Melo: "[tip:perf/urgent] tools lib string: Adopt prefixcmp() from perf and subcmd"
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