[PATCH 1/1] perf symbol: Don't assume .text section is the firstsection of vmlinux

[Lu Zhigang]

The start address derived from /proc/kallsyms in is the start address of
kernel, but not the start address of .text section of kernel. If the .text
section is not at the beginning of vmlinux, perf will mess up the sections'
address range, thus failing to resolve the kernel symbols.

Verified on TILE architecture whose kernel sections are as following.
Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .intrpt1      00003fe8  fffffff700000000  0000000000000000  00010000  2**3
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .text         008485a0  fffffff700020000  0000000000020000  00020000  2**6
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  2 .init.text    00047e88  fffffff700870000  0000000000870000  00870000  2**3
...

Signed-off-by: Lu Zhigang <zlu@xxxxxxxxxx>
---
 tools/perf/util/symbol-elf.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index db0cc92..7fc219b 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -645,6 +645,7 @@ int dso__load_sym(struct dso *dso, struct map *map,
        Elf_Scn *sec, *sec_strndx;
        Elf *elf;
        int nr = 0;
+       u64 kernel_start = map->start;
 
        dso->symtab_type = syms_ss->type;
 
@@ -746,6 +747,7 @@ int dso__load_sym(struct dso *dso, struct map *map,
                                goto new_symbol;
 
                        if (strcmp(section_name, ".text") == 0) {
+                               map->start = kernel_start + shdr.sh_offset;
                                curr_map = map;
                                curr_dso = dso;
                                goto new_symbol;
@@ -759,7 +761,7 @@ int dso__load_sym(struct dso *dso, struct map *map,
                                u64 start = sym.st_value;
 
                                if (kmodule)
-                                       start += map->start + shdr.sh_offset;
+                                       start += kernel_start + shdr.sh_offset;
 
                                curr_dso = dso__new(dso_name);
                                if (curr_dso == NULL)
-- 
1.7.10.3
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