+++ Josh Poimboeuf [21/03/16 12:36 -0500]:
On Mon, Mar 21, 2016 at 11:46:51AM -0500, Josh Poimboeuf wrote:
On Mon, Mar 21, 2016 at 05:31:57PM +0100, Petr Mladek wrote:
> > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > index 780f00c..2aa20fa 100644
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> > +static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
> > +{
> > + int i, cnt, vmlinux, ret;
> > + struct klp_buf bufs = {0};
> > + Elf_Rela *relas;
> > + Elf_Sym *sym;
> > + char *symname;
> > + unsigned long sympos;
> > +
> > + relas = (Elf_Rela *) relasec->sh_addr;
> > + /* For each rela in this klp relocation section */
> > + for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
> > + sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
> > + if (sym->st_shndx != SHN_LIVEPATCH)
> > + return -EINVAL;
> > +
> > + klp_clear_buf(&bufs);
> > +
> > + /* Format: .klp.sym.objname.symbol_name,sympos */
> > + symname = pmod->core_kallsyms.strtab + sym->st_name;
> > + cnt = sscanf(symname, ".klp.sym.%64[^.].%128[^,],%lu",
> > + bufs.objname, bufs.symname, &sympos);
>
> Note that MODULE_NAME_LEN even is not 64. It is defined by:
>
> #define MAX_PARAM_PREFIX_LEN (64 - sizeof(unsigned long))
>
> I strongly suggest to use the proposal from Josh.
Hm, looks like my suggestion to use __stringify(MODULE_NAME_LEN) doesn't
work. It results in the string "MODULE_NAME_LEN". Which surprises me:
isn't is supposed to resolve the macro before applying the '#' operation
to it?
Turns out I hadn't included module.h. When I do so,
__stringify(MODULE_NAME_LEN) becomes "(64 - sizeof(unsigned long))".
Which is still not going to work :-/
Hm, we probably won't be able to make use of preprocessor tricks here,
since I don't think the preprocessor can even evaluate that expression
(esp. with that sizeof there). This might mean building the format
string at runtime, which may be more trouble than it's worth...
I was going to suggest another idea: hard-code it at 63 and then do
something like
BUILD_BUG_ON(MODULE_NAME_LEN != 64)
But you're right... it's not even 64!
Need to think on this some more...
--
Josh
--
To unsubscribe from this list: send the line "unsubscribe linux-api" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
