#endif
#ifdef CONFIG_PRINTK_NMI
-extern void printk_nmi_init(void);
+extern void printk_safe_init(void);
extern void printk_nmi_enter(void);
extern void printk_nmi_exit(void);
-extern void printk_nmi_flush(void);
-extern void printk_nmi_flush_on_panic(void);
+extern void printk_safe_flush(void);
+extern void printk_safe_flush_on_panic(void);
#else
-static inline void printk_nmi_init(void) { }
+static inline void printk_safe_init(void) { }
static inline void printk_nmi_enter(void) { }
static inline void printk_nmi_exit(void) { }
-static inline void printk_nmi_flush(void) { }
-static inline void printk_nmi_flush_on_panic(void) { }
+static inline void printk_safe_flush(void) { }
+static inline void printk_safe_flush_on_panic(void) { }
#endif /* PRINTK_NMI */
#ifdef CONFIG_PRINTK
13 => 8 KB for each CPU
12 => 4 KB for each CPU
-config NMI_LOG_BUF_SHIFT
- int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)"
+config PRINTK_SAFE_LOG_BUF_SHIFT
+ int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
range 10 21
default 13
- depends on PRINTK_NMI
+ depends on PRINTK
help
- Select the size of a per-CPU buffer where NMI messages are temporary
- stored. They are copied to the main log buffer in a safe context
- to avoid a deadlock. The value defines the size as a power of 2.
+ Select the size of an alternate printk per-CPU buffer where messages
+ printed from usafe contexts are temporary stored. One example would
+ be NMI messages, another one - printk recursion. The messages are
+ copied to the main log buffer in a safe context to avoid a deadlock.
+ The value defines the size as a power of 2.
- NMI messages are rare and limited. The largest one is when
+ Those messages are rare and limited. The largest one is when
a backtrace is printed. It usually fits into 4KB. Select
8KB if you want to be on the safe side.
timekeeping_init();
time_init();
sched_clock_postinit();
- printk_nmi_init();
+ printk_safe_init();
perf_event_init();
profile_init();
call_function_init();
old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
if (old_cpu == PANIC_CPU_INVALID) {
/* This is the 1st CPU which comes here, so go ahead. */
- printk_nmi_flush_on_panic();
+ printk_safe_flush_on_panic();
__crash_kexec(regs);
/*
* Bypass the panic_cpu check and call __crash_kexec directly.
*/
if (!_crash_kexec_post_notifiers) {
- printk_nmi_flush_on_panic();
+ printk_safe_flush_on_panic();
__crash_kexec(NULL);
/*
atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
/* Call flush even twice. It tries harder with a single online CPU */
- printk_nmi_flush_on_panic();
+ printk_safe_flush_on_panic();
kmsg_dump(KMSG_DUMP_PANIC);
/*
obj-y = printk.o
-obj-$(CONFIG_PRINTK_NMI) += nmi.o
+obj-$(CONFIG_PRINTK_NMI) += printk_safe.o
obj-$(CONFIG_A11Y_BRAILLE_CONSOLE) += braille.o
+++ /dev/null
-/*
- * nmi.c - Safe printk in NMI context
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, see <http://www.gnu.org/licenses/>.
- */
-
-#include <linux/preempt.h>
-#include <linux/spinlock.h>
-#include <linux/debug_locks.h>
-#include <linux/smp.h>
-#include <linux/cpumask.h>
-#include <linux/irq_work.h>
-#include <linux/printk.h>
-
-#include "internal.h"
-
-/*
- * printk() could not take logbuf_lock in NMI context. Instead,
- * it uses an alternative implementation that temporary stores
- * the strings into a per-CPU buffer. The content of the buffer
- * is later flushed into the main ring buffer via IRQ work.
- *
- * The alternative implementation is chosen transparently
- * via @printk_func per-CPU variable.
- *
- * The implementation allows to flush the strings also from another CPU.
- * There are situations when we want to make sure that all buffers
- * were handled or when IRQs are blocked.
- */
-DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
-static int printk_nmi_irq_ready;
-atomic_t nmi_message_lost;
-
-#define NMI_LOG_BUF_LEN ((1 << CONFIG_NMI_LOG_BUF_SHIFT) - \
- sizeof(atomic_t) - sizeof(struct irq_work))
-
-struct nmi_seq_buf {
- atomic_t len; /* length of written data */
- struct irq_work work; /* IRQ work that flushes the buffer */
- unsigned char buffer[NMI_LOG_BUF_LEN];
-};
-static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq);
-
-/*
- * Safe printk() for NMI context. It uses a per-CPU buffer to
- * store the message. NMIs are not nested, so there is always only
- * one writer running. But the buffer might get flushed from another
- * CPU, so we need to be careful.
- */
-static int vprintk_nmi(const char *fmt, va_list args)
-{
- struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
- int add = 0;
- size_t len;
-
-again:
- len = atomic_read(&s->len);
-
- /* The trailing '\0' is not counted into len. */
- if (len >= sizeof(s->buffer) - 1) {
- atomic_inc(&nmi_message_lost);
- return 0;
- }
-
- /*
- * Make sure that all old data have been read before the buffer was
- * reseted. This is not needed when we just append data.
- */
- if (!len)
- smp_rmb();
-
- add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, args);
-
- /*
- * Do it once again if the buffer has been flushed in the meantime.
- * Note that atomic_cmpxchg() is an implicit memory barrier that
- * makes sure that the data were written before updating s->len.
- */
- if (atomic_cmpxchg(&s->len, len, len + add) != len)
- goto again;
-
- /* Get flushed in a more safe context. */
- if (add && printk_nmi_irq_ready) {
- /* Make sure that IRQ work is really initialized. */
- smp_rmb();
- irq_work_queue(&s->work);
- }
-
- return add;
-}
-
-static void printk_nmi_flush_line(const char *text, int len)
-{
- /*
- * The buffers are flushed in NMI only on panic. The messages must
- * go only into the ring buffer at this stage. Consoles will get
- * explicitly called later when a crashdump is not generated.
- */
- if (in_nmi())
- printk_deferred("%.*s", len, text);
- else
- printk("%.*s", len, text);
-
-}
-
-/* printk part of the temporary buffer line by line */
-static int printk_nmi_flush_buffer(const char *start, size_t len)
-{
- const char *c, *end;
- bool header;
-
- c = start;
- end = start + len;
- header = true;
-
- /* Print line by line. */
- while (c < end) {
- if (*c == '\n') {
- printk_nmi_flush_line(start, c - start + 1);
- start = ++c;
- header = true;
- continue;
- }
-
- /* Handle continuous lines or missing new line. */
- if ((c + 1 < end) && printk_get_level(c)) {
- if (header) {
- c = printk_skip_level(c);
- continue;
- }
-
- printk_nmi_flush_line(start, c - start);
- start = c++;
- header = true;
- continue;
- }
-
- header = false;
- c++;
- }
-
- /* Check if there was a partial line. Ignore pure header. */
- if (start < end && !header) {
- static const char newline[] = KERN_CONT "\n";
-
- printk_nmi_flush_line(start, end - start);
- printk_nmi_flush_line(newline, strlen(newline));
- }
-
- return len;
-}
-
-/*
- * Flush data from the associated per_CPU buffer. The function
- * can be called either via IRQ work or independently.
- */
-static void __printk_nmi_flush(struct irq_work *work)
-{
- static raw_spinlock_t read_lock =
- __RAW_SPIN_LOCK_INITIALIZER(read_lock);
- struct nmi_seq_buf *s = container_of(work, struct nmi_seq_buf, work);
- unsigned long flags;
- size_t len;
- int i;
-
- /*
- * The lock has two functions. First, one reader has to flush all
- * available message to make the lockless synchronization with
- * writers easier. Second, we do not want to mix messages from
- * different CPUs. This is especially important when printing
- * a backtrace.
- */
- raw_spin_lock_irqsave(&read_lock, flags);
-
- i = 0;
-more:
- len = atomic_read(&s->len);
-
- /*
- * This is just a paranoid check that nobody has manipulated
- * the buffer an unexpected way. If we printed something then
- * @len must only increase. Also it should never overflow the
- * buffer size.
- */
- if ((i && i >= len) || len > sizeof(s->buffer)) {
- const char *msg = "printk_nmi_flush: internal error\n";
-
- printk_nmi_flush_line(msg, strlen(msg));
- len = 0;
- }
-
- if (!len)
- goto out; /* Someone else has already flushed the buffer. */
-
- /* Make sure that data has been written up to the @len */
- smp_rmb();
- i += printk_nmi_flush_buffer(s->buffer + i, len - i);
-
- /*
- * Check that nothing has got added in the meantime and truncate
- * the buffer. Note that atomic_cmpxchg() is an implicit memory
- * barrier that makes sure that the data were copied before
- * updating s->len.
- */
- if (atomic_cmpxchg(&s->len, len, 0) != len)
- goto more;
-
-out:
- raw_spin_unlock_irqrestore(&read_lock, flags);
-}
-
-/**
- * printk_nmi_flush - flush all per-cpu nmi buffers.
- *
- * The buffers are flushed automatically via IRQ work. This function
- * is useful only when someone wants to be sure that all buffers have
- * been flushed at some point.
- */
-void printk_nmi_flush(void)
-{
- int cpu;
-
- for_each_possible_cpu(cpu)
- __printk_nmi_flush(&per_cpu(nmi_print_seq, cpu).work);
-}
-
-/**
- * printk_nmi_flush_on_panic - flush all per-cpu nmi buffers when the system
- * goes down.
- *
- * Similar to printk_nmi_flush() but it can be called even in NMI context when
- * the system goes down. It does the best effort to get NMI messages into
- * the main ring buffer.
- *
- * Note that it could try harder when there is only one CPU online.
- */
-void printk_nmi_flush_on_panic(void)
-{
- /*
- * Make sure that we could access the main ring buffer.
- * Do not risk a double release when more CPUs are up.
- */
- if (in_nmi() && raw_spin_is_locked(&logbuf_lock)) {
- if (num_online_cpus() > 1)
- return;
-
- debug_locks_off();
- raw_spin_lock_init(&logbuf_lock);
- }
-
- printk_nmi_flush();
-}
-
-void __init printk_nmi_init(void)
-{
- int cpu;
-
- for_each_possible_cpu(cpu) {
- struct nmi_seq_buf *s = &per_cpu(nmi_print_seq, cpu);
-
- init_irq_work(&s->work, __printk_nmi_flush);
- }
-
- /* Make sure that IRQ works are initialized before enabling. */
- smp_wmb();
- printk_nmi_irq_ready = 1;
-
- /* Flush pending messages that did not have scheduled IRQ works. */
- printk_nmi_flush();
-}
-
-void printk_nmi_enter(void)
-{
- this_cpu_write(printk_func, vprintk_nmi);
-}
-
-void printk_nmi_exit(void)
-{
- this_cpu_write(printk_func, vprintk_default);
-}
--- /dev/null
+/*
+ * printk_safe.c - Safe printk in NMI context
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/preempt.h>
+#include <linux/spinlock.h>
+#include <linux/debug_locks.h>
+#include <linux/smp.h>
+#include <linux/cpumask.h>
+#include <linux/irq_work.h>
+#include <linux/printk.h>
+
+#include "internal.h"
+
+/*
+ * printk() could not take logbuf_lock in NMI context. Instead,
+ * it uses an alternative implementation that temporary stores
+ * the strings into a per-CPU buffer. The content of the buffer
+ * is later flushed into the main ring buffer via IRQ work.
+ *
+ * The alternative implementation is chosen transparently
+ * via @printk_func per-CPU variable.
+ *
+ * The implementation allows to flush the strings also from another CPU.
+ * There are situations when we want to make sure that all buffers
+ * were handled or when IRQs are blocked.
+ */
+DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
+static int printk_safe_irq_ready;
+atomic_t nmi_message_lost;
+
+#define SAFE_LOG_BUF_LEN ((1 << CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT) - \
+ sizeof(atomic_t) - sizeof(struct irq_work))
+
+struct printk_safe_seq_buf {
+ atomic_t len; /* length of written data */
+ struct irq_work work; /* IRQ work that flushes the buffer */
+ unsigned char buffer[SAFE_LOG_BUF_LEN];
+};
+static DEFINE_PER_CPU(struct printk_safe_seq_buf, nmi_print_seq);
+
+/*
+ * Safe printk() for NMI context. It uses a per-CPU buffer to
+ * store the message. NMIs are not nested, so there is always only
+ * one writer running. But the buffer might get flushed from another
+ * CPU, so we need to be careful.
+ */
+static int vprintk_nmi(const char *fmt, va_list args)
+{
+ struct printk_safe_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
+ int add = 0;
+ size_t len;
+
+again:
+ len = atomic_read(&s->len);
+
+ /* The trailing '\0' is not counted into len. */
+ if (len >= sizeof(s->buffer) - 1) {
+ atomic_inc(&nmi_message_lost);
+ return 0;
+ }
+
+ /*
+ * Make sure that all old data have been read before the buffer was
+ * reseted. This is not needed when we just append data.
+ */
+ if (!len)
+ smp_rmb();
+
+ add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, args);
+
+ /*
+ * Do it once again if the buffer has been flushed in the meantime.
+ * Note that atomic_cmpxchg() is an implicit memory barrier that
+ * makes sure that the data were written before updating s->len.
+ */
+ if (atomic_cmpxchg(&s->len, len, len + add) != len)
+ goto again;
+
+ /* Get flushed in a more safe context. */
+ if (add && printk_safe_irq_ready) {
+ /* Make sure that IRQ work is really initialized. */
+ smp_rmb();
+ irq_work_queue(&s->work);
+ }
+
+ return add;
+}
+
+static void printk_safe_flush_line(const char *text, int len)
+{
+ /*
+ * The buffers are flushed in NMI only on panic. The messages must
+ * go only into the ring buffer at this stage. Consoles will get
+ * explicitly called later when a crashdump is not generated.
+ */
+ if (in_nmi())
+ printk_deferred("%.*s", len, text);
+ else
+ printk("%.*s", len, text);
+}
+
+/* printk part of the temporary buffer line by line */
+static int printk_safe_flush_buffer(const char *start, size_t len)
+{
+ const char *c, *end;
+ bool header;
+
+ c = start;
+ end = start + len;
+ header = true;
+
+ /* Print line by line. */
+ while (c < end) {
+ if (*c == '\n') {
+ printk_safe_flush_line(start, c - start + 1);
+ start = ++c;
+ header = true;
+ continue;
+ }
+
+ /* Handle continuous lines or missing new line. */
+ if ((c + 1 < end) && printk_get_level(c)) {
+ if (header) {
+ c = printk_skip_level(c);
+ continue;
+ }
+
+ printk_safe_flush_line(start, c - start);
+ start = c++;
+ header = true;
+ continue;
+ }
+
+ header = false;
+ c++;
+ }
+
+ /* Check if there was a partial line. Ignore pure header. */
+ if (start < end && !header) {
+ static const char newline[] = KERN_CONT "\n";
+
+ printk_safe_flush_line(start, end - start);
+ printk_safe_flush_line(newline, strlen(newline));
+ }
+
+ return len;
+}
+
+/*
+ * Flush data from the associated per_CPU buffer. The function
+ * can be called either via IRQ work or independently.
+ */
+static void __printk_safe_flush(struct irq_work *work)
+{
+ static raw_spinlock_t read_lock =
+ __RAW_SPIN_LOCK_INITIALIZER(read_lock);
+ struct printk_safe_seq_buf *s =
+ container_of(work, struct printk_safe_seq_buf, work);
+ unsigned long flags;
+ size_t len;
+ int i;
+
+ /*
+ * The lock has two functions. First, one reader has to flush all
+ * available message to make the lockless synchronization with
+ * writers easier. Second, we do not want to mix messages from
+ * different CPUs. This is especially important when printing
+ * a backtrace.
+ */
+ raw_spin_lock_irqsave(&read_lock, flags);
+
+ i = 0;
+more:
+ len = atomic_read(&s->len);
+
+ /*
+ * This is just a paranoid check that nobody has manipulated
+ * the buffer an unexpected way. If we printed something then
+ * @len must only increase. Also it should never overflow the
+ * buffer size.
+ */
+ if ((i && i >= len) || len > sizeof(s->buffer)) {
+ const char *msg = "printk_safe_flush: internal error\n";
+
+ printk_safe_flush_line(msg, strlen(msg));
+ len = 0;
+ }
+
+ if (!len)
+ goto out; /* Someone else has already flushed the buffer. */
+
+ /* Make sure that data has been written up to the @len */
+ smp_rmb();
+ i += printk_safe_flush_buffer(s->buffer + i, len - i);
+
+ /*
+ * Check that nothing has got added in the meantime and truncate
+ * the buffer. Note that atomic_cmpxchg() is an implicit memory
+ * barrier that makes sure that the data were copied before
+ * updating s->len.
+ */
+ if (atomic_cmpxchg(&s->len, len, 0) != len)
+ goto more;
+
+out:
+ raw_spin_unlock_irqrestore(&read_lock, flags);
+}
+
+/**
+ * printk_safe_flush - flush all per-cpu nmi buffers.
+ *
+ * The buffers are flushed automatically via IRQ work. This function
+ * is useful only when someone wants to be sure that all buffers have
+ * been flushed at some point.
+ */
+void printk_safe_flush(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ __printk_safe_flush(&per_cpu(nmi_print_seq, cpu).work);
+}
+
+/**
+ * printk_safe_flush_on_panic - flush all per-cpu nmi buffers when the system
+ * goes down.
+ *
+ * Similar to printk_safe_flush() but it can be called even in NMI context when
+ * the system goes down. It does the best effort to get NMI messages into
+ * the main ring buffer.
+ *
+ * Note that it could try harder when there is only one CPU online.
+ */
+void printk_safe_flush_on_panic(void)
+{
+ /*
+ * Make sure that we could access the main ring buffer.
+ * Do not risk a double release when more CPUs are up.
+ */
+ if (in_nmi() && raw_spin_is_locked(&logbuf_lock)) {
+ if (num_online_cpus() > 1)
+ return;
+
+ debug_locks_off();
+ raw_spin_lock_init(&logbuf_lock);
+ }
+
+ printk_safe_flush();
+}
+
+void __init printk_safe_init(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ struct printk_safe_seq_buf *s = &per_cpu(nmi_print_seq, cpu);
+
+ init_irq_work(&s->work, __printk_safe_flush);
+ }
+
+ /* Make sure that IRQ works are initialized before enabling. */
+ smp_wmb();
+ printk_safe_irq_ready = 1;
+
+ /* Flush pending messages that did not have scheduled IRQ works. */
+ printk_safe_flush();
+}
+
+void printk_nmi_enter(void)
+{
+ this_cpu_write(printk_func, vprintk_nmi);
+}
+
+void printk_nmi_exit(void)
+{
+ this_cpu_write(printk_func, vprintk_default);
+}
* Force flush any remote buffers that might be stuck in IRQ context
* and therefore could not run their irq_work.
*/
- printk_nmi_flush();
+ printk_safe_flush();
clear_bit_unlock(0, &backtrace_flag);
put_cpu();
projects / GitHub / MotorolaMobilityLLC / kernel-slsi.git / commitdiff