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Subject[PATCH v3 4/8] powerpc/pseries: Read/Write oops nvram partition via pstore
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IBM's p series machines provide persistent storage for LPARs through NVRAM.
NVRAM's lnx,oops-log partition is used to log oops messages.
Currently the kernel provides the contents of p-series NVRAM only as a
simple stream of bytes via /dev/nvram, which must be interpreted in user
space by the nvram command in the powerpc-utils package.

This patch set exploits the pstore subsystem to expose oops partition in
NVRAM as a separate file in /dev/pstore. For instance, Oops messages will be
stored in a file named [dmesg-nvram-2]. In case pstore registration fails it
will fall back to kmsg_dump mechanism.

This patch will read/write the oops messages from/to this partition via pstore.

Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
---
arch/powerpc/platforms/pseries/nvram.c | 172 +++++++++++++++++++++++++++++---
1 file changed, 157 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/nvram.c b/arch/powerpc/platforms/pseries/nvram.c
index 088f023..9edec8e 100644
--- a/arch/powerpc/platforms/pseries/nvram.c
+++ b/arch/powerpc/platforms/pseries/nvram.c
@@ -18,6 +18,7 @@
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/kmsg_dump.h>
+#include <linux/pstore.h>
#include <linux/ctype.h>
#include <linux/zlib.h>
#include <asm/uaccess.h>
@@ -127,6 +128,14 @@ static size_t oops_data_sz;
#define MEM_LEVEL 4
static struct z_stream_s stream;

+#ifdef CONFIG_PSTORE
+static enum pstore_type_id nvram_type_ids[] = {
+ PSTORE_TYPE_DMESG,
+ -1
+};
+static int read_type;
+#endif
+
static ssize_t pSeries_nvram_read(char *buf, size_t count, loff_t *index)
{
unsigned int i;
@@ -430,6 +439,149 @@ static int __init pseries_nvram_init_os_partition(struct nvram_os_partition
return 0;
}

+/*
+ * Are we using the ibm,rtas-log for oops/panic reports? And if so,
+ * would logging this oops/panic overwrite an RTAS event that rtas_errd
+ * hasn't had a chance to read and process? Return 1 if so, else 0.
+ *
+ * We assume that if rtas_errd hasn't read the RTAS event in
+ * NVRAM_RTAS_READ_TIMEOUT seconds, it's probably not going to.
+ */
+static int clobbering_unread_rtas_event(void)
+{
+ return (oops_log_partition.index == rtas_log_partition.index
+ && last_unread_rtas_event
+ && get_seconds() - last_unread_rtas_event <=
+ NVRAM_RTAS_READ_TIMEOUT);
+}
+
+#ifdef CONFIG_PSTORE
+static int nvram_pstore_open(struct pstore_info *psi)
+{
+ /* Reset the iterator to start reading partitions again */
+ read_type = -1;
+ return 0;
+}
+
+/**
+ * nvram_pstore_write - pstore write callback for nvram
+ * @type: Type of message logged
+ * @reason: reason behind dump (oops/panic)
+ * @id: identifier to indicate the write performed
+ * @part: pstore writes data to registered buffer in parts,
+ * part number will indicate the same.
+ * @count: Indicates oops count
+ * @size: number of bytes written to the registered buffer
+ * @psi: registered pstore_info structure
+ *
+ * Called by pstore_dump() when an oops or panic report is logged in the
+ * printk buffer.
+ * Returns 0 on successful write.
+ */
+static int nvram_pstore_write(enum pstore_type_id type,
+ enum kmsg_dump_reason reason,
+ u64 *id, unsigned int part, int count,
+ size_t size, struct pstore_info *psi)
+{
+ int rc;
+ struct oops_log_info *oops_hdr = (struct oops_log_info *) oops_buf;
+
+ /* part 1 has the recent messages from printk buffer */
+ if (part > 1 || type != PSTORE_TYPE_DMESG ||
+ clobbering_unread_rtas_event())
+ return -1;
+
+ oops_hdr->version = OOPS_HDR_VERSION;
+ oops_hdr->report_length = (u16) size;
+ oops_hdr->timestamp = get_seconds();
+ rc = nvram_write_os_partition(&oops_log_partition, oops_buf,
+ (int) (sizeof(*oops_hdr) + size), ERR_TYPE_KERNEL_PANIC,
+ count);
+
+ if (rc != 0)
+ return rc;
+
+ *id = part;
+ return 0;
+}
+
+/*
+ * Reads the oops/panic report.
+ * Returns the length of the data we read from each partition.
+ * Returns 0 if we've been called before.
+ */
+static ssize_t nvram_pstore_read(u64 *id, enum pstore_type_id *type,
+ int *count, struct timespec *time, char **buf,
+ struct pstore_info *psi)
+{
+ struct oops_log_info *oops_hdr;
+ unsigned int err_type, id_no;
+ struct nvram_os_partition *part = NULL;
+ char *buff = NULL;
+
+ read_type++;
+
+ switch (nvram_type_ids[read_type]) {
+ case PSTORE_TYPE_DMESG:
+ part = &oops_log_partition;
+ *type = PSTORE_TYPE_DMESG;
+ break;
+ default:
+ return 0;
+ }
+
+ buff = kmalloc(part->size, GFP_KERNEL);
+
+ if (!buff)
+ return -ENOMEM;
+
+ if (nvram_read_partition(part, buff, part->size, &err_type, &id_no)) {
+ kfree(buff);
+ return 0;
+ }
+
+ *count = 0;
+ *id = id_no;
+ oops_hdr = (struct oops_log_info *)buff;
+ *buf = buff + sizeof(*oops_hdr);
+ time->tv_sec = oops_hdr->timestamp;
+ time->tv_nsec = 0;
+ return oops_hdr->report_length;
+}
+
+static struct pstore_info nvram_pstore_info = {
+ .owner = THIS_MODULE,
+ .name = "nvram",
+ .open = nvram_pstore_open,
+ .read = nvram_pstore_read,
+ .write = nvram_pstore_write,
+};
+
+static int nvram_pstore_init(void)
+{
+ int rc = 0;
+
+ nvram_pstore_info.buf = oops_data;
+ nvram_pstore_info.bufsize = oops_data_sz;
+
+ rc = pstore_register(&nvram_pstore_info);
+ if (rc != 0)
+ pr_err("nvram: pstore_register() failed, defaults to "
+ "kmsg_dump; returned %d\n", rc);
+ else
+ /*TODO: Support compression when pstore is configured */
+ pr_info("nvram: Compression of oops text supported only when "
+ "pstore is not configured");
+
+ return rc;
+}
+#else
+static int nvram_pstore_init(void)
+{
+ return -1;
+}
+#endif
+
static void __init nvram_init_oops_partition(int rtas_partition_exists)
{
int rc;
@@ -453,6 +605,11 @@ static void __init nvram_init_oops_partition(int rtas_partition_exists)
oops_data = oops_buf + sizeof(struct oops_log_info);
oops_data_sz = oops_log_partition.size - sizeof(struct oops_log_info);

+ rc = nvram_pstore_init();
+
+ if (!rc)
+ return;
+
/*
* Figure compression (preceded by elimination of each line's <n>
* severity prefix) will reduce the oops/panic report to at most
@@ -525,21 +682,6 @@ int __init pSeries_nvram_init(void)
return 0;
}

-/*
- * Are we using the ibm,rtas-log for oops/panic reports? And if so,
- * would logging this oops/panic overwrite an RTAS event that rtas_errd
- * hasn't had a chance to read and process? Return 1 if so, else 0.
- *
- * We assume that if rtas_errd hasn't read the RTAS event in
- * NVRAM_RTAS_READ_TIMEOUT seconds, it's probably not going to.
- */
-static int clobbering_unread_rtas_event(void)
-{
- return (oops_log_partition.index == rtas_log_partition.index
- && last_unread_rtas_event
- && get_seconds() - last_unread_rtas_event <=
- NVRAM_RTAS_READ_TIMEOUT);
-}

/* Derived from logfs_compress() */
static int nvram_compress(const void *in, void *out, size_t inlen,


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