x86/alternatives: Teach text_poke_bp() to emulate instructions

In preparation for static_call and variable size jump_label support,
teach text_poke_bp() to emulate instructions, namely:

  JMP32, JMP8, CALL, NOP2, NOP_ATOMIC5, INT3

The current text_poke_bp() takes a @handler argument which is used as
a jump target when the temporary INT3 is hit by a different CPU.

When patching CALL instructions, this doesn't work because we'd miss
the PUSH of the return address. Instead, teach poke_int3_handler() to
emulate an instruction, typically the instruction we're patching in.

This fits almost all text_poke_bp() users, except
arch_unoptimize_kprobe() which restores random text, and for that site
we have to build an explicit emulate instruction.

Tested-by: Alexei Starovoitov <[email protected]>
Tested-by: Steven Rostedt (VMware) <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Reviewed-by: Daniel Bristot de Oliveira <[email protected]>
Acked-by: Alexei Starovoitov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
(cherry picked from commit 8c7eebc10687af45ac8e40ad1bac0cf7893dba9f)
Signed-off-by: Alexei Starovoitov <[email protected]>

1 files changed, 3 insertions, 6 deletions

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index 044053235302..c1a8b9e71408 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -89,8 +89,7 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
 		return;
 	}
 
-	text_poke_bp((void *)jump_entry_code(entry), &code, JUMP_LABEL_NOP_SIZE,
-		     (void *)jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
+	text_poke_bp((void *)jump_entry_code(entry), &code, JUMP_LABEL_NOP_SIZE, NULL);
 }
 
 void arch_jump_label_transform(struct jump_entry *entry,
@@ -147,11 +146,9 @@ bool arch_jump_label_transform_queue(struct jump_entry *entry,
 	}
 
 	__jump_label_set_jump_code(entry, type,
-				   (union jump_code_union *) &tp->opcode, 0);
+				   (union jump_code_union *)&tp->text, 0);
 
-	tp->addr = entry_code;
-	tp->detour = entry_code + JUMP_LABEL_NOP_SIZE;
-	tp->len = JUMP_LABEL_NOP_SIZE;
+	text_poke_loc_init(tp, entry_code, NULL, JUMP_LABEL_NOP_SIZE, NULL);
 
 	tp_vec_nr++;