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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/arch/alpha/kernel/process.c
4 *
5 * Copyright (C) 1995 Linus Torvalds
6 */
7
8/*
9 * This file handles the architecture-dependent parts of process handling.
10 */
11
12#include <linux/errno.h>
13#include <linux/module.h>
14#include <linux/sched.h>
15#include <linux/sched/debug.h>
16#include <linux/sched/task.h>
17#include <linux/sched/task_stack.h>
18#include <linux/kernel.h>
19#include <linux/mm.h>
20#include <linux/smp.h>
21#include <linux/stddef.h>
22#include <linux/unistd.h>
23#include <linux/ptrace.h>
24#include <linux/user.h>
25#include <linux/time.h>
26#include <linux/major.h>
27#include <linux/stat.h>
28#include <linux/vt.h>
29#include <linux/mman.h>
30#include <linux/elfcore.h>
31#include <linux/reboot.h>
32#include <linux/tty.h>
33#include <linux/console.h>
34#include <linux/slab.h>
35#include <linux/rcupdate.h>
36
37#include <asm/reg.h>
38#include <linux/uaccess.h>
39#include <asm/io.h>
40#include <asm/hwrpb.h>
41#include <asm/fpu.h>
42
43#include "proto.h"
44#include "pci_impl.h"
45
46/*
47 * Power off function, if any
48 */
49void (*pm_power_off)(void) = machine_power_off;
50EXPORT_SYMBOL(pm_power_off);
51
52#ifdef CONFIG_ALPHA_WTINT
53/*
54 * Sleep the CPU.
55 * EV6, LCA45 and QEMU know how to power down, skipping N timer interrupts.
56 */
57void arch_cpu_idle(void)
58{
59 wtint(0);
60 local_irq_enable();
61}
62
63void arch_cpu_idle_dead(void)
64{
65 wtint(INT_MAX);
66}
67#endif /* ALPHA_WTINT */
68
69struct halt_info {
70 int mode;
71 char *restart_cmd;
72};
73
74static void
75common_shutdown_1(void *generic_ptr)
76{
77 struct halt_info *how = (struct halt_info *)generic_ptr;
78 struct percpu_struct *cpup;
79 unsigned long *pflags, flags;
80 int cpuid = smp_processor_id();
81
82 /* No point in taking interrupts anymore. */
83 local_irq_disable();
84
85 cpup = (struct percpu_struct *)
86 ((unsigned long)hwrpb + hwrpb->processor_offset
87 + hwrpb->processor_size * cpuid);
88 pflags = &cpup->flags;
89 flags = *pflags;
90
91 /* Clear reason to "default"; clear "bootstrap in progress". */
92 flags &= ~0x00ff0001UL;
93
94#ifdef CONFIG_SMP
95 /* Secondaries halt here. */
96 if (cpuid != boot_cpuid) {
97 flags |= 0x00040000UL; /* "remain halted" */
98 *pflags = flags;
99 set_cpu_present(cpuid, false);
100 set_cpu_possible(cpuid, false);
101 halt();
102 }
103#endif
104
105 if (how->mode == LINUX_REBOOT_CMD_RESTART) {
106 if (!how->restart_cmd) {
107 flags |= 0x00020000UL; /* "cold bootstrap" */
108 } else {
109 /* For SRM, we could probably set environment
110 variables to get this to work. We'd have to
111 delay this until after srm_paging_stop unless
112 we ever got srm_fixup working.
113
114 At the moment, SRM will use the last boot device,
115 but the file and flags will be the defaults, when
116 doing a "warm" bootstrap. */
117 flags |= 0x00030000UL; /* "warm bootstrap" */
118 }
119 } else {
120 flags |= 0x00040000UL; /* "remain halted" */
121 }
122 *pflags = flags;
123
124#ifdef CONFIG_SMP
125 /* Wait for the secondaries to halt. */
126 set_cpu_present(boot_cpuid, false);
127 set_cpu_possible(boot_cpuid, false);
128 while (cpumask_weight(cpu_present_mask))
129 barrier();
130#endif
131
132 /* If booted from SRM, reset some of the original environment. */
133 if (alpha_using_srm) {
134#ifdef CONFIG_DUMMY_CONSOLE
135 /* If we've gotten here after SysRq-b, leave interrupt
136 context before taking over the console. */
137 if (in_interrupt())
138 irq_exit();
139 /* This has the effect of resetting the VGA video origin. */
140 console_lock();
141 do_take_over_console(&dummy_con, 0, MAX_NR_CONSOLES-1, 1);
142 console_unlock();
143#endif
144 pci_restore_srm_config();
145 set_hae(srm_hae);
146 }
147
148 if (alpha_mv.kill_arch)
149 alpha_mv.kill_arch(how->mode);
150
151 if (! alpha_using_srm && how->mode != LINUX_REBOOT_CMD_RESTART) {
152 /* Unfortunately, since MILO doesn't currently understand
153 the hwrpb bits above, we can't reliably halt the
154 processor and keep it halted. So just loop. */
155 return;
156 }
157
158 if (alpha_using_srm)
159 srm_paging_stop();
160
161 halt();
162}
163
164static void
165common_shutdown(int mode, char *restart_cmd)
166{
167 struct halt_info args;
168 args.mode = mode;
169 args.restart_cmd = restart_cmd;
170 on_each_cpu(common_shutdown_1, &args, 0);
171}
172
173void
174machine_restart(char *restart_cmd)
175{
176 common_shutdown(LINUX_REBOOT_CMD_RESTART, restart_cmd);
177}
178
179
180void
181machine_halt(void)
182{
183 common_shutdown(LINUX_REBOOT_CMD_HALT, NULL);
184}
185
186
187void
188machine_power_off(void)
189{
190 common_shutdown(LINUX_REBOOT_CMD_POWER_OFF, NULL);
191}
192
193
194/* Used by sysrq-p, among others. I don't believe r9-r15 are ever
195 saved in the context it's used. */
196
197void
198show_regs(struct pt_regs *regs)
199{
200 show_regs_print_info(KERN_DEFAULT);
201 dik_show_regs(regs, NULL);
202}
203
204/*
205 * Re-start a thread when doing execve()
206 */
207void
208start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
209{
210 regs->pc = pc;
211 regs->ps = 8;
212 wrusp(sp);
213}
214EXPORT_SYMBOL(start_thread);
215
216void
217flush_thread(void)
218{
219 /* Arrange for each exec'ed process to start off with a clean slate
220 with respect to the FPU. This is all exceptions disabled. */
221 current_thread_info()->ieee_state = 0;
222 wrfpcr(FPCR_DYN_NORMAL | ieee_swcr_to_fpcr(0));
223
224 /* Clean slate for TLS. */
225 current_thread_info()->pcb.unique = 0;
226}
227
228void
229release_thread(struct task_struct *dead_task)
230{
231}
232
233/*
234 * Copy architecture-specific thread state
235 */
236int copy_thread(unsigned long clone_flags, unsigned long usp,
237 unsigned long kthread_arg, struct task_struct *p,
238 unsigned long tls)
239{
240 extern void ret_from_fork(void);
241 extern void ret_from_kernel_thread(void);
242
243 struct thread_info *childti = task_thread_info(p);
244 struct pt_regs *childregs = task_pt_regs(p);
245 struct pt_regs *regs = current_pt_regs();
246 struct switch_stack *childstack, *stack;
247
248 childstack = ((struct switch_stack *) childregs) - 1;
249 childti->pcb.ksp = (unsigned long) childstack;
250 childti->pcb.flags = 1; /* set FEN, clear everything else */
251
252 if (unlikely(p->flags & PF_KTHREAD)) {
253 /* kernel thread */
254 memset(childstack, 0,
255 sizeof(struct switch_stack) + sizeof(struct pt_regs));
256 childstack->r26 = (unsigned long) ret_from_kernel_thread;
257 childstack->r9 = usp; /* function */
258 childstack->r10 = kthread_arg;
259 childregs->hae = alpha_mv.hae_cache,
260 childti->pcb.usp = 0;
261 return 0;
262 }
263 /* Note: if CLONE_SETTLS is not set, then we must inherit the
264 value from the parent, which will have been set by the block
265 copy in dup_task_struct. This is non-intuitive, but is
266 required for proper operation in the case of a threaded
267 application calling fork. */
268 if (clone_flags & CLONE_SETTLS)
269 childti->pcb.unique = tls;
270 else
271 regs->r20 = 0; /* OSF/1 has some strange fork() semantics. */
272 childti->pcb.usp = usp ?: rdusp();
273 *childregs = *regs;
274 childregs->r0 = 0;
275 childregs->r19 = 0;
276 childregs->r20 = 1; /* OSF/1 has some strange fork() semantics. */
277 stack = ((struct switch_stack *) regs) - 1;
278 *childstack = *stack;
279 childstack->r26 = (unsigned long) ret_from_fork;
280 return 0;
281}
282
283/*
284 * Fill in the user structure for a ELF core dump.
285 */
286void
287dump_elf_thread(elf_greg_t *dest, struct pt_regs *pt, struct thread_info *ti)
288{
289 /* switch stack follows right below pt_regs: */
290 struct switch_stack * sw = ((struct switch_stack *) pt) - 1;
291
292 dest[ 0] = pt->r0;
293 dest[ 1] = pt->r1;
294 dest[ 2] = pt->r2;
295 dest[ 3] = pt->r3;
296 dest[ 4] = pt->r4;
297 dest[ 5] = pt->r5;
298 dest[ 6] = pt->r6;
299 dest[ 7] = pt->r7;
300 dest[ 8] = pt->r8;
301 dest[ 9] = sw->r9;
302 dest[10] = sw->r10;
303 dest[11] = sw->r11;
304 dest[12] = sw->r12;
305 dest[13] = sw->r13;
306 dest[14] = sw->r14;
307 dest[15] = sw->r15;
308 dest[16] = pt->r16;
309 dest[17] = pt->r17;
310 dest[18] = pt->r18;
311 dest[19] = pt->r19;
312 dest[20] = pt->r20;
313 dest[21] = pt->r21;
314 dest[22] = pt->r22;
315 dest[23] = pt->r23;
316 dest[24] = pt->r24;
317 dest[25] = pt->r25;
318 dest[26] = pt->r26;
319 dest[27] = pt->r27;
320 dest[28] = pt->r28;
321 dest[29] = pt->gp;
322 dest[30] = ti == current_thread_info() ? rdusp() : ti->pcb.usp;
323 dest[31] = pt->pc;
324
325 /* Once upon a time this was the PS value. Which is stupid
326 since that is always 8 for usermode. Usurped for the more
327 useful value of the thread's UNIQUE field. */
328 dest[32] = ti->pcb.unique;
329}
330EXPORT_SYMBOL(dump_elf_thread);
331
332int
333dump_elf_task(elf_greg_t *dest, struct task_struct *task)
334{
335 dump_elf_thread(dest, task_pt_regs(task), task_thread_info(task));
336 return 1;
337}
338EXPORT_SYMBOL(dump_elf_task);
339
340int
341dump_elf_task_fp(elf_fpreg_t *dest, struct task_struct *task)
342{
343 struct switch_stack *sw = (struct switch_stack *)task_pt_regs(task) - 1;
344 memcpy(dest, sw->fp, 32 * 8);
345 return 1;
346}
347EXPORT_SYMBOL(dump_elf_task_fp);
348
349/*
350 * Return saved PC of a blocked thread. This assumes the frame
351 * pointer is the 6th saved long on the kernel stack and that the
352 * saved return address is the first long in the frame. This all
353 * holds provided the thread blocked through a call to schedule() ($15
354 * is the frame pointer in schedule() and $15 is saved at offset 48 by
355 * entry.S:do_switch_stack).
356 *
357 * Under heavy swap load I've seen this lose in an ugly way. So do
358 * some extra sanity checking on the ranges we expect these pointers
359 * to be in so that we can fail gracefully. This is just for ps after
360 * all. -- r~
361 */
362
363static unsigned long
364thread_saved_pc(struct task_struct *t)
365{
366 unsigned long base = (unsigned long)task_stack_page(t);
367 unsigned long fp, sp = task_thread_info(t)->pcb.ksp;
368
369 if (sp > base && sp+6*8 < base + 16*1024) {
370 fp = ((unsigned long*)sp)[6];
371 if (fp > sp && fp < base + 16*1024)
372 return *(unsigned long *)fp;
373 }
374
375 return 0;
376}
377
378unsigned long
379get_wchan(struct task_struct *p)
380{
381 unsigned long schedule_frame;
382 unsigned long pc;
383 if (!p || p == current || p->state == TASK_RUNNING)
384 return 0;
385 /*
386 * This one depends on the frame size of schedule(). Do a
387 * "disass schedule" in gdb to find the frame size. Also, the
388 * code assumes that sleep_on() follows immediately after
389 * interruptible_sleep_on() and that add_timer() follows
390 * immediately after interruptible_sleep(). Ugly, isn't it?
391 * Maybe adding a wchan field to task_struct would be better,
392 * after all...
393 */
394
395 pc = thread_saved_pc(p);
396 if (in_sched_functions(pc)) {
397 schedule_frame = ((unsigned long *)task_thread_info(p)->pcb.ksp)[6];
398 return ((unsigned long *)schedule_frame)[12];
399 }
400 return pc;
401}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/arch/alpha/kernel/process.c
4 *
5 * Copyright (C) 1995 Linus Torvalds
6 */
7
8/*
9 * This file handles the architecture-dependent parts of process handling.
10 */
11
12#include <linux/errno.h>
13#include <linux/module.h>
14#include <linux/sched.h>
15#include <linux/sched/debug.h>
16#include <linux/sched/task.h>
17#include <linux/sched/task_stack.h>
18#include <linux/kernel.h>
19#include <linux/mm.h>
20#include <linux/smp.h>
21#include <linux/stddef.h>
22#include <linux/unistd.h>
23#include <linux/ptrace.h>
24#include <linux/user.h>
25#include <linux/time.h>
26#include <linux/major.h>
27#include <linux/stat.h>
28#include <linux/vt.h>
29#include <linux/mman.h>
30#include <linux/elfcore.h>
31#include <linux/reboot.h>
32#include <linux/tty.h>
33#include <linux/console.h>
34#include <linux/slab.h>
35#include <linux/rcupdate.h>
36
37#include <asm/reg.h>
38#include <linux/uaccess.h>
39#include <asm/io.h>
40#include <asm/hwrpb.h>
41#include <asm/fpu.h>
42
43#include "proto.h"
44#include "pci_impl.h"
45
46/*
47 * Power off function, if any
48 */
49void (*pm_power_off)(void) = machine_power_off;
50EXPORT_SYMBOL(pm_power_off);
51
52#ifdef CONFIG_ALPHA_WTINT
53/*
54 * Sleep the CPU.
55 * EV6, LCA45 and QEMU know how to power down, skipping N timer interrupts.
56 */
57void arch_cpu_idle(void)
58{
59 wtint(0);
60 raw_local_irq_enable();
61}
62
63void arch_cpu_idle_dead(void)
64{
65 wtint(INT_MAX);
66}
67#endif /* ALPHA_WTINT */
68
69struct halt_info {
70 int mode;
71 char *restart_cmd;
72};
73
74static void
75common_shutdown_1(void *generic_ptr)
76{
77 struct halt_info *how = (struct halt_info *)generic_ptr;
78 struct percpu_struct *cpup;
79 unsigned long *pflags, flags;
80 int cpuid = smp_processor_id();
81
82 /* No point in taking interrupts anymore. */
83 local_irq_disable();
84
85 cpup = (struct percpu_struct *)
86 ((unsigned long)hwrpb + hwrpb->processor_offset
87 + hwrpb->processor_size * cpuid);
88 pflags = &cpup->flags;
89 flags = *pflags;
90
91 /* Clear reason to "default"; clear "bootstrap in progress". */
92 flags &= ~0x00ff0001UL;
93
94#ifdef CONFIG_SMP
95 /* Secondaries halt here. */
96 if (cpuid != boot_cpuid) {
97 flags |= 0x00040000UL; /* "remain halted" */
98 *pflags = flags;
99 set_cpu_present(cpuid, false);
100 set_cpu_possible(cpuid, false);
101 halt();
102 }
103#endif
104
105 if (how->mode == LINUX_REBOOT_CMD_RESTART) {
106 if (!how->restart_cmd) {
107 flags |= 0x00020000UL; /* "cold bootstrap" */
108 } else {
109 /* For SRM, we could probably set environment
110 variables to get this to work. We'd have to
111 delay this until after srm_paging_stop unless
112 we ever got srm_fixup working.
113
114 At the moment, SRM will use the last boot device,
115 but the file and flags will be the defaults, when
116 doing a "warm" bootstrap. */
117 flags |= 0x00030000UL; /* "warm bootstrap" */
118 }
119 } else {
120 flags |= 0x00040000UL; /* "remain halted" */
121 }
122 *pflags = flags;
123
124#ifdef CONFIG_SMP
125 /* Wait for the secondaries to halt. */
126 set_cpu_present(boot_cpuid, false);
127 set_cpu_possible(boot_cpuid, false);
128 while (!cpumask_empty(cpu_present_mask))
129 barrier();
130#endif
131
132 /* If booted from SRM, reset some of the original environment. */
133 if (alpha_using_srm) {
134#ifdef CONFIG_DUMMY_CONSOLE
135 /* If we've gotten here after SysRq-b, leave interrupt
136 context before taking over the console. */
137 if (in_irq())
138 irq_exit();
139 /* This has the effect of resetting the VGA video origin. */
140 console_lock();
141 do_take_over_console(&dummy_con, 0, MAX_NR_CONSOLES-1, 1);
142 console_unlock();
143#endif
144 pci_restore_srm_config();
145 set_hae(srm_hae);
146 }
147
148 if (alpha_mv.kill_arch)
149 alpha_mv.kill_arch(how->mode);
150
151 if (! alpha_using_srm && how->mode != LINUX_REBOOT_CMD_RESTART) {
152 /* Unfortunately, since MILO doesn't currently understand
153 the hwrpb bits above, we can't reliably halt the
154 processor and keep it halted. So just loop. */
155 return;
156 }
157
158 if (alpha_using_srm)
159 srm_paging_stop();
160
161 halt();
162}
163
164static void
165common_shutdown(int mode, char *restart_cmd)
166{
167 struct halt_info args;
168 args.mode = mode;
169 args.restart_cmd = restart_cmd;
170 on_each_cpu(common_shutdown_1, &args, 0);
171}
172
173void
174machine_restart(char *restart_cmd)
175{
176 common_shutdown(LINUX_REBOOT_CMD_RESTART, restart_cmd);
177}
178
179
180void
181machine_halt(void)
182{
183 common_shutdown(LINUX_REBOOT_CMD_HALT, NULL);
184}
185
186
187void
188machine_power_off(void)
189{
190 common_shutdown(LINUX_REBOOT_CMD_POWER_OFF, NULL);
191}
192
193
194/* Used by sysrq-p, among others. I don't believe r9-r15 are ever
195 saved in the context it's used. */
196
197void
198show_regs(struct pt_regs *regs)
199{
200 show_regs_print_info(KERN_DEFAULT);
201 dik_show_regs(regs, NULL);
202}
203
204/*
205 * Re-start a thread when doing execve()
206 */
207void
208start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
209{
210 regs->pc = pc;
211 regs->ps = 8;
212 wrusp(sp);
213}
214EXPORT_SYMBOL(start_thread);
215
216void
217flush_thread(void)
218{
219 /* Arrange for each exec'ed process to start off with a clean slate
220 with respect to the FPU. This is all exceptions disabled. */
221 current_thread_info()->ieee_state = 0;
222 wrfpcr(FPCR_DYN_NORMAL | ieee_swcr_to_fpcr(0));
223
224 /* Clean slate for TLS. */
225 current_thread_info()->pcb.unique = 0;
226}
227
228/*
229 * Copy architecture-specific thread state
230 */
231int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
232{
233 unsigned long clone_flags = args->flags;
234 unsigned long usp = args->stack;
235 unsigned long tls = args->tls;
236 extern void ret_from_fork(void);
237 extern void ret_from_kernel_thread(void);
238
239 struct thread_info *childti = task_thread_info(p);
240 struct pt_regs *childregs = task_pt_regs(p);
241 struct pt_regs *regs = current_pt_regs();
242 struct switch_stack *childstack, *stack;
243
244 childstack = ((struct switch_stack *) childregs) - 1;
245 childti->pcb.ksp = (unsigned long) childstack;
246 childti->pcb.flags = 1; /* set FEN, clear everything else */
247
248 if (unlikely(args->fn)) {
249 /* kernel thread */
250 memset(childstack, 0,
251 sizeof(struct switch_stack) + sizeof(struct pt_regs));
252 childstack->r26 = (unsigned long) ret_from_kernel_thread;
253 childstack->r9 = (unsigned long) args->fn;
254 childstack->r10 = (unsigned long) args->fn_arg;
255 childregs->hae = alpha_mv.hae_cache;
256 childti->pcb.usp = 0;
257 return 0;
258 }
259 /* Note: if CLONE_SETTLS is not set, then we must inherit the
260 value from the parent, which will have been set by the block
261 copy in dup_task_struct. This is non-intuitive, but is
262 required for proper operation in the case of a threaded
263 application calling fork. */
264 if (clone_flags & CLONE_SETTLS)
265 childti->pcb.unique = tls;
266 else
267 regs->r20 = 0; /* OSF/1 has some strange fork() semantics. */
268 childti->pcb.usp = usp ?: rdusp();
269 *childregs = *regs;
270 childregs->r0 = 0;
271 childregs->r19 = 0;
272 childregs->r20 = 1; /* OSF/1 has some strange fork() semantics. */
273 stack = ((struct switch_stack *) regs) - 1;
274 *childstack = *stack;
275 childstack->r26 = (unsigned long) ret_from_fork;
276 return 0;
277}
278
279/*
280 * Fill in the user structure for a ELF core dump.
281 */
282void
283dump_elf_thread(elf_greg_t *dest, struct pt_regs *pt, struct thread_info *ti)
284{
285 /* switch stack follows right below pt_regs: */
286 struct switch_stack * sw = ((struct switch_stack *) pt) - 1;
287
288 dest[ 0] = pt->r0;
289 dest[ 1] = pt->r1;
290 dest[ 2] = pt->r2;
291 dest[ 3] = pt->r3;
292 dest[ 4] = pt->r4;
293 dest[ 5] = pt->r5;
294 dest[ 6] = pt->r6;
295 dest[ 7] = pt->r7;
296 dest[ 8] = pt->r8;
297 dest[ 9] = sw->r9;
298 dest[10] = sw->r10;
299 dest[11] = sw->r11;
300 dest[12] = sw->r12;
301 dest[13] = sw->r13;
302 dest[14] = sw->r14;
303 dest[15] = sw->r15;
304 dest[16] = pt->r16;
305 dest[17] = pt->r17;
306 dest[18] = pt->r18;
307 dest[19] = pt->r19;
308 dest[20] = pt->r20;
309 dest[21] = pt->r21;
310 dest[22] = pt->r22;
311 dest[23] = pt->r23;
312 dest[24] = pt->r24;
313 dest[25] = pt->r25;
314 dest[26] = pt->r26;
315 dest[27] = pt->r27;
316 dest[28] = pt->r28;
317 dest[29] = pt->gp;
318 dest[30] = ti == current_thread_info() ? rdusp() : ti->pcb.usp;
319 dest[31] = pt->pc;
320
321 /* Once upon a time this was the PS value. Which is stupid
322 since that is always 8 for usermode. Usurped for the more
323 useful value of the thread's UNIQUE field. */
324 dest[32] = ti->pcb.unique;
325}
326EXPORT_SYMBOL(dump_elf_thread);
327
328int
329dump_elf_task(elf_greg_t *dest, struct task_struct *task)
330{
331 dump_elf_thread(dest, task_pt_regs(task), task_thread_info(task));
332 return 1;
333}
334EXPORT_SYMBOL(dump_elf_task);
335
336int elf_core_copy_task_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
337{
338 struct switch_stack *sw = (struct switch_stack *)task_pt_regs(t) - 1;
339 memcpy(fpu, sw->fp, 32 * 8);
340 return 1;
341}
342
343/*
344 * Return saved PC of a blocked thread. This assumes the frame
345 * pointer is the 6th saved long on the kernel stack and that the
346 * saved return address is the first long in the frame. This all
347 * holds provided the thread blocked through a call to schedule() ($15
348 * is the frame pointer in schedule() and $15 is saved at offset 48 by
349 * entry.S:do_switch_stack).
350 *
351 * Under heavy swap load I've seen this lose in an ugly way. So do
352 * some extra sanity checking on the ranges we expect these pointers
353 * to be in so that we can fail gracefully. This is just for ps after
354 * all. -- r~
355 */
356
357static unsigned long
358thread_saved_pc(struct task_struct *t)
359{
360 unsigned long base = (unsigned long)task_stack_page(t);
361 unsigned long fp, sp = task_thread_info(t)->pcb.ksp;
362
363 if (sp > base && sp+6*8 < base + 16*1024) {
364 fp = ((unsigned long*)sp)[6];
365 if (fp > sp && fp < base + 16*1024)
366 return *(unsigned long *)fp;
367 }
368
369 return 0;
370}
371
372unsigned long
373__get_wchan(struct task_struct *p)
374{
375 unsigned long schedule_frame;
376 unsigned long pc;
377
378 /*
379 * This one depends on the frame size of schedule(). Do a
380 * "disass schedule" in gdb to find the frame size. Also, the
381 * code assumes that sleep_on() follows immediately after
382 * interruptible_sleep_on() and that add_timer() follows
383 * immediately after interruptible_sleep(). Ugly, isn't it?
384 * Maybe adding a wchan field to task_struct would be better,
385 * after all...
386 */
387
388 pc = thread_saved_pc(p);
389 if (in_sched_functions(pc)) {
390 schedule_frame = ((unsigned long *)task_thread_info(p)->pcb.ksp)[6];
391 return ((unsigned long *)schedule_frame)[12];
392 }
393 return pc;
394}