Commit 1f9a1b74 authored by Josh Poimboeuf's avatar Josh Poimboeuf
Browse files

objtool: Fix retpoline detection in asm code 



The JMP_NOSPEC macro branches to __x86_retpoline_*() rather than the
__x86_indirect_thunk_*() wrappers used by C code.  Detect jumps to
__x86_retpoline_*() as retpoline dynamic jumps.

Presumably this doesn't trigger a user-visible bug.  I only found it
when testing vmlinux.o validation.

Fixes: 39b73533 ("objtool: Detect jumps to retpoline thunks")
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/31f5833e2e4f01e3d755889ac77e3661e906c09f.1611263461.git.jpoimboe@redhat.com
parent 6f567c93

tools/objtool/arch/x86/special.c

+1 −1
Original line number Diff line number Diff line
@@ -48,7 +48,7 @@ bool arch_support_alt_relocation(struct special_alt *special_alt, 
	 * replacement group.

	 */

	return insn->offset == special_alt->new_off &&

	       (insn->type == INSN_CALL || is_static_jump(insn));

	       (insn->type == INSN_CALL || is_jump(insn));

}



/*

tools/objtool/check.c

+2 −1
Original line number Diff line number Diff line
@@ -785,7 +785,8 @@ static int add_jump_destinations(struct objtool_file *file) 
			dest_sec = reloc->sym->sec;

			dest_off = reloc->sym->sym.st_value +

				   arch_dest_reloc_offset(reloc->addend);

		} else if (strstr(reloc->sym->name, "_indirect_thunk_")) {

		} else if (!strncmp(reloc->sym->name, "__x86_indirect_thunk_", 21) ||

			   !strncmp(reloc->sym->name, "__x86_retpoline_", 16)) {

			/*

			 * Retpoline jumps are really dynamic jumps in

			 * disguise, so convert them accordingly.

tools/objtool/include/objtool/check.h

+11 −0
Original line number Diff line number Diff line
@@ -68,6 +68,17 @@ static inline bool is_static_jump(struct instruction *insn) 
	       insn->type == INSN_JUMP_UNCONDITIONAL;

}



static inline bool is_dynamic_jump(struct instruction *insn)

{

	return insn->type == INSN_JUMP_DYNAMIC ||

	       insn->type == INSN_JUMP_DYNAMIC_CONDITIONAL;

}



static inline bool is_jump(struct instruction *insn)

{

	return is_static_jump(insn) || is_dynamic_jump(insn);

}



struct instruction *find_insn(struct objtool_file *file,

			      struct section *sec, unsigned long offset);