[PATCH] vmcore-dmesg: vmcore-dmesg: Make it work with new structured logging format

Vivek Goyal
2012-07-30T17:32:55Z

Now kernel has made kernel logging structured and exsisting vmcore-dmesg
does not work with this new format. Hence kernel version 3.5 is broken. In
3.6 now a kernel patch has been put which exports relevant fields. This
patch parses those fields and makes vmcore-dmesg work with new logging
format.

Currently it does not display log levels or dictionary. I personally think
that log levels are not very useful and it also requires additional kernel
patches so that log levels are not bitfields and relevant information is
exported to user space properly.

Concept of dictionary is new and relevant information is exported. One can
possibly enahnce vmcore-dmesg to also print dictionary contents based on
a user command line option.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
vmcore-dmesg/vmcore-dmesg.c | 227 ++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 221 insertions(+), 6 deletions(-)

Index: kexec-tools/vmcore-dmesg/vmcore-dmesg.c
===================================================================
--- kexec-tools.orig/vmcore-dmesg/vmcore-dmesg.c 2012-08-01 20:06:21.263781247 -0400
+++ kexec-tools/vmcore-dmesg/vmcore-dmesg.c 2012-08-01 20:06:23.114781564 -0400
@@ -15,6 +15,7 @@
#include <fcntl.h>
#include <elf.h>
#include <stdbool.h>
+#include <inttypes.h>

/* The 32bit and 64bit note headers make it clear we don't care */
typedef Elf32_Nhdr Elf_Nhdr;
@@ -29,6 +30,18 @@ static loff_t log_end_vaddr;
static loff_t log_buf_len_vaddr;
static loff_t logged_chars_vaddr;

+/* record format logs */
+static loff_t log_first_idx_vaddr;
+static loff_t log_next_idx_vaddr;
+
+/* struct log size */
+static uint64_t log_sz;
+
+/* struct log field offsets */
+static uint64_t log_offset_ts_nsec = UINT64_MAX;
+static uint16_t log_offset_len = UINT16_MAX;
+static uint16_t log_offset_text_len = UINT16_MAX;
+
#if __BYTE_ORDER == __LITTLE_ENDIAN
#define ELFDATANATIVE ELFDATA2LSB
#elif __BYTE_ORDER == __BIG_ENDIAN
@@ -240,6 +253,8 @@ static void scan_vmcoreinfo(char *start,
SYMBOL(log_end),
SYMBOL(log_buf_len),
SYMBOL(logged_chars),
+ SYMBOL(log_first_idx),
+ SYMBOL(log_next_idx),
};

for (pos = start; pos <= last; pos = eol + 1) {
@@ -291,6 +306,20 @@ static void scan_vmcoreinfo(char *start,
*symbol[i].vaddr = vaddr;
}

+ /* Check for "SIZE(log)=" */
+ if (memcmp("SIZE(log)=", pos, 10) == 0)
+ log_sz = strtoull(pos + 10, NULL, 10);
+
+ /* Check for struct log field offsets */
+ if (memcmp("OFFSET(log.ts_nsec)=", pos, 20) == 0)
+ log_offset_ts_nsec = strtoull(pos + 20, NULL, 10);
+
+ if (memcmp("OFFSET(log.len)=", pos, 16) == 0)
+ log_offset_len = strtoul(pos + 16, NULL, 10);
+
+ if (memcmp("OFFSET(log.text_len)=", pos, 21) == 0)
+ log_offset_text_len = strtoul(pos + 21, NULL, 10);
+
if (last_line)
break;
}
@@ -400,7 +429,19 @@ static int32_t read_file_s32(int fd, uin
return read_file_u32(fd, addr);
}

-static void dump_dmesg(int fd)
+static void write_to_stdout(char *buf, unsigned int nr)
+{
+ ssize_t ret;
+
+ ret = write(STDOUT_FILENO, buf, nr);
+ if (ret != nr) {
+ fprintf(stderr, "Failed to write out the dmesg log buffer!:"
+ " %s\n", strerror(errno));
+ exit(54);
+ }
+}
+
+static void dump_dmesg_legacy(int fd)
{
uint64_t log_buf, log_buf_offset;
unsigned log_end, logged_chars, log_end_wrapped;
@@ -455,12 +496,186 @@ static void dump_dmesg(int fd)
strerror(errno));
exit(53);
}
- ret = write(STDOUT_FILENO, buf + (log_buf_len - logged_chars), logged_chars);
- if (ret != logged_chars) {
- fprintf(stderr, "Failed to write out the dmesg log buffer!: %s\n",
- strerror(errno));
- exit(54);
+
+ write_to_stdout(buf + (log_buf_len - logged_chars), logged_chars);
+}
+
+static inline uint16_t struct_val_u16(char *ptr, unsigned int offset)
+{
+ return(file16_to_cpu(*(uint16_t *)(ptr + offset)));
+}
+
+static inline uint32_t struct_val_u32(char *ptr, unsigned int offset)
+{
+ return(file32_to_cpu(*(uint32_t *)(ptr + offset)));
+}
+
+static inline uint32_t struct_val_u64(char *ptr, unsigned int offset)
+{
+ return(file64_to_cpu(*(uint64_t *)(ptr + offset)));
+}
+
+/* human readable text of the record */
+static char *log_text(char *msg)
+{
+ return msg + log_sz;
+}
+
+/* get record by index; idx must point to valid msg */
+static char *log_from_idx(char *log_buf, uint32_t idx)
+{
+ char *msg = log_buf + idx;
+
+ /*
+ * A length == 0 record is the end of buffer marker. Wrap around and
+ * read the message at the start of the buffer.
+ */
+ if (!struct_val_u16(msg, log_offset_len))
+ return log_buf;
+ return msg;
+}
+
+/* get next record; idx must point to valid msg */
+static uint32_t log_next(char *log_buf, uint32_t idx)
+{
+ char *msg = log_buf + idx;
+ uint16_t len;
+
+ /* length == 0 indicates the end of the buffer; wrap */
+ /*
+ * A length == 0 record is the end of buffer marker. Wrap around and
+ * read the message at the start of the buffer as *this* one, and
+ * return the one after that.
+ */
+ len = struct_val_u16(msg, log_offset_len);
+ if (!len) {
+ msg = log_buf;
+ return struct_val_u16(msg, log_offset_len);
+ }
+ return idx + len;
+}
+
+/* Read headers of log records and dump accordingly */
+static void dump_dmesg_structured(int fd)
+{
+#define OUT_BUF_SIZE 4096
+ uint64_t log_buf, log_buf_offset, ts_nsec;
+ uint32_t log_first_idx, log_next_idx, current_idx, len = 0, i;
+ int log_buf_len;
+ char *buf, out_buf[OUT_BUF_SIZE];
+ ssize_t ret;
+ char *msg;
+ uint16_t text_len;
+ imaxdiv_t imaxdiv_sec, imaxdiv_usec;
+
+ if (!log_buf_vaddr) {
+ fprintf(stderr, "Missing the log_buf symbol\n");
+ exit(60);
+ }
+
+ if (!log_buf_len_vaddr) {
+ fprintf(stderr, "Missing the log_bug_len symbol\n");
+ exit(61);
+ }
+
+ if (!log_first_idx_vaddr) {
+ fprintf(stderr, "Missing the log_first_idx symbol\n");
+ exit(62);
+ }
+
+ if (!log_next_idx_vaddr) {
+ fprintf(stderr, "Missing the log_next_idx symbol\n");
+ exit(63);
+ }
+
+ if (!log_sz) {
+ fprintf(stderr, "Missing the struct log size export\n");
+ exit(64);
+ }
+
+ if (log_offset_ts_nsec == UINT64_MAX) {
+ fprintf(stderr, "Missing the log.ts_nsec offset export\n");
+ exit(65);
+ }
+
+ if (log_offset_len == UINT16_MAX) {
+ fprintf(stderr, "Missing the log.len offset export\n");
+ exit(66);
+ }
+
+ if (log_offset_text_len == UINT16_MAX) {
+ fprintf(stderr, "Missing the log.text_len offset export\n");
+ exit(67);
+ }
+
+ log_buf = read_file_pointer(fd, vaddr_to_offset(log_buf_vaddr));
+ log_buf_len = read_file_s32(fd, vaddr_to_offset(log_buf_len_vaddr));
+
+ log_first_idx = read_file_u32(fd, vaddr_to_offset(log_first_idx_vaddr));
+ log_next_idx = read_file_u32(fd, vaddr_to_offset(log_next_idx_vaddr));
+
+ log_buf_offset = vaddr_to_offset(log_buf);
+
+ buf = calloc(1, log_buf_len);
+ if (!buf) {
+ fprintf(stderr, "Failed to malloc %d bytes for the logbuf:"
+ " %s\n", log_buf_len, strerror(errno));
+ exit(64);
+ }
+
+ ret = pread(fd, buf, log_buf_len, log_buf_offset);
+ if (ret != log_buf_len) {
+ fprintf(stderr, "Failed to read log buffer of size %d bytes:"
+ " %s\n", log_buf_len, strerror(errno));
+ exit(65);
+ }
+
+ /* Parse records and write out data at standard output */
+
+ current_idx = log_first_idx;
+ len = 0;
+ while (current_idx != log_next_idx) {
+ msg = log_from_idx(buf, current_idx);
+ ts_nsec = struct_val_u64(msg, log_offset_ts_nsec);
+ imaxdiv_sec = imaxdiv(ts_nsec, 1000000000);
+ imaxdiv_usec = imaxdiv(imaxdiv_sec.rem, 1000);
+
+ len += sprintf(out_buf + len, "[%5llu.%06llu] ",
+ (long long unsigned int)imaxdiv_sec.quot,
+ (long long unsigned int)imaxdiv_usec.quot);
+
+ /* escape non-printable characters */
+ text_len = struct_val_u16(msg, log_offset_text_len);
+ for (i = 0; i < text_len; i++) {
+ unsigned char c = log_text(msg)[i];
+
+ if (c < ' ' || c >= 128)
+ len += sprintf(out_buf + len, "\\x%02x", c);
+ else
+ out_buf[len++] = c;
+
+ if (len >= OUT_BUF_SIZE - 16) {
+ write_to_stdout(out_buf, len);
+ len = 0;
+ }
+ }
+
+ out_buf[len++] = '\n';
+
+ /* Move to next record */
+ current_idx = log_next(buf, current_idx);
}
+
+ if (len)
+ write_to_stdout(out_buf, len);
+}
+
+static void dump_dmesg(int fd)
+{
+ if (log_first_idx_vaddr)
+ dump_dmesg_structured(fd);
+ else
+ dump_dmesg_legacy(fd);
}

int main(int argc, char **argv)

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