>From 8f23543a314f359ee0625345bbc6d54b0e278358 Mon Sep 17 00:00:00 2001 Message-Id: <8f23543a314f359ee0625345bbc6d54b0e278358.1485877985.git.jstancek@redhat.com> In-Reply-To: <9bf8ece1e397b851beedaeceeb0cd07421ff6f43.1485877985.git.jstancek@redhat.com> References: <9bf8ece1e397b851beedaeceeb0cd07421ff6f43.1485877985.git.jstancek@redhat.com> From: Jan Stancek Date: Tue, 31 Jan 2017 14:44:57 +0100 Subject: [PATCH 2/3 v2] perf: make build_cpu_topology skip offline/absent CPUs When build_cpu_topo() encounters offline/absent CPUs, it fails to find any sysfs entries and returns failure. This leads to build_cpu_topology() and write_cpu_topology() failing as well. Because HEADER_CPU_TOPOLOGY has not been written, read leaves cpu_topology_map NULL and we get NULL ptr deref at: ... cmd_test __cmd_test test_and_print run_test test_session_topology check_cpu_topology 36: Session topology : --- start --- test child forked, pid 14902 templ file: /tmp/perf-test-4CKocW failed to write feature HEADER_CPU_TOPOLOGY perf: Segmentation fault Obtained 9 stack frames. ./perf(sighandler_dump_stack+0x41) [0x5095f1] /lib64/libc.so.6(+0x35250) [0x7f4b7c3c9250] ./perf(test_session_topology+0x1db) [0x490ceb] ./perf() [0x475b68] ./perf(cmd_test+0x5b9) [0x4763c9] ./perf() [0x4945a3] ./perf(main+0x69f) [0x427e8f] /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f4b7c3b5b35] ./perf() [0x427fb9] test child interrupted ---- end ---- Session topology: FAILED! This patch makes build_cpu_topology() skip offline/absent CPUs, by checking their presence against cpu_map built from online CPUs. Signed-off-by: Jan Stancek --- tools/perf/util/header.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c index d89c9c7ef4e5..2b7ed52df807 100644 --- a/tools/perf/util/header.c +++ b/tools/perf/util/header.c @@ -503,24 +503,31 @@ static void free_cpu_topo(struct cpu_topo *tp) static struct cpu_topo *build_cpu_topology(void) { - struct cpu_topo *tp; + struct cpu_topo *tp = NULL; void *addr; u32 nr, i; size_t sz; long ncpus; - int ret = -1; + int ret = 0; + struct cpu_map *map; ncpus = sysconf(_SC_NPROCESSORS_CONF); if (ncpus < 0) - return NULL; + goto out; + + /* build online CPU map */ + map = cpu_map__new(NULL); + if (map == NULL) { + pr_debug("failed to get system cpumap\n"); + goto out; + } nr = (u32)(ncpus & UINT_MAX); sz = nr * sizeof(char *); - addr = calloc(1, sizeof(*tp) + 2 * sz); if (!addr) - return NULL; + goto out_free; tp = addr; tp->cpu_nr = nr; @@ -530,14 +537,21 @@ static struct cpu_topo *build_cpu_topology(void) tp->thread_siblings = addr; for (i = 0; i < nr; i++) { + if (!cpu_map__has(map, i)) + continue; + ret = build_cpu_topo(tp, i); if (ret < 0) break; } + +out_free: + cpu_map__put(map); if (ret) { free_cpu_topo(tp); tp = NULL; } +out: return tp; } -- 1.8.3.1