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Printk changes for 4.20

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Merge tag 'printk-for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

Pull printk updates from Petr Mladek:

 - Fix two more locations where printf formatting leaked pointers

 - Better log_buf_len parameter handling

 - Add prefix to messages from printk code

 - Do not miss messages on other consoles when the log is replayed on a
   new one

 - Reduce race between console registration and panic() when the log
   might get replayed on all consoles

 - Some cont buffer code clean up

 - Call console only when there is something to do (log vs cont buffer)

* tag 'printk-for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  lib/vsprintf: Hash printed address for netdev bits fallback
  lib/vsprintf: Hash legacy clock addresses
  lib/vsprintf: Prepare for more general use of ptr_to_id()
  lib/vsprintf: Make ptr argument conts in ptr_to_id()
  printk: fix integer overflow in setup_log_buf()
  printk: do not preliminary split up cont buffer
  printk: lock/unlock console only for new logbuf entries
  printk: keep kernel cont support always enabled
  printk: Give error on attempt to set log buffer length to over 2G
  printk: Add KBUILD_MODNAME and remove a redundant print prefix
  printk: Correct wrong casting
  printk: Fix panic caused by passing log_buf_len to command line
  printk: CON_PRINTBUFFER console registration is a bit racy
  printk: Do not miss new messages when replaying the log
This commit is contained in:
Linus Torvalds 2018-10-25 17:11:52 -07:00
commit a67eefad99
3 changed files with 158 additions and 149 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
Documentation/core-api/printk-formats.rst
View File

@ -420,9 +420,8 @@ struct clk
%pC pll1
%pCn pll1
For printing struct clk structures. %pC and %pCn print the name
(Common Clock Framework) or address (legacy clock framework) of the
structure.
For printing struct clk structures. %pC and %pCn print the name of the clock
(Common Clock Framework) or a unique 32-bit ID (legacy clock framework).
Passed by reference.

86
kernel/printk/printk.c
View File

@ -16,6 +16,8 @@
* 01Mar01 Andrew Morton
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/tty.h>
@ -192,16 +194,7 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
return 0;
}
/*
* Number of registered extended console drivers.
*
* If extended consoles are present, in-kernel cont reassembly is disabled
* and each fragment is stored as a separate log entry with proper
* continuation flag so that every emitted message has full metadata. This
* doesn't change the result for regular consoles or /proc/kmsg. For
* /dev/kmsg, as long as the reader concatenates messages according to
* consecutive continuation flags, the end result should be the same too.
*/
/* Number of registered extended console drivers. */
static int nr_ext_console_drivers;
/*
@ -423,6 +416,7 @@ static u32 log_next_idx;
/* the next printk record to write to the console */
static u64 console_seq;
static u32 console_idx;
static u64 exclusive_console_stop_seq;
/* the next printk record to read after the last 'clear' command */
static u64 clear_seq;
@ -437,6 +431,7 @@ static u32 clear_idx;
/* record buffer */
#define LOG_ALIGN __alignof__(struct printk_log)
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
#define LOG_BUF_LEN_MAX (u32)(1 << 31)
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
static char *log_buf = __log_buf;
static u32 log_buf_len = __LOG_BUF_LEN;
@ -1037,18 +1032,28 @@ void log_buf_vmcoreinfo_setup(void)
static unsigned long __initdata new_log_buf_len;
/* we practice scaling the ring buffer by powers of 2 */
static void __init log_buf_len_update(unsigned size)
static void __init log_buf_len_update(u64 size)
{
if (size > (u64)LOG_BUF_LEN_MAX) {
size = (u64)LOG_BUF_LEN_MAX;
pr_err("log_buf over 2G is not supported.\n");
}
if (size)
size = roundup_pow_of_two(size);
if (size > log_buf_len)
new_log_buf_len = size;
new_log_buf_len = (unsigned long)size;
}
/* save requested log_buf_len since it's too early to process it */
static int __init log_buf_len_setup(char *str)
{
unsigned size = memparse(str, &str);
u64 size;
if (!str)
return -EINVAL;
size = memparse(str, &str);
log_buf_len_update(size);
@ -1093,7 +1098,7 @@ void __init setup_log_buf(int early)
{
unsigned long flags;
char *new_log_buf;
int free;
unsigned int free;
if (log_buf != __log_buf)
return;
@ -1113,7 +1118,7 @@ void __init setup_log_buf(int early)
}
if (unlikely(!new_log_buf)) {
pr_err("log_buf_len: %ld bytes not available\n",
pr_err("log_buf_len: %lu bytes not available\n",
new_log_buf_len);
return;
}
@ -1126,8 +1131,8 @@ void __init setup_log_buf(int early)
memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
logbuf_unlock_irqrestore(flags);
pr_info("log_buf_len: %d bytes\n", log_buf_len);
pr_info("early log buf free: %d(%d%%)\n",
pr_info("log_buf_len: %u bytes\n", log_buf_len);
pr_info("early log buf free: %u(%u%%)\n",
free, (free * 100) / __LOG_BUF_LEN);
}
@ -1767,12 +1772,8 @@ static void cont_flush(void)
static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len)
{
/*
* If ext consoles are present, flush and skip in-kernel
* continuation. See nr_ext_console_drivers definition. Also, if
* the line gets too long, split it up in separate records.
*/
if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
/* If the line gets too long, split it up in separate records. */
if (cont.len + len > sizeof(cont.buf)) {
cont_flush();
return false;
}
@ -1795,9 +1796,6 @@ static bool cont_add(int facility, int level, enum log_flags flags, const char *
cont_flush();
}
if (cont.len > (sizeof(cont.buf) * 80) / 100)
cont_flush();
return true;
}
@ -1889,8 +1887,9 @@ asmlinkage int vprintk_emit(int facility, int level,
const char *fmt, va_list args)
{
int printed_len;
bool in_sched = false;
bool in_sched = false, pending_output;
unsigned long flags;
u64 curr_log_seq;
if (level == LOGLEVEL_SCHED) {
level = LOGLEVEL_DEFAULT;
@ -1902,11 +1901,13 @@ asmlinkage int vprintk_emit(int facility, int level,
/* This stops the holder of console_sem just where we want him */
logbuf_lock_irqsave(flags);
curr_log_seq = log_next_seq;
printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args);
pending_output = (curr_log_seq != log_next_seq);
logbuf_unlock_irqrestore(flags);
/* If called from the scheduler, we can not call up(). */
if (!in_sched) {
if (!in_sched && pending_output) {
/*
* Disable preemption to avoid being preempted while holding
* console_sem which would prevent anyone from printing to
@ -1923,7 +1924,8 @@ asmlinkage int vprintk_emit(int facility, int level,
preempt_enable();
}
wake_up_klogd();
if (pending_output)
wake_up_klogd();
return printed_len;
}
EXPORT_SYMBOL(vprintk_emit);
@ -2009,6 +2011,7 @@ static u64 syslog_seq;
static u32 syslog_idx;
static u64 console_seq;
static u32 console_idx;
static u64 exclusive_console_stop_seq;
static u64 log_first_seq;
static u32 log_first_idx;
static u64 log_next_seq;
@ -2351,8 +2354,9 @@ again:
printk_safe_enter_irqsave(flags);
raw_spin_lock(&logbuf_lock);
if (console_seq < log_first_seq) {
len = sprintf(text, "** %u printk messages dropped **\n",
(unsigned)(log_first_seq - console_seq));
len = sprintf(text,
"** %llu printk messages dropped **\n",
log_first_seq - console_seq);
/* messages are gone, move to first one */
console_seq = log_first_seq;
@ -2376,6 +2380,12 @@ skip:
goto skip;
}
/* Output to all consoles once old messages replayed. */
if (unlikely(exclusive_console &&
console_seq >= exclusive_console_stop_seq)) {
exclusive_console = NULL;
}
len += msg_print_text(msg,
console_msg_format & MSG_FORMAT_SYSLOG,
text + len,
@ -2418,10 +2428,6 @@ skip:
console_locked = 0;
/* Release the exclusive_console once it is used */
if (unlikely(exclusive_console))
exclusive_console = NULL;
raw_spin_unlock(&logbuf_lock);
up_console_sem();
@ -2688,8 +2694,7 @@ void register_console(struct console *newcon)
}
if (newcon->flags & CON_EXTENDED)
if (!nr_ext_console_drivers++)
pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
nr_ext_console_drivers++;
if (newcon->flags & CON_PRINTBUFFER) {
/*
@ -2699,13 +2704,18 @@ void register_console(struct console *newcon)
logbuf_lock_irqsave(flags);
console_seq = syslog_seq;
console_idx = syslog_idx;
logbuf_unlock_irqrestore(flags);
/*
* We're about to replay the log buffer. Only do this to the
* just-registered console to avoid excessive message spam to
* the already-registered consoles.
*
* Set exclusive_console with disabled interrupts to reduce
* race window with eventual console_flush_on_panic() that
* ignores console_lock.
*/
exclusive_console = newcon;
exclusive_console_stop_seq = console_seq;
logbuf_unlock_irqrestore(flags);
}
console_unlock();
console_sysfs_notify();

216
lib/vsprintf.c
View File

@ -612,6 +612,109 @@ char *string(char *buf, char *end, const char *s, struct printf_spec spec)
return widen_string(buf, len, end, spec);
}
static noinline_for_stack
char *pointer_string(char *buf, char *end, const void *ptr,
struct printf_spec spec)
{
spec.base = 16;
spec.flags |= SMALL;
if (spec.field_width == -1) {
spec.field_width = 2 * sizeof(ptr);
spec.flags |= ZEROPAD;
}
return number(buf, end, (unsigned long int)ptr, spec);
}
/* Make pointers available for printing early in the boot sequence. */
static int debug_boot_weak_hash __ro_after_init;
static int __init debug_boot_weak_hash_enable(char *str)
{
debug_boot_weak_hash = 1;
pr_info("debug_boot_weak_hash enabled\n");
return 0;
}
early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);
static DEFINE_STATIC_KEY_TRUE(not_filled_random_ptr_key);
static siphash_key_t ptr_key __read_mostly;
static void enable_ptr_key_workfn(struct work_struct *work)
{
get_random_bytes(&ptr_key, sizeof(ptr_key));
/* Needs to run from preemptible context */
static_branch_disable(&not_filled_random_ptr_key);
}
static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);
static void fill_random_ptr_key(struct random_ready_callback *unused)
{
/* This may be in an interrupt handler. */
queue_work(system_unbound_wq, &enable_ptr_key_work);
}
static struct random_ready_callback random_ready = {
.func = fill_random_ptr_key
};
static int __init initialize_ptr_random(void)
{
int key_size = sizeof(ptr_key);
int ret;
/* Use hw RNG if available. */
if (get_random_bytes_arch(&ptr_key, key_size) == key_size) {
static_branch_disable(&not_filled_random_ptr_key);
return 0;
}
ret = add_random_ready_callback(&random_ready);
if (!ret) {
return 0;
} else if (ret == -EALREADY) {
/* This is in preemptible context */
enable_ptr_key_workfn(&enable_ptr_key_work);
return 0;
}
return ret;
}
early_initcall(initialize_ptr_random);
/* Maps a pointer to a 32 bit unique identifier. */
static char *ptr_to_id(char *buf, char *end, const void *ptr,
struct printf_spec spec)
{
const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
unsigned long hashval;
/* When debugging early boot use non-cryptographically secure hash. */
if (unlikely(debug_boot_weak_hash)) {
hashval = hash_long((unsigned long)ptr, 32);
return pointer_string(buf, end, (const void *)hashval, spec);
}
if (static_branch_unlikely(&not_filled_random_ptr_key)) {
spec.field_width = 2 * sizeof(ptr);
/* string length must be less than default_width */
return string(buf, end, str, spec);
}
#ifdef CONFIG_64BIT
hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);
/*
* Mask off the first 32 bits, this makes explicit that we have
* modified the address (and 32 bits is plenty for a unique ID).
*/
hashval = hashval & 0xffffffff;
#else
hashval = (unsigned long)siphash_1u32((u32)ptr, &ptr_key);
#endif
return pointer_string(buf, end, (const void *)hashval, spec);
}
static noinline_for_stack
char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_spec spec,
const char *fmt)
@ -1357,20 +1460,6 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
return string(buf, end, uuid, spec);
}
static noinline_for_stack
char *pointer_string(char *buf, char *end, const void *ptr,
struct printf_spec spec)
{
spec.base = 16;
spec.flags |= SMALL;
if (spec.field_width == -1) {
spec.field_width = 2 * sizeof(ptr);
spec.flags |= ZEROPAD;
}
return number(buf, end, (unsigned long int)ptr, spec);
}
int kptr_restrict __read_mostly;
static noinline_for_stack
@ -1421,7 +1510,8 @@ char *restricted_pointer(char *buf, char *end, const void *ptr,
}
static noinline_for_stack
char *netdev_bits(char *buf, char *end, const void *addr, const char *fmt)
char *netdev_bits(char *buf, char *end, const void *addr,
struct printf_spec spec, const char *fmt)
{
unsigned long long num;
int size;
@ -1432,9 +1522,7 @@ char *netdev_bits(char *buf, char *end, const void *addr, const char *fmt)
size = sizeof(netdev_features_t);
break;
default:
num = (unsigned long)addr;
size = sizeof(unsigned long);
break;
return ptr_to_id(buf, end, addr, spec);
}
return special_hex_number(buf, end, num, size);
@ -1474,7 +1562,7 @@ char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
#ifdef CONFIG_COMMON_CLK
return string(buf, end, __clk_get_name(clk), spec);
#else
return special_hex_number(buf, end, (unsigned long)clk, sizeof(unsigned long));
return ptr_to_id(buf, end, clk, spec);
#endif
}
}
@ -1651,94 +1739,6 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
return widen_string(buf, buf - buf_start, end, spec);
}
/* Make pointers available for printing early in the boot sequence. */
static int debug_boot_weak_hash __ro_after_init;
static int __init debug_boot_weak_hash_enable(char *str)
{
debug_boot_weak_hash = 1;
pr_info("debug_boot_weak_hash enabled\n");
return 0;
}
early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);
static DEFINE_STATIC_KEY_TRUE(not_filled_random_ptr_key);
static siphash_key_t ptr_key __read_mostly;
static void enable_ptr_key_workfn(struct work_struct *work)
{
get_random_bytes(&ptr_key, sizeof(ptr_key));
/* Needs to run from preemptible context */
static_branch_disable(&not_filled_random_ptr_key);
}
static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);
static void fill_random_ptr_key(struct random_ready_callback *unused)
{
/* This may be in an interrupt handler. */
queue_work(system_unbound_wq, &enable_ptr_key_work);
}
static struct random_ready_callback random_ready = {
.func = fill_random_ptr_key
};
static int __init initialize_ptr_random(void)
{
int key_size = sizeof(ptr_key);
int ret;
/* Use hw RNG if available. */
if (get_random_bytes_arch(&ptr_key, key_size) == key_size) {
static_branch_disable(&not_filled_random_ptr_key);
return 0;
}
ret = add_random_ready_callback(&random_ready);
if (!ret) {
return 0;
} else if (ret == -EALREADY) {
/* This is in preemptible context */
enable_ptr_key_workfn(&enable_ptr_key_work);
return 0;
}
return ret;
}
early_initcall(initialize_ptr_random);
/* Maps a pointer to a 32 bit unique identifier. */
static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec)
{
const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
unsigned long hashval;
/* When debugging early boot use non-cryptographically secure hash. */
if (unlikely(debug_boot_weak_hash)) {
hashval = hash_long((unsigned long)ptr, 32);
return pointer_string(buf, end, (const void *)hashval, spec);
}
if (static_branch_unlikely(&not_filled_random_ptr_key)) {
spec.field_width = 2 * sizeof(ptr);
/* string length must be less than default_width */
return string(buf, end, str, spec);
}
#ifdef CONFIG_64BIT
hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);
/*
* Mask off the first 32 bits, this makes explicit that we have
* modified the address (and 32 bits is plenty for a unique ID).
*/
hashval = hashval & 0xffffffff;
#else
hashval = (unsigned long)siphash_1u32((u32)ptr, &ptr_key);
#endif
return pointer_string(buf, end, (const void *)hashval, spec);
}
/*
* Show a '%p' thing. A kernel extension is that the '%p' is followed
* by an extra set of alphanumeric characters that are extended format
@ -1942,7 +1942,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
break;
return restricted_pointer(buf, end, ptr, spec);
case 'N':
return netdev_bits(buf, end, ptr, fmt);
return netdev_bits(buf, end, ptr, spec, fmt);
case 'a':
return address_val(buf, end, ptr, fmt);
case 'd':