--- /dev/null
+From 9ad4652b66f19a60f07e63b942b80b5c2d7465bf Mon Sep 17 00:00:00 2001
+From: Thomas Richter <tmricht@linux.vnet.ibm.com>
+Date: Thu, 3 Aug 2017 15:49:02 +0200
+Subject: perf record: Fix wrong size in perf_record_mmap for last kernel module
+
+From: Thomas Richter <tmricht@linux.vnet.ibm.com>
+
+commit 9ad4652b66f19a60f07e63b942b80b5c2d7465bf upstream.
+
+During work on perf report for s390 I ran into the following issue:
+
+0 0x318 [0x78]: PERF_RECORD_MMAP -1/0:
+ [0x3ff804d6990(0xfffffc007fb2966f) @ 0]:
+ x /lib/modules/4.12.0perf1+/kernel/drivers/s390/net/qeth_l2.ko
+
+This is a PERF_RECORD_MMAP entry of the perf.data file with an invalid
+module size for qeth_l2.ko (the s390 ethernet device driver).
+
+Even a mainframe does not have 0xfffffc007fb2966f bytes of main memory.
+
+It turned out that this wrong size is created by the perf record
+command. What happens is this function call sequence from
+__cmd_record():
+
+ perf_session__new():
+ perf_session__create_kernel_maps():
+ machine__create_kernel_maps():
+ machine__create_modules(): Creates map for all loaded kernel modules.
+ modules__parse(): Reads /proc/modules and extracts module name and
+ load address (1st and last column)
+ machine__create_module(): Called for every module found in /proc/modules.
+ Creates a new map for every module found and enters
+ module name and start address into the map. Since the
+ module end address is unknown it is set to zero.
+
+This ends up with a kernel module map list sorted by module start
+addresses. All module end addresses are zero.
+
+Last machine__create_kernel_maps() calls function map_groups__fixup_end().
+This function iterates through the maps and assigns each map entry's
+end address the successor map entry start address. The last entry of the
+map group has no successor, so ~0 is used as end to consume the remaining
+memory.
+
+Later __cmd_record calls function record__synthesize() which in turn calls
+perf_event__synthesize_kernel_mmap() and perf_event__synthesize_modules()
+to create PERF_REPORT_MMAP entries into the perf.data file.
+
+On s390 this results in the last module qeth_l2.ko
+(which has highest start address, see module table:
+ [root@s8360047 perf]# cat /proc/modules
+ qeth_l2 86016 1 - Live 0x000003ff804d6000
+ qeth 266240 1 qeth_l2, Live 0x000003ff80296000
+ ccwgroup 24576 1 qeth, Live 0x000003ff80218000
+ vmur 36864 0 - Live 0x000003ff80182000
+ qdio 143360 2 qeth_l2,qeth, Live 0x000003ff80002000
+ [root@s8360047 perf]# )
+to be the last entry and its map has an end address of ~0.
+
+When the PERF_RECORD_MMAP entry is created for kernel module qeth_l2.ko
+its start address and length is written. The length is calculated in line:
+ event->mmap.len = pos->end - pos->start;
+and results in 0xffffffffffffffff - 0x3ff804d6990(*) = 0xfffffc007fb2966f
+
+(*) On s390 the module start address is actually determined by a __weak function
+named arch__fix_module_text_start() in machine__create_module().
+
+I think this improvable. We can use the module size (2nd column of /proc/modules)
+to get each loaded kernel module size and calculate its end address.
+Only for map entries which do not have a valid end address (end is still zero)
+we can use the heuristic we have now, that is use successor start address or ~0.
+
+Signed-off-by: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
+Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
+Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
+Cc: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
+Cc: Zvonko Kosic <zvonko.kosic@de.ibm.com>
+LPU-Reference: 20170803134902.47207-2-tmricht@linux.vnet.ibm.com
+Link: http://lkml.kernel.org/n/tip-nmoqij5b5vxx7rq2ckwu8iaj@git.kernel.org
+Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
+Cc: Daniel Daz <daniel.diaz@linaro.org>
+Cc: Guenter Roeck <linux@roeck-us.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ tools/perf/util/machine.c | 4 +++-
+ tools/perf/util/symbol-elf.c | 2 +-
+ tools/perf/util/symbol.c | 21 ++++++++++++++-------
+ tools/perf/util/symbol.h | 2 +-
+ 4 files changed, 19 insertions(+), 10 deletions(-)
+
+--- a/tools/perf/util/machine.c
++++ b/tools/perf/util/machine.c
+@@ -1079,7 +1079,8 @@ int __weak arch__fix_module_text_start(u
+ return 0;
+ }
+
+-static int machine__create_module(void *arg, const char *name, u64 start)
++static int machine__create_module(void *arg, const char *name, u64 start,
++ u64 size)
+ {
+ struct machine *machine = arg;
+ struct map *map;
+@@ -1090,6 +1091,7 @@ static int machine__create_module(void *
+ map = machine__findnew_module_map(machine, start, name);
+ if (map == NULL)
+ return -1;
++ map->end = start + size;
+
+ dso__kernel_module_get_build_id(map->dso, machine->root_dir);
+
+--- a/tools/perf/util/symbol-elf.c
++++ b/tools/perf/util/symbol-elf.c
+@@ -1478,7 +1478,7 @@ static int kcore_copy__parse_kallsyms(st
+
+ static int kcore_copy__process_modules(void *arg,
+ const char *name __maybe_unused,
+- u64 start)
++ u64 start, u64 size __maybe_unused)
+ {
+ struct kcore_copy_info *kci = arg;
+
+--- a/tools/perf/util/symbol.c
++++ b/tools/perf/util/symbol.c
+@@ -217,7 +217,8 @@ void __map_groups__fixup_end(struct map_
+ goto out_unlock;
+
+ for (next = map__next(curr); next; next = map__next(curr)) {
+- curr->end = next->start;
++ if (!curr->end)
++ curr->end = next->start;
+ curr = next;
+ }
+
+@@ -225,7 +226,8 @@ void __map_groups__fixup_end(struct map_
+ * We still haven't the actual symbols, so guess the
+ * last map final address.
+ */
+- curr->end = ~0ULL;
++ if (!curr->end)
++ curr->end = ~0ULL;
+
+ out_unlock:
+ pthread_rwlock_unlock(&maps->lock);
+@@ -512,7 +514,7 @@ void dso__sort_by_name(struct dso *dso,
+
+ int modules__parse(const char *filename, void *arg,
+ int (*process_module)(void *arg, const char *name,
+- u64 start))
++ u64 start, u64 size))
+ {
+ char *line = NULL;
+ size_t n;
+@@ -525,8 +527,8 @@ int modules__parse(const char *filename,
+
+ while (1) {
+ char name[PATH_MAX];
+- u64 start;
+- char *sep;
++ u64 start, size;
++ char *sep, *endptr;
+ ssize_t line_len;
+
+ line_len = getline(&line, &n, file);
+@@ -558,7 +560,11 @@ int modules__parse(const char *filename,
+
+ scnprintf(name, sizeof(name), "[%s]", line);
+
+- err = process_module(arg, name, start);
++ size = strtoul(sep + 1, &endptr, 0);
++ if (*endptr != ' ' && *endptr != '\t')
++ continue;
++
++ err = process_module(arg, name, start, size);
+ if (err)
+ break;
+ }
+@@ -905,7 +911,8 @@ static struct module_info *find_module(c
+ return NULL;
+ }
+
+-static int __read_proc_modules(void *arg, const char *name, u64 start)
++static int __read_proc_modules(void *arg, const char *name, u64 start,
++ u64 size __maybe_unused)
+ {
+ struct rb_root *modules = arg;
+ struct module_info *mi;
+--- a/tools/perf/util/symbol.h
++++ b/tools/perf/util/symbol.h
+@@ -268,7 +268,7 @@ int filename__read_build_id(const char *
+ int sysfs__read_build_id(const char *filename, void *bf, size_t size);
+ int modules__parse(const char *filename, void *arg,
+ int (*process_module)(void *arg, const char *name,
+- u64 start));
++ u64 start, u64 size));
+ int filename__read_debuglink(const char *filename, char *debuglink,
+ size_t size);
+
projects / thirdparty / kernel / stable-queue.git / commitdiff
