Commit a28726b4 authored by Ben Zhang's avatar Ben Zhang Committed by Tony Luck
Browse files

pstore/ram: Strip ramoops header for correct decompression

pstore compression/decompression was added during 3.12.
The ramoops driver prepends a "====timestamp.timestamp-C|D\n"
header to the compressed record before handing it over to pstore
driver which doesn't know about the header. In pstore_decompress(),
the pstore driver reads the first "==" as a zlib header, so the
decompression always fails. For example, this causes the driver
to write /dev/pstore/dmesg-ramoops-0.enc.z instead of

This patch makes the ramoops driver remove the header before
pstore decompression.
Signed-off-by: default avatarBen Zhang <>
Acked-by: default avatarKees Cook <>
Signed-off-by: default avatarTony Luck <>
parent 0df1f248
......@@ -135,25 +135,27 @@ ramoops_get_next_prz(struct persistent_ram_zone *przs[], uint *c, uint max,
return prz;
static void ramoops_read_kmsg_hdr(char *buffer, struct timespec *time,
static int ramoops_read_kmsg_hdr(char *buffer, struct timespec *time,
bool *compressed)
char data_type;
int header_length = 0;
if (sscanf(buffer, RAMOOPS_KERNMSG_HDR "%lu.%lu-%c\n",
&time->tv_sec, &time->tv_nsec, &data_type) == 3) {
if (sscanf(buffer, RAMOOPS_KERNMSG_HDR "%lu.%lu-%c\n%n", &time->tv_sec,
&time->tv_nsec, &data_type, &header_length) == 3) {
if (data_type == 'C')
*compressed = true;
*compressed = false;
} else if (sscanf(buffer, RAMOOPS_KERNMSG_HDR "%lu.%lu\n",
&time->tv_sec, &time->tv_nsec) == 2) {
} else if (sscanf(buffer, RAMOOPS_KERNMSG_HDR "%lu.%lu\n%n",
&time->tv_sec, &time->tv_nsec, &header_length) == 2) {
*compressed = false;
} else {
time->tv_sec = 0;
time->tv_nsec = 0;
*compressed = false;
return header_length;
static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
......@@ -165,6 +167,7 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
ssize_t ecc_notice_size;
struct ramoops_context *cxt = psi->data;
struct persistent_ram_zone *prz;
int header_length;
prz = ramoops_get_next_prz(cxt->przs, &cxt->dump_read_cnt,
cxt->max_dump_cnt, id, type,
......@@ -178,7 +181,13 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
if (!prz)
return 0;
if (!persistent_ram_old(prz))
return 0;
size = persistent_ram_old_size(prz);
header_length = ramoops_read_kmsg_hdr(persistent_ram_old(prz), time,
size -= header_length;
/* ECC correction notice */
ecc_notice_size = persistent_ram_ecc_string(prz, NULL, 0);
......@@ -187,8 +196,7 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
if (*buf == NULL)
return -ENOMEM;
memcpy(*buf, persistent_ram_old(prz), size);
ramoops_read_kmsg_hdr(*buf, time, compressed);
memcpy(*buf, (char *)persistent_ram_old(prz) + header_length, size);
persistent_ram_ecc_string(prz, *buf + size, ecc_notice_size + 1);
return size + ecc_notice_size;
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