[lkml]   [2019]   [Dec]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 3/4] perf map: Set kmap->kmaps backpointer for main kernel map chunks
From: Arnaldo Carvalho de Melo <>

When a map is create to represent the main kernel area (vmlinux) with
map__new2() we allocate an extra area to store a pointer to the 'struct
maps' for the kernel maps, so that we can access that struct when
loading ELF files or kallsyms, as we will need to split it in multiple
maps, one per kernel module or ELF section (such as ".init.text").

So when map->dso->kernel is non-zero, it is expected that
map__kmap(map)->kmaps to be set to the tree of kernel maps (modules,
chunks of the main kernel, bpf progs put in place via
PERF_RECORD_KSYMBOL, the main kernel).

This was not the case when we were splitting the main kernel into chunks
for its ELF sections, which ended up making 'perf report --children'
processing a file with callchains to trip on
__map__is_kernel(), when we press ENTER to see the popup menu for main
histogram entries that starts at a symbol in the ".init.text" ELF
section, e.g.:

- 8.83% 0.00% swapper [kernel.vmlinux].init.text [k] start_kernel

Fix it.

Reviewed-by: Jiri Olsa <>
Cc: Adrian Hunter <>
Cc: Namhyung Kim <>
Signed-off-by: Arnaldo Carvalho de Melo <>
tools/perf/util/symbol-elf.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 6658fbf196e6..1965aefccb02 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -920,6 +920,9 @@ static int dso__process_kernel_symbol(struct dso *dso, struct map *map,
if (curr_map == NULL)
return -1;

+ if (curr_dso->kernel)
+ map__kmap(curr_map)->kmaps = kmaps;
if (adjust_kernel_syms) {
curr_map->start = shdr->sh_addr + ref_reloc(kmap);
curr_map->end = curr_map->start + shdr->sh_size;
 \ /
  Last update: 2019-12-23 14:33    [W:0.122 / U:4.968 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site