Hi,
2012/11/22 Greg Kroah-Hartman <gre...@linuxfoundation.org>:
> 3.6-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Rusty Russell <ru...@rustcorp.com.au>
>
> commit 59ef28b1f14899b10d6b2682c7057ca00a9a3f47 upstream.
>
> Masaki found and patched a kallsyms issue: the last symbol in a
> module's symtab wasn't transferred. This is because we manually copy
> the zero'th entry (which is always empty) then copy the rest in a loop
> starting at 1, though from src[0]. His fix was minimal, I prefer to
> rewrite the loops in more standard form.
>
> There are two loops: one to get the size, and one to copy. Make these
> identical: always count entry 0 and any defined symbol in an allocated
> non-init section.
>
> This bug exists since the following commit was introduced.
> module: reduce symbol table for loaded modules (v2)
> commit: 4a4962263f07d14660849ec134ee42b63e95ea9a
>
> LKML: http://lkml.org/lkml/2012/10/24/27
> Reported-by: Masaki Kimura <masaki.kimura...@hitachi.com>
> Signed-off-by: Rusty Russell <ru...@rustcorp.com.au>
> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
>
> ---
> kernel/module.c | 27 ++++++++++++++++-----------
> 1 file changed, 16 insertions(+), 11 deletions(-)
>
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2273,12 +2273,17 @@ static void layout_symtab(struct module
> src = (void *)info->hdr + symsect->sh_offset;
> nsrc = symsect->sh_size / sizeof(*src);
>
> + /* strtab always starts with a nul, so offset 0 is the empty string.
> */
> + strtab_size = 1;
> +
I suspect above code sniped is not needed since the size of src[0](always 1) is
counted at the following code("strtab_size += strlen(..) + 1;").
> /* Compute total space required for the core symbols' strtab. */
> - for (ndst = i = strtab_size = 1; i < nsrc; ++i, ++src)
> - if (is_core_symbol(src, info->sechdrs, info->hdr->e_shnum)) {
> - strtab_size += strlen(&info->strtab[src->st_name]) +
> 1;
> + for (ndst = i = 0; i < nsrc; i++) {
> + if (i == 0 ||
> + is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum))
> {
src[i] rather than src+1 is better as kallsyms();
> + strtab_size +=
> strlen(&info->strtab[src[i].st_name])+1;
> ndst++;
> }
> + }
>
> /* Append room for core symbols at end of core part. */
> info->symoffs = ALIGN(mod->core_size, symsect->sh_addralign ?: 1);
> @@ -2312,15 +2317,15 @@ static void add_kallsyms(struct module *
> mod->core_symtab = dst = mod->module_core + info->symoffs;
> mod->core_strtab = s = mod->module_core + info->stroffs;
> src = mod->symtab;
> - *dst = *src;
> *s++ = 0;
This "*s++"line is also not needed since the content of src[0] is copied in the
following loop.
If my understanding is correct, the allsym table becomes as follows by
applying this patch.
==================
\0\0<first core symbol>\0<second core symbol>\0... # "\0" means null
character in this case
==================
It should be as follows.
====================
\0<first core symbol>\0<second core symbol>\0...
====================
This patch would work, but need extra one byte per module. Olease let
us know if I misunderstand something.
I didn't confirm with real machine.
Thanks,
Satoru
> - for (ndst = i = 1; i < mod->num_symtab; ++i, ++src) {
> - if (!is_core_symbol(src, info->sechdrs, info->hdr->e_shnum))
> - continue;
> -
> - dst[ndst] = *src;
> - dst[ndst++].st_name = s - mod->core_strtab;
> - s += strlcpy(s, &mod->strtab[src->st_name], KSYM_NAME_LEN) +
> 1;
> + for (ndst = i = 0; i < mod->num_symtab; i++) {
> + if (i == 0 ||
> + is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum))
> {
> + dst[ndst] = src[i];
> + dst[ndst++].st_name = s - mod->core_strtab;
> + s += strlcpy(s, &mod->strtab[src[i].st_name],
> + KSYM_NAME_LEN) + 1;
> + }
> }
> mod->core_num_syms = ndst;
> }
>
>
> --
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