Doug / smarc-fsl-linux-kernel

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Commit f2df3f65d0b4337cfb5b19eab3ee28b177427c49

Authored by Paulo Marques
Committed by Linus Torvalds
1 parent a6752f3f53
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

kallsyms should prefer non weak symbols 

When resolving symbol names from addresses with aliased symbol names,
kallsyms_lookup always returns the first symbol, even if it is a weak
symbol.

This patch changes this by sorting the symbols with the weak symbols last
before feeding them to the kernel.  This way the kernel runtime isn't
changed at all, only the kallsyms build system is changed.

Another side effect is that the symbols get sorted by address, too.  So,
even if future binutils version have some bug in "nm" that makes it fail to
correctly sort symbols by address, the kernel won't be affected by this.

Mathieu says:

  I created a module in LTTng that uses kallsyms to get the symbol
  corresponding to a specific system call address.  Unfortunately, all the
  unimplemented syscalls were all referring to the (same) weak symbol
  identifying an unrelated system call rather that sys_ni (or whatever
  non-weak symbol would be expected).  Kallsyms was dumbly returning the first
  symbol that matched.

  This patch makes sure kallsyms returns the non-weak symbol when there is
  one, which seems to be the expected result.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Looks-great-to: Rusty Russell <rusty@rustcorp.com.au>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 34 additions and 3 deletions Side-by-side Diff

... ... @@ -31,14 +31,13 @@
31 31  
32 32 #define KSYM_NAME_LEN 128
33 33  
34   -
35 34 struct sym_entry {
36 35 unsigned long long addr;
37 36 unsigned int len;
  37 + unsigned int start_pos;
38 38 unsigned char *sym;
39 39 };
40 40  
41   -
42 41 static struct sym_entry *table;
43 42 static unsigned int table_size, table_cnt;
44 43 static unsigned long long _text, _stext, _etext, _sinittext, _einittext;
45 44  
... ... @@ -198,8 +197,10 @@
198 197 exit (1);
199 198 }
200 199 }
201   - if (read_symbol(in, &table[table_cnt]) == 0)
  200 + if (read_symbol(in, &table[table_cnt]) == 0) {
  201 + table[table_cnt].start_pos = table_cnt;
202 202 table_cnt++;
  203 + }
203 204 }
204 205 }
205 206  
206 207  
... ... @@ -502,7 +503,36 @@
502 503 optimize_result();
503 504 }
504 505  
  506 +static int compare_symbols(const void *a, const void *b)
  507 +{
  508 + const struct sym_entry *sa;
  509 + const struct sym_entry *sb;
  510 + int wa, wb;
505 511  
  512 + sa = a;
  513 + sb = b;
  514 +
  515 + /* sort by address first */
  516 + if (sa->addr > sb->addr)
  517 + return 1;
  518 + if (sa->addr < sb->addr)
  519 + return -1;
  520 +
  521 + /* sort by "weakness" type */
  522 + wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
  523 + wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
  524 + if (wa != wb)
  525 + return wa - wb;
  526 +
  527 + /* sort by initial order, so that other symbols are left undisturbed */
  528 + return sa->start_pos - sb->start_pos;
  529 +}
  530 +
  531 +static void sort_symbols(void)
  532 +{
  533 + qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
  534 +}
  535 +
506 536 int main(int argc, char **argv)
507 537 {
508 538 if (argc >= 2) {
... ... @@ -523,6 +553,7 @@
523 553 usage();
524 554  
525 555 read_map(stdin);
  556 + sort_symbols();
526 557 optimize_token_table();
527 558 write_src();
528 559