From 58498ee3e573dc03be651b6839dbdf865ae7ee38 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Tue, 9 Dec 2014 10:18:49 +0100 Subject: [PATCH] s390/ftrace: add code replacement sanity checks Always verify that the to be replaced code matches what we expect to see. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/ftrace.c | 95 ++++++++++++++++++++------------------- 1 file changed, 49 insertions(+), 46 deletions(-) diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index b86bb8823f15..3dabcae40e04 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -59,62 +59,65 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { - struct ftrace_insn insn; - unsigned short op; - void *from, *to; - size_t size; - - ftrace_generate_nop_insn(&insn); - size = sizeof(insn); - from = &insn; - to = (void *) rec->ip; - if (probe_kernel_read(&op, (void *) rec->ip, sizeof(op))) + struct ftrace_insn orig, new, old; + + if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old))) return -EFAULT; - /* - * If we find a breakpoint instruction, a kprobe has been placed - * at the beginning of the function. We write the constant - * KPROBE_ON_FTRACE_NOP into the remaining four bytes of the original - * instruction so that the kprobes handler can execute a nop, if it - * reaches this breakpoint. - */ - if (op == BREAKPOINT_INSTRUCTION) { - size -= 2; - from += 2; - to += 2; - insn.disp = KPROBE_ON_FTRACE_NOP; + if (addr == MCOUNT_ADDR) { + /* Initial code replacement; we expect to see stg r14,8(r15) */ + orig.opc = 0xe3e0; + orig.disp = 0xf0080024; + ftrace_generate_nop_insn(&new); + } else if (old.opc == BREAKPOINT_INSTRUCTION) { + /* + * If we find a breakpoint instruction, a kprobe has been + * placed at the beginning of the function. We write the + * constant KPROBE_ON_FTRACE_NOP into the remaining four + * bytes of the original instruction so that the kprobes + * handler can execute a nop, if it reaches this breakpoint. + */ + new.opc = orig.opc = BREAKPOINT_INSTRUCTION; + orig.disp = KPROBE_ON_FTRACE_CALL; + new.disp = KPROBE_ON_FTRACE_NOP; + } else { + /* Replace ftrace call with a nop. */ + ftrace_generate_call_insn(&orig, rec->ip); + ftrace_generate_nop_insn(&new); } - if (probe_kernel_write(to, from, size)) + /* Verify that the to be replaced code matches what we expect. */ + if (memcmp(&orig, &old, sizeof(old))) + return -EINVAL; + if (probe_kernel_write((void *) rec->ip, &new, sizeof(new))) return -EPERM; return 0; } int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { - struct ftrace_insn insn; - unsigned short op; - void *from, *to; - size_t size; - - ftrace_generate_call_insn(&insn, rec->ip); - size = sizeof(insn); - from = &insn; - to = (void *) rec->ip; - if (probe_kernel_read(&op, (void *) rec->ip, sizeof(op))) + struct ftrace_insn orig, new, old; + + if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old))) return -EFAULT; - /* - * If we find a breakpoint instruction, a kprobe has been placed - * at the beginning of the function. We write the constant - * KPROBE_ON_FTRACE_CALL into the remaining four bytes of the original - * instruction so that the kprobes handler can execute a brasl if it - * reaches this breakpoint. - */ - if (op == BREAKPOINT_INSTRUCTION) { - size -= 2; - from += 2; - to += 2; - insn.disp = KPROBE_ON_FTRACE_CALL; + if (old.opc == BREAKPOINT_INSTRUCTION) { + /* + * If we find a breakpoint instruction, a kprobe has been + * placed at the beginning of the function. We write the + * constant KPROBE_ON_FTRACE_CALL into the remaining four + * bytes of the original instruction so that the kprobes + * handler can execute a brasl if it reaches this breakpoint. + */ + new.opc = orig.opc = BREAKPOINT_INSTRUCTION; + orig.disp = KPROBE_ON_FTRACE_NOP; + new.disp = KPROBE_ON_FTRACE_CALL; + } else { + /* Replace nop with an ftrace call. */ + ftrace_generate_nop_insn(&orig); + ftrace_generate_call_insn(&new, rec->ip); } - if (probe_kernel_write(to, from, size)) + /* Verify that the to be replaced code matches what we expect. */ + if (memcmp(&orig, &old, sizeof(old))) + return -EINVAL; + if (probe_kernel_write((void *) rec->ip, &new, sizeof(new))) return -EPERM; return 0; } -- 2.20.1