diff options
| -rw-r--r-- | include/linux/console.h | 7 | ||||
| -rw-r--r-- | kernel/printk/internal.h | 12 | ||||
| -rw-r--r-- | kernel/printk/nbcon.c | 73 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 22 |
4 files changed, 99 insertions, 15 deletions
diff --git a/include/linux/console.h b/include/linux/console.h index 98210fd01f18..ca1ef8700e55 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -231,6 +231,7 @@ enum nbcon_prio { }; struct console; +struct printk_buffers; /** * struct nbcon_context - Context for console acquire/release @@ -241,6 +242,7 @@ struct console; * be used only with NBCON_PRIO_PANIC @prio. It * might cause a system freeze when the console * is used later. + * @pbufs: Pointer to the text buffer for this context */ struct nbcon_context { /* members set by caller */ @@ -248,6 +250,9 @@ struct nbcon_context { unsigned int spinwait_max_us; enum nbcon_prio prio; unsigned int allow_unsafe_takeover : 1; + + /* members set by acquire */ + struct printk_buffers *pbufs; }; /** @@ -271,6 +276,7 @@ struct nbcon_context { * @node: hlist node for the console list * * @nbcon_state: State for nbcon consoles + * @pbufs: Pointer to nbcon private buffer */ struct console { char name[16]; @@ -293,6 +299,7 @@ struct console { /* nbcon console specific members */ atomic_t __private nbcon_state; + struct printk_buffers *pbufs; }; #ifdef CONFIG_LOCKDEP diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index 7199d60bfc25..f6161cd75d7d 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -13,6 +13,12 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, #define printk_sysctl_init() do { } while (0) #endif +#define con_printk(lvl, con, fmt, ...) \ + printk(lvl pr_fmt("%s%sconsole [%s%d] " fmt), \ + (con->flags & CON_NBCON) ? "" : "legacy ", \ + (con->flags & CON_BOOT) ? "boot" : "", \ + con->name, con->index, ##__VA_ARGS__) + #ifdef CONFIG_PRINTK #ifdef CONFIG_PRINTK_CALLER @@ -63,8 +69,9 @@ void defer_console_output(void); u16 printk_parse_prefix(const char *text, int *level, enum printk_info_flags *flags); +bool nbcon_alloc(struct console *con); void nbcon_init(struct console *con); -void nbcon_cleanup(struct console *con); +void nbcon_free(struct console *con); #else @@ -81,8 +88,9 @@ void nbcon_cleanup(struct console *con); #define printk_safe_exit_irqrestore(flags) local_irq_restore(flags) static inline bool printk_percpu_data_ready(void) { return false; } +static inline bool nbcon_alloc(struct console *con) { return false; } static inline void nbcon_init(struct console *con) { } -static inline void nbcon_cleanup(struct console *con) { } +static inline void nbcon_free(struct console *con) { } #endif /* CONFIG_PRINTK */ diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index a2a354f859f9..ba1febf15db6 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -5,6 +5,7 @@ #include <linux/kernel.h> #include <linux/console.h> #include <linux/delay.h> +#include <linux/slab.h> #include "internal.h" /* * Printk console printing implementation for consoles which does not depend @@ -70,6 +71,10 @@ * console is an unsafe state. It is used only in panic() by the final * attempt to flush consoles in a try and hope mode. * + * Note that separate record buffers are used in panic(). As a result, + * the messages can be read and formatted without any risk even after + * using the hostile takeover in unsafe state. + * * The release function simply clears the 'prio' field. * * All operations on @console::nbcon_state are atomic cmpxchg based to @@ -459,6 +464,8 @@ static int nbcon_context_try_acquire_hostile(struct nbcon_context *ctxt, return 0; } +static struct printk_buffers panic_nbcon_pbufs; + /** * nbcon_context_try_acquire - Try to acquire nbcon console * @ctxt: The context of the caller @@ -473,6 +480,7 @@ static int nbcon_context_try_acquire_hostile(struct nbcon_context *ctxt, __maybe_unused static bool nbcon_context_try_acquire(struct nbcon_context *ctxt) { + unsigned int cpu = smp_processor_id(); struct console *con = ctxt->console; struct nbcon_state cur; int err; @@ -491,7 +499,18 @@ try_again: err = nbcon_context_try_acquire_hostile(ctxt, &cur); out: - return !err; + if (err) + return false; + + /* Acquire succeeded. */ + + /* Assign the appropriate buffer for this context. */ + if (atomic_read(&panic_cpu) == cpu) + ctxt->pbufs = &panic_nbcon_pbufs; + else + ctxt->pbufs = con->pbufs; + + return true; } static bool nbcon_owner_matches(struct nbcon_state *cur, int expected_cpu, @@ -530,7 +549,7 @@ static void nbcon_context_release(struct nbcon_context *ctxt) do { if (!nbcon_owner_matches(&cur, cpu, ctxt->prio)) - return; + break; new.atom = cur.atom; new.prio = NBCON_PRIO_NONE; @@ -542,26 +561,70 @@ static void nbcon_context_release(struct nbcon_context *ctxt) new.unsafe |= cur.unsafe_takeover; } while (!nbcon_state_try_cmpxchg(con, &cur, &new)); + + ctxt->pbufs = NULL; +} + +/** + * nbcon_alloc - Allocate buffers needed by the nbcon console + * @con: Console to allocate buffers for + * + * Return: True on success. False otherwise and the console cannot + * be used. + * + * This is not part of nbcon_init() because buffer allocation must + * be performed earlier in the console registration process. + */ +bool nbcon_alloc(struct console *con) +{ + if (con->flags & CON_BOOT) { + /* + * Boot console printing is synchronized with legacy console + * printing, so boot consoles can share the same global printk + * buffers. + */ + con->pbufs = &printk_shared_pbufs; + } else { + con->pbufs = kmalloc(sizeof(*con->pbufs), GFP_KERNEL); + if (!con->pbufs) { + con_printk(KERN_ERR, con, "failed to allocate printing buffer\n"); + return false; + } + } + + return true; } /** * nbcon_init - Initialize the nbcon console specific data * @con: Console to initialize + * + * nbcon_alloc() *must* be called and succeed before this function + * is called. */ void nbcon_init(struct console *con) { struct nbcon_state state = { }; + /* nbcon_alloc() must have been called and successful! */ + BUG_ON(!con->pbufs); + nbcon_state_set(con, &state); } /** - * nbcon_cleanup - Cleanup the nbcon console specific data - * @con: Console to cleanup + * nbcon_free - Free and cleanup the nbcon console specific data + * @con: Console to free/cleanup nbcon data */ -void nbcon_cleanup(struct console *con) +void nbcon_free(struct console *con) { struct nbcon_state state = { }; nbcon_state_set(con, &state); + + /* Boot consoles share global printk buffers. */ + if (!(con->flags & CON_BOOT)) + kfree(con->pbufs); + + con->pbufs = NULL; } diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 17def3791bc0..1c9720acd960 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3331,12 +3331,6 @@ static void try_enable_default_console(struct console *newcon) newcon->flags |= CON_CONSDEV; } -#define con_printk(lvl, con, fmt, ...) \ - printk(lvl pr_fmt("%s%sconsole [%s%d] " fmt), \ - (con->flags & CON_NBCON) ? "" : "legacy ", \ - (con->flags & CON_BOOT) ? "boot" : "", \ - con->name, con->index, ##__VA_ARGS__) - static void console_init_seq(struct console *newcon, bool bootcon_registered) { struct console *con; @@ -3450,6 +3444,15 @@ void register_console(struct console *newcon) goto unlock; } + if (newcon->flags & CON_NBCON) { + /* + * Ensure the nbcon console buffers can be allocated + * before modifying any global data. + */ + if (!nbcon_alloc(newcon)) + goto unlock; + } + /* * See if we want to enable this console driver by default. * @@ -3477,8 +3480,11 @@ void register_console(struct console *newcon) err = try_enable_preferred_console(newcon, false); /* printk() messages are not printed to the Braille console. */ - if (err || newcon->flags & CON_BRL) + if (err || newcon->flags & CON_BRL) { + if (newcon->flags & CON_NBCON) + nbcon_free(newcon); goto unlock; + } /* * If we have a bootconsole, and are switching to a real console, @@ -3589,7 +3595,7 @@ static int unregister_console_locked(struct console *console) synchronize_srcu(&console_srcu); if (console->flags & CON_NBCON) - nbcon_cleanup(console); + nbcon_free(console); console_sysfs_notify(); |