From: Peter Zijlstra peterz@infradead.org
commit 24ff652573754fe4c03213ebd26b17e86842feb3 upstream.
Occasionally objtool encounters symbol (as opposed to section) relocations in .altinstructions. Typically they are the alternatives written by elf_add_alternative() as encountered on a noinstr validation run on vmlinux after having already ran objtool on the individual .o files.
Basically this is the counterpart of commit 44f6a7c0755d ("objtool: Fix seg fault with Clang non-section symbols"), because when these new assemblers (binutils now also does this) strip the section symbols, elf_add_reloc_to_insn() is forced to emit symbol based relocations.
As such, teach get_alt_entry() about different relocation types.
Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Reported-by: Stephen Rothwell sfr@canb.auug.org.au Reported-by: Borislav Petkov bp@alien8.de Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Josh Poimboeuf jpoimboe@redhat.com Tested-by: Nathan Chancellor nathan@kernel.org Link: https://lore.kernel.org/r/YVWUvknIEVNkPvnP@hirez.programming.kicks-ass.net Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/objtool/special.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-)
--- a/tools/objtool/special.c +++ b/tools/objtool/special.c @@ -55,6 +55,24 @@ void __weak arch_handle_alternative(unsi { }
+static bool reloc2sec_off(struct reloc *reloc, struct section **sec, unsigned long *off) +{ + switch (reloc->sym->type) { + case STT_FUNC: + *sec = reloc->sym->sec; + *off = reloc->sym->offset + reloc->addend; + return true; + + case STT_SECTION: + *sec = reloc->sym->sec; + *off = reloc->addend; + return true; + + default: + return false; + } +} + static int get_alt_entry(struct elf *elf, struct special_entry *entry, struct section *sec, int idx, struct special_alt *alt) @@ -87,15 +105,12 @@ static int get_alt_entry(struct elf *elf WARN_FUNC("can't find orig reloc", sec, offset + entry->orig); return -1; } - if (orig_reloc->sym->type != STT_SECTION) { - WARN_FUNC("don't know how to handle non-section reloc symbol %s", + if (!reloc2sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off)) { + WARN_FUNC("don't know how to handle reloc symbol type: %s", sec, offset + entry->orig, orig_reloc->sym->name); return -1; }
- alt->orig_sec = orig_reloc->sym->sec; - alt->orig_off = orig_reloc->addend; - if (!entry->group || alt->new_len) { new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new); if (!new_reloc) { @@ -112,8 +127,11 @@ static int get_alt_entry(struct elf *elf if (arch_is_retpoline(new_reloc->sym)) return 1;
- alt->new_sec = new_reloc->sym->sec; - alt->new_off = (unsigned int)new_reloc->addend; + if (!reloc2sec_off(new_reloc, &alt->new_sec, &alt->new_off)) { + WARN_FUNC("don't know how to handle reloc symbol type: %s", + sec, offset + entry->new, new_reloc->sym->name); + return -1; + }
/* _ASM_EXTABLE_EX hack */ if (alt->new_off >= 0x7ffffff0)