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Date: Sun, 04 May 2008 21:07:10 +0200
From: Johannes Berg <johannes@...solutions.net>
To: netdev <netdev@...r.kernel.org>
Subject: [ARCHIVE] store skb allocation stacktrace in skb
I needed this patch, so here it is for the archive just in case somebody
else needs some similar debugging feature in the future.
---
include/linux/skbuff.h | 12 ++++++++++++
kernel/stacktrace.c | 3 +++
net/Kconfig | 12 ++++++++++++
net/core/skbuff.c | 30 ++++++++++++++++++++++++++++++
4 files changed, 57 insertions(+)
--- everything.orig/include/linux/skbuff.h 2008-05-04 13:21:14.000000000 +0200
+++ everything/include/linux/skbuff.h 2008-05-04 13:22:41.000000000 +0200
@@ -28,6 +28,7 @@
#include <linux/rcupdate.h>
#include <linux/dmaengine.h>
#include <linux/hrtimer.h>
+#include <linux/stacktrace.h>
#define HAVE_ALLOC_SKB /* For the drivers to know */
#define HAVE_ALIGNABLE_SKB /* Ditto 8) */
@@ -188,6 +189,8 @@ enum {
#define NET_SKBUFF_DATA_USES_OFFSET 1
#endif
+#define NET_SKBUFF_STACKTRACE_ENTRIES 20
+
#ifdef NET_SKBUFF_DATA_USES_OFFSET
typedef unsigned int sk_buff_data_t;
#else
@@ -245,6 +248,8 @@ typedef unsigned char *sk_buff_data_t;
* @dma_cookie: a cookie to one of several possible DMA operations
* done by skb DMA functions
* @secmark: security marking
+ * @stacktrace: allocation stack trace
+ * @stacktracedata: allocation stack trace entries
*/
struct sk_buff {
@@ -321,6 +326,11 @@ struct sk_buff {
__u32 mark;
+#ifdef CONFIG_SKBUFF_ALLOC_TRACE
+ struct stack_trace stacktrace;
+ unsigned long stacktracedata[NET_SKBUFF_STACKTRACE_ENTRIES];
+#endif
+
sk_buff_data_t transport_header;
sk_buff_data_t network_header;
sk_buff_data_t mac_header;
@@ -341,6 +351,8 @@ struct sk_buff {
#include <asm/system.h>
+extern void print_skb_alloc_trace(struct sk_buff *skb);
+
extern void kfree_skb(struct sk_buff *skb);
extern void __kfree_skb(struct sk_buff *skb);
extern struct sk_buff *__alloc_skb(unsigned int size,
--- everything.orig/net/Kconfig 2008-05-04 13:21:14.000000000 +0200
+++ everything/net/Kconfig 2008-05-04 13:22:41.000000000 +0200
@@ -35,6 +35,18 @@ config NET_NS
Allow user space to create what appear to be multiple instances
of the network stack.
+config SKBUFF_ALLOC_TRACE
+ bool "SKB allocation stack tracking"
+ depends on EXPERIMENTAL && STACKTRACE_SUPPORT
+ select STACKTRACE
+ help
+ This option makes the skb allocation functions store a stack trace
+ into an SKB when allocated so that later one can dump it if
+ something is wrong with the SKB to find out where it came from.
+
+ Say N unless you're debugging SKB problems and need this
+ information, you can print the trace using print_skb_alloc_trace().
+
source "net/packet/Kconfig"
source "net/unix/Kconfig"
source "net/xfrm/Kconfig"
--- everything.orig/net/core/skbuff.c 2008-05-04 13:21:14.000000000 +0200
+++ everything/net/core/skbuff.c 2008-05-04 14:04:07.000000000 +0200
@@ -227,6 +227,13 @@ struct sk_buff *__alloc_skb(unsigned int
shinfo->ip6_frag_id = 0;
shinfo->frag_list = NULL;
+#ifdef CONFIG_SKBUFF_ALLOC_TRACE
+ skb->stacktrace.max_entries = NET_SKBUFF_STACKTRACE_ENTRIES;
+ skb->stacktrace.entries = skb->stacktracedata;
+ skb->stacktrace.skip = 1;
+ save_stack_trace(&skb->stacktrace);
+#endif
+
if (fclone) {
struct sk_buff *child = skb + 1;
atomic_t *fclone_ref = (atomic_t *) (child + 1);
@@ -244,6 +251,24 @@ nodata:
goto out;
}
+#ifdef CONFIG_SKBUFF_ALLOC_TRACE
+/**
+ * print_skb_alloc_trace - print skbuff allocation trace
+ * @skb: skb to print trace for
+ *
+ * This function prints the stacktrace from the location where
+ * the skb was allocated.
+ */
+void print_skb_alloc_trace(struct sk_buff *skb)
+{
+ if (WARN_ON(!skb))
+ return;
+
+ print_stack_trace(&skb->stacktrace, 0);
+}
+EXPORT_SYMBOL(print_skb_alloc_trace);
+#endif
+
/**
* __netdev_alloc_skb - allocate an skbuff for rx on a specific device
* @dev: network device to receive on
@@ -446,6 +471,11 @@ static void __copy_skb_header(struct sk_
#endif
#endif
skb_copy_secmark(new, old);
+#ifdef CONFIG_SKBUFF_ALLOC_TRACE
+ memcpy(&new->stacktrace, &old->stacktrace, sizeof(old->stacktrace));
+ memcpy(&new->stacktracedata, &old->stacktracedata, sizeof(old->stacktracedata));
+ new->stacktrace.entries = new->stacktracedata;
+#endif
}
static struct sk_buff *__skb_clone(struct sk_buff *n, struct sk_buff *skb)
--
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