From 98c0d24d1e7576a853b0812d95e599ba1a909e21 Mon Sep 17 00:00:00 2001 From: Sven Schnelle Date: Sun, 23 Jan 2022 20:20:09 +0100 Subject: s390/ftrace: verify opcode before applying patch commit 72b3942a173c ("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: Sven Schnelle Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- arch/s390/kernel/ftrace.c | 43 +++++++++++++++++++++++++++---------------- 1 file changed, 27 insertions(+), 16 deletions(-) (limited to 'arch') diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index 61f72c7fb0da..1db9cc795034 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -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; } -- cgit v1.2.3