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Date: Sun, 25 Mar 2007 12:17:29 -0700
From: Randy Dunlap <randy.dunlap@...cle.com>
To: Wink Saville <wink@...ille.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] Trec driver.
On Sat, 24 Mar 2007 16:51:38 -0700 Wink Saville wrote:
> This is the Trec driver, Makefile, header files.
> Enable trec in Kernel hacking configuration menu.
>
> Signed-off-by: Wink Saville <wink@...ille.com>
> ---
> diff --git a/drivers/trec/trec.c b/drivers/trec/trec.c
> new file mode 100644
> index 0000000..0b04b71
> --- /dev/null
> +++ b/drivers/trec/trec.c
> @@ -0,0 +1,404 @@
...
> +
> +struct trec_dev_struct
> +{
> + struct cdev cdev; /* Character device structure */
Fit in 80 columns, please.
> +};
> +
> +MODULE_AUTHOR("Wink Saville");
> +MODULE_LICENSE("Dual BSD/GPL");
> +
> +/*
> + * Module parameters
> + */
> +int major = 240; /* 240 a "local/expermental" device number for the moment */
> +int minor = 1;
> +
> +module_param(major, int, S_IRUGO);
> +module_param(minor, int, S_IRUGO);
> +
> +/*
> + * Forward declarations
> + */
> +static int trec_open(struct inode *inode, struct file *file);
> +static int trec_release(struct inode *inode, struct file *file);
> +
> +/*
> + * File operations
> + */
> +struct file_operations trec_f_ops = {
> + .owner = THIS_MODULE,
> + .open = trec_open,
> + .release = trec_release,
> +};
> +
> +struct trec_struct {
> + uint64_t tsc;
> + unsigned long pc;
> + unsigned long tsk;
> + unsigned int pid;
> + unsigned long v1;
> + unsigned long v2;
> +};
> +
> +/*
> + * Change trec_buffer_struct.data to be a pointer to a PAGE in the future
> + */
> +#define TREC_DATA_SIZE 0x200
> +struct trec_buffer_struct {
> + struct trec_buffer_struct * next;
> + struct trec_struct * cur;
> + struct trec_struct * end;
> + struct trec_struct data[TREC_DATA_SIZE];
Kernel style is:
sturct trec_struct *cur;
> +};
> +
> +/*
> + * Number of buffers must be a multiple of two so we can
> + * snapshot the buffers and the minimum should be 4.
> + */
> +#define TREC_COUNT 2
> +struct trec_buffer_struct trec_buffers[2][TREC_COUNT];
> +int trec_idx = 0;
> +spinlock_t trec_lock = SPIN_LOCK_UNLOCKED;
> +
> +struct trec_buffer_struct * trec_buffer_cur = NULL;
> +struct trec_buffer_struct * trec_buffer_snapshot = NULL;
Pointer style. + don't init to NULL.
> +
> +struct trec_dev_struct trec_dev;
> +
> +/**
> + * Print an address symbol if available to the buffer
> + * this is from traps.c
> + */
Don't use kernel-doc indicator ("/**") unless the function block
comment is actually in kernel-doc syntax (see
Documentation/kernel-doc-nano-HOWTO.txt).
> +static int snprint_address(char *b, int bsize, unsigned long address)
> +{
> +#ifdef CONFIG_KALLSYMS
> + unsigned long offset = 0, symsize;
> + const char *symname;
> + char *modname;
> + char *delim = ":";
> + int n;
> + char namebuf[128];
> +
> + symname = kallsyms_lookup(address, &symsize, &offset, &modname, namebuf);
> + if (!symname) {
> + n = 0;
> + } else {
> + if (!modname)
> + modname = delim = "";
> + n = snprintf(b, bsize, "0x%016lx %s%s%s%s+0x%lx/0x%lx",
> + address, delim, modname, delim, symname, offset, symsize);
> + }
> + return n;
> +#else
> + return snprintf(b, bsize, "0x%016lx", address);
> +#endif
> +}
> +/*
> + * Snapshot the current trecs
> + */
> +void trec_snapshot(void)
> +{
> + int flags;
> +
> + spin_lock_irqsave(&trec_lock, flags);
> + trec_buffer_snapshot = trec_buffer_cur;
> + trec_idx = trec_idx ^ 1;
> + trec_buffer_cur = &trec_buffers[trec_idx][0];
> + spin_unlock_irqrestore(&trec_lock, flags);
> +}
> +EXPORT_SYMBOL(trec_snapshot);
What (if anything) prevents multiple snapshots from overwriting
each other, or from being overwritten while one is printing?
> +/*
> + * trec_print
> + */
> +void trec_print_snapshot(void)
> +{
> + int i;
> + struct trec_buffer_struct *cur_buffer;
> +
> + if (!trec_buffer_snapshot)
> + trec_snapshot();
> +
> + cur_buffer = trec_buffer_snapshot->next;
> + for (i = 0; i < TREC_COUNT; i++) {
> + struct trec_struct *cur;
> +
> + for (cur = &cur_buffer->data[0];
> + cur < cur_buffer->cur;
> + cur += 1) {
> + char b[256];
> + int n;
> +
> + n = snprintf(b, sizeof(b), KERN_ERR "t=%20llu pid=%5u tsk=%p v1=%p v2=%p ",
> + cur->tsc, cur->pid, (void *)cur->tsk, (void *)cur->v1, (void *)cur->v2);
> + n += snprint_address(b+n, sizeof(b)-n, cur->pc);
> + printk("%s\n", b);
> + }
> + cur_buffer = cur_buffer->next;
> + }
> +}
> +EXPORT_SYMBOL(trec_print_snapshot);
> +
> +/*
> + * Sysrq support for trec's
> + */
> +#ifdef CONFIG_MAGIC_SYSRQ
> +/*
> + * trec print snapshot handler for sysrq
> + */
> +static void sysrq_handle_trec_print_snapshot(int key, struct tty_struct *tty)
> +{
> + trec_print_snapshot();
> +}
> +
> +/*
> + * trec snapshot handler for sysrq
> + */
> +static void sysrq_handle_trec_snapshot(int key, struct tty_struct *tty)
> +{
> + trec_snapshot();
> +}
> +
> +static struct sysrq_key_op sysrq_trec_snapshot_op =
> +{
> + .handler = sysrq_handle_trec_snapshot,
> + .help_msg = "Trec snapshot(Y)",
> + .action_msg = "Trec snapshot",
> +};
> +
> +static struct sysrq_key_op sysrq_trec_print_snapshot_op =
> +{
> + .handler = sysrq_handle_trec_print_snapshot,
> + .help_msg = "Print current trec snapshot",
(Z) should be on the help_msg, not on the action_msg.
> + .action_msg = "Trec print snapshot(Z)",
> +};
> +
> +/*
> + * Initilize trec sysrq support
Initialize
> + */
> +static int __init setup_trec_sysrq(void)
> +{
> + DPK("setup_trec_sysrq y=trec_snapshot z=trec_print_snapshot\n");
> + register_sysrq_key('y', &sysrq_trec_snapshot_op);
> + register_sysrq_key('z', &sysrq_trec_print_snapshot_op);
> + return 0;
> +}
> +__initcall(setup_trec_sysrq);
> +#endif /* CONFIG_MAGIC_SYSRQ */
> +/*
> + * Init routine for the trec device
> + */
> +static int __init trec_device_init(void)
> +{
> + int result;
> + dev_t dev_number = 0;
> + static struct class *trec_class;
> +
> + DPK("trec_device_init: E\n");
> +
> + if (major) {
> + dev_number = MKDEV(major, minor);
> + result = register_chrdev_region(dev_number, 1, "trec");
> + DPK("trec_device_init: static major result=%d\n", result);
> + } else {
> + result = alloc_chrdev_region(&dev_number, minor, 1, "trec");
> + major = MAJOR(dev_number);
> + DPK("trec_device_init: dynamic major result=%d\n", result);
> + }
> +
> + if (result < 0) {
> + printk(KERN_WARNING "trec: can't get major %d\n", major);
> + goto err;
> + }
> +
> + cdev_init(&trec_dev.cdev, &trec_f_ops);
> + trec_dev.cdev.owner = THIS_MODULE;
> + trec_dev.cdev.ops = &trec_f_ops;
> +
> + result = cdev_add(&trec_dev.cdev, dev_number, 1);
> + if (result)
> + {
> + DPK("trec_device_init: cdev_add failed\n");
> + goto err;
> + }
> +
> + /*
> + * Make a trec class and create the device
> + */
> + trec_class = class_create(THIS_MODULE, "trec");
> + class_device_create(trec_class, NULL, dev_number, NULL, "trec");
> +
> + /*
> + * If the trec buffers have not been initialized do so
> + */
> + if (trec_buffer_cur == NULL) {
> + trec_init();
> + }
Style: no braces on one-statement "blocks".
> +}
> diff --git a/include/asm-i386/trec.h b/include/asm-i386/trec.h
> new file mode 100644
> index 0000000..1de4dc6
> --- /dev/null
> +++ b/include/asm-i386/trec.h
> @@ -0,0 +1,33 @@
> +/*
> + * Copyright (C) 2007 Saville Software, Inc.
> + *
> + * This code may be used for any purpose whatsoever, but
> + * no warranty of any kind is provided.
> + */
> +
> +#ifndef _ASM_I386_TREC_H
> +#define _ASM_I386_TREC_H
> +
> +#ifndef __ASSEMBLY__
> +
> +#if CONFIG_X86_TSC
> +#include <asm/msr.h>
> +
> +/*
> + * read x86 time stamp counter.
> + */
> +static uint64_t inline rd_tsc(void)
> +{
> + volatile uint64_t value;
> +
> + rdtscll(value);
> +
> + return value;
> +}
> +#else
> + #define rd_tsc() (0)
We don't typically indent (#if/) #else block contents like this.
> +#endif /* CONFIG_X86_TSC */
> +
> +#endif /* !__ASSEMBLY__ */
> +
> +#endif /* _ASM_I386_TREC_H */
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 3f3e740..db53fdb 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -303,6 +303,13 @@ config STACKTRACE
> depends on DEBUG_KERNEL
> depends on STACKTRACE_SUPPORT
>
> +config TREC
> + def_bool n
> + bool "Trace record support"
> + depends on DEBUG_KERNEL
> + help
> + Trace records are a light weight tracing facility
lightweight ... facility.
> +
> config DEBUG_KOBJECT
> bool "kobject debugging"
> depends on DEBUG_KERNEL
---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
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