Commit 98c0d24d authored by Sven Schnelle's avatar Sven Schnelle Committed by Vasily Gorbik
Browse files

s390/ftrace: verify opcode before applying patch 



commit 72b3942a ("scripts: ftrace - move the
sort-processing in ftrace_init") had the unexpected
side effect that wrong code locations were patched.
To prevent this from happening again, verify the
opcode before patching it.

Signed-off-by: default avatarSven Schnelle <svens@linux.ibm.com>
Reviewed-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent f36e7c98

arch/s390/kernel/ftrace.c

+27 −16
Original line number Diff line number Diff line
@@ -164,31 +164,32 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, 
	return 0;

}



static void brcl_disable(void *brcl)

static int ftrace_patch_branch_mask(void *addr, u16 expected, bool enable)

{

	u8 op = 0x04; /* set mask field to zero */

	u16 old;

	u8 op;



	s390_kernel_write((char *)brcl + 1, &op, sizeof(op));

	if (get_kernel_nofault(old, addr))

		return -EFAULT;

	if (old != expected)

		return -EINVAL;

	/* set mask field to all ones or zeroes */

	op = enable ? 0xf4 : 0x04;

	s390_kernel_write((char *)addr + 1, &op, sizeof(op));

	return 0;

}



int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,

		    unsigned long addr)

{

	brcl_disable((void *)rec->ip);

	return 0;

}



static void brcl_enable(void *brcl)

{

	u8 op = 0xf4; /* set mask field to all ones */



	s390_kernel_write((char *)brcl + 1, &op, sizeof(op));

	/* Expect brcl 0xf,... */

	return ftrace_patch_branch_mask((void *)rec->ip, 0xc0f4, false);

}



int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)

{

	brcl_enable((void *)rec->ip);

	return 0;

	/* Expect brcl 0x0,... */

	return ftrace_patch_branch_mask((void *)rec->ip, 0xc004, true);

}



int ftrace_update_ftrace_func(ftrace_func_t func)
@@ -261,14 +262,24 @@ NOKPROBE_SYMBOL(prepare_ftrace_return); 
 */

int ftrace_enable_ftrace_graph_caller(void)

{

	brcl_disable(ftrace_graph_caller);

	int rc;



	/* Expect brc 0xf,... */

	rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false);

	if (rc)

		return rc;

	text_poke_sync_lock();

	return 0;

}



int ftrace_disable_ftrace_graph_caller(void)

{

	brcl_enable(ftrace_graph_caller);

	int rc;



	/* Expect brc 0x0,... */

	rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true);

	if (rc)

		return rc;

	text_poke_sync_lock();

	return 0;

}