diff options
Diffstat (limited to 'features/rt/printk-track-limit-recursion.patch')
| -rw-r--r-- | features/rt/printk-track-limit-recursion.patch | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/features/rt/printk-track-limit-recursion.patch b/features/rt/printk-track-limit-recursion.patch new file mode 100644 index 00000000..0eba8c25 --- /dev/null +++ b/features/rt/printk-track-limit-recursion.patch @@ -0,0 +1,142 @@ +From 23b2babe079f76add633021e717676da7f238ff8 Mon Sep 17 00:00:00 2001 +From: John Ogness <john.ogness@linutronix.de> +Date: Fri, 11 Dec 2020 00:55:25 +0106 +Subject: [PATCH 021/191] printk: track/limit recursion + +Limit printk() recursion to 1 level. This is enough to print a +stacktrace for the printk call, should a WARN or BUG occur. + +Signed-off-by: John Ogness <john.ogness@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/printk/printk.c | 74 ++++++++++++++++++++++++++++++++++++++++-- + 1 file changed, 71 insertions(+), 3 deletions(-) + +diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c +index 523621889a72..008a0ede8b05 100644 +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -1940,6 +1940,65 @@ static void call_console_drivers(const char *ext_text, size_t ext_len, + } + } + ++#ifdef CONFIG_PRINTK_NMI ++#define NUM_RECURSION_CTX 2 ++#else ++#define NUM_RECURSION_CTX 1 ++#endif ++ ++struct printk_recursion { ++ char count[NUM_RECURSION_CTX]; ++}; ++ ++static DEFINE_PER_CPU(struct printk_recursion, percpu_printk_recursion); ++static char printk_recursion_count[NUM_RECURSION_CTX]; ++ ++static char *printk_recursion_counter(void) ++{ ++ struct printk_recursion *rec; ++ char *count; ++ ++ if (!printk_percpu_data_ready()) { ++ count = &printk_recursion_count[0]; ++ } else { ++ rec = this_cpu_ptr(&percpu_printk_recursion); ++ ++ count = &rec->count[0]; ++ } ++ ++#ifdef CONFIG_PRINTK_NMI ++ if (in_nmi()) ++ count++; ++#endif ++ ++ return count; ++} ++ ++static bool printk_enter_irqsave(unsigned long *flags) ++{ ++ char *count; ++ ++ local_irq_save(*flags); ++ count = printk_recursion_counter(); ++ /* Only 1 level of recursion allowed. */ ++ if (*count > 1) { ++ local_irq_restore(*flags); ++ return false; ++ } ++ (*count)++; ++ ++ return true; ++} ++ ++static void printk_exit_irqrestore(unsigned long flags) ++{ ++ char *count; ++ ++ count = printk_recursion_counter(); ++ (*count)--; ++ local_irq_restore(flags); ++} ++ + int printk_delay_msec __read_mostly; + + static inline void printk_delay(void) +@@ -2040,11 +2099,13 @@ int vprintk_store(int facility, int level, + struct prb_reserved_entry e; + enum log_flags lflags = 0; + struct printk_record r; ++ unsigned long irqflags; + u16 trunc_msg_len = 0; + char prefix_buf[8]; + u16 reserve_size; + va_list args2; + u16 text_len; ++ int ret = 0; + u64 ts_nsec; + + /* +@@ -2055,6 +2116,9 @@ int vprintk_store(int facility, int level, + */ + ts_nsec = local_clock(); + ++ if (!printk_enter_irqsave(&irqflags)) ++ return 0; ++ + /* + * The sprintf needs to come first since the syslog prefix might be + * passed in as a parameter. An extra byte must be reserved so that +@@ -2092,7 +2156,8 @@ int vprintk_store(int facility, int level, + prb_commit(&e); + } + +- return text_len; ++ ret = text_len; ++ goto out; + } + } + +@@ -2108,7 +2173,7 @@ int vprintk_store(int facility, int level, + + prb_rec_init_wr(&r, reserve_size + trunc_msg_len); + if (!prb_reserve(&e, prb, &r)) +- return 0; ++ goto out; + } + + /* fill message */ +@@ -2130,7 +2195,10 @@ int vprintk_store(int facility, int level, + else + prb_final_commit(&e); + +- return (text_len + trunc_msg_len); ++ ret = text_len + trunc_msg_len; ++out: ++ printk_exit_irqrestore(irqflags); ++ return ret; + } + + asmlinkage int vprintk_emit(int facility, int level, +-- +2.19.1 + |