[PATCH 11/23] bpf: factor out a bpf_trace_copy_string helper

Christoph Hellwig
2020-05-21T15:25:27Z

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>
---
kernel/trace/bpf_trace.c | 42 +++++++++++++++++++++++-----------------
1 file changed, 24 insertions(+), 18 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index f5231ffea85b9..9d4080590f711 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -321,6 +321,28 @@ 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
@@ -403,24 +425,8 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
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;
}

--
2.26.2