diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 9 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 85 | ||||
| -rw-r--r-- | kernel/printk/printk_ringbuffer.c | 52 | ||||
| -rw-r--r-- | kernel/printk/printk_ringbuffer.h | 2 | ||||
| -rw-r--r-- | lib/vsprintf.c | 49 |
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); } /* |