>>> On 13.06.17 at 22:51, <andrew.coop...@citrix.com> wrote:
> --- a/xen/arch/x86/livepatch.c
> +++ b/xen/arch/x86/livepatch.c
> @@ -170,14 +170,22 @@ int arch_livepatch_perform_rela(struct livepatch_elf
> *elf,
> uint8_t *dest = base->load_addr + r->r_offset;
> uint64_t val;
>
> - if ( symndx > elf->nsym )
> + if ( symndx == STN_UNDEF )
> + val = 0;
> + else if ( symndx > elf->nsym )
> {
> dprintk(XENLOG_ERR, LIVEPATCH "%s: Relative relocation wants
> symbol@%u which is past end!\n",
> elf->name, symndx);
> return -EINVAL;
> }
> -
> - val = r->r_addend + elf->sym[symndx].sym->st_value;
> + else if ( !elf->sym[symndx].sym )
> + {
> + dprintk(XENLOG_ERR, LIVEPATCH "%s: No symbol@%u\n",
> + elf->name, symndx);
> + return -EINVAL;
> + }
> + else
> + val = r->r_addend + elf->sym[symndx].sym->st_value;
I don't understand this: st_value for STN_UNDEF is going to be zero
(so far there's also no extension defined for the first entry, afaict),
so there should be no difference between hard-coding the zero and
reading the symbol table entry. Furthermore r_addend would still
need applying. And finally "val" is never being cast to a pointer, and
hence I miss the connection to whatever crash you've been
observing.
Jan
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