1 // SPDX-License-Identifier: GPL-2.0-only
3 * stacktrace.c : stacktracing APIs needed by rest of kernel
4 * (wrappers over ARC dwarf based unwinder)
6 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
9 * -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
10 * for displaying task's kernel mode call stack in /proc/<pid>/stack
11 * -Iterator based approach to have single copy of unwinding core and APIs
12 * needing unwinding, implement the logic in iterator regarding:
13 * = which frame onwards to start capture
14 * = which frame to stop capturing (wchan)
15 * = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
18 * -Implemented correct versions of thread_saved_pc() and get_wchan()
21 * -Initial implementation
24 #include <linux/ptrace.h>
25 #include <linux/export.h>
26 #include <linux/stacktrace.h>
27 #include <linux/kallsyms.h>
28 #include <linux/sched/debug.h>
30 #include <asm/arcregs.h>
31 #include <asm/unwind.h>
32 #include <asm/switch_to.h>
34 /*-------------------------------------------------------------------------
36 *-------------------------------------------------------------------------
39 #ifdef CONFIG_ARC_DW2_UNWIND
41 static void seed_unwind_frame_info(struct task_struct *tsk,
43 struct unwind_frame_info *frame_info)
46 * synchronous unwinding (e.g. dump_stack)
47 * - uses current values of SP and friends
49 if (tsk == NULL && regs == NULL) {
50 unsigned long fp, sp, blink, ret;
51 frame_info->task = current;
58 : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
61 frame_info->regs.r27 = fp;
62 frame_info->regs.r28 = sp;
63 frame_info->regs.r31 = blink;
64 frame_info->regs.r63 = ret;
65 frame_info->call_frame = 0;
66 } else if (regs == NULL) {
68 * Asynchronous unwinding of sleeping task
69 * - Gets SP etc from task's pt_regs (saved bottom of kernel
73 frame_info->task = tsk;
75 frame_info->regs.r27 = TSK_K_FP(tsk);
76 frame_info->regs.r28 = TSK_K_ESP(tsk);
77 frame_info->regs.r31 = TSK_K_BLINK(tsk);
78 frame_info->regs.r63 = (unsigned int)__switch_to;
80 /* In the prologue of __switch_to, first FP is saved on stack
81 * and then SP is copied to FP. Dwarf assumes cfa as FP based
82 * but we didn't save FP. The value retrieved above is FP's
83 * state in previous frame.
84 * As a work around for this, we unwind from __switch_to start
85 * and adjust SP accordingly. The other limitation is that
86 * __switch_to macro is dwarf rules are not generated for inline
89 frame_info->regs.r27 = 0;
90 frame_info->regs.r28 += 60;
91 frame_info->call_frame = 0;
95 * Asynchronous unwinding of intr/exception
96 * - Just uses the pt_regs passed
98 frame_info->task = tsk;
100 frame_info->regs.r27 = regs->fp;
101 frame_info->regs.r28 = regs->sp;
102 frame_info->regs.r31 = regs->blink;
103 frame_info->regs.r63 = regs->ret;
104 frame_info->call_frame = 0;
110 notrace noinline unsigned int
111 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
112 int (*consumer_fn) (unsigned int, void *), void *arg)
114 #ifdef CONFIG_ARC_DW2_UNWIND
115 int ret = 0, cnt = 0;
116 unsigned int address;
117 struct unwind_frame_info frame_info;
119 seed_unwind_frame_info(tsk, regs, &frame_info);
122 address = UNW_PC(&frame_info);
124 if (!address || !__kernel_text_address(address))
127 if (consumer_fn(address, arg) == -1)
130 ret = arc_unwind(&frame_info);
134 frame_info.regs.r63 = frame_info.regs.r31;
137 printk("unwinder looping too long, aborting !\n");
142 return address; /* return the last address it saw */
144 /* On ARC, only Dward based unwinder works. fp based backtracing is
145 * not possible (-fno-omit-frame-pointer) because of the way function
146 * prelogue is setup (callee regs saved and then fp set and not other
149 pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
155 /*-------------------------------------------------------------------------
156 * callbacks called by unwinder iterator to implement kernel APIs
158 * The callback can return -1 to force the iterator to stop, which by default
159 * keeps going till the bottom-most frame.
160 *-------------------------------------------------------------------------
163 /* Call-back which plugs into unwinding core to dump the stack in
164 * case of panic/OOPs/BUG etc
166 static int __print_sym(unsigned int address, void *arg)
168 const char *loglvl = arg;
170 printk("%s %pS\n", loglvl, (void *)address);
174 #ifdef CONFIG_STACKTRACE
176 /* Call-back which plugs into unwinding core to capture the
177 * traces needed by kernel on /proc/<pid>/stack
179 static int __collect_all(unsigned int address, void *arg)
181 struct stack_trace *trace = arg;
186 trace->entries[trace->nr_entries++] = address;
188 if (trace->nr_entries >= trace->max_entries)
194 static int __collect_all_but_sched(unsigned int address, void *arg)
196 struct stack_trace *trace = arg;
198 if (in_sched_functions(address))
204 trace->entries[trace->nr_entries++] = address;
206 if (trace->nr_entries >= trace->max_entries)
214 static int __get_first_nonsched(unsigned int address, void *unused)
216 if (in_sched_functions(address))
222 /*-------------------------------------------------------------------------
223 * APIs expected by various kernel sub-systems
224 *-------------------------------------------------------------------------
227 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs,
230 printk("%s\nStack Trace:\n", loglvl);
231 arc_unwind_core(tsk, regs, __print_sym, (void *)loglvl);
233 EXPORT_SYMBOL(show_stacktrace);
235 /* Expected by sched Code */
236 void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
238 show_stacktrace(tsk, NULL, loglvl);
241 /* Another API expected by schedular, shows up in "ps" as Wait Channel
242 * Of course just returning schedule( ) would be pointless so unwind until
243 * the function is not in schedular code
245 unsigned int get_wchan(struct task_struct *tsk)
247 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
250 #ifdef CONFIG_STACKTRACE
253 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
254 * A typical use is when /proc/<pid>/stack is queried by userland
256 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
258 /* Assumes @tsk is sleeping so unwinds from __switch_to */
259 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
262 void save_stack_trace(struct stack_trace *trace)
264 /* Pass NULL for task so it unwinds the current call frame */
265 arc_unwind_core(NULL, NULL, __collect_all, trace);
267 EXPORT_SYMBOL_GPL(save_stack_trace);