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printk: introduce a kmsg_dump iterator 

Rather than storing the iterator information in the registered
kmsg_dumper structure, create a separate iterator structure. The
kmsg_dump_iter structure can reside on the stack of the caller, thus
allowing lockless use of the kmsg_dump functions.

Update code that accesses the kernel logs using the kmsg_dumper
structure to use the new kmsg_dump_iter structure. For kmsg_dumpers,
this also means adding a call to kmsg_dump_rewind() to initialize
the iterator.

All this is in preparation for removal of @logbuf_lock.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org> # pstore
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-13-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2021-03-03 11:15:25 +01:00 committed by Petr Mladek
parent 5f6c7648e5
commit f9f3f02db9
9 changed files with 80 additions and 62 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/powerpc/kernel/nvram_64.c
View File

@ -647,6 +647,7 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
{
struct oops_log_info *oops_hdr = (struct oops_log_info *)oops_buf;
static unsigned int oops_count = 0;
static struct kmsg_dump_iter iter;
static bool panicking = false;
static DEFINE_SPINLOCK(lock);
unsigned long flags;
@ -681,13 +682,14 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
return;
if (big_oops_buf) {
kmsg_dump_get_buffer(dumper, false,
kmsg_dump_rewind(&iter);
kmsg_dump_get_buffer(&iter, false,
big_oops_buf, big_oops_buf_sz, &text_len);
rc = zip_oops(text_len);
}
if (rc != 0) {
kmsg_dump_rewind(dumper);
kmsg_dump_get_buffer(dumper, false,
kmsg_dump_rewind(&iter);
kmsg_dump_get_buffer(&iter, false,
oops_data, oops_data_sz, &text_len);
err_type = ERR_TYPE_KERNEL_PANIC;
oops_hdr->version = cpu_to_be16(OOPS_HDR_VERSION);

6
arch/powerpc/xmon/xmon.c
View File

@ -3005,7 +3005,7 @@ print_address(unsigned long addr)
static void
dump_log_buf(void)
{
struct kmsg_dumper dumper;
struct kmsg_dump_iter iter;
unsigned char buf[128];
size_t len;
@ -3017,9 +3017,9 @@ dump_log_buf(void)
catch_memory_errors = 1;
sync();
kmsg_dump_rewind_nolock(&dumper);
kmsg_dump_rewind_nolock(&iter);
xmon_start_pagination();
while (kmsg_dump_get_line_nolock(&dumper, false, buf, sizeof(buf), &len)) {
while (kmsg_dump_get_line_nolock(&iter, false, buf, sizeof(buf), &len)) {
buf[len] = '\0';
printf("%s", buf);
}

5
arch/um/kernel/kmsg_dump.c
View File

@ -10,6 +10,7 @@
static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
enum kmsg_dump_reason reason)
{
static struct kmsg_dump_iter iter;
static DEFINE_SPINLOCK(lock);
static char line[1024];
struct console *con;
@ -35,8 +36,10 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
if (!spin_trylock_irqsave(&lock, flags))
return;
kmsg_dump_rewind(&iter);
printf("kmsg_dump:\n");
while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) {
while (kmsg_dump_get_line(&iter, true, line, sizeof(line), &len)) {
line[len] = '\0';
printf("%s", line);
}

4
drivers/hv/vmbus_drv.c
View File

@ -1391,6 +1391,7 @@ static void vmbus_isr(void)
static void hv_kmsg_dump(struct kmsg_dumper *dumper,
enum kmsg_dump_reason reason)
{
struct kmsg_dump_iter iter;
size_t bytes_written;
phys_addr_t panic_pa;
@ -1404,7 +1405,8 @@ static void hv_kmsg_dump(struct kmsg_dumper *dumper,
* Write dump contents to the page. No need to synchronize; panic should
* be single-threaded.
*/
kmsg_dump_get_buffer(dumper, false, hv_panic_page, HV_HYP_PAGE_SIZE,
kmsg_dump_rewind(&iter);
kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE,
&bytes_written);
if (bytes_written)
hyperv_report_panic_msg(panic_pa, bytes_written);

5
drivers/mtd/mtdoops.c
View File

@ -277,14 +277,17 @@ static void mtdoops_do_dump(struct kmsg_dumper *dumper,
{
struct mtdoops_context *cxt = container_of(dumper,
struct mtdoops_context, dump);
struct kmsg_dump_iter iter;
/* Only dump oopses if dump_oops is set */
if (reason == KMSG_DUMP_OOPS && !dump_oops)
return;
kmsg_dump_rewind(&iter);
if (test_and_set_bit(0, &cxt->oops_buf_busy))
return;
kmsg_dump_get_buffer(dumper, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
kmsg_dump_get_buffer(&iter, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
record_size - MTDOOPS_HEADER_SIZE, NULL);
clear_bit(0, &cxt->oops_buf_busy);

5
fs/pstore/platform.c
View File

@ -385,6 +385,7 @@ void pstore_record_init(struct pstore_record *record,
static void pstore_dump(struct kmsg_dumper *dumper,
enum kmsg_dump_reason reason)
{
struct kmsg_dump_iter iter;
unsigned long total = 0;
const char *why;
unsigned int part = 1;
@ -405,6 +406,8 @@ static void pstore_dump(struct kmsg_dumper *dumper,
}
}
kmsg_dump_rewind(&iter);
oopscount++;
while (total < kmsg_bytes) {
char *dst;
@ -435,7 +438,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
dst_size -= header_size;
/* Write dump contents. */
if (!kmsg_dump_get_buffer(dumper, true, dst + header_size,
if (!kmsg_dump_get_buffer(&iter, true, dst + header_size,
dst_size, &dump_size))
break;

36
include/linux/kmsg_dump.h
View File

@ -29,6 +29,16 @@ enum kmsg_dump_reason {
KMSG_DUMP_MAX
};
/**
* struct kmsg_dump_iter - iterator for retrieving kernel messages
* @cur_seq: Points to the oldest message to dump
* @next_seq: Points after the newest message to dump
*/
struct kmsg_dump_iter {
u64 cur_seq;
u64 next_seq;
};
/**
* struct kmsg_dumper - kernel crash message dumper structure
* @list: Entry in the dumper list (private)
@ -36,35 +46,29 @@ enum kmsg_dump_reason {
* through the record iterator
* @max_reason: filter for highest reason number that should be dumped
* @registered: Flag that specifies if this is already registered
* @cur_seq: Points to the oldest message to dump
* @next_seq: Points after the newest message to dump
*/
struct kmsg_dumper {
struct list_head list;
void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason);
enum kmsg_dump_reason max_reason;
bool registered;
/* private state of the kmsg iterator */
u64 cur_seq;
u64 next_seq;
};
#ifdef CONFIG_PRINTK
void kmsg_dump(enum kmsg_dump_reason reason);
bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog,
char *line, size_t size, size_t *len);
bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
char *line, size_t size, size_t *len);
bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
char *buf, size_t size, size_t *len_out);
void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);
void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter);
void kmsg_dump_rewind(struct kmsg_dumper *dumper);
void kmsg_dump_rewind(struct kmsg_dump_iter *iter);
int kmsg_dump_register(struct kmsg_dumper *dumper);
@ -76,30 +80,30 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason)
{
}
static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper,
static inline bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter,
bool syslog, const char *line,
size_t size, size_t *len)
{
return false;
}
static inline bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
static inline bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
const char *line, size_t size, size_t *len)
{
return false;
}
static inline bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
static inline bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
char *buf, size_t size, size_t *len)
{
return false;
}
static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
static inline void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter)
{
}
static inline void kmsg_dump_rewind(struct kmsg_dumper *dumper)
static inline void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
{
}

10
kernel/debug/kdb/kdb_main.c
View File

@ -2101,7 +2101,7 @@ static int kdb_dmesg(int argc, const char **argv)
int adjust = 0;
int n = 0;
int skip = 0;
struct kmsg_dumper dumper;
struct kmsg_dump_iter iter;
size_t len;
char buf[201];
@ -2126,8 +2126,8 @@ static int kdb_dmesg(int argc, const char **argv)
kdb_set(2, setargs);
}
kmsg_dump_rewind_nolock(&dumper);
while (kmsg_dump_get_line_nolock(&dumper, 1, NULL, 0, NULL))
kmsg_dump_rewind_nolock(&iter);
while (kmsg_dump_get_line_nolock(&iter, 1, NULL, 0, NULL))
n++;
if (lines < 0) {
@ -2159,8 +2159,8 @@ static int kdb_dmesg(int argc, const char **argv)
if (skip >= n || skip < 0)
return 0;
kmsg_dump_rewind_nolock(&dumper);
while (kmsg_dump_get_line_nolock(&dumper, 1, buf, sizeof(buf), &len)) {
kmsg_dump_rewind_nolock(&iter);
while (kmsg_dump_get_line_nolock(&iter, 1, buf, sizeof(buf), &len)) {
if (skip) {
skip--;
continue;

63
kernel/printk/printk.c
View File

@ -3390,7 +3390,6 @@ EXPORT_SYMBOL_GPL(kmsg_dump_reason_str);
void kmsg_dump(enum kmsg_dump_reason reason)
{
struct kmsg_dumper *dumper;
unsigned long flags;
rcu_read_lock();
list_for_each_entry_rcu(dumper, &dump_list, list) {
@ -3407,12 +3406,6 @@ void kmsg_dump(enum kmsg_dump_reason reason)
if (reason > max_reason)
continue;
/* initialize iterator with data about the stored records */
logbuf_lock_irqsave(flags);
dumper->cur_seq = latched_seq_read_nolock(&clear_seq);
dumper->next_seq = prb_next_seq(prb);
logbuf_unlock_irqrestore(flags);
/* invoke dumper which will iterate over records */
dumper->dump(dumper, reason);
}
@ -3421,7 +3414,7 @@ void kmsg_dump(enum kmsg_dump_reason reason)
/**
* kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
* @syslog: include the "<4>" prefixes
* @line: buffer to copy the line to
* @size: maximum size of the buffer
@ -3438,24 +3431,28 @@ void kmsg_dump(enum kmsg_dump_reason reason)
*
* The function is similar to kmsg_dump_get_line(), but grabs no locks.
*/
bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog,
char *line, size_t size, size_t *len)
{
u64 min_seq = latched_seq_read_nolock(&clear_seq);
struct printk_info info;
unsigned int line_count;
struct printk_record r;
size_t l = 0;
bool ret = false;
if (iter->cur_seq < min_seq)
iter->cur_seq = min_seq;
prb_rec_init_rd(&r, &info, line, size);
/* Read text or count text lines? */
if (line) {
if (!prb_read_valid(prb, dumper->cur_seq, &r))
if (!prb_read_valid(prb, iter->cur_seq, &r))
goto out;
l = record_print_text(&r, syslog, printk_time);
} else {
if (!prb_read_valid_info(prb, dumper->cur_seq,
if (!prb_read_valid_info(prb, iter->cur_seq,
&info, &line_count)) {
goto out;
}
@ -3464,7 +3461,7 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
}
dumper->cur_seq = r.info->seq + 1;
iter->cur_seq = r.info->seq + 1;
ret = true;
out:
if (len)
@ -3474,7 +3471,7 @@ out:
/**
* kmsg_dump_get_line - retrieve one kmsg log line
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
* @syslog: include the "<4>" prefixes
* @line: buffer to copy the line to
* @size: maximum size of the buffer
@ -3489,14 +3486,14 @@ out:
* A return value of FALSE indicates that there are no more records to
* read.
*/
bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
char *line, size_t size, size_t *len)
{
unsigned long flags;
bool ret;
logbuf_lock_irqsave(flags);
ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
ret = kmsg_dump_get_line_nolock(iter, syslog, line, size, len);
logbuf_unlock_irqrestore(flags);
return ret;
@ -3505,7 +3502,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
/**
* kmsg_dump_get_buffer - copy kmsg log lines
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
* @syslog: include the "<4>" prefixes
* @buf: buffer to copy the line to
* @size: maximum size of the buffer
@ -3522,9 +3519,10 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
* A return value of FALSE indicates that there are no more records to
* read.
*/
bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
char *buf, size_t size, size_t *len_out)
{
u64 min_seq = latched_seq_read_nolock(&clear_seq);
struct printk_info info;
struct printk_record r;
unsigned long flags;
@ -3537,16 +3535,19 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
if (!buf || !size)
goto out;
if (iter->cur_seq < min_seq)
iter->cur_seq = min_seq;
logbuf_lock_irqsave(flags);
if (prb_read_valid_info(prb, dumper->cur_seq, &info, NULL)) {
if (info.seq != dumper->cur_seq) {
if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) {
if (info.seq != iter->cur_seq) {
/* messages are gone, move to first available one */
dumper->cur_seq = info.seq;
iter->cur_seq = info.seq;
}
}
/* last entry */
if (dumper->cur_seq >= dumper->next_seq) {
if (iter->cur_seq >= iter->next_seq) {
logbuf_unlock_irqrestore(flags);
goto out;
}
@ -3557,7 +3558,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
* because this function (by way of record_print_text()) will
* not write more than size-1 bytes of text into @buf.
*/
seq = find_first_fitting_seq(dumper->cur_seq, dumper->next_seq,
seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq,
size - 1, syslog, time);
/*
@ -3570,7 +3571,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
len = 0;
prb_for_each_record(seq, prb, seq, &r) {
if (r.info->seq >= dumper->next_seq)
if (r.info->seq >= iter->next_seq)
break;
len += record_print_text(&r, syslog, time);
@ -3579,7 +3580,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
prb_rec_init_rd(&r, &info, buf + len, size - len);
}
dumper->next_seq = next_seq;
iter->next_seq = next_seq;
ret = true;
logbuf_unlock_irqrestore(flags);
out:
@ -3591,7 +3592,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
/**
* kmsg_dump_rewind_nolock - reset the iterator (unlocked version)
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
*
* Reset the dumper's iterator so that kmsg_dump_get_line() and
* kmsg_dump_get_buffer() can be called again and used multiple
@ -3599,26 +3600,26 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
*
* The function is similar to kmsg_dump_rewind(), but grabs no locks.
*/
void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter)
{
dumper->cur_seq = latched_seq_read_nolock(&clear_seq);
dumper->next_seq = prb_next_seq(prb);
iter->cur_seq = latched_seq_read_nolock(&clear_seq);
iter->next_seq = prb_next_seq(prb);
}
/**
* kmsg_dump_rewind - reset the iterator
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
*
* Reset the dumper's iterator so that kmsg_dump_get_line() and
* kmsg_dump_get_buffer() can be called again and used multiple
* times within the same dumper.dump() callback.
*/
void kmsg_dump_rewind(struct kmsg_dumper *dumper)
void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
{
unsigned long flags;
logbuf_lock_irqsave(flags);
kmsg_dump_rewind_nolock(dumper);
kmsg_dump_rewind_nolock(iter);
logbuf_unlock_irqrestore(flags);
}
EXPORT_SYMBOL_GPL(kmsg_dump_rewind);