s390/ftrace: add code replacement sanity checks (58498ee3) · Commits · jan.koester / Linux

arch/s390/kernel/ftrace.c

+49 −46

Original line number	Original line	Diff line number	Diff line
	@@ -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,		int ftrace_make_nop(struct module mod, struct dyn_ftrace rec,
	unsigned long addr)		unsigned long addr)
	{		{
	struct ftrace_insn insn;		struct ftrace_insn orig, new, old;
	unsigned short op;
	void from, to;		if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
	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)))
	return -EFAULT;		return -EFAULT;
			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		* If we find a breakpoint instruction, a kprobe has been
	* at the beginning of the function. We write the constant		* placed at the beginning of the function. We write the
	* KPROBE_ON_FTRACE_NOP into the remaining four bytes of the original		* constant KPROBE_ON_FTRACE_NOP into the remaining four
	* instruction so that the kprobes handler can execute a nop, if it		* bytes of the original instruction so that the kprobes
	* reaches this breakpoint.		* handler can execute a nop, if it reaches this breakpoint.
	*/		*/
	if (op == BREAKPOINT_INSTRUCTION) {		new.opc = orig.opc = BREAKPOINT_INSTRUCTION;
	size -= 2;		orig.disp = KPROBE_ON_FTRACE_CALL;
	from += 2;		new.disp = KPROBE_ON_FTRACE_NOP;
	to += 2;		} else {
	insn.disp = KPROBE_ON_FTRACE_NOP;		/* 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 -EPERM;
	return 0;		return 0;
	}		}

	int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)		int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	{		{
	struct ftrace_insn insn;		struct ftrace_insn orig, new, old;
	unsigned short op;
	void from, to;		if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
	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)))
	return -EFAULT;		return -EFAULT;
			if (old.opc == BREAKPOINT_INSTRUCTION) {
	/*		/*
	* If we find a breakpoint instruction, a kprobe has been placed		* If we find a breakpoint instruction, a kprobe has been
	* at the beginning of the function. We write the constant		* placed at the beginning of the function. We write the
	* KPROBE_ON_FTRACE_CALL into the remaining four bytes of the original		* constant KPROBE_ON_FTRACE_CALL into the remaining four
	* instruction so that the kprobes handler can execute a brasl if it		* bytes of the original instruction so that the kprobes
	* reaches this breakpoint.		* handler can execute a brasl if it reaches this breakpoint.
	*/		*/
	if (op == BREAKPOINT_INSTRUCTION) {		new.opc = orig.opc = BREAKPOINT_INSTRUCTION;
	size -= 2;		orig.disp = KPROBE_ON_FTRACE_NOP;
	from += 2;		new.disp = KPROBE_ON_FTRACE_CALL;
	to += 2;		} else {
	insn.disp = KPROBE_ON_FTRACE_CALL;		/* 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 -EPERM;
	return 0;		return 0;
	}		}