[Crash-utility] [PATCH] log: output logs of printk safe buffers
We sometimes overlook logs written to printk safe buffers
(safe_print_seq/nmi_print_seq) which have not been flushed yet.
This patch will output unflushed logs of the safe buffers
at the bottom of log command output as follows:
[nmi_print_seq] CPU: 0 BUFFER: ffff888063c18ac0 LEN: 28
nmi print seq test message
[safe_print_seq] CPU: 1 BUFFER: ffff888063d19ae0 LEN: 30
safe print seq test message
Note that the safe buffer (struct printk_safe_seq_buf) was introduced
in kernel-4.11 and removed in kernel-5.15.
Signed-off-by: Shogo Matsumoto <shogo.matsumoto(a)fujitsu.com>
---
defs.h | 3 +++
kernel.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 61 insertions(+)
diff --git a/defs.h b/defs.h
index 7e2a16e..3ee51e0 100644
--- a/defs.h
+++ b/defs.h
@@ -2146,6 +2146,8 @@ struct offset_table { /* stash of commonly-used
offsets */
long wait_queue_entry_private;
long wait_queue_head_head;
long wait_queue_entry_entry;
+ long printk_safe_seq_buf_len;
+ long printk_safe_seq_buf_buffer;
};
struct size_table { /* stash of commonly-used sizes */
@@ -2310,6 +2312,7 @@ struct size_table { /* stash of commonly-used sizes */
long prb_desc;
long wait_queue_entry;
long task_struct_state;
+ long printk_safe_seq_buf_buffer;
};
struct array_table {
diff --git a/kernel.c b/kernel.c
index f4598ea..cc97176 100644
--- a/kernel.c
+++ b/kernel.c
@@ -93,6 +93,7 @@ static void source_tree_init(void);
static ulong dump_audit_skb_queue(ulong);
static ulong __dump_audit(char *);
static void dump_audit(void);
+static void dump_printk_safe_seq_buf(void);
static char *vmcoreinfo_read_string(const char *);
static void check_vmcoreinfo(void);
static int is_pvops_xen(void);
@@ -5048,6 +5049,7 @@ cmd_log(void)
}
dump_log(msg_flags);
+ dump_printk_safe_seq_buf();
}
@@ -11534,6 +11536,62 @@ dump_audit(void)
error(INFO, "kernel audit log is empty\n");
}
+static void
+__dump_printk_safe_seq_buf(char *buf_name)
+{
+ int cpu, buffer_size;
+ char *buffer;
+
+ if (!symbol_exists(buf_name)) {
+ return;
+ }
+
+ buffer_size = SIZE(printk_safe_seq_buf_buffer);
+ buffer = GETBUF(buffer_size);
+ for (cpu = 0; cpu < kt->cpus; cpu++) {
+ ulong len_addr, buffer_addr;
+ int len;
+
+ len_addr = symbol_value(buf_name) + kt->__per_cpu_offset[cpu] +
OFFSET(printk_safe_seq_buf_len);
+ buffer_addr = symbol_value(buf_name) + kt->__per_cpu_offset[cpu] +
OFFSET(printk_safe_seq_buf_buffer);
+ readmem(len_addr, KVADDR, &len, STRUCT_SIZE("atomic_t"),
"printk_safe_seq_buf len", FAULT_ON_ERROR);
+ readmem(buffer_addr, KVADDR, buffer, buffer_size, "printk_safe_seq_buf
buffer", FAULT_ON_ERROR);
+
+ if (len > 0) {
+ int i, n;
+ char *p;
+ fprintf(fp, "[%s] CPU: %d BUFFER: %lx LEN: %d\n", buf_name, cpu,
buffer_addr, len);
+ n = (len <= buffer_size) ? len : buffer_size;
+ for (i = 0, p = buffer; i < n; i++, p++) {
+ if (*p == 0x1) { //SOH
+ i++; p++;
+ continue;
+ } else {
+ fputc(ascii(*p) ? *p : '.', fp);
+ }
+ }
+ fputc('\n', fp);
+ }
+ }
+ FREEBUF(buffer);
+}
+
+static void
+dump_printk_safe_seq_buf(void)
+{
+ if (!STRUCT_EXISTS("printk_safe_seq_buf"))
+ return;
+
+ if (INVALID_SIZE(printk_safe_seq_buf_buffer)) {
+ MEMBER_OFFSET_INIT(printk_safe_seq_buf_len, "printk_safe_seq_buf",
"len");
+ MEMBER_OFFSET_INIT(printk_safe_seq_buf_buffer, "printk_safe_seq_buf",
"buffer");
+ MEMBER_SIZE_INIT(printk_safe_seq_buf_buffer, "printk_safe_seq_buf",
"buffer");
+ }
+
+ __dump_printk_safe_seq_buf("nmi_print_seq");
+ __dump_printk_safe_seq_buf("safe_print_seq");
+}
+
/*
* Reads a string value from the VMCOREINFO data stored in (live) memory.
*
--
2.29.2