linux-kernel - [PATCH 11/23] bpf: factor out a bpf_trace_copy

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Message-Id: <20200521152301.2587579-12-hch@lst.de>
Date:   Thu, 21 May 2020 17:22:49 +0200
From:   Christoph Hellwig <hch@....de>
To:     x86@...nel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-parisc@...r.kernel.org, linux-um@...ts.infradead.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 11/23] 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@....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