bpf: factor out a bpf_trace_copy_string helper

Split out a helper to do the fault free access to the string pointer
to get it out of a crazy indentation level.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200521152301.2587579-12-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 879ee67..60e82c7 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -324,6 +324,28 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void)
        return &bpf_probe_write_user_proto;
 }
 
+static void bpf_trace_copy_string(char *buf, void *unsafe_ptr, char fmt_ptype,
+               size_t bufsz)
+{
+       void __user *user_ptr = (__force void __user *)unsafe_ptr;
+
+       buf[0] = 0;
+
+       switch (fmt_ptype) {
+       case 's':
+#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+               strncpy_from_unsafe(buf, unsafe_ptr, bufsz);
+               break;
+#endif
+       case 'k':
+               strncpy_from_kernel_nofault(buf, unsafe_ptr, bufsz);
+               break;
+       case 'u':
+               strncpy_from_user_nofault(buf, user_ptr, bufsz);
+               break;
+       }
+}
+
 /*
  * Only limited trace_printk() conversion specifiers allowed:
  * %d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %pks %pus %s
@@ -406,24 +428,8 @@ fmt_str:
                                break;
                        }
 
-                       buf[0] = 0;
-                       switch (fmt_ptype) {
-                       case 's':
-#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
-                               strncpy_from_unsafe(buf, unsafe_ptr,
-                                                   sizeof(buf));
-                               break;
-#endif
-                       case 'k':
-                               strncpy_from_kernel_nofault(buf, unsafe_ptr,
-                                                          sizeof(buf));
-                               break;
-                       case 'u':
-                               strncpy_from_user_nofault(buf,
-                                       (__force void __user *)unsafe_ptr,
-                                                        sizeof(buf));
-                               break;
-                       }
+                       bpf_trace_copy_string(buf, unsafe_ptr, fmt_ptype,
+                                       sizeof(buf));
                        goto fmt_next;
                }