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-rw-r--r--Documentation/admin-guide/kernel-parameters.txt9
-rw-r--r--kernel/printk/printk.c85
-rw-r--r--kernel/printk/printk_ringbuffer.c52
-rw-r--r--kernel/printk/printk_ringbuffer.h2
-rw-r--r--lib/vsprintf.c49
5 files changed, 161 insertions, 36 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 09cdee9e3bad..1a9f89a835b3 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -724,6 +724,12 @@
hvc<n> Use the hypervisor console device <n>. This is for
both Xen and PowerPC hypervisors.
+ { null | "" }
+ Use to disable console output, i.e., to have kernel
+ console messages discarded.
+ This must be the only console= parameter used on the
+ kernel command line.
+
If the device connected to the port is not a TTY but a braille
device, prepend "brl," before the device type, for instance
console=brl,ttyS0
@@ -3516,8 +3522,7 @@
difficult since unequal pointers can no longer be
compared. However, if this command-line option is
specified, then all normal pointers will have their true
- value printed. Pointers printed via %pK may still be
- hashed. This option should only be specified when
+ value printed. This option should only be specified when
debugging the kernel. Please do not use on production
kernels.
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 82abfaf3c2aa..da03c15ecc89 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -93,6 +93,12 @@ EXPORT_SYMBOL_GPL(console_drivers);
*/
int __read_mostly suppress_printk;
+/*
+ * During panic, heavy printk by other CPUs can delay the
+ * panic and risk deadlock on console resources.
+ */
+static int __read_mostly suppress_panic_printk;
+
#ifdef CONFIG_LOCKDEP
static struct lockdep_map console_lock_dep_map = {
.name = "console_lock"
@@ -146,8 +152,10 @@ static int __control_devkmsg(char *str)
static int __init control_devkmsg(char *str)
{
- if (__control_devkmsg(str) < 0)
+ if (__control_devkmsg(str) < 0) {
+ pr_warn("printk.devkmsg: bad option string '%s'\n", str);
return 1;
+ }
/*
* Set sysctl string accordingly:
@@ -166,7 +174,7 @@ static int __init control_devkmsg(char *str)
*/
devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;
- return 0;
+ return 1;
}
__setup("printk.devkmsg=", control_devkmsg);
@@ -257,6 +265,11 @@ static void __up_console_sem(unsigned long ip)
}
#define up_console_sem() __up_console_sem(_RET_IP_)
+static bool panic_in_progress(void)
+{
+ return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);
+}
+
/*
* This is used for debugging the mess that is the VT code by
* keeping track if we have the console semaphore held. It's
@@ -1843,6 +1856,16 @@ static int console_trylock_spinning(void)
if (console_trylock())
return 1;
+ /*
+ * It's unsafe to spin once a panic has begun. If we are the
+ * panic CPU, we may have already halted the owner of the
+ * console_sem. If we are not the panic CPU, then we should
+ * avoid taking console_sem, so the panic CPU has a better
+ * chance of cleanly acquiring it later.
+ */
+ if (panic_in_progress())
+ return 0;
+
printk_safe_enter_irqsave(flags);
raw_spin_lock(&console_owner_lock);
@@ -2218,6 +2241,10 @@ asmlinkage int vprintk_emit(int facility, int level,
if (unlikely(suppress_printk))
return 0;
+ if (unlikely(suppress_panic_printk) &&
+ atomic_read(&panic_cpu) != raw_smp_processor_id())
+ return 0;
+
if (level == LOGLEVEL_SCHED) {
level = LOGLEVEL_DEFAULT;
in_sched = true;
@@ -2324,6 +2351,20 @@ asmlinkage __visible void early_printk(const char *fmt, ...)
}
#endif
+static void set_user_specified(struct console_cmdline *c, bool user_specified)
+{
+ if (!user_specified)
+ return;
+
+ /*
+ * @c console was defined by the user on the command line.
+ * Do not clear when added twice also by SPCR or the device tree.
+ */
+ c->user_specified = true;
+ /* At least one console defined by the user on the command line. */
+ console_set_on_cmdline = 1;
+}
+
static int __add_preferred_console(char *name, int idx, char *options,
char *brl_options, bool user_specified)
{
@@ -2340,8 +2381,7 @@ static int __add_preferred_console(char *name, int idx, char *options,
if (strcmp(c->name, name) == 0 && c->index == idx) {
if (!brl_options)
preferred_console = i;
- if (user_specified)
- c->user_specified = true;
+ set_user_specified(c, user_specified);
return 0;
}
}
@@ -2351,7 +2391,7 @@ static int __add_preferred_console(char *name, int idx, char *options,
preferred_console = i;
strlcpy(c->name, name, sizeof(c->name));
c->options = options;
- c->user_specified = user_specified;
+ set_user_specified(c, user_specified);
braille_set_options(c, brl_options);
c->index = idx;
@@ -2417,7 +2457,6 @@ static int __init console_setup(char *str)
*s = 0;
__add_preferred_console(buf, idx, options, brl_options, true);
- console_set_on_cmdline = 1;
return 1;
}
__setup("console=", console_setup);
@@ -2574,6 +2613,25 @@ static int have_callable_console(void)
}
/*
+ * Return true when this CPU should unlock console_sem without pushing all
+ * messages to the console. This reduces the chance that the console is
+ * locked when the panic CPU tries to use it.
+ */
+static bool abandon_console_lock_in_panic(void)
+{
+ if (!panic_in_progress())
+ return false;
+
+ /*
+ * We can use raw_smp_processor_id() here because it is impossible for
+ * the task to be migrated to the panic_cpu, or away from it. If
+ * panic_cpu has already been set, and we're not currently executing on
+ * that CPU, then we never will be.
+ */
+ return atomic_read(&panic_cpu) != raw_smp_processor_id();
+}
+
+/*
* Can we actually use the console at this time on this cpu?
*
* Console drivers may assume that per-cpu resources have been allocated. So
@@ -2603,6 +2661,7 @@ void console_unlock(void)
{
static char ext_text[CONSOLE_EXT_LOG_MAX];
static char text[CONSOLE_LOG_MAX];
+ static int panic_console_dropped;
unsigned long flags;
bool do_cond_resched, retry;
struct printk_info info;
@@ -2657,6 +2716,10 @@ skip:
if (console_seq != r.info->seq) {
console_dropped += r.info->seq - console_seq;
console_seq = r.info->seq;
+ if (panic_in_progress() && panic_console_dropped++ > 10) {
+ suppress_panic_printk = 1;
+ pr_warn_once("Too many dropped messages. Suppress messages on non-panic CPUs to prevent livelock.\n");
+ }
}
if (suppress_message_printing(r.info->level)) {
@@ -2716,6 +2779,10 @@ skip:
if (handover)
return;
+ /* Allow panic_cpu to take over the consoles safely */
+ if (abandon_console_lock_in_panic())
+ break;
+
if (do_cond_resched)
cond_resched();
}
@@ -2733,7 +2800,7 @@ skip:
* flush, no worries.
*/
retry = prb_read_valid(prb, next_seq, NULL);
- if (retry && console_trylock())
+ if (retry && !abandon_console_lock_in_panic() && console_trylock())
goto again;
}
EXPORT_SYMBOL(console_unlock);
@@ -3228,7 +3295,7 @@ static DEFINE_PER_CPU(int, printk_pending);
static void wake_up_klogd_work_func(struct irq_work *irq_work)
{
- int pending = __this_cpu_xchg(printk_pending, 0);
+ int pending = this_cpu_xchg(printk_pending, 0);
if (pending & PRINTK_PENDING_OUTPUT) {
/* If trylock fails, someone else is doing the printing */
@@ -3262,7 +3329,7 @@ void defer_console_output(void)
return;
preempt_disable();
- __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
+ this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
preempt_enable();
}
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c
index 8a7b7362c0dd..2b7b6ddab4f7 100644
--- a/kernel/printk/printk_ringbuffer.c
+++ b/kernel/printk/printk_ringbuffer.c
@@ -474,8 +474,10 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring,
* state has been re-checked. A memcpy() for all of @desc
* cannot be used because of the atomic_t @state_var field.
*/
- memcpy(&desc_out->text_blk_lpos, &desc->text_blk_lpos,
- sizeof(desc_out->text_blk_lpos)); /* LMM(desc_read:C) */
+ if (desc_out) {
+ memcpy(&desc_out->text_blk_lpos, &desc->text_blk_lpos,
+ sizeof(desc_out->text_blk_lpos)); /* LMM(desc_read:C) */
+ }
if (seq_out)
*seq_out = info->seq; /* also part of desc_read:C */
if (caller_id_out)
@@ -528,7 +530,8 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring,
state_val = atomic_long_read(state_var); /* LMM(desc_read:E) */
d_state = get_desc_state(id, state_val);
out:
- atomic_long_set(&desc_out->state_var, state_val);
+ if (desc_out)
+ atomic_long_set(&desc_out->state_var, state_val);
return d_state;
}
@@ -1449,6 +1452,9 @@ static void desc_make_final(struct prb_desc_ring *desc_ring, unsigned long id)
atomic_long_cmpxchg_relaxed(&d->state_var, prev_state_val,
DESC_SV(id, desc_finalized)); /* LMM(desc_make_final:A) */
+
+ /* Best effort to remember the last finalized @id. */
+ atomic_long_set(&desc_ring->last_finalized_id, id);
}
/**
@@ -1657,7 +1663,12 @@ void prb_commit(struct prb_reserved_entry *e)
*/
void prb_final_commit(struct prb_reserved_entry *e)
{
+ struct prb_desc_ring *desc_ring = &e->rb->desc_ring;
+
_prb_commit(e, desc_finalized);
+
+ /* Best effort to remember the last finalized @id. */
+ atomic_long_set(&desc_ring->last_finalized_id, e->id);
}
/*
@@ -2005,9 +2016,39 @@ u64 prb_first_valid_seq(struct printk_ringbuffer *rb)
*/
u64 prb_next_seq(struct printk_ringbuffer *rb)
{
- u64 seq = 0;
+ struct prb_desc_ring *desc_ring = &rb->desc_ring;
+ enum desc_state d_state;
+ unsigned long id;
+ u64 seq;
+
+ /* Check if the cached @id still points to a valid @seq. */
+ id = atomic_long_read(&desc_ring->last_finalized_id);
+ d_state = desc_read(desc_ring, id, NULL, &seq, NULL);
- /* Search forward from the oldest descriptor. */
+ if (d_state == desc_finalized || d_state == desc_reusable) {
+ /*
+ * Begin searching after the last finalized record.
+ *
+ * On 0, the search must begin at 0 because of hack#2
+ * of the bootstrapping phase it is not known if a
+ * record at index 0 exists.
+ */
+ if (seq != 0)
+ seq++;
+ } else {
+ /*
+ * The information about the last finalized sequence number
+ * has gone. It should happen only when there is a flood of
+ * new messages and the ringbuffer is rapidly recycled.
+ * Give up and start from the beginning.
+ */
+ seq = 0;
+ }
+
+ /*
+ * The information about the last finalized @seq might be inaccurate.
+ * Search forward to find the current one.
+ */
while (_prb_read_valid(rb, &seq, NULL, NULL))
seq++;
@@ -2044,6 +2085,7 @@ void prb_init(struct printk_ringbuffer *rb,
rb->desc_ring.infos = infos;
atomic_long_set(&rb->desc_ring.head_id, DESC0_ID(descbits));
atomic_long_set(&rb->desc_ring.tail_id, DESC0_ID(descbits));
+ atomic_long_set(&rb->desc_ring.last_finalized_id, DESC0_ID(descbits));
rb->text_data_ring.size_bits = textbits;
rb->text_data_ring.data = text_buf;
diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h
index 73cc80e01cef..18cd25e489b8 100644
--- a/kernel/printk/printk_ringbuffer.h
+++ b/kernel/printk/printk_ringbuffer.h
@@ -75,6 +75,7 @@ struct prb_desc_ring {
struct printk_info *infos;
atomic_long_t head_id;
atomic_long_t tail_id;
+ atomic_long_t last_finalized_id;
};
/*
@@ -258,6 +259,7 @@ static struct printk_ringbuffer name = { \
.infos = &_##name##_infos[0], \
.head_id = ATOMIC_INIT(DESC0_ID(descbits)), \
.tail_id = ATOMIC_INIT(DESC0_ID(descbits)), \
+ .last_finalized_id = ATOMIC_INIT(DESC0_ID(descbits)), \
}, \
.text_data_ring = { \
.size_bits = (avgtextbits) + (descbits), \
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 36574a806a81..53fe73a48adf 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -49,10 +49,15 @@
#include <asm/page.h> /* for PAGE_SIZE */
#include <asm/byteorder.h> /* cpu_to_le16 */
+#include <asm/unaligned.h>
#include <linux/string_helpers.h>
#include "kstrtox.h"
+/* Disable pointer hashing if requested */
+bool no_hash_pointers __ro_after_init;
+EXPORT_SYMBOL_GPL(no_hash_pointers);
+
static noinline unsigned long long simple_strntoull(const char *startp, size_t max_chars, char **endp, unsigned int base)
{
const char *cp;
@@ -850,6 +855,19 @@ static char *ptr_to_id(char *buf, char *end, const void *ptr,
return pointer_string(buf, end, (const void *)hashval, spec);
}
+static char *default_pointer(char *buf, char *end, const void *ptr,
+ struct printf_spec spec)
+{
+ /*
+ * default is to _not_ leak addresses, so hash before printing,
+ * unless no_hash_pointers is specified on the command line.
+ */
+ if (unlikely(no_hash_pointers))
+ return pointer_string(buf, end, ptr, spec);
+
+ return ptr_to_id(buf, end, ptr, spec);
+}
+
int kptr_restrict __read_mostly;
static noinline_for_stack
@@ -859,7 +877,7 @@ char *restricted_pointer(char *buf, char *end, const void *ptr,
switch (kptr_restrict) {
case 0:
/* Handle as %p, hash and do _not_ leak addresses. */
- return ptr_to_id(buf, end, ptr, spec);
+ return default_pointer(buf, end, ptr, spec);
case 1: {
const struct cred *cred;
@@ -1763,7 +1781,7 @@ char *fourcc_string(char *buf, char *end, const u32 *fourcc,
char output[sizeof("0123 little-endian (0x01234567)")];
char *p = output;
unsigned int i;
- u32 val;
+ u32 orig, val;
if (fmt[1] != 'c' || fmt[2] != 'c')
return error_string(buf, end, "(%p4?)", spec);
@@ -1771,21 +1789,23 @@ char *fourcc_string(char *buf, char *end, const u32 *fourcc,
if (check_pointer(&buf, end, fourcc, spec))
return buf;
- val = *fourcc & ~BIT(31);
+ orig = get_unaligned(fourcc);
+ val = orig & ~BIT(31);
- for (i = 0; i < sizeof(*fourcc); i++) {
+ for (i = 0; i < sizeof(u32); i++) {
unsigned char c = val >> (i * 8);
/* Print non-control ASCII characters as-is, dot otherwise */
*p++ = isascii(c) && isprint(c) ? c : '.';
}
- strcpy(p, *fourcc & BIT(31) ? " big-endian" : " little-endian");
+ *p++ = ' ';
+ strcpy(p, orig & BIT(31) ? "big-endian" : "little-endian");
p += strlen(p);
*p++ = ' ';
*p++ = '(';
- p = special_hex_number(p, output + sizeof(output) - 2, *fourcc, sizeof(u32));
+ p = special_hex_number(p, output + sizeof(output) - 2, orig, sizeof(u32));
*p++ = ')';
*p = '\0';
@@ -2225,10 +2245,6 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
return widen_string(buf, buf - buf_start, end, spec);
}
-/* Disable pointer hashing if requested */
-bool no_hash_pointers __ro_after_init;
-EXPORT_SYMBOL_GPL(no_hash_pointers);
-
int __init no_hash_pointers_enable(char *str)
{
if (no_hash_pointers)
@@ -2457,7 +2473,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
case 'e':
/* %pe with a non-ERR_PTR gets treated as plain %p */
if (!IS_ERR(ptr))
- break;
+ return default_pointer(buf, end, ptr, spec);
return err_ptr(buf, end, ptr, spec);
case 'u':
case 'k':
@@ -2467,16 +2483,9 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
default:
return error_string(buf, end, "(einval)", spec);
}
+ default:
+ return default_pointer(buf, end, ptr, spec);
}
-
- /*
- * default is to _not_ leak addresses, so hash before printing,
- * unless no_hash_pointers is specified on the command line.
- */
- if (unlikely(no_hash_pointers))
- return pointer_string(buf, end, ptr, spec);
- else
- return ptr_to_id(buf, end, ptr, spec);
}
/*