[PATCH 5.15 18/78] x86/alternative: Add debug prints to apply_retpolines()
From: Greg Kroah-Hartman
Date: Tue Jul 12 2022 - 15:00:02 EST
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit d4b5a5c993009ffeb5febe3b701da3faab6adb96 upstream.
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: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Tested-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211026120310.422273830@xxxxxxxxxxxxx
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/alternative.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -492,9 +492,15 @@ void __init_or_module noinline apply_ret
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);
}
}