2 * stacktrace.c : stacktracing APIs needed by rest of kernel
3 * (wrappers over ARC dwarf based unwinder)
5 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
12 * -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
13 * for displaying task's kernel mode call stack in /proc/<pid>/stack
14 * -Iterator based approach to have single copy of unwinding core and APIs
15 * needing unwinding, implement the logic in iterator regarding:
16 * = which frame onwards to start capture
17 * = which frame to stop capturing (wchan)
18 * = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
21 * -Implemented correct versions of thread_saved_pc() and get_wchan()
24 * -Initial implementation
27 #include <linux/ptrace.h>
28 #include <linux/export.h>
29 #include <linux/stacktrace.h>
30 #include <linux/kallsyms.h>
31 #include <linux/sched/debug.h>
33 #include <asm/arcregs.h>
34 #include <asm/unwind.h>
35 #include <asm/switch_to.h>
37 /*-------------------------------------------------------------------------
39 *-------------------------------------------------------------------------
42 #ifdef CONFIG_ARC_DW2_UNWIND
45 seed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs,
46 struct unwind_frame_info *frame_info)
49 * synchronous unwinding (e.g. dump_stack)
50 * - uses current values of SP and friends
52 if (regs == NULL && (tsk == NULL || tsk == current)) {
53 unsigned long fp, sp, blink, ret;
54 frame_info->task = current;
61 : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
64 frame_info->regs.r27 = fp;
65 frame_info->regs.r28 = sp;
66 frame_info->regs.r31 = blink;
67 frame_info->regs.r63 = ret;
68 frame_info->call_frame = 0;
69 } else if (regs == NULL) {
71 * Asynchronous unwinding of a likely sleeping task
72 * - first ensure it is actually sleeping
73 * - if so, it will be in __switch_to, kernel mode SP of task
74 * is safe-kept and BLINK at a well known location in there
77 if (tsk->state == TASK_RUNNING)
80 frame_info->task = tsk;
82 frame_info->regs.r27 = TSK_K_FP(tsk);
83 frame_info->regs.r28 = TSK_K_ESP(tsk);
84 frame_info->regs.r31 = TSK_K_BLINK(tsk);
85 frame_info->regs.r63 = (unsigned int)__switch_to;
87 /* In the prologue of __switch_to, first FP is saved on stack
88 * and then SP is copied to FP. Dwarf assumes cfa as FP based
89 * but we didn't save FP. The value retrieved above is FP's
90 * state in previous frame.
91 * As a work around for this, we unwind from __switch_to start
92 * and adjust SP accordingly. The other limitation is that
93 * __switch_to macro is dwarf rules are not generated for inline
96 frame_info->regs.r27 = 0;
97 frame_info->regs.r28 += 60;
98 frame_info->call_frame = 0;
102 * Asynchronous unwinding of intr/exception
103 * - Just uses the pt_regs passed
105 frame_info->task = tsk;
107 frame_info->regs.r27 = regs->fp;
108 frame_info->regs.r28 = regs->sp;
109 frame_info->regs.r31 = regs->blink;
110 frame_info->regs.r63 = regs->ret;
111 frame_info->call_frame = 0;
119 notrace noinline unsigned int
120 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
121 int (*consumer_fn) (unsigned int, void *), void *arg)
123 #ifdef CONFIG_ARC_DW2_UNWIND
124 int ret = 0, cnt = 0;
125 unsigned int address;
126 struct unwind_frame_info frame_info;
128 if (seed_unwind_frame_info(tsk, regs, &frame_info))
132 address = UNW_PC(&frame_info);
134 if (!address || !__kernel_text_address(address))
137 if (consumer_fn(address, arg) == -1)
140 ret = arc_unwind(&frame_info);
144 frame_info.regs.r63 = frame_info.regs.r31;
147 printk("unwinder looping too long, aborting !\n");
152 return address; /* return the last address it saw */
154 /* On ARC, only Dward based unwinder works. fp based backtracing is
155 * not possible (-fno-omit-frame-pointer) because of the way function
156 * prelogue is setup (callee regs saved and then fp set and not other
159 pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
165 /*-------------------------------------------------------------------------
166 * callbacks called by unwinder iterator to implement kernel APIs
168 * The callback can return -1 to force the iterator to stop, which by default
169 * keeps going till the bottom-most frame.
170 *-------------------------------------------------------------------------
173 /* Call-back which plugs into unwinding core to dump the stack in
174 * case of panic/OOPs/BUG etc
176 static int __print_sym(unsigned int address, void *unused)
178 __print_symbol(" %s\n", address);
182 #ifdef CONFIG_STACKTRACE
184 /* Call-back which plugs into unwinding core to capture the
185 * traces needed by kernel on /proc/<pid>/stack
187 static int __collect_all(unsigned int address, void *arg)
189 struct stack_trace *trace = arg;
194 trace->entries[trace->nr_entries++] = address;
196 if (trace->nr_entries >= trace->max_entries)
202 static int __collect_all_but_sched(unsigned int address, void *arg)
204 struct stack_trace *trace = arg;
206 if (in_sched_functions(address))
212 trace->entries[trace->nr_entries++] = address;
214 if (trace->nr_entries >= trace->max_entries)
222 static int __get_first_nonsched(unsigned int address, void *unused)
224 if (in_sched_functions(address))
230 /*-------------------------------------------------------------------------
231 * APIs expected by various kernel sub-systems
232 *-------------------------------------------------------------------------
235 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
237 pr_info("\nStack Trace:\n");
238 arc_unwind_core(tsk, regs, __print_sym, NULL);
240 EXPORT_SYMBOL(show_stacktrace);
242 /* Expected by sched Code */
243 void show_stack(struct task_struct *tsk, unsigned long *sp)
245 show_stacktrace(tsk, NULL);
248 /* Another API expected by schedular, shows up in "ps" as Wait Channel
249 * Of course just returning schedule( ) would be pointless so unwind until
250 * the function is not in schedular code
252 unsigned int get_wchan(struct task_struct *tsk)
254 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
257 #ifdef CONFIG_STACKTRACE
260 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
261 * A typical use is when /proc/<pid>/stack is queried by userland
263 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
265 /* Assumes @tsk is sleeping so unwinds from __switch_to */
266 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
269 void save_stack_trace(struct stack_trace *trace)
271 /* Pass NULL for task so it unwinds the current call frame */
272 arc_unwind_core(NULL, NULL, __collect_all, trace);
274 EXPORT_SYMBOL_GPL(save_stack_trace);