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lookup: fix symtab parsing 

symtab_read tries to skip '.dynsym' symbol table and only
read '.symtab' symbol table. Newer readelf from binutils 2.37
now adds section names (see the diff):

--- vmlinux.symtab      2022-02-18 02:10:06.691220932 +0100
+++ vmlinux.symtab.new  2022-02-18 01:16:06.161210458 +0100
Symbol table '.dynsym' contains 1541 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000100000     0 SECTION LOCAL  DEFAULT    1 .text
     2: 00000000017a3ac0     4 OBJECT  GLOBAL DEFAULT   19 sclp_console_pages
Symbol table '.symtab' contains 159980 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
-    41: 0000000001a93600     0 SECTION LOCAL  DEFAULT   41
-    42: 0000000001a9c678     0 SECTION LOCAL  DEFAULT   42
...
+    41: 0000000001a93600     0 SECTION LOCAL  DEFAULT   41 .dynsym
+    42: 0000000001a9c678     0 SECTION LOCAL  DEFAULT   42 .rela.dyn
...
     54: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS main.c

Simple matching of ".dynsym" in the line buffer is not enough anymore,
because it hits not just

Symbol table '.dynsym' contains 1541 entries:

line, but also

    41: 0000000001a93600     0 SECTION LOCAL  DEFAULT   41 .dynsym

skipping the rest of the file and leading to an error:

create-diff-object: ERROR: *.o: find_local_syms: 189: couldn't find matching
*.c local symbols in vmlinux symbol table

Limit matching only to lines containing "Symbol table" header.
This works with readelf from the binutils, as well as readelf from
elfutils (its output looks slightly different).

Symbol table [41] '.dynsym' contains 1541 entries:

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2022-03-29 10:20:08 +02:00 committed by Sumanth Korikkar
parent f6e1838ab9
commit c6d0b5450b
1 changed files with 8 additions and 6 deletions
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14
kpatch-build/lookup.c
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@ -272,12 +272,14 @@ static void symtab_read(struct lookup_table *table, char *path)
* tables. .dynsym is just a subset of .symtab, so skip it to * tables. .dynsym is just a subset of .symtab, so skip it to
* avoid duplicates. * avoid duplicates.
*/ */
if (strstr(line, ".dynsym")) { if (!strncmp(line, "Symbol table ", 13)) {
skip = true; if (strstr(line, ".dynsym")) {
continue; skip = true;
} else if (strstr(line, ".symtab")) { continue;
skip = false; } else if (strstr(line, ".symtab")) {
continue; skip = false;
continue;
}
} }
if (skip) if (skip)
continue; continue;