From c3d6324f841bab2403be6419986e2b1d1068d423 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 5 Jun 2019 10:48:37 +0200 Subject: 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 Tested-by: Steven Rostedt (VMware) Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Masami Hiramatsu Reviewed-by: Daniel Bristot de Oliveira Acked-by: Alexei Starovoitov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Steven Rostedt Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20191111132457.529086974@infradead.org Signed-off-by: Ingo Molnar (cherry picked from commit 8c7eebc10687af45ac8e40ad1bac0cf7893dba9f) Signed-off-by: Alexei Starovoitov --- arch/x86/kernel/kprobes/opt.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'arch/x86/kernel/kprobes/opt.c') diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c index b348dd506d58..8900329c28a7 100644 --- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -437,8 +437,7 @@ void arch_optimize_kprobes(struct list_head *oplist) insn_buff[0] = RELATIVEJUMP_OPCODE; *(s32 *)(&insn_buff[1]) = rel; - text_poke_bp(op->kp.addr, insn_buff, RELATIVEJUMP_SIZE, - op->optinsn.insn); + text_poke_bp(op->kp.addr, insn_buff, RELATIVEJUMP_SIZE, NULL); list_del_init(&op->list); } @@ -448,12 +447,18 @@ void arch_optimize_kprobes(struct list_head *oplist) void arch_unoptimize_kprobe(struct optimized_kprobe *op) { u8 insn_buff[RELATIVEJUMP_SIZE]; + u8 emulate_buff[RELATIVEJUMP_SIZE]; /* Set int3 to first byte for kprobes */ insn_buff[0] = BREAKPOINT_INSTRUCTION; memcpy(insn_buff + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE); + + emulate_buff[0] = RELATIVEJUMP_OPCODE; + *(s32 *)(&emulate_buff[1]) = (s32)((long)op->optinsn.insn - + ((long)op->kp.addr + RELATIVEJUMP_SIZE)); + text_poke_bp(op->kp.addr, insn_buff, RELATIVEJUMP_SIZE, - op->optinsn.insn); + emulate_buff); } /* -- cgit v1.2.3