[for-next][PATCH 10/21] tracing: Make trace_seq_putmem_hex() more robust

Steven Rostedt
2014-07-03T16:18:21Z

[-- Attachment #1: 0010-tracing-Make-trace_seq_putmem_hex-more-robust.patch --]
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From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

Currently trace_seq_putmem_hex() can only take as a parameter a pointer
to something that is 8 bytes or less, otherwise it will overflow the
buffer. This is protected by a macro that encompasses the call to
trace_seq_putmem_hex() that has a BUILD_BUG_ON() for the variable before
it is passed in. This is not very robust and if trace_seq_putmem_hex() ever
gets used outside that macro it will cause issues.

Instead of only being able to produce a hex output of memory that is for
a single word, change it to be more robust and allow any size input.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
include/linux/trace_seq.h | 2 --
kernel/trace/trace_output.h | 1 -
kernel/trace/trace_seq.c | 26 +++++++++++++++++++-------
3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 1f05317f51c4..8283762ab7ef 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -25,8 +25,6 @@ trace_seq_init(struct trace_seq *s)
s->full = 0;
}

-#define MAX_MEMHEX_BYTES 8
-
/*
* Currently only defined when tracing is enabled.
*/
diff --git a/kernel/trace/trace_output.h b/kernel/trace/trace_output.h
index bf7daf2237ed..80b25b585a70 100644
--- a/kernel/trace/trace_output.h
+++ b/kernel/trace/trace_output.h
@@ -43,7 +43,6 @@ do { \

#define SEQ_PUT_HEX_FIELD_RET(s, x) \
do { \
- BUILD_BUG_ON(sizeof(x) > MAX_MEMHEX_BYTES); \
if (!trace_seq_putmem_hex(s, &(x), sizeof(x))) \
return TRACE_TYPE_PARTIAL_LINE; \
} while (0)
diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c
index 0fabca773e51..88c0f80f0a1f 100644
--- a/kernel/trace/trace_seq.c
+++ b/kernel/trace/trace_seq.c
@@ -291,6 +291,7 @@ int trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
}
EXPORT_SYMBOL_GPL(trace_seq_putmem);

+#define MAX_MEMHEX_BYTES 8U
#define HEX_CHARS (MAX_MEMHEX_BYTES*2 + 1)

/**
@@ -310,22 +311,33 @@ int trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
{
unsigned char hex[HEX_CHARS];
const unsigned char *data = mem;
+ unsigned int start_len;
int i, j;
+ int cnt = 0;

if (s->full)
return 0;

+ while (len) {
+ start_len = min(len, HEX_CHARS - 1);
#ifdef __BIG_ENDIAN
- for (i = 0, j = 0; i < len; i++) {
+ for (i = 0, j = 0; i < start_len; i++) {
#else
- for (i = len-1, j = 0; i >= 0; i--) {
+ for (i = start_len-1, j = 0; i >= 0; i--) {
#endif
- hex[j++] = hex_asc_hi(data[i]);
- hex[j++] = hex_asc_lo(data[i]);
- }
- hex[j++] = ' ';
+ hex[j++] = hex_asc_hi(data[i]);
+ hex[j++] = hex_asc_lo(data[i]);
+ }
+ if (WARN_ON_ONCE(j == 0 || j/2 > len))
+ break;
+
+ /* j increments twice per loop */
+ len -= j / 2;
+ hex[j++] = ' ';

- return trace_seq_putmem(s, hex, j);
+ cnt += trace_seq_putmem(s, hex, j);
+ }
+ return cnt;
}
EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);

--
2.0.0