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 <asm/arcregs.h>
32 #include <asm/unwind.h>
33 #include <asm/switch_to.h>
35 /*-------------------------------------------------------------------------
37 *-------------------------------------------------------------------------
40 #ifdef CONFIG_ARC_DW2_UNWIND
42 static void seed_unwind_frame_info(struct task_struct *tsk,
44 struct unwind_frame_info *frame_info)
47 * synchronous unwinding (e.g. dump_stack)
48 * - uses current values of SP and friends
50 if (tsk == NULL && regs == NULL) {
51 unsigned long fp, sp, blink, ret;
52 frame_info->task = current;
59 : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
62 frame_info->regs.r27 = fp;
63 frame_info->regs.r28 = sp;
64 frame_info->regs.r31 = blink;
65 frame_info->regs.r63 = ret;
66 frame_info->call_frame = 0;
67 } else if (regs == NULL) {
69 * Asynchronous unwinding of sleeping task
70 * - Gets SP etc from task's pt_regs (saved bottom of kernel
74 frame_info->task = tsk;
76 frame_info->regs.r27 = TSK_K_FP(tsk);
77 frame_info->regs.r28 = TSK_K_ESP(tsk);
78 frame_info->regs.r31 = TSK_K_BLINK(tsk);
79 frame_info->regs.r63 = (unsigned int)__switch_to;
81 /* In the prologue of __switch_to, first FP is saved on stack
82 * and then SP is copied to FP. Dwarf assumes cfa as FP based
83 * but we didn't save FP. The value retrieved above is FP's
84 * state in previous frame.
85 * As a work around for this, we unwind from __switch_to start
86 * and adjust SP accordingly. The other limitation is that
87 * __switch_to macro is dwarf rules are not generated for inline
90 frame_info->regs.r27 = 0;
91 frame_info->regs.r28 += 60;
92 frame_info->call_frame = 0;
96 * Asynchronous unwinding of intr/exception
97 * - Just uses the pt_regs passed
99 frame_info->task = tsk;
101 frame_info->regs.r27 = regs->fp;
102 frame_info->regs.r28 = regs->sp;
103 frame_info->regs.r31 = regs->blink;
104 frame_info->regs.r63 = regs->ret;
105 frame_info->call_frame = 0;
111 notrace noinline unsigned int
112 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
113 int (*consumer_fn) (unsigned int, void *), void *arg)
115 #ifdef CONFIG_ARC_DW2_UNWIND
117 unsigned int address;
118 struct unwind_frame_info frame_info;
120 seed_unwind_frame_info(tsk, regs, &frame_info);
123 address = UNW_PC(&frame_info);
125 if (address && __kernel_text_address(address)) {
126 if (consumer_fn(address, arg) == -1)
130 ret = arc_unwind(&frame_info);
133 frame_info.regs.r63 = frame_info.regs.r31;
140 return address; /* return the last address it saw */
142 /* On ARC, only Dward based unwinder works. fp based backtracing is
143 * not possible (-fno-omit-frame-pointer) because of the way function
144 * prelogue is setup (callee regs saved and then fp set and not other
147 pr_warn("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
153 /*-------------------------------------------------------------------------
154 * callbacks called by unwinder iterator to implement kernel APIs
156 * The callback can return -1 to force the iterator to stop, which by default
157 * keeps going till the bottom-most frame.
158 *-------------------------------------------------------------------------
161 /* Call-back which plugs into unwinding core to dump the stack in
162 * case of panic/OOPs/BUG etc
164 static int __print_sym(unsigned int address, void *unused)
166 __print_symbol(" %s\n", address);
170 #ifdef CONFIG_STACKTRACE
172 /* Call-back which plugs into unwinding core to capture the
173 * traces needed by kernel on /proc/<pid>/stack
175 static int __collect_all(unsigned int address, void *arg)
177 struct stack_trace *trace = arg;
182 trace->entries[trace->nr_entries++] = address;
184 if (trace->nr_entries >= trace->max_entries)
190 static int __collect_all_but_sched(unsigned int address, void *arg)
192 struct stack_trace *trace = arg;
194 if (in_sched_functions(address))
200 trace->entries[trace->nr_entries++] = address;
202 if (trace->nr_entries >= trace->max_entries)
210 static int __get_first_nonsched(unsigned int address, void *unused)
212 if (in_sched_functions(address))
218 /*-------------------------------------------------------------------------
219 * APIs expected by various kernel sub-systems
220 *-------------------------------------------------------------------------
223 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
225 pr_info("\nStack Trace:\n");
226 arc_unwind_core(tsk, regs, __print_sym, NULL);
228 EXPORT_SYMBOL(show_stacktrace);
230 /* Expected by sched Code */
231 void show_stack(struct task_struct *tsk, unsigned long *sp)
233 show_stacktrace(tsk, NULL);
236 /* Another API expected by schedular, shows up in "ps" as Wait Channel
237 * Ofcourse just returning schedule( ) would be pointless so unwind until
238 * the function is not in schedular code
240 unsigned int get_wchan(struct task_struct *tsk)
242 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
245 #ifdef CONFIG_STACKTRACE
248 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
249 * A typical use is when /proc/<pid>/stack is queried by userland
251 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
253 /* Assumes @tsk is sleeping so unwinds from __switch_to */
254 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
257 void save_stack_trace(struct stack_trace *trace)
259 /* Pass NULL for task so it unwinds the current call frame */
260 arc_unwind_core(NULL, NULL, __collect_all, trace);
262 EXPORT_SYMBOL_GPL(save_stack_trace);