The following commit has been merged into the perf/core branch of tip: Commit-ID: 51d9635582c55479bf7904fa47e39aef2b323a50 Gitweb: https://git.kernel.org/tip/51d9635582c55479bf7904fa47e39aef2b323a50 Author: Thomas Richter <tmricht@xxxxxxxxxxxxx> AuthorDate: Wed, 15 Apr 2020 09:07:44 +02:00 Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> CommitterDate: Tue, 05 May 2020 16:35:32 -03:00 perf symbol: Fix kernel symbol address display Running commands ./perf record -e rb0000 -- find . ./perf report -v reveals symbol names and its addresses. There is a mismatch between kernel symbol and address. Here is an example for kernel symbol check_chain_key: 3.55% find /lib/modules/.../build/vmlinux 0xf11ec v [k] check_chain_key This address is off by 0xff000 as can be seen with: [root@t35lp46 ~]# fgrep check_chain_key /proc/kallsyms 00000000001f00d0 t check_chain_key [root@t35lp46 ~]# objdump -t ~/linux/vmlinux| fgrep check_chain_key 00000000001f00d0 l F .text 00000000000001e8 check_chain_key [root@t35lp46 ~]# This function is located in main memory 0x1f00d0 - 0x1f02b4. It has several entries in the perf data file with the correct address: [root@t35lp46 perf]# ./perf report -D -i perf.data.find-bad | \ fgrep SAMPLE| fgrep 0x1f01ec PERF_RECORD_SAMPLE(IP, 0x1): 22228/22228: 0x1f01ec period: 1300000 addr: 0 PERF_RECORD_SAMPLE(IP, 0x1): 22228/22228: 0x1f01ec period: 1300000 addr: 0 The root cause happens when reading symbol tables during perf report. A long gdb call chain leads to machine__deliver_events perf_evlist__deliver_event perf_evlist__deliver_sample build_id__mark_dso_hits thread__find_map(1) Read correct address from sample entry map__load dso__load Some more functions to end up in .... dso__load_sym. Function dso__load_syms checks for kernel relocation and symbol adjustment for the kernel and results in kernel map adjustment of kernel .text segment address (0x100000 on s390) kernel .text segment offset in file (0x1000 on s390). This results in all kernel symbol addresses to be changed by subtracting 0xff000 (on s390). For the symbol check_chain_key we end up with 0x1f00d0 - 0x100000 + 0x1000 = 0xf11d0 and this address is saved in the perf symbol table. This calculation is also applied by the mapping functions map__mapip() and map__unmapip() to map IP addresses to dso mappings. During perf report processing functions process_sample_event (builtin-report.c) machine__resolve thread__find_map hist_entry_iter_add are called. Function thread__find_map(1) takes the correct sample address and applies the mapping function map__mapip() from the kernel dso and saves the modified address in struct addr_location for further reference. From now on this address is used. Funktion process_sample_event() then calls hist_entry_iter_add() to save the address in member ip of struct hist_entry. When samples are displayed using perf_evlist__tty_browse_hists hists__fprintf hist_entry__fprintf hist_entry__snprintf __hist_entry__snprintf _hist_entry__sym_snprintf() This simply displays the address of the symbol and ignores the dso <-> map mappings done in function thread__find_map. This leads to the address mismatch. Output before: ot@t35lp46 perf]# ./perf report -v | fgrep check_chain_key 3.55% find /lib/modules/5.6.0d-perf+/build/vmlinux 0xf11ec v [k] check_chain_key [root@t35lp46 perf]# Output after: [root@t35lp46 perf]# ./perf report -v | fgrep check_chain_key 3.55% find /lib/modules/5.6.0d-perf+/build/vmlinux 0x1f01ec v [k] check_chain_key [root@t35lp46 perf]# Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx> Acked-by: Sumanth Korikkar <sumanthk@xxxxxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> Link: http://lore.kernel.org/lkml/20200415070744.59919-1-tmricht@xxxxxxxxxxxxx Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> --- tools/perf/util/sort.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c index dc23b34..c1f8879 100644 --- a/tools/perf/util/sort.c +++ b/tools/perf/util/sort.c @@ -300,8 +300,14 @@ static int _hist_entry__sym_snprintf(struct map_symbol *ms, if (verbose > 0) { char o = map ? dso__symtab_origin(map->dso) : '!'; + u64 rip = ip; + + if (map && map->dso && map->dso->kernel + && map->dso->adjust_symbols) + rip = map->unmap_ip(map, ip); + ret += repsep_snprintf(bf, size, "%-#*llx %c ", - BITS_PER_LONG / 4 + 2, ip, o); + BITS_PER_LONG / 4 + 2, rip, o); } ret += repsep_snprintf(bf + ret, size - ret, "[%c] ", level);
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