From 7efa84b5cdd6d473c7e80912638fca9d7167f202 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Fri, 4 Apr 2025 15:10:02 -0700 Subject: [PATCH 1/5] compiler-gcc.h: Introduce __diag_GCC_all It is not possible disabling a diagnostic for all versions of GCC without hard coding the minimum supported version at the site, as the GCC specific macros require a minimum version to disable the warning for: __diag_ignore(GCC, 5, ...); __diag_ignore_all() does not solve this issue because it disables a diagnostic for all versions of both GCC and clang, not just one or the other. Introduce __diag_GCC_all so that developers can write __diag_ignore(GCC, all, ...); to disable a particular diagnostic for all versions of GCC, while not affecting clang. Closes: https://lore.kernel.org/r/CAHk-=wgfX9nBGE0Ap9GjhOy7Mn=RSy=rx0MvqfYFFDx31KJXqQ@mail.gmail.com Signed-off-by: Nathan Chancellor Tested-by: Andy Shevchenko Reviewed-by: Petr Mladek Link: https://patch.msgid.link/20250404-vsprintf-convert-pragmas-to-__diag-v1-1-5d6c5c55b2bd@kernel.org Signed-off-by: Petr Mladek --- include/linux/compiler-gcc.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index c9b58188ec61..c75a222880f9 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -127,6 +127,8 @@ #define __diag_GCC_8(s) #endif +#define __diag_GCC_all(s) __diag(s) + #define __diag_ignore_all(option, comment) \ __diag(__diag_GCC_ignore option) From b5960a06b90eeba147c50c2d14de57b923371651 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Fri, 4 Apr 2025 15:10:03 -0700 Subject: [PATCH 2/5] vsprintf: Use __diag macros to disable '-Wsuggest-attribute=format' The GCC specific warning '-Wsuggest-attribute=format' is disabled around va_format() using raw #pragma statements, which includes an '#ifndef __clang__' to avoid a warning about an unknown warning option from clang (which recognizes '#pragma GCC' for compatibility reasons): lib/vsprintf.c:1703:32: error: unknown warning group '-Wsuggest-attribute=format', ignored [-Werror,-Wunknown-warning-option] 1703 | #pragma GCC diagnostic ignored "-Wsuggest-attribute=format" | ^ While the current solution works, it is not visually appealing. The kernel already has some infrastructure that wraps these #pragma statements to give more specific control over diagnostics without needing #ifdef blocks for different compilers. Convert the existing statements over to the __diag macros. Closes: https://lore.kernel.org/r/CAHk-=wgfX9nBGE0Ap9GjhOy7Mn=RSy=rx0MvqfYFFDx31KJXqQ@mail.gmail.com Signed-off-by: Nathan Chancellor Tested-by: Andy Shevchenko Reviewed-by: Petr Mladek Link: https://patch.msgid.link/20250404-vsprintf-convert-pragmas-to-__diag-v1-2-5d6c5c55b2bd@kernel.org Signed-off-by: Petr Mladek --- lib/vsprintf.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index a2195bc81723..8a6cdee0d4ad 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -1699,10 +1699,9 @@ char *escaped_string(char *buf, char *end, u8 *addr, struct printf_spec spec, return buf; } -#pragma GCC diagnostic push -#ifndef __clang__ -#pragma GCC diagnostic ignored "-Wsuggest-attribute=format" -#endif +__diag_push(); +__diag_ignore(GCC, all, "-Wsuggest-attribute=format", + "Not a valid __printf() conversion candidate."); static char *va_format(char *buf, char *end, struct va_format *va_fmt, struct printf_spec spec) { @@ -1717,7 +1716,7 @@ static char *va_format(char *buf, char *end, struct va_format *va_fmt, return buf; } -#pragma GCC diagnostic pop +__diag_pop(); static noinline_for_stack char *uuid_string(char *buf, char *end, const u8 *addr, From de1c831a7898f164c1c2703c6b2b9e4fb4bebefc Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 15 Apr 2025 10:02:33 -0700 Subject: [PATCH 3/5] slab: Decouple slab_debug and no_hash_pointers Some system owners use slab_debug=FPZ (or similar) as a hardening option, but do not want to be forced into having kernel addresses exposed due to the implicit "no_hash_pointers" boot param setting.[1] Introduce the "hash_pointers" boot param, which defaults to "auto" (the current behavior), but also includes "always" (forcing on hashing even when "slab_debug=..." is defined), and "never". The existing "no_hash_pointers" boot param becomes an alias for "hash_pointers=never". This makes it possible to boot with "slab_debug=FPZ hash_pointers=always". Link: https://github.com/KSPP/linux/issues/368 [1] Fixes: 792702911f58 ("slub: force on no_hash_pointers when slub_debug is enabled") Co-developed-by: Sergio Perez Gonzalez Signed-off-by: Sergio Perez Gonzalez Acked-by: Vlastimil Babka Acked-by: David Rientjes Reviewed-by: Bagas Sanjaya Signed-off-by: Kees Cook Reviewed-by: Harry Yoo Acked-by: Rafael Aquini Tested-by: Petr Mladek Reviewed-by: Petr Mladek Link: https://patch.msgid.link/20250415170232.it.467-kees@kernel.org [kees@kernel.org: Add note about hash_pointers into slab_debug kernel parameter documentation.] Signed-off-by: Petr Mladek --- .../admin-guide/kernel-parameters.txt | 38 ++++++++---- include/linux/sprintf.h | 2 +- lib/vsprintf.c | 61 +++++++++++++++++-- mm/slub.c | 5 +- 4 files changed, 86 insertions(+), 20 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 3f35d5b8c296..0dd5cd17e87e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1798,6 +1798,27 @@ backtraces on all cpus. Format: 0 | 1 + hash_pointers= + [KNL,EARLY] + By default, when pointers are printed to the console + or buffers via the %p format string, that pointer is + "hashed", i.e. obscured by hashing the pointer value. + This is a security feature that hides actual kernel + addresses from unprivileged users, but it also makes + debugging the kernel more difficult since unequal + pointers can no longer be compared. The choices are: + Format: { auto | always | never } + Default: auto + + auto - Hash pointers unless slab_debug is enabled. + always - Always hash pointers (even if slab_debug is + enabled). + never - Never hash pointers. This option should only + be specified when debugging the kernel. Do + not use on production kernels. The boot + param "no_hash_pointers" is an alias for + this mode. + hashdist= [KNL,NUMA] Large hashes allocated during boot are distributed across NUMA nodes. Defaults on for 64-bit NUMA, off otherwise. @@ -4120,18 +4141,7 @@ no_hash_pointers [KNL,EARLY] - Force pointers printed to the console or buffers to be - unhashed. By default, when a pointer is printed via %p - format string, that pointer is "hashed", i.e. obscured - by hashing the pointer value. This is a security feature - that hides actual kernel addresses from unprivileged - users, but it also makes debugging the kernel more - 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. This option should only be specified when - debugging the kernel. Please do not use on production - kernels. + Alias for "hash_pointers=never". nohibernate [HIBERNATION] Disable hibernation and resume. @@ -6481,6 +6491,10 @@ Documentation/mm/slub.rst. (slub_debug legacy name also accepted for now) + Using this option implies the "no_hash_pointers" + option which can be undone by adding the + "hash_pointers=always" option. + slab_max_order= [MM] Determines the maximum allowed order for slabs. A high setting may cause OOMs due to memory diff --git a/include/linux/sprintf.h b/include/linux/sprintf.h index 51cab2def9ec..521bb2cd2648 100644 --- a/include/linux/sprintf.h +++ b/include/linux/sprintf.h @@ -22,7 +22,7 @@ __scanf(2, 0) int vsscanf(const char *, const char *, va_list); /* These are for specific cases, do not use without real need */ extern bool no_hash_pointers; -int no_hash_pointers_enable(char *str); +void hash_pointers_finalize(bool slub_debug); /* Used for Rust formatting ('%pA') */ char *rust_fmt_argument(char *buf, char *end, const void *ptr); diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 01699852f30c..22cbd75266ef 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -60,6 +60,20 @@ bool no_hash_pointers __ro_after_init; EXPORT_SYMBOL_GPL(no_hash_pointers); +/* + * Hashed pointers policy selected by "hash_pointers=..." boot param + * + * `auto` - Hashed pointers enabled unless disabled by slub_debug_enabled=true + * `always` - Hashed pointers enabled unconditionally + * `never` - Hashed pointers disabled unconditionally + */ +enum hash_pointers_policy { + HASH_PTR_AUTO = 0, + HASH_PTR_ALWAYS, + HASH_PTR_NEVER +}; +static enum hash_pointers_policy hash_pointers_mode __initdata; + noinline static unsigned long long simple_strntoull(const char *startp, char **endp, unsigned int base, size_t max_chars) { @@ -2271,12 +2285,23 @@ char *resource_or_range(const char *fmt, char *buf, char *end, void *ptr, return resource_string(buf, end, ptr, spec, fmt); } -int __init no_hash_pointers_enable(char *str) +void __init hash_pointers_finalize(bool slub_debug) { - if (no_hash_pointers) - return 0; + switch (hash_pointers_mode) { + case HASH_PTR_ALWAYS: + no_hash_pointers = false; + break; + case HASH_PTR_NEVER: + no_hash_pointers = true; + break; + case HASH_PTR_AUTO: + default: + no_hash_pointers = slub_debug; + break; + } - no_hash_pointers = true; + if (!no_hash_pointers) + return; pr_warn("**********************************************************\n"); pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n"); @@ -2289,11 +2314,39 @@ int __init no_hash_pointers_enable(char *str) pr_warn("** the kernel, report this immediately to your system **\n"); pr_warn("** administrator! **\n"); pr_warn("** **\n"); + pr_warn("** Use hash_pointers=always to force this mode off **\n"); + pr_warn("** **\n"); pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n"); pr_warn("**********************************************************\n"); +} + +static int __init hash_pointers_mode_parse(char *str) +{ + if (!str) { + pr_warn("Hash pointers mode empty; falling back to auto.\n"); + hash_pointers_mode = HASH_PTR_AUTO; + } else if (strncmp(str, "auto", 4) == 0) { + pr_info("Hash pointers mode set to auto.\n"); + hash_pointers_mode = HASH_PTR_AUTO; + } else if (strncmp(str, "never", 5) == 0) { + pr_info("Hash pointers mode set to never.\n"); + hash_pointers_mode = HASH_PTR_NEVER; + } else if (strncmp(str, "always", 6) == 0) { + pr_info("Hash pointers mode set to always.\n"); + hash_pointers_mode = HASH_PTR_ALWAYS; + } else { + pr_warn("Unknown hash_pointers mode '%s' specified; assuming auto.\n", str); + hash_pointers_mode = HASH_PTR_AUTO; + } return 0; } +early_param("hash_pointers", hash_pointers_mode_parse); + +static int __init no_hash_pointers_enable(char *str) +{ + return hash_pointers_mode_parse("never"); +} early_param("no_hash_pointers", no_hash_pointers_enable); /* diff --git a/mm/slub.c b/mm/slub.c index b46f87662e71..f3d61b330a76 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -6314,9 +6314,8 @@ void __init kmem_cache_init(void) if (debug_guardpage_minorder()) slub_max_order = 0; - /* Print slub debugging pointers without hashing */ - if (__slub_debug_enabled()) - no_hash_pointers_enable(NULL); + /* Inform pointer hashing choice about slub debugging state. */ + hash_pointers_finalize(__slub_debug_enabled()); kmem_cache_node = &boot_kmem_cache_node; kmem_cache = &boot_kmem_cache; From cf5543870186d6f99b631faaeca27beaa996d52f Mon Sep 17 00:00:00 2001 From: Petr Mladek Date: Wed, 4 Jun 2025 16:20:45 +0200 Subject: [PATCH 4/5] printk: Allow to use the printk kthread immediately even for 1st nbcon The kthreads for nbcon consoles are created by nbcon_alloc() at the beginning of the console registration. But it currently works only for the 2nd or later nbcon console because the code checks @printk_kthreads_running. The kthread for the 1st registered nbcon console is created at the very end of register_console() by printk_kthreads_check_locked(). As a result, the entire log is replayed synchronously when the "enabled" message gets printed. It might block the boot for a long time with a slow serial console. Prevent the synchronous flush by creating the kthread even for the 1st nbcon console when it is safe (kthreads ready and no boot consoles). Also inform printk() to use the kthread by setting @printk_kthreads_running. Note that the kthreads already must be running when it is safe and this is not the 1st nbcon console. Symmetrically, clear @printk_kthreads_running when the last nbcon console was unregistered by nbcon_free(). This requires updating @have_nbcon_console before nbcon_free() gets called. Note that there is _no_ problem when the 1st nbcon console replaces boot consoles. In this case, the kthread will be started at the end of registration after the boot consoles are removed. But the console does not reply the entire log buffer in this case. Note that the flag CON_PRINTBUFFER is always cleared when the boot consoles are removed and vice versa. Closes: https://lore.kernel.org/r/20250514173514.2117832-1-mcobb@thegoodpenguin.co.uk Tested-by: Michael Cobb Reviewed-by: John Ogness Link: https://patch.msgid.link/20250604142045.253301-1-pmladek@suse.com Signed-off-by: Petr Mladek --- kernel/printk/internal.h | 2 ++ kernel/printk/nbcon.c | 26 ++++++++++++++++++++++++-- kernel/printk/printk.c | 20 +++++++++++--------- 3 files changed, 37 insertions(+), 11 deletions(-) diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index 48a24e7b309d..567c9e100d47 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -64,6 +64,7 @@ struct dev_printk_info; extern struct printk_ringbuffer *prb; extern bool printk_kthreads_running; +extern bool printk_kthreads_ready; extern bool debug_non_panic_cpus; __printf(4, 0) @@ -180,6 +181,7 @@ static inline void nbcon_kthread_wake(struct console *con) #define PRINTKRB_RECORD_MAX 0 #define printk_kthreads_running (false) +#define printk_kthreads_ready (false) /* * In !PRINTK builds we still export console_sem diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index fd12efcc4aed..d60596777d27 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -1671,6 +1671,9 @@ bool nbcon_alloc(struct console *con) { struct nbcon_state state = { }; + /* Synchronize the kthread start. */ + lockdep_assert_console_list_lock_held(); + /* The write_thread() callback is mandatory. */ if (WARN_ON(!con->write_thread)) return false; @@ -1701,12 +1704,15 @@ bool nbcon_alloc(struct console *con) return false; } - if (printk_kthreads_running) { + if (printk_kthreads_ready && !have_boot_console) { if (!nbcon_kthread_create(con)) { kfree(con->pbufs); con->pbufs = NULL; return false; } + + /* Might be the first kthread. */ + printk_kthreads_running = true; } } @@ -1716,14 +1722,30 @@ bool nbcon_alloc(struct console *con) /** * nbcon_free - Free and cleanup the nbcon console specific data * @con: Console to free/cleanup nbcon data + * + * Important: @have_nbcon_console must be updated before calling + * this function. In particular, it can be set only when there + * is still another nbcon console registered. */ void nbcon_free(struct console *con) { struct nbcon_state state = { }; - if (printk_kthreads_running) + /* Synchronize the kthread stop. */ + lockdep_assert_console_list_lock_held(); + + if (printk_kthreads_running) { nbcon_kthread_stop(con); + /* Might be the last nbcon console. + * + * Do not rely on printk_kthreads_check_locked(). It is not + * called in some code paths, see nbcon_free() callers. + */ + if (!have_nbcon_console) + printk_kthreads_running = false; + } + nbcon_state_set(con, &state); /* Boot consoles share global printk buffers. */ diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 1eea80d0648e..0efbcdda9aab 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3574,7 +3574,7 @@ EXPORT_SYMBOL(console_resume); static int unregister_console_locked(struct console *console); /* True when system boot is far enough to create printer threads. */ -static bool printk_kthreads_ready __ro_after_init; +bool printk_kthreads_ready __ro_after_init; static struct task_struct *printk_legacy_kthread; @@ -3713,6 +3713,7 @@ static void printk_kthreads_check_locked(void) if (!printk_kthreads_ready) return; + /* Start or stop the legacy kthread when needed. */ if (have_legacy_console || have_boot_console) { if (!printk_legacy_kthread && force_legacy_kthread() && @@ -4204,14 +4205,6 @@ static int unregister_console_locked(struct console *console) */ synchronize_srcu(&console_srcu); - if (console->flags & CON_NBCON) - nbcon_free(console); - - console_sysfs_notify(); - - if (console->exit) - res = console->exit(console); - /* * With this console gone, the global flags tracking registered * console types may have changed. Update them. @@ -4232,6 +4225,15 @@ static int unregister_console_locked(struct console *console) if (!found_nbcon_con) have_nbcon_console = found_nbcon_con; + /* @have_nbcon_console must be updated before calling nbcon_free(). */ + if (console->flags & CON_NBCON) + nbcon_free(console); + + console_sysfs_notify(); + + if (console->exit) + res = console->exit(console); + /* Changed console list, may require printer threads to start/stop. */ printk_kthreads_check_locked(); From 571c1ea91a73db56bd94054fabecd0f070dc90db Mon Sep 17 00:00:00 2001 From: John Ogness Date: Fri, 6 Jun 2025 21:01:49 +0206 Subject: [PATCH 5/5] printk: nbcon: Allow reacquire during panic If a console printer is interrupted during panic, it will never be able to reacquire ownership in order to perform and cleanup. That in itself is not a problem, since the non-panic CPU will simply quiesce in an endless loop within nbcon_reacquire_nobuf(). However, in this state, platforms that do not support a true NMI to interrupt the quiesced CPU will not be able to shutdown that CPU from within panic(). This then causes problems for such as being unable to load and run a kdump kernel. Fix this by allowing non-panic CPUs to reacquire ownership using a direct acquire. Then the non-panic CPUs can successfullyl exit the nbcon_reacquire_nobuf() loop and the console driver can perform any necessary cleanup. But more importantly, the CPU is no longer quiesced and is free to process any interrupts necessary for panic() to shutdown the CPU. All other forms of acquire are still not allowed for non-panic CPUs since it is safer to have them avoid gaining console ownership that is not strictly necessary. Reported-by: Michael Kelley Closes: https://lore.kernel.org/r/SN6PR02MB4157A4C5E8CB219A75263A17D46DA@SN6PR02MB4157.namprd02.prod.outlook.com Signed-off-by: John Ogness Reviewed-by: Petr Mladek Tested-by: Michael Kelley Link: https://patch.msgid.link/20250606185549.900611-1-john.ogness@linutronix.de Signed-off-by: Petr Mladek --- kernel/printk/nbcon.c | 63 ++++++++++++++++++++++++++++--------------- 1 file changed, 41 insertions(+), 22 deletions(-) diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index fd12efcc4aed..e7a3af81b173 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -214,8 +214,9 @@ static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq) /** * nbcon_context_try_acquire_direct - Try to acquire directly - * @ctxt: The context of the caller - * @cur: The current console state + * @ctxt: The context of the caller + * @cur: The current console state + * @is_reacquire: This acquire is a reacquire * * Acquire the console when it is released. Also acquire the console when * the current owner has a lower priority and the console is in a safe state. @@ -225,17 +226,17 @@ static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq) * * Errors: * - * -EPERM: A panic is in progress and this is not the panic CPU. - * Or the current owner or waiter has the same or higher - * priority. No acquire method can be successful in - * this case. + * -EPERM: A panic is in progress and this is neither the panic + * CPU nor is this a reacquire. Or the current owner or + * waiter has the same or higher priority. No acquire + * method can be successful in these cases. * * -EBUSY: The current owner has a lower priority but the console * in an unsafe state. The caller should try using * the handover acquire method. */ static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt, - struct nbcon_state *cur) + struct nbcon_state *cur, bool is_reacquire) { unsigned int cpu = smp_processor_id(); struct console *con = ctxt->console; @@ -243,14 +244,20 @@ static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt, do { /* - * Panic does not imply that the console is owned. However, it - * is critical that non-panic CPUs during panic are unable to - * acquire ownership in order to satisfy the assumptions of - * nbcon_waiter_matches(). In particular, the assumption that - * lower priorities are ignored during panic. + * Panic does not imply that the console is owned. However, + * since all non-panic CPUs are stopped during panic(), it + * is safer to have them avoid gaining console ownership. + * + * If this acquire is a reacquire (and an unsafe takeover + * has not previously occurred) then it is allowed to attempt + * a direct acquire in panic. This gives console drivers an + * opportunity to perform any necessary cleanup if they were + * interrupted by the panic CPU while printing. */ - if (other_cpu_in_panic()) + if (other_cpu_in_panic() && + (!is_reacquire || cur->unsafe_takeover)) { return -EPERM; + } if (ctxt->prio <= cur->prio || ctxt->prio <= cur->req_prio) return -EPERM; @@ -301,8 +308,9 @@ static bool nbcon_waiter_matches(struct nbcon_state *cur, int expected_prio) * Event #1 implies this context is EMERGENCY. * Event #2 implies the new context is PANIC. * Event #3 occurs when panic() has flushed the console. - * Events #4 and #5 are not possible due to the other_cpu_in_panic() - * check in nbcon_context_try_acquire_direct(). + * Event #4 occurs when a non-panic CPU reacquires. + * Event #5 is not possible due to the other_cpu_in_panic() check + * in nbcon_context_try_acquire_handover(). */ return (cur->req_prio == expected_prio); @@ -431,6 +439,16 @@ static int nbcon_context_try_acquire_handover(struct nbcon_context *ctxt, WARN_ON_ONCE(ctxt->prio <= cur->prio || ctxt->prio <= cur->req_prio); WARN_ON_ONCE(!cur->unsafe); + /* + * Panic does not imply that the console is owned. However, it + * is critical that non-panic CPUs during panic are unable to + * wait for a handover in order to satisfy the assumptions of + * nbcon_waiter_matches(). In particular, the assumption that + * lower priorities are ignored during panic. + */ + if (other_cpu_in_panic()) + return -EPERM; + /* Handover is not possible on the same CPU. */ if (cur->cpu == cpu) return -EBUSY; @@ -558,7 +576,8 @@ static struct printk_buffers panic_nbcon_pbufs; /** * nbcon_context_try_acquire - Try to acquire nbcon console - * @ctxt: The context of the caller + * @ctxt: The context of the caller + * @is_reacquire: This acquire is a reacquire * * Context: Under @ctxt->con->device_lock() or local_irq_save(). * Return: True if the console was acquired. False otherwise. @@ -568,7 +587,7 @@ static struct printk_buffers panic_nbcon_pbufs; * in an unsafe state. Otherwise, on success the caller may assume * the console is not in an unsafe state. */ -static bool nbcon_context_try_acquire(struct nbcon_context *ctxt) +static bool nbcon_context_try_acquire(struct nbcon_context *ctxt, bool is_reacquire) { unsigned int cpu = smp_processor_id(); struct console *con = ctxt->console; @@ -577,7 +596,7 @@ static bool nbcon_context_try_acquire(struct nbcon_context *ctxt) nbcon_state_read(con, &cur); try_again: - err = nbcon_context_try_acquire_direct(ctxt, &cur); + err = nbcon_context_try_acquire_direct(ctxt, &cur, is_reacquire); if (err != -EBUSY) goto out; @@ -913,7 +932,7 @@ void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt) { struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); - while (!nbcon_context_try_acquire(ctxt)) + while (!nbcon_context_try_acquire(ctxt, true)) cpu_relax(); nbcon_write_context_set_buf(wctxt, NULL, 0); @@ -1101,7 +1120,7 @@ static bool nbcon_emit_one(struct nbcon_write_context *wctxt, bool use_atomic) cant_migrate(); } - if (!nbcon_context_try_acquire(ctxt)) + if (!nbcon_context_try_acquire(ctxt, false)) goto out; /* @@ -1486,7 +1505,7 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq, ctxt->prio = nbcon_get_default_prio(); ctxt->allow_unsafe_takeover = allow_unsafe_takeover; - if (!nbcon_context_try_acquire(ctxt)) + if (!nbcon_context_try_acquire(ctxt, false)) return -EPERM; while (nbcon_seq_read(con) < stop_seq) { @@ -1762,7 +1781,7 @@ bool nbcon_device_try_acquire(struct console *con) ctxt->console = con; ctxt->prio = NBCON_PRIO_NORMAL; - if (!nbcon_context_try_acquire(ctxt)) + if (!nbcon_context_try_acquire(ctxt, false)) return false; if (!nbcon_context_enter_unsafe(ctxt))