diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/irq/debug.h | 14 | ||||
| -rw-r--r-- | kernel/kallsyms.c | 46 | ||||
| -rw-r--r-- | kernel/module.c | 6 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 215 | ||||
| -rw-r--r-- | kernel/sched/autogroup.c | 5 |
5 files changed, 206 insertions, 80 deletions
diff --git a/kernel/irq/debug.h b/kernel/irq/debug.h index e4d3819a91cc..8ccb326d2977 100644 --- a/kernel/irq/debug.h +++ b/kernel/irq/debug.h @@ -3,8 +3,6 @@ * Debugging printout: */ -#include <linux/kallsyms.h> - #define ___P(f) if (desc->status_use_accessors & f) printk("%14s set\n", #f) #define ___PS(f) if (desc->istate & f) printk("%14s set\n", #f) /* FIXME */ @@ -19,14 +17,14 @@ static inline void print_irq_desc(unsigned int irq, struct irq_desc *desc) printk("irq %d, desc: %p, depth: %d, count: %d, unhandled: %d\n", irq, desc, desc->depth, desc->irq_count, desc->irqs_unhandled); - printk("->handle_irq(): %p, ", desc->handle_irq); - print_symbol("%s\n", (unsigned long)desc->handle_irq); - printk("->irq_data.chip(): %p, ", desc->irq_data.chip); - print_symbol("%s\n", (unsigned long)desc->irq_data.chip); + printk("->handle_irq(): %p, %pS\n", + desc->handle_irq, desc->handle_irq); + printk("->irq_data.chip(): %p, %pS\n", + desc->irq_data.chip, desc->irq_data.chip); printk("->action(): %p\n", desc->action); if (desc->action) { - printk("->action->handler(): %p, ", desc->action->handler); - print_symbol("%s\n", (unsigned long)desc->action->handler); + printk("->action->handler(): %p, %pS\n", + desc->action->handler, desc->action->handler); } ___P(IRQ_LEVEL); diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index d5fa4116688a..a23e21ada81b 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -12,7 +12,6 @@ * compression (see scripts/kallsyms.c for a more complete description) */ #include <linux/kallsyms.h> -#include <linux/module.h> #include <linux/init.h> #include <linux/seq_file.h> #include <linux/fs.h> @@ -20,15 +19,12 @@ #include <linux/err.h> #include <linux/proc_fs.h> #include <linux/sched.h> /* for cond_resched */ -#include <linux/mm.h> #include <linux/ctype.h> #include <linux/slab.h> #include <linux/filter.h> #include <linux/ftrace.h> #include <linux/compiler.h> -#include <asm/sections.h> - /* * These will be re-linked against their real values * during the second link stage. @@ -52,37 +48,6 @@ extern const u16 kallsyms_token_index[] __weak; extern const unsigned long kallsyms_markers[] __weak; -static inline int is_kernel_inittext(unsigned long addr) -{ - if (addr >= (unsigned long)_sinittext - && addr <= (unsigned long)_einittext) - return 1; - return 0; -} - -static inline int is_kernel_text(unsigned long addr) -{ - if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) || - arch_is_kernel_text(addr)) - return 1; - return in_gate_area_no_mm(addr); -} - -static inline int is_kernel(unsigned long addr) -{ - if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end) - return 1; - return in_gate_area_no_mm(addr); -} - -static int is_ksym_addr(unsigned long addr) -{ - if (IS_ENABLED(CONFIG_KALLSYMS_ALL)) - return is_kernel(addr); - - return is_kernel_text(addr) || is_kernel_inittext(addr); -} - /* * Expand a compressed symbol data into the resulting uncompressed string, * if uncompressed string is too long (>= maxlen), it will be truncated, @@ -464,17 +429,6 @@ int sprint_backtrace(char *buffer, unsigned long address) return __sprint_symbol(buffer, address, -1, 1); } -/* Look up a kernel symbol and print it to the kernel messages. */ -void __print_symbol(const char *fmt, unsigned long address) -{ - char buffer[KSYM_SYMBOL_LEN]; - - sprint_symbol(buffer, address); - - printk(fmt, buffer); -} -EXPORT_SYMBOL(__print_symbol); - /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */ struct kallsym_iter { loff_t pos; diff --git a/kernel/module.c b/kernel/module.c index 1d65b2cc4f80..ccdf24c4949e 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3953,6 +3953,12 @@ static const char *get_ksymbol(struct module *mod, return symname(kallsyms, best); } +void * __weak dereference_module_function_descriptor(struct module *mod, + void *ptr) +{ + return ptr; +} + /* For kallsyms to ask for address resolution. NULL means not found. Careful * not to lock to avoid deadlock on oopses, simply disable preemption. */ const char *module_address_lookup(unsigned long addr, diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index c2e713f6ae2e..db4b9b8929eb 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -131,13 +131,10 @@ static int __init control_devkmsg(char *str) /* * Set sysctl string accordingly: */ - if (devkmsg_log == DEVKMSG_LOG_MASK_ON) { - memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE); - strncpy(devkmsg_log_str, "on", 2); - } else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) { - memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE); - strncpy(devkmsg_log_str, "off", 3); - } + if (devkmsg_log == DEVKMSG_LOG_MASK_ON) + strcpy(devkmsg_log_str, "on"); + else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) + strcpy(devkmsg_log_str, "off"); /* else "ratelimit" which is set by default. */ /* @@ -277,6 +274,13 @@ EXPORT_SYMBOL(console_set_on_cmdline); /* Flag: console code may call schedule() */ static int console_may_schedule; +enum con_msg_format_flags { + MSG_FORMAT_DEFAULT = 0, + MSG_FORMAT_SYSLOG = (1 << 0), +}; + +static int console_msg_format = MSG_FORMAT_DEFAULT; + /* * The printk log buffer consists of a chain of concatenated variable * length records. Every record starts with a record header, containing @@ -1544,6 +1548,146 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) } /* + * Special console_lock variants that help to reduce the risk of soft-lockups. + * They allow to pass console_lock to another printk() call using a busy wait. + */ + +#ifdef CONFIG_LOCKDEP +static struct lockdep_map console_owner_dep_map = { + .name = "console_owner" +}; +#endif + +static DEFINE_RAW_SPINLOCK(console_owner_lock); +static struct task_struct *console_owner; +static bool console_waiter; + +/** + * console_lock_spinning_enable - mark beginning of code where another + * thread might safely busy wait + * + * This basically converts console_lock into a spinlock. This marks + * the section where the console_lock owner can not sleep, because + * there may be a waiter spinning (like a spinlock). Also it must be + * ready to hand over the lock at the end of the section. + */ +static void console_lock_spinning_enable(void) +{ + raw_spin_lock(&console_owner_lock); + console_owner = current; + raw_spin_unlock(&console_owner_lock); + + /* The waiter may spin on us after setting console_owner */ + spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); +} + +/** + * console_lock_spinning_disable_and_check - mark end of code where another + * thread was able to busy wait and check if there is a waiter + * + * This is called at the end of the section where spinning is allowed. + * It has two functions. First, it is a signal that it is no longer + * safe to start busy waiting for the lock. Second, it checks if + * there is a busy waiter and passes the lock rights to her. + * + * Important: Callers lose the lock if there was a busy waiter. + * They must not touch items synchronized by console_lock + * in this case. + * + * Return: 1 if the lock rights were passed, 0 otherwise. + */ +static int console_lock_spinning_disable_and_check(void) +{ + int waiter; + + raw_spin_lock(&console_owner_lock); + waiter = READ_ONCE(console_waiter); + console_owner = NULL; + raw_spin_unlock(&console_owner_lock); + + if (!waiter) { + spin_release(&console_owner_dep_map, 1, _THIS_IP_); + return 0; + } + + /* The waiter is now free to continue */ + WRITE_ONCE(console_waiter, false); + + spin_release(&console_owner_dep_map, 1, _THIS_IP_); + + /* + * Hand off console_lock to waiter. The waiter will perform + * the up(). After this, the waiter is the console_lock owner. + */ + mutex_release(&console_lock_dep_map, 1, _THIS_IP_); + return 1; +} + +/** + * console_trylock_spinning - try to get console_lock by busy waiting + * + * This allows to busy wait for the console_lock when the current + * owner is running in specially marked sections. It means that + * the current owner is running and cannot reschedule until it + * is ready to lose the lock. + * + * Return: 1 if we got the lock, 0 othrewise + */ +static int console_trylock_spinning(void) +{ + struct task_struct *owner = NULL; + bool waiter; + bool spin = false; + unsigned long flags; + + if (console_trylock()) + return 1; + + printk_safe_enter_irqsave(flags); + + raw_spin_lock(&console_owner_lock); + owner = READ_ONCE(console_owner); + waiter = READ_ONCE(console_waiter); + if (!waiter && owner && owner != current) { + WRITE_ONCE(console_waiter, true); + spin = true; + } + raw_spin_unlock(&console_owner_lock); + + /* + * If there is an active printk() writing to the + * consoles, instead of having it write our data too, + * see if we can offload that load from the active + * printer, and do some printing ourselves. + * Go into a spin only if there isn't already a waiter + * spinning, and there is an active printer, and + * that active printer isn't us (recursive printk?). + */ + if (!spin) { + printk_safe_exit_irqrestore(flags); + return 0; + } + + /* We spin waiting for the owner to release us */ + spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); + /* Owner will clear console_waiter on hand off */ + while (READ_ONCE(console_waiter)) + cpu_relax(); + spin_release(&console_owner_dep_map, 1, _THIS_IP_); + + printk_safe_exit_irqrestore(flags); + /* + * The owner passed the console lock to us. + * Since we did not spin on console lock, annotate + * this as a trylock. Otherwise lockdep will + * complain. + */ + mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_); + + return 1; +} + +/* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. * The console_lock must be held. @@ -1749,12 +1893,19 @@ asmlinkage int vprintk_emit(int facility, int level, /* If called from the scheduler, we can not call up(). */ if (!in_sched) { /* + * Disable preemption to avoid being preempted while holding + * console_sem which would prevent anyone from printing to + * console + */ + preempt_disable(); + /* * Try to acquire and then immediately release the console * semaphore. The release will print out buffers and wake up * /dev/kmsg and syslog() users. */ - if (console_trylock()) + if (console_trylock_spinning()) console_unlock(); + preempt_enable(); } return printed_len; @@ -1855,6 +2006,8 @@ static ssize_t msg_print_ext_header(char *buf, size_t size, static ssize_t msg_print_ext_body(char *buf, size_t size, char *dict, size_t dict_len, char *text, size_t text_len) { return 0; } +static void console_lock_spinning_enable(void) { } +static int console_lock_spinning_disable_and_check(void) { return 0; } static void call_console_drivers(const char *ext_text, size_t ext_len, const char *text, size_t len) {} static size_t msg_print_text(const struct printk_log *msg, @@ -1913,6 +2066,17 @@ static int __add_preferred_console(char *name, int idx, char *options, c->index = idx; return 0; } + +static int __init console_msg_format_setup(char *str) +{ + if (!strcmp(str, "syslog")) + console_msg_format = MSG_FORMAT_SYSLOG; + if (!strcmp(str, "default")) + console_msg_format = MSG_FORMAT_DEFAULT; + return 1; +} +__setup("console_msg_format=", console_msg_format_setup); + /* * Set up a console. Called via do_early_param() in init/main.c * for each "console=" parameter in the boot command line. @@ -2069,20 +2233,7 @@ int console_trylock(void) return 0; } console_locked = 1; - /* - * When PREEMPT_COUNT disabled we can't reliably detect if it's - * safe to schedule (e.g. calling printk while holding a spin_lock), - * because preempt_disable()/preempt_enable() are just barriers there - * and preempt_count() is always 0. - * - * RCU read sections have a separate preemption counter when - * PREEMPT_RCU enabled thus we must take extra care and check - * rcu_preempt_depth(), otherwise RCU read sections modify - * preempt_count(). - */ - console_may_schedule = !oops_in_progress && - preemptible() && - !rcu_preempt_depth(); + console_may_schedule = 0; return 1; } EXPORT_SYMBOL(console_trylock); @@ -2215,7 +2366,10 @@ skip: goto skip; } - len += msg_print_text(msg, false, text + len, sizeof(text) - len); + len += msg_print_text(msg, + console_msg_format & MSG_FORMAT_SYSLOG, + text + len, + sizeof(text) - len); if (nr_ext_console_drivers) { ext_len = msg_print_ext_header(ext_text, sizeof(ext_text), @@ -2229,14 +2383,29 @@ skip: console_seq++; raw_spin_unlock(&logbuf_lock); + /* + * While actively printing out messages, if another printk() + * were to occur on another CPU, it may wait for this one to + * finish. This task can not be preempted if there is a + * waiter waiting to take over. + */ + console_lock_spinning_enable(); + stop_critical_timings(); /* don't trace print latency */ call_console_drivers(ext_text, ext_len, text, len); start_critical_timings(); + + if (console_lock_spinning_disable_and_check()) { + printk_safe_exit_irqrestore(flags); + return; + } + printk_safe_exit_irqrestore(flags); if (do_cond_resched) cond_resched(); } + console_locked = 0; /* Release the exclusive_console once it is used */ diff --git a/kernel/sched/autogroup.c b/kernel/sched/autogroup.c index a43df5193538..bb4b9fe026a1 100644 --- a/kernel/sched/autogroup.c +++ b/kernel/sched/autogroup.c @@ -1,13 +1,12 @@ // SPDX-License-Identifier: GPL-2.0 -#include "sched.h" - #include <linux/proc_fs.h> #include <linux/seq_file.h> -#include <linux/kallsyms.h> #include <linux/utsname.h> #include <linux/security.h> #include <linux/export.h> +#include "sched.h" + unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1; static struct autogroup autogroup_default; static atomic_t autogroup_seq_nr; |