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kernel/trace/trace_printk.c
8.68 KB
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// SPDX-License-Identifier: GPL-2.0 |
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/* * trace binary printk * * Copyright (C) 2008 Lai Jiangshan <laijs@cn.fujitsu.com> * */ |
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#include <linux/seq_file.h> |
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#include <linux/security.h> |
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#include <linux/uaccess.h> |
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#include <linux/kernel.h> #include <linux/ftrace.h> #include <linux/string.h> |
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#include <linux/module.h> |
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#include <linux/mutex.h> |
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#include <linux/ctype.h> #include <linux/list.h> |
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#include <linux/slab.h> |
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#include "trace.h" |
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#ifdef CONFIG_MODULES |
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/* |
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* modules trace_printk()'s formats are autosaved in struct trace_bprintk_fmt |
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* which are queued on trace_bprintk_fmt_list. */ static LIST_HEAD(trace_bprintk_fmt_list); |
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/* serialize accesses to trace_bprintk_fmt_list */ static DEFINE_MUTEX(btrace_mutex); |
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struct trace_bprintk_fmt { struct list_head list; |
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const char *fmt; |
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}; |
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static inline struct trace_bprintk_fmt *lookup_format(const char *fmt) |
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{ |
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struct trace_bprintk_fmt *pos; |
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if (!fmt) return ERR_PTR(-EINVAL); |
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list_for_each_entry(pos, &trace_bprintk_fmt_list, list) { if (!strcmp(pos->fmt, fmt)) return pos; } return NULL; |
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} |
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static void hold_module_trace_bprintk_format(const char **start, const char **end) |
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{ |
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const char **iter; |
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char *fmt; |
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|
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/* allocate the trace_printk per cpu buffers */ if (start != end) trace_printk_init_buffers(); |
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mutex_lock(&btrace_mutex); |
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for (iter = start; iter < end; iter++) { struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter); if (tb_fmt) { |
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if (!IS_ERR(tb_fmt)) *iter = tb_fmt->fmt; |
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continue; } |
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fmt = NULL; |
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tb_fmt = kmalloc(sizeof(*tb_fmt), GFP_KERNEL); |
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if (tb_fmt) { |
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fmt = kmalloc(strlen(*iter) + 1, GFP_KERNEL); |
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if (fmt) { list_add_tail(&tb_fmt->list, &trace_bprintk_fmt_list); strcpy(fmt, *iter); tb_fmt->fmt = fmt; } else kfree(tb_fmt); |
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} |
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*iter = fmt; |
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} |
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mutex_unlock(&btrace_mutex); |
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} |
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static int module_trace_bprintk_format_notify(struct notifier_block *self, unsigned long val, void *data) { struct module *mod = data; if (mod->num_trace_bprintk_fmt) { const char **start = mod->trace_bprintk_fmt_start; const char **end = start + mod->num_trace_bprintk_fmt; if (val == MODULE_STATE_COMING) hold_module_trace_bprintk_format(start, end); } return 0; } |
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/* * The debugfs/tracing/printk_formats file maps the addresses with * the ASCII formats that are used in the bprintk events in the * buffer. For userspace tools to be able to decode the events from * the buffer, they need to be able to map the address with the format. * * The addresses of the bprintk formats are in their own section * __trace_printk_fmt. But for modules we copy them into a link list. * The code to print the formats and their addresses passes around the * address of the fmt string. If the fmt address passed into the seq * functions is within the kernel core __trace_printk_fmt section, then * it simply uses the next pointer in the list. * * When the fmt pointer is outside the kernel core __trace_printk_fmt * section, then we need to read the link list pointers. The trick is * we pass the address of the string to the seq function just like * we do for the kernel core formats. To get back the structure that |
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* holds the format, we simply use container_of() and then go to the |
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* next format in the list. */ static const char ** find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos) { struct trace_bprintk_fmt *mod_fmt; if (list_empty(&trace_bprintk_fmt_list)) return NULL; /* * v will point to the address of the fmt record from t_next * v will be NULL from t_start. * If this is the first pointer or called from start * then we need to walk the list. */ if (!v || start_index == *pos) { struct trace_bprintk_fmt *p; /* search the module list */ list_for_each_entry(p, &trace_bprintk_fmt_list, list) { if (start_index == *pos) return &p->fmt; start_index++; } /* pos > index */ return NULL; } /* * v points to the address of the fmt field in the mod list * structure that holds the module print format. */ mod_fmt = container_of(v, typeof(*mod_fmt), fmt); if (mod_fmt->list.next == &trace_bprintk_fmt_list) return NULL; mod_fmt = container_of(mod_fmt->list.next, typeof(*mod_fmt), list); return &mod_fmt->fmt; } static void format_mod_start(void) { mutex_lock(&btrace_mutex); } static void format_mod_stop(void) { mutex_unlock(&btrace_mutex); } |
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#else /* !CONFIG_MODULES */ __init static int module_trace_bprintk_format_notify(struct notifier_block *self, unsigned long val, void *data) { return 0; } |
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static inline const char ** find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos) { return NULL; } static inline void format_mod_start(void) { } static inline void format_mod_stop(void) { } |
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#endif /* CONFIG_MODULES */ |
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static bool __read_mostly trace_printk_enabled = true; void trace_printk_control(bool enabled) { trace_printk_enabled = enabled; } |
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__initdata_or_module static struct notifier_block module_trace_bprintk_format_nb = { .notifier_call = module_trace_bprintk_format_notify, }; |
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int __trace_bprintk(unsigned long ip, const char *fmt, ...) |
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{ |
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int ret; va_list ap; |
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if (unlikely(!fmt)) return 0; |
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if (!trace_printk_enabled) |
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return 0; va_start(ap, fmt); |
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ret = trace_vbprintk(ip, fmt, ap); |
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va_end(ap); return ret; |
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} |
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EXPORT_SYMBOL_GPL(__trace_bprintk); |
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|
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int __ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap) |
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{ |
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if (unlikely(!fmt)) return 0; |
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if (!trace_printk_enabled) |
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return 0; |
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return trace_vbprintk(ip, fmt, ap); |
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} EXPORT_SYMBOL_GPL(__ftrace_vbprintk); int __trace_printk(unsigned long ip, const char *fmt, ...) { int ret; va_list ap; |
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if (!trace_printk_enabled) |
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return 0; va_start(ap, fmt); |
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ret = trace_vprintk(ip, fmt, ap); |
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va_end(ap); return ret; } EXPORT_SYMBOL_GPL(__trace_printk); int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap) { |
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if (!trace_printk_enabled) |
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return 0; |
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return trace_vprintk(ip, fmt, ap); |
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} |
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EXPORT_SYMBOL_GPL(__ftrace_vprintk); |
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static const char **find_next(void *v, loff_t *pos) { const char **fmt = v; int start_index; |
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int last_index; |
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start_index = __stop___trace_bprintk_fmt - __start___trace_bprintk_fmt; if (*pos < start_index) |
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return __start___trace_bprintk_fmt + *pos; |
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/* * The __tracepoint_str section is treated the same as the * __trace_printk_fmt section. The difference is that the * __trace_printk_fmt section should only be used by trace_printk() * in a debugging environment, as if anything exists in that section * the trace_prink() helper buffers are allocated, which would just * waste space in a production environment. * * The __tracepoint_str sections on the other hand are used by * tracepoints which need to map pointers to their strings to * the ASCII text for userspace. */ last_index = start_index; start_index = __stop___tracepoint_str - __start___tracepoint_str; if (*pos < last_index + start_index) return __start___tracepoint_str + (*pos - last_index); |
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start_index += last_index; |
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return find_next_mod_format(start_index, v, fmt, pos); } |
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static void * |
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t_start(struct seq_file *m, loff_t *pos) |
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{ |
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format_mod_start(); return find_next(NULL, pos); |
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} |
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static void *t_next(struct seq_file *m, void * v, loff_t *pos) |
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{ |
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(*pos)++; |
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return find_next(v, pos); |
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} static int t_show(struct seq_file *m, void *v) { const char **fmt = v; const char *str = *fmt; int i; |
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if (!*fmt) return 0; |
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seq_printf(m, "0x%lx : \"", *(unsigned long *)fmt); |
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/* * Tabs and new lines need to be converted. */ for (i = 0; str[i]; i++) { switch (str[i]) { case ' ': seq_puts(m, "\ "); break; case '\t': seq_puts(m, "\\t"); break; case '\\': |
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seq_putc(m, '\\'); |
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break; case '"': seq_puts(m, "\\\""); break; default: seq_putc(m, str[i]); } } seq_puts(m, "\" "); return 0; } static void t_stop(struct seq_file *m, void *p) { |
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format_mod_stop(); |
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} static const struct seq_operations show_format_seq_ops = { .start = t_start, .next = t_next, .show = t_show, .stop = t_stop, }; static int ftrace_formats_open(struct inode *inode, struct file *file) { |
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int ret; ret = security_locked_down(LOCKDOWN_TRACEFS); if (ret) return ret; |
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return seq_open(file, &show_format_seq_ops); |
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} static const struct file_operations ftrace_formats_fops = { .open = ftrace_formats_open, .read = seq_read, .llseek = seq_lseek, .release = seq_release, }; static __init int init_trace_printk_function_export(void) { struct dentry *d_tracer; |
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d_tracer = tracing_init_dentry(); |
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if (IS_ERR(d_tracer)) |
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return 0; |
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trace_create_file("printk_formats", 0444, d_tracer, |
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NULL, &ftrace_formats_fops); |
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return 0; } fs_initcall(init_trace_printk_function_export); |
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static __init int init_trace_printk(void) |
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{ |
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return register_module_notifier(&module_trace_bprintk_format_nb); |
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} |
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early_initcall(init_trace_printk); |