Commit d4b5a5c9 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

x86/alternative: Add debug prints to apply_retpolines() 



Make sure we can see the text changes when booting with
'debug-alternative'.

Example output:

 [ ] SMP alternatives: retpoline at: __traceiter_initcall_level+0x1f/0x30 (ffffffff8100066f) len: 5 to: __x86_indirect_thunk_rax+0x0/0x20
 [ ] SMP alternatives: ffffffff82603e58: [2:5) optimized NOPs: ff d0 0f 1f 00
 [ ] SMP alternatives: ffffffff8100066f: orig: e8 cc 30 00 01
 [ ] SMP alternatives: ffffffff8100066f: repl: ff d0 0f 1f 00

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Tested-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211026120310.422273830@infradead.org
parent bbe2df3f

arch/x86/kernel/alternative.c

+6 −0
Original line number Diff line number Diff line
@@ -492,9 +492,15 @@ void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) 
			continue;

		}



		DPRINTK("retpoline at: %pS (%px) len: %d to: %pS",

			addr, addr, insn.length,

			addr + insn.length + insn.immediate.value);



		len = patch_retpoline(addr, &insn, bytes);

		if (len == insn.length) {

			optimize_nops(bytes, len);

			DUMP_BYTES(((u8*)addr),  len, "%px: orig: ", addr);

			DUMP_BYTES(((u8*)bytes), len, "%px: repl: ", addr);

			text_poke_early(addr, bytes, len);

		}

	}