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authorJoel Fernandes <joelaf@google.com>2016-10-20 09:34:05 +0200
committerKees Cook <keescook@chromium.org>2016-11-16 01:34:27 +0100
commitfbccdeb8d77d6830556bc4079eeed80298cc97dc (patch)
treec423e1973a8107db2ee1f6dd8ac70539fdee3fef /fs/pstore
parentramoops: Split ftrace buffer space into per-CPU zones (diff)
downloadlinux-fbccdeb8d77d6830556bc4079eeed80298cc97dc.tar.xz
linux-fbccdeb8d77d6830556bc4079eeed80298cc97dc.zip
pstore: Add ftrace timestamp counter
In preparation for merging the per CPU buffers into one buffer when we retrieve the pstore ftrace data, we store the timestamp as a counter in the ftrace pstore record. We store the CPU number as well if !PSTORE_CPU_IN_IP, in this case we shift the counter and may lose ordering there but we preserve the same record size. The timestamp counter is also racy, and not doing any locking or synchronization here results in the benefit of lower overhead. Since we don't care much here for exact ordering of function traces across CPUs, we don't synchronize and may lose some counter updates but I'm ok with that. Using trace_clock() results in much lower performance so avoid using it since we don't want accuracy in timestamp and need a rough ordering to perform merge. Signed-off-by: Joel Fernandes <joelaf@google.com> [kees: updated commit message, added comments] Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'fs/pstore')
-rw-r--r--fs/pstore/ftrace.c4
-rw-r--r--fs/pstore/inode.c8
-rw-r--r--fs/pstore/internal.h34
3 files changed, 9 insertions, 37 deletions
diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
index d4887705bb61..31548cc09e7b 100644
--- a/fs/pstore/ftrace.c
+++ b/fs/pstore/ftrace.c
@@ -27,6 +27,9 @@
#include <asm/barrier.h>
#include "internal.h"
+/* This doesn't need to be atomic: speed is chosen over correctness here. */
+static u64 pstore_ftrace_stamp;
+
static void notrace pstore_ftrace_call(unsigned long ip,
unsigned long parent_ip,
struct ftrace_ops *op,
@@ -42,6 +45,7 @@ static void notrace pstore_ftrace_call(unsigned long ip,
rec.ip = ip;
rec.parent_ip = parent_ip;
+ pstore_ftrace_write_timestamp(&rec, pstore_ftrace_stamp++);
pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
0, sizeof(rec), psinfo);
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 1781dc50762e..0d6bbcf47d52 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -107,9 +107,11 @@ static int pstore_ftrace_seq_show(struct seq_file *s, void *v)
struct pstore_ftrace_seq_data *data = v;
struct pstore_ftrace_record *rec = (void *)(ps->data + data->off);
- seq_printf(s, "%d %08lx %08lx %pf <- %pF\n",
- pstore_ftrace_decode_cpu(rec), rec->ip, rec->parent_ip,
- (void *)rec->ip, (void *)rec->parent_ip);
+ seq_printf(s, "CPU:%d ts:%llu %08lx %08lx %pf <- %pF\n",
+ pstore_ftrace_decode_cpu(rec),
+ pstore_ftrace_read_timestamp(rec),
+ rec->ip, rec->parent_ip, (void *)rec->ip,
+ (void *)rec->parent_ip);
return 0;
}
diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
index e38a22b31282..da416e6591c9 100644
--- a/fs/pstore/internal.h
+++ b/fs/pstore/internal.h
@@ -5,40 +5,6 @@
#include <linux/time.h>
#include <linux/pstore.h>
-#if NR_CPUS <= 2 && defined(CONFIG_ARM_THUMB)
-#define PSTORE_CPU_IN_IP 0x1
-#elif NR_CPUS <= 4 && defined(CONFIG_ARM)
-#define PSTORE_CPU_IN_IP 0x3
-#endif
-
-struct pstore_ftrace_record {
- unsigned long ip;
- unsigned long parent_ip;
-#ifndef PSTORE_CPU_IN_IP
- unsigned int cpu;
-#endif
-};
-
-static inline void
-pstore_ftrace_encode_cpu(struct pstore_ftrace_record *rec, unsigned int cpu)
-{
-#ifndef PSTORE_CPU_IN_IP
- rec->cpu = cpu;
-#else
- rec->ip |= cpu;
-#endif
-}
-
-static inline unsigned int
-pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec)
-{
-#ifndef PSTORE_CPU_IN_IP
- return rec->cpu;
-#else
- return rec->ip & PSTORE_CPU_IN_IP;
-#endif
-}
-
#ifdef CONFIG_PSTORE_FTRACE
extern void pstore_register_ftrace(void);
extern void pstore_unregister_ftrace(void);