The patch titled kallsyms should prefer non weak symbols has been added to the -mm tree. Its filename is kallsyms-should-prefer-non-weak-symbols.patch *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this ------------------------------------------------------ Subject: kallsyms should prefer non weak symbols From: Paulo Marques <pmarques@xxxxxxxxxxxx> 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. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> Looks-great-to: Rusty Russell <rusty@xxxxxxxxxxxxxxx> Cc: Sam Ravnborg <sam@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- scripts/kallsyms.c | 36 ++++++++++++++++++++++++++++++++++-- 1 file changed, 34 insertions(+), 2 deletions(-) diff -puN scripts/kallsyms.c~kallsyms-should-prefer-non-weak-symbols scripts/kallsyms.c --- a/scripts/kallsyms.c~kallsyms-should-prefer-non-weak-symbols +++ a/scripts/kallsyms.c @@ -34,7 +34,7 @@ struct sym_entry { unsigned long long addr; - unsigned int len; + unsigned int len, start_pos; unsigned char *sym; }; @@ -198,8 +198,10 @@ static void read_map(FILE *in) exit (1); } } - if (read_symbol(in, &table[table_cnt]) == 0) + if (read_symbol(in, &table[table_cnt]) == 0) { + table[table_cnt].start_pos = table_cnt; table_cnt++; + } } } @@ -503,6 +505,35 @@ static void optimize_token_table(void) } +static int compare_symbols(const void *a, const void *b) +{ + struct sym_entry *sa, *sb; + int wa, wb; + + sa = (struct sym_entry *) a; + sb = (struct sym_entry *) b; + + // sort by address first + if (sa->addr > sb->addr) + return 1; + if (sa->addr < sb->addr) + return -1; + + // sort by "weakness" type + wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W'); + wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W'); + if (wa != wb) + return wa - wb; + + // sort by initial order, so that other symbols are left undisturbed + return sa->start_pos - sb->start_pos; +} + +static void sort_symbols(void) +{ + qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols); +} + int main(int argc, char **argv) { if (argc >= 2) { @@ -523,6 +554,7 @@ int main(int argc, char **argv) usage(); read_map(stdin); + sort_symbols(); optimize_token_table(); write_src(); _ Patches currently in -mm which might be from pmarques@xxxxxxxxxxxx are kallsyms-should-prefer-non-weak-symbols.patch - To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html