[PATCH/RFC] Add Alternative Log Buffer Support for printk Messages

Message ID	1227638045-12862-1-git-send-email-gerickson@nuovations.com (mailing list archive)
State	Changes Requested, archived
Headers	show Return-Path: <linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@ozlabs.org> From: Grant Erickson <gerickson@nuovations.com> To: linuxppc-dev@ozlabs.org Subject: [PATCH/RFC] Add Alternative Log Buffer Support for printk Messages Date: Tue, 25 Nov 2008 10:34:05 -0800 Message-Id: <1227638045-12862-1-git-send-email-gerickson@nuovations.com> Organization: Nuovation System Designs, LLC Cc: Stefan Roese <sr@denx.de>, Wolfgang Denx <wd@denx.de>, linux-embedded@vger.kernel.org Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@ozlabs.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@ozlabs.org

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c index 3a2dc7e..60282f1 100644 --- a/arch/powerpc/kernel/prom.c +++ b/arch/powerpc/kernel/prom.c @@ -32,6 +32,7 @@ #include <linux/debugfs.h> #include <linux/irq.h> #include <linux/lmb.h> +#include <linux/logbuff.h> #include <asm/prom.h> #include <asm/rtas.h> @@ -61,6 +62,15 @@ #define DBG(fmt...) #endif +#ifdef CONFIG_LOGBUFFER +#ifdef CONFIG_ALT_LB_LOCATION +# if !defined(BOARD_ALT_LH_ADDR) || !defined(BOARD_ALT_LB_ADDR) +# error "Please specify BOARD_ALT_LH_ADDR & BOARD_ALT_LB_ADDR." +# endif +#else /* !CONFIG_ALT_LB_LOCATION */ +static phys_addr_t ext_logbuff; +#endif /* CONFIG_ALT_LB_LOCATION */ +#endif /* CONFIG_LOGBUFFER */ static int __initdata dt_root_addr_cells; static int __initdata dt_root_size_cells; @@ -1018,6 +1028,85 @@ static int __init early_init_dt_scan_memory(unsigned long node, return 0; } +#ifdef CONFIG_LOGBUFFER +#ifdef CONFIG_ALT_LB_LOCATION +/* Alternative external log buffer mapping: log metadata header & the + * character buffer are separated and allocated not in RAM but in some + * other memory-mapped I/O region (e.g. log head in unused registers, + * and log buffer in OCM memory) + */ +int __init setup_ext_logbuff_mem(volatile logbuff_t **lhead, char **lbuf) +{ + void *h, *b; + + if (unlikely(!lhead) || unlikely(!lbuf)) + return -EINVAL; + + /* map log head */ + h = ioremap(BOARD_ALT_LH_ADDR, sizeof(logbuff_t)); + if (unlikely(!h)) + return -EFAULT; + + /* map log buffer */ + b = ioremap(BOARD_ALT_LB_ADDR, LOGBUFF_LEN); + if (unlikely(!b)) { + iounmap(h); + return -EFAULT; + } + + *lhead = h; + *lbuf = b; + + return 0; +} +#else /* !CONFIG_ALT_LB_LOCATION */ +/* Usual external log-buffer mapping: log metadata header & the character + * buffer are both contiguous in system RAM. + */ +int __init setup_ext_logbuff_mem(logbuff_t **lhead, char **lbuf) +{ + void *p; + + if (unlikely(!lhead) || unlikely(!lbuf)) + return -EINVAL; + + if (unlikely(!ext_logbuff) || !lmb_is_reserved(ext_logbuff)) + return -EFAULT; + + p = ioremap(ext_logbuff, LOGBUFF_RESERVE); + + if (unlikely(!p)) + return -EFAULT; + + *lhead = (logbuff_t *)(p + LOGBUFF_OVERHEAD - + sizeof(logbuff_t) + + sizeof(((logbuff_t *)0)->buf)); + *lbuf = (*lhead)->buf; + + return 0; +} + +/* When the external log buffer configuration is used with the + * non-alternate location, the log head metadata and character buffer + * lie in the LOGBUFF_RESERVE bytes at the end of system RAM. Add this + * block of memory to the reserved memory pool so that it is not + * allocated for other purposes. + */ +static void __init reserve_ext_logbuff_mem(void) +{ + phys_addr_t top = lmb_end_of_DRAM(); + phys_addr_t size = LOGBUFF_RESERVE; + phys_addr_t base = top - size; + + if (top > base) { + ext_logbuff = base; + DBG("reserving: %x -> %x\n", base, size); + lmb_reserve(base, size); + } +} +#endif /* CONFIG_ALT_LB_LOCATION */ +#endif /* CONFIG_LOGBUFFER */ + static void __init early_reserve_mem(void) { u64 base, size; @@ -1033,6 +1122,10 @@ static void __init early_reserve_mem(void) self_size = initial_boot_params->totalsize; lmb_reserve(self_base, self_size); +#if defined(CONFIG_LOGBUFFER) && !defined(CONFIG_ALT_LB_LOCATION) + reserve_ext_logbuff_mem(); +#endif /* defined(CONFIG_LOGBUFFER) && !defined(CONFIG_ALT_LB_LOCATION) */ + #ifdef CONFIG_BLK_DEV_INITRD /* then reserve the initrd, if any */ if (initrd_start && (initrd_end > initrd_start)) diff --git a/include/linux/logbuff.h b/include/linux/logbuff.h new file mode 100644 index 0000000..22a51c0 --- /dev/null +++ b/include/linux/logbuff.h @@ -0,0 +1,56 @@ +/* + * (C) Copyright 2007 + * Wolfgang Denk, DENX Software Engineering, wd@denx.de. + * + * See file CREDITS for list of people who contributed to this + * project. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of + * the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, + * MA 02111-1307 USA + */ +#ifndef _LOGBUFF_H_ +#define _LOGBUFF_H_ + +#ifdef CONFIG_LOGBUFFER + +#define LOGBUFF_MAGIC 0xc0de4ced +#define LOGBUFF_LEN 16384 +#define LOGBUFF_OVERHEAD 4096 +#define LOGBUFF_RESERVE (LOGBUFF_LEN + LOGBUFF_OVERHEAD) + +/* The mapping used here has to be the same as in logbuff_init_ptrs () + in u-boot/common/cmd_log.c */ + +typedef struct { + unsigned long tag; + unsigned long start; + unsigned long con; /* next char to be sent to consoles */ + unsigned long end; + unsigned long chars; + unsigned char buf[0]; +} logbuff_t; + +#ifdef CONFIG_ALT_LB_LOCATION +# define LOGBUFF_VOLATILE volatile +#else +# define LOGBUFF_VOLATILE +#endif /* defined(CONFIG_ALT_LB_LOCATION) */ + +extern void setup_ext_logbuff(void); +/* arch specific */ +extern int setup_ext_logbuff_mem(LOGBUFF_VOLATILE logbuff_t **lhead, char **lbuf); + +#endif /* CONFIG_LOGBUFFER */ +#endif /* _LOGBUFF_H_ */ diff --git a/init/Kconfig b/init/Kconfig index f763762..e1a1b59 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -619,6 +619,31 @@ config PRINTK very difficult to diagnose system problems, saying N here is strongly discouraged. +config LOGBUFFER + bool "External logbuffer" if PRINTK + default n + help + This option enables support for an alternative, "external" + printk log buffer. When enabled, an architecture- or machine- + specific log buffer is used for all printk messages. This + allows entities such as boot loaders to place printk-compatible + messages into this buffer and for the kernel to coalesce them + with its normal messages. + +config ALT_LB_LOCATION + bool "Alternative logbuffer" if LOGBUFFER + default n + help + When using an alternative, "external" printk log buffer, an + architecture- or machine-specific log buffer with contiguous + metadata and message storage is used. This option enables + support for discontiguous metadata and message storage + memory (e.g. a set of scratch registers and an SRAM + buffer). By saying Y here, you must also ensure your + architecture- or machine-code specify BOARD_ALT_LH_ADDR and + BOARD_ALT_LB_ADDR, for the metadata and message memory, + respectively. + config BUG bool "BUG() support" if EMBEDDED default y diff --git a/init/main.c b/init/main.c index 7e117a2..5687b98 100644 --- a/init/main.c +++ b/init/main.c @@ -61,6 +61,7 @@ #include <linux/kthread.h> #include <linux/sched.h> #include <linux/signal.h> +#include <linux/logbuff.h> #include <linux/idr.h> #include <linux/ftrace.h> @@ -563,6 +564,9 @@ asmlinkage void __init start_kernel(void) * Interrupts are still disabled. Do necessary setups, then * enable them */ +#ifdef CONFIG_LOGBUFFER + setup_ext_logbuff(); +#endif lock_kernel(); tick_init(); boot_cpu_init(); diff --git a/kernel/printk.c b/kernel/printk.c index f492f15..59884e2 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -32,6 +32,7 @@ #include <linux/security.h> #include <linux/bootmem.h> #include <linux/syscalls.h> +#include <linux/logbuff.h> #include <asm/uaccess.h> @@ -101,9 +102,39 @@ static DEFINE_SPINLOCK(logbuf_lock); * The indices into log_buf are not constrained to log_buf_len - they * must be masked before subscripting */ +#ifdef CONFIG_LOGBUFFER +/* Indexes to the local log buffer */ +static unsigned long _log_start; +static unsigned long _con_start; +static unsigned long _log_end; +static unsigned long _logged_chars; +/* These will be switched to the external log buffer */ +#ifndef CONFIG_ALT_LB_LOCATION +/* usual logbuffer location */ +static unsigned long *ext_log_start = &_log_start; +static unsigned long *ext_con_start = &_con_start; +static unsigned long *ext_log_end = &_log_end; +static unsigned long *ext_logged_chars = &_logged_chars; +#define log_start (*ext_log_start) +#define con_start (*ext_con_start) +#define log_end (*ext_log_end) +#define logged_chars (*ext_logged_chars) +#else /* defined(CONFIG_ALT_LB_LOCATION) */ +/* alternative logbuffer location */ +static volatile unsigned long *ext_log_start = &_log_start; +static volatile unsigned long *ext_con_start = &_con_start; +static volatile unsigned long *ext_log_end = &_log_end; +static volatile unsigned long *ext_logged_chars = &_logged_chars; +#define log_start (*((volatile u32 *)ext_log_start)) +#define con_start (*((volatile u32 *)ext_con_start)) +#define log_end (*((volatile u32 *)ext_log_end)) +#define logged_chars (*((volatile u32 *)ext_logged_chars)) +#endif /* !defined(CONFIG_ALT_LB_LOCATION) */ +#else /* !defined(CONFIG_LOGBUFFER) */ static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */ static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */ static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */ +#endif /* CONFIG_LOGBUFFER */ /* * Array of consoles built from command line options (console=) @@ -134,10 +165,121 @@ static int console_may_schedule; static char __log_buf[__LOG_BUF_LEN]; static char *log_buf = __log_buf; static int log_buf_len = __LOG_BUF_LEN; +#ifndef CONFIG_LOGBUFFER static unsigned logged_chars; /* Number of chars produced since last read+clear operation */ +#endif /* !defined(CONFIG_LOGBUFFER) */ +#ifdef CONFIG_LOGBUFFER +/* Sanity check the external log buffer metadata. When an the external + * log buffer is enabled, the log metadata is effectively non-volatile + * in that the values are preserved from reboot to reboot (until/unless + * the system loses power). + */ +static void __init logbuff_check_metadata(LOGBUFF_VOLATILE logbuff_t *log) +{ + unsigned long chars; + + /* Sanity check the producer and consumer indices. */ + + if (log->end - log->start > LOGBUFF_LEN) + log->start = log->end - LOGBUFF_LEN; + + if (log->end - log->con > LOGBUFF_LEN) + log->con = log->end - LOGBUFF_LEN; + + /* Occasionally, particularly following a reboot, the start + * consumer index is not properly caught up to the console + * consumer index. If this is the case, catch it up so that + * the log buffer doesn't start with, for example, + * "<0>Restarting system.\n" followed by the 'real' start of + * the log. + */ + + if (log->con > log->start) + log->start = log->con; + + /* Ensure that the number of characters logged reflects the + * characters actually logged based on the producer and + * consumer indices rather than all characters cumulatively + * logged across all reboots since a power-loss event. + */ + + chars = log->end - log->start; + + if (log->chars > chars) + log->chars = chars; +} + +/* Coalesce the current log bounded buffer and the external log + * bounded buffer by appending the former to the latter. Precedence is + * given to the external log buffer when there is more data to be + * appended than space exists, so the current log buffer is truncated + * instead of overwritting the external buffer. + */ +static void __init logbuff_coalesce_buffers(LOGBUFF_VOLATILE logbuff_t *log) +{ + unsigned long dspace, ssize, len; + + dspace = LOGBUFF_LEN - (log->end - log->start); + ssize = log_end - log_start; + len = min(dspace, ssize); + + while (len-- > 0) { + log->buf[log->end++ & (LOGBUFF_LEN-1)] = LOG_BUF(log_start++); + log->chars++; + } +} +void __init setup_ext_logbuff(void) +{ + LOGBUFF_VOLATILE logbuff_t *log; + char *ext_log_buf = NULL; + unsigned long flags; + + if (setup_ext_logbuff_mem(&log, &ext_log_buf) < 0) { + printk(KERN_WARNING + "Failed to setup external logbuffer - ignoring it\n"); + return; + } + + /* When no properly setup buffer is found, reset pointers */ + if (log->tag != LOGBUFF_MAGIC) { + printk(KERN_WARNING + "Unexpected external log buffer magic number. " + "Got %08lx, expected %08x. Resetting pointers and using " + "the buffer anyway.\n", + log->tag, LOGBUFF_MAGIC); + log->tag = LOGBUFF_MAGIC; + log->start = log->end = log->con = log->chars = 0; + } + + spin_lock_irqsave(&logbuf_lock, flags); + + logbuff_check_metadata(log); + logbuff_coalesce_buffers(log); + + /* Switch to the external log buffer */ + ext_log_start = &log->start; + ext_con_start = &log->con; + ext_log_end = &log->end; + ext_logged_chars = &log->chars; + + log_buf = ext_log_buf; + log_buf_len = LOGBUFF_LEN; + + spin_unlock_irqrestore(&logbuf_lock, flags); + + printk(KERN_NOTICE "log_buf=%p\n", log_buf); +} +#endif /* CONFIG_LOGBUFFER */ static int __init log_buf_len_setup(char *str) { +#ifdef CONFIG_LOGBUFFER + /* Log buffer size is LOGBUFF_LEN bytes */ + printk(KERN_NOTICE + "External log buffer configured; " + "ignoring log_buf_len param.\n"); + return 1; +#else unsigned size = memparse(str, &str); unsigned long flags; @@ -173,6 +315,7 @@ static int __init log_buf_len_setup(char *str) } out: return 1; +#endif /* CONFIG_LOGBUFFER */ } __setup("log_buf_len=", log_buf_len_setup); @@ -230,7 +373,7 @@ static void boot_delay_msec(void) static inline void boot_delay_msec(void) { } -#endif +#endif /* CONFIG_BOOT_PRINTK_DELAY */ /* * Commands to do_syslog: @@ -740,7 +883,7 @@ out_restore_irqs: EXPORT_SYMBOL(printk); EXPORT_SYMBOL(vprintk); -#else +#else /* !CONFIG_PRINTK */ asmlinkage long sys_syslog(int type, char __user *buf, int len) { @@ -751,7 +894,7 @@ static void call_console_drivers(unsigned start, unsigned end) { } -#endif +#endif /* CONFIG_PRINTK */ static int __add_preferred_console(char *name, int idx, char *options, char *brl_options)

[PATCH/RFC] Add Alternative Log Buffer Support for printk Messages

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