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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/pgtable.h>
41#include <asm/hwrpb.h>
42#include <asm/fpu.h>
43
44#include "proto.h"
45#include "pci_impl.h"
46
47/*
48 * Power off function, if any
49 */
50void (*pm_power_off)(void) = machine_power_off;
51EXPORT_SYMBOL(pm_power_off);
52
53#ifdef CONFIG_ALPHA_WTINT
54/*
55 * Sleep the CPU.
56 * EV6, LCA45 and QEMU know how to power down, skipping N timer interrupts.
57 */
58void arch_cpu_idle(void)
59{
60 wtint(0);
61 local_irq_enable();
62}
63
64void arch_cpu_idle_dead(void)
65{
66 wtint(INT_MAX);
67}
68#endif /* ALPHA_WTINT */
69
70struct halt_info {
71 int mode;
72 char *restart_cmd;
73};
74
75static void
76common_shutdown_1(void *generic_ptr)
77{
78 struct halt_info *how = (struct halt_info *)generic_ptr;
79 struct percpu_struct *cpup;
80 unsigned long *pflags, flags;
81 int cpuid = smp_processor_id();
82
83 /* No point in taking interrupts anymore. */
84 local_irq_disable();
85
86 cpup = (struct percpu_struct *)
87 ((unsigned long)hwrpb + hwrpb->processor_offset
88 + hwrpb->processor_size * cpuid);
89 pflags = &cpup->flags;
90 flags = *pflags;
91
92 /* Clear reason to "default"; clear "bootstrap in progress". */
93 flags &= ~0x00ff0001UL;
94
95#ifdef CONFIG_SMP
96 /* Secondaries halt here. */
97 if (cpuid != boot_cpuid) {
98 flags |= 0x00040000UL; /* "remain halted" */
99 *pflags = flags;
100 set_cpu_present(cpuid, false);
101 set_cpu_possible(cpuid, false);
102 halt();
103 }
104#endif
105
106 if (how->mode == LINUX_REBOOT_CMD_RESTART) {
107 if (!how->restart_cmd) {
108 flags |= 0x00020000UL; /* "cold bootstrap" */
109 } else {
110 /* For SRM, we could probably set environment
111 variables to get this to work. We'd have to
112 delay this until after srm_paging_stop unless
113 we ever got srm_fixup working.
114
115 At the moment, SRM will use the last boot device,
116 but the file and flags will be the defaults, when
117 doing a "warm" bootstrap. */
118 flags |= 0x00030000UL; /* "warm bootstrap" */
119 }
120 } else {
121 flags |= 0x00040000UL; /* "remain halted" */
122 }
123 *pflags = flags;
124
125#ifdef CONFIG_SMP
126 /* Wait for the secondaries to halt. */
127 set_cpu_present(boot_cpuid, false);
128 set_cpu_possible(boot_cpuid, false);
129 while (cpumask_weight(cpu_present_mask))
130 barrier();
131#endif
132
133 /* If booted from SRM, reset some of the original environment. */
134 if (alpha_using_srm) {
135#ifdef CONFIG_DUMMY_CONSOLE
136 /* If we've gotten here after SysRq-b, leave interrupt
137 context before taking over the console. */
138 if (in_interrupt())
139 irq_exit();
140 /* This has the effect of resetting the VGA video origin. */
141 console_lock();
142 do_take_over_console(&dummy_con, 0, MAX_NR_CONSOLES-1, 1);
143 console_unlock();
144#endif
145 pci_restore_srm_config();
146 set_hae(srm_hae);
147 }
148
149 if (alpha_mv.kill_arch)
150 alpha_mv.kill_arch(how->mode);
151
152 if (! alpha_using_srm && how->mode != LINUX_REBOOT_CMD_RESTART) {
153 /* Unfortunately, since MILO doesn't currently understand
154 the hwrpb bits above, we can't reliably halt the
155 processor and keep it halted. So just loop. */
156 return;
157 }
158
159 if (alpha_using_srm)
160 srm_paging_stop();
161
162 halt();
163}
164
165static void
166common_shutdown(int mode, char *restart_cmd)
167{
168 struct halt_info args;
169 args.mode = mode;
170 args.restart_cmd = restart_cmd;
171 on_each_cpu(common_shutdown_1, &args, 0);
172}
173
174void
175machine_restart(char *restart_cmd)
176{
177 common_shutdown(LINUX_REBOOT_CMD_RESTART, restart_cmd);
178}
179
180
181void
182machine_halt(void)
183{
184 common_shutdown(LINUX_REBOOT_CMD_HALT, NULL);
185}
186
187
188void
189machine_power_off(void)
190{
191 common_shutdown(LINUX_REBOOT_CMD_POWER_OFF, NULL);
192}
193
194
195/* Used by sysrq-p, among others. I don't believe r9-r15 are ever
196 saved in the context it's used. */
197
198void
199show_regs(struct pt_regs *regs)
200{
201 show_regs_print_info(KERN_DEFAULT);
202 dik_show_regs(regs, NULL);
203}
204
205/*
206 * Re-start a thread when doing execve()
207 */
208void
209start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
210{
211 regs->pc = pc;
212 regs->ps = 8;
213 wrusp(sp);
214}
215EXPORT_SYMBOL(start_thread);
216
217void
218flush_thread(void)
219{
220 /* Arrange for each exec'ed process to start off with a clean slate
221 with respect to the FPU. This is all exceptions disabled. */
222 current_thread_info()->ieee_state = 0;
223 wrfpcr(FPCR_DYN_NORMAL | ieee_swcr_to_fpcr(0));
224
225 /* Clean slate for TLS. */
226 current_thread_info()->pcb.unique = 0;
227}
228
229void
230release_thread(struct task_struct *dead_task)
231{
232}
233
234/*
235 * Copy architecture-specific thread state
236 */
237int
238copy_thread(unsigned long clone_flags, unsigned long usp,
239 unsigned long kthread_arg,
240 struct task_struct *p)
241{
242 extern void ret_from_fork(void);
243 extern void ret_from_kernel_thread(void);
244
245 struct thread_info *childti = task_thread_info(p);
246 struct pt_regs *childregs = task_pt_regs(p);
247 struct pt_regs *regs = current_pt_regs();
248 struct switch_stack *childstack, *stack;
249
250 childstack = ((struct switch_stack *) childregs) - 1;
251 childti->pcb.ksp = (unsigned long) childstack;
252 childti->pcb.flags = 1; /* set FEN, clear everything else */
253
254 if (unlikely(p->flags & PF_KTHREAD)) {
255 /* kernel thread */
256 memset(childstack, 0,
257 sizeof(struct switch_stack) + sizeof(struct pt_regs));
258 childstack->r26 = (unsigned long) ret_from_kernel_thread;
259 childstack->r9 = usp; /* function */
260 childstack->r10 = kthread_arg;
261 childregs->hae = alpha_mv.hae_cache,
262 childti->pcb.usp = 0;
263 return 0;
264 }
265 /* Note: if CLONE_SETTLS is not set, then we must inherit the
266 value from the parent, which will have been set by the block
267 copy in dup_task_struct. This is non-intuitive, but is
268 required for proper operation in the case of a threaded
269 application calling fork. */
270 if (clone_flags & CLONE_SETTLS)
271 childti->pcb.unique = regs->r20;
272 else
273 regs->r20 = 0; /* OSF/1 has some strange fork() semantics. */
274 childti->pcb.usp = usp ?: rdusp();
275 *childregs = *regs;
276 childregs->r0 = 0;
277 childregs->r19 = 0;
278 childregs->r20 = 1; /* OSF/1 has some strange fork() semantics. */
279 stack = ((struct switch_stack *) regs) - 1;
280 *childstack = *stack;
281 childstack->r26 = (unsigned long) ret_from_fork;
282 return 0;
283}
284
285/*
286 * Fill in the user structure for a ELF core dump.
287 */
288void
289dump_elf_thread(elf_greg_t *dest, struct pt_regs *pt, struct thread_info *ti)
290{
291 /* switch stack follows right below pt_regs: */
292 struct switch_stack * sw = ((struct switch_stack *) pt) - 1;
293
294 dest[ 0] = pt->r0;
295 dest[ 1] = pt->r1;
296 dest[ 2] = pt->r2;
297 dest[ 3] = pt->r3;
298 dest[ 4] = pt->r4;
299 dest[ 5] = pt->r5;
300 dest[ 6] = pt->r6;
301 dest[ 7] = pt->r7;
302 dest[ 8] = pt->r8;
303 dest[ 9] = sw->r9;
304 dest[10] = sw->r10;
305 dest[11] = sw->r11;
306 dest[12] = sw->r12;
307 dest[13] = sw->r13;
308 dest[14] = sw->r14;
309 dest[15] = sw->r15;
310 dest[16] = pt->r16;
311 dest[17] = pt->r17;
312 dest[18] = pt->r18;
313 dest[19] = pt->r19;
314 dest[20] = pt->r20;
315 dest[21] = pt->r21;
316 dest[22] = pt->r22;
317 dest[23] = pt->r23;
318 dest[24] = pt->r24;
319 dest[25] = pt->r25;
320 dest[26] = pt->r26;
321 dest[27] = pt->r27;
322 dest[28] = pt->r28;
323 dest[29] = pt->gp;
324 dest[30] = ti == current_thread_info() ? rdusp() : ti->pcb.usp;
325 dest[31] = pt->pc;
326
327 /* Once upon a time this was the PS value. Which is stupid
328 since that is always 8 for usermode. Usurped for the more
329 useful value of the thread's UNIQUE field. */
330 dest[32] = ti->pcb.unique;
331}
332EXPORT_SYMBOL(dump_elf_thread);
333
334int
335dump_elf_task(elf_greg_t *dest, struct task_struct *task)
336{
337 dump_elf_thread(dest, task_pt_regs(task), task_thread_info(task));
338 return 1;
339}
340EXPORT_SYMBOL(dump_elf_task);
341
342int
343dump_elf_task_fp(elf_fpreg_t *dest, struct task_struct *task)
344{
345 struct switch_stack *sw = (struct switch_stack *)task_pt_regs(task) - 1;
346 memcpy(dest, sw->fp, 32 * 8);
347 return 1;
348}
349EXPORT_SYMBOL(dump_elf_task_fp);
350
351/*
352 * Return saved PC of a blocked thread. This assumes the frame
353 * pointer is the 6th saved long on the kernel stack and that the
354 * saved return address is the first long in the frame. This all
355 * holds provided the thread blocked through a call to schedule() ($15
356 * is the frame pointer in schedule() and $15 is saved at offset 48 by
357 * entry.S:do_switch_stack).
358 *
359 * Under heavy swap load I've seen this lose in an ugly way. So do
360 * some extra sanity checking on the ranges we expect these pointers
361 * to be in so that we can fail gracefully. This is just for ps after
362 * all. -- r~
363 */
364
365static unsigned long
366thread_saved_pc(struct task_struct *t)
367{
368 unsigned long base = (unsigned long)task_stack_page(t);
369 unsigned long fp, sp = task_thread_info(t)->pcb.ksp;
370
371 if (sp > base && sp+6*8 < base + 16*1024) {
372 fp = ((unsigned long*)sp)[6];
373 if (fp > sp && fp < base + 16*1024)
374 return *(unsigned long *)fp;
375 }
376
377 return 0;
378}
379
380unsigned long
381get_wchan(struct task_struct *p)
382{
383 unsigned long schedule_frame;
384 unsigned long pc;
385 if (!p || p == current || p->state == TASK_RUNNING)
386 return 0;
387 /*
388 * This one depends on the frame size of schedule(). Do a
389 * "disass schedule" in gdb to find the frame size. Also, the
390 * code assumes that sleep_on() follows immediately after
391 * interruptible_sleep_on() and that add_timer() follows
392 * immediately after interruptible_sleep(). Ugly, isn't it?
393 * Maybe adding a wchan field to task_struct would be better,
394 * after all...
395 */
396
397 pc = thread_saved_pc(p);
398 if (in_sched_functions(pc)) {
399 schedule_frame = ((unsigned long *)task_thread_info(p)->pcb.ksp)[6];
400 return ((unsigned long *)schedule_frame)[12];
401 }
402 return pc;
403}
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/cpu.h>
13#include <linux/errno.h>
14#include <linux/module.h>
15#include <linux/sched.h>
16#include <linux/sched/debug.h>
17#include <linux/sched/task.h>
18#include <linux/sched/task_stack.h>
19#include <linux/kernel.h>
20#include <linux/mm.h>
21#include <linux/smp.h>
22#include <linux/stddef.h>
23#include <linux/unistd.h>
24#include <linux/ptrace.h>
25#include <linux/user.h>
26#include <linux/time.h>
27#include <linux/major.h>
28#include <linux/stat.h>
29#include <linux/vt.h>
30#include <linux/mman.h>
31#include <linux/elfcore.h>
32#include <linux/reboot.h>
33#include <linux/tty.h>
34#include <linux/console.h>
35#include <linux/slab.h>
36#include <linux/rcupdate.h>
37
38#include <asm/reg.h>
39#include <linux/uaccess.h>
40#include <asm/io.h>
41#include <asm/hwrpb.h>
42#include <asm/fpu.h>
43
44#include "proto.h"
45#include "pci_impl.h"
46
47/*
48 * Power off function, if any
49 */
50void (*pm_power_off)(void) = machine_power_off;
51EXPORT_SYMBOL(pm_power_off);
52
53#ifdef CONFIG_ALPHA_WTINT
54/*
55 * Sleep the CPU.
56 * EV6, LCA45 and QEMU know how to power down, skipping N timer interrupts.
57 */
58void arch_cpu_idle(void)
59{
60 wtint(0);
61}
62
63void __noreturn arch_cpu_idle_dead(void)
64{
65 wtint(INT_MAX);
66 BUG();
67}
68#endif /* ALPHA_WTINT */
69
70struct halt_info {
71 int mode;
72 char *restart_cmd;
73};
74
75static void
76common_shutdown_1(void *generic_ptr)
77{
78 struct halt_info *how = generic_ptr;
79 struct percpu_struct *cpup;
80 unsigned long *pflags, flags;
81 int cpuid = smp_processor_id();
82
83 /* No point in taking interrupts anymore. */
84 local_irq_disable();
85
86 cpup = (struct percpu_struct *)
87 ((unsigned long)hwrpb + hwrpb->processor_offset
88 + hwrpb->processor_size * cpuid);
89 pflags = &cpup->flags;
90 flags = *pflags;
91
92 /* Clear reason to "default"; clear "bootstrap in progress". */
93 flags &= ~0x00ff0001UL;
94
95#ifdef CONFIG_SMP
96 /* Secondaries halt here. */
97 if (cpuid != boot_cpuid) {
98 flags |= 0x00040000UL; /* "remain halted" */
99 *pflags = flags;
100 set_cpu_present(cpuid, false);
101 set_cpu_possible(cpuid, false);
102 halt();
103 }
104#endif
105
106 if (how->mode == LINUX_REBOOT_CMD_RESTART) {
107 if (!how->restart_cmd) {
108 flags |= 0x00020000UL; /* "cold bootstrap" */
109 } else {
110 /* For SRM, we could probably set environment
111 variables to get this to work. We'd have to
112 delay this until after srm_paging_stop unless
113 we ever got srm_fixup working.
114
115 At the moment, SRM will use the last boot device,
116 but the file and flags will be the defaults, when
117 doing a "warm" bootstrap. */
118 flags |= 0x00030000UL; /* "warm bootstrap" */
119 }
120 } else {
121 flags |= 0x00040000UL; /* "remain halted" */
122 }
123 *pflags = flags;
124
125#ifdef CONFIG_SMP
126 /* Wait for the secondaries to halt. */
127 set_cpu_present(boot_cpuid, false);
128 set_cpu_possible(boot_cpuid, false);
129 while (!cpumask_empty(cpu_present_mask))
130 barrier();
131#endif
132
133 /* If booted from SRM, reset some of the original environment. */
134 if (alpha_using_srm) {
135#ifdef CONFIG_DUMMY_CONSOLE
136 /* If we've gotten here after SysRq-b, leave interrupt
137 context before taking over the console. */
138 if (in_hardirq())
139 irq_exit();
140 /* This has the effect of resetting the VGA video origin. */
141 console_lock();
142 do_take_over_console(&dummy_con, 0, MAX_NR_CONSOLES-1, 1);
143 console_unlock();
144#endif
145 pci_restore_srm_config();
146 set_hae(srm_hae);
147 }
148
149 if (alpha_mv.kill_arch)
150 alpha_mv.kill_arch(how->mode);
151
152 if (! alpha_using_srm && how->mode != LINUX_REBOOT_CMD_RESTART) {
153 /* Unfortunately, since MILO doesn't currently understand
154 the hwrpb bits above, we can't reliably halt the
155 processor and keep it halted. So just loop. */
156 return;
157 }
158
159 if (alpha_using_srm)
160 srm_paging_stop();
161
162 halt();
163}
164
165static void
166common_shutdown(int mode, char *restart_cmd)
167{
168 struct halt_info args;
169 args.mode = mode;
170 args.restart_cmd = restart_cmd;
171 on_each_cpu(common_shutdown_1, &args, 0);
172}
173
174void
175machine_restart(char *restart_cmd)
176{
177 common_shutdown(LINUX_REBOOT_CMD_RESTART, restart_cmd);
178}
179
180
181void
182machine_halt(void)
183{
184 common_shutdown(LINUX_REBOOT_CMD_HALT, NULL);
185}
186
187
188void
189machine_power_off(void)
190{
191 common_shutdown(LINUX_REBOOT_CMD_POWER_OFF, NULL);
192}
193
194
195/* Used by sysrq-p, among others. I don't believe r9-r15 are ever
196 saved in the context it's used. */
197
198void
199show_regs(struct pt_regs *regs)
200{
201 show_regs_print_info(KERN_DEFAULT);
202 dik_show_regs(regs, NULL);
203}
204
205/*
206 * Re-start a thread when doing execve()
207 */
208void
209start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
210{
211 regs->pc = pc;
212 regs->ps = 8;
213 wrusp(sp);
214}
215EXPORT_SYMBOL(start_thread);
216
217void
218flush_thread(void)
219{
220 /* Arrange for each exec'ed process to start off with a clean slate
221 with respect to the FPU. This is all exceptions disabled. */
222 current_thread_info()->ieee_state = 0;
223 wrfpcr(FPCR_DYN_NORMAL | ieee_swcr_to_fpcr(0));
224
225 /* Clean slate for TLS. */
226 current_thread_info()->pcb.unique = 0;
227}
228
229/*
230 * Copy architecture-specific thread state
231 */
232int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
233{
234 unsigned long clone_flags = args->flags;
235 unsigned long usp = args->stack;
236 unsigned long tls = args->tls;
237 extern void ret_from_fork(void);
238 extern void ret_from_kernel_thread(void);
239
240 struct thread_info *childti = task_thread_info(p);
241 struct pt_regs *childregs = task_pt_regs(p);
242 struct pt_regs *regs = current_pt_regs();
243 struct switch_stack *childstack, *stack;
244
245 childstack = ((struct switch_stack *) childregs) - 1;
246 childti->pcb.ksp = (unsigned long) childstack;
247 childti->pcb.flags = 1; /* set FEN, clear everything else */
248 childti->status |= TS_SAVED_FP | TS_RESTORE_FP;
249
250 if (unlikely(args->fn)) {
251 /* kernel thread */
252 memset(childstack, 0,
253 sizeof(struct switch_stack) + sizeof(struct pt_regs));
254 childstack->r26 = (unsigned long) ret_from_kernel_thread;
255 childstack->r9 = (unsigned long) args->fn;
256 childstack->r10 = (unsigned long) args->fn_arg;
257 childregs->hae = alpha_mv.hae_cache;
258 memset(childti->fp, '\0', sizeof(childti->fp));
259 childti->pcb.usp = 0;
260 return 0;
261 }
262 /* Note: if CLONE_SETTLS is not set, then we must inherit the
263 value from the parent, which will have been set by the block
264 copy in dup_task_struct. This is non-intuitive, but is
265 required for proper operation in the case of a threaded
266 application calling fork. */
267 if (clone_flags & CLONE_SETTLS)
268 childti->pcb.unique = tls;
269 else
270 regs->r20 = 0; /* OSF/1 has some strange fork() semantics. */
271 childti->pcb.usp = usp ?: rdusp();
272 *childregs = *regs;
273 childregs->r0 = 0;
274 childregs->r19 = 0;
275 childregs->r20 = 1; /* OSF/1 has some strange fork() semantics. */
276 stack = ((struct switch_stack *) regs) - 1;
277 *childstack = *stack;
278 childstack->r26 = (unsigned long) ret_from_fork;
279 return 0;
280}
281
282/*
283 * Fill in the user structure for a ELF core dump.
284 */
285void
286dump_elf_thread(elf_greg_t *dest, struct pt_regs *pt, struct thread_info *ti)
287{
288 /* switch stack follows right below pt_regs: */
289 struct switch_stack * sw = ((struct switch_stack *) pt) - 1;
290
291 dest[ 0] = pt->r0;
292 dest[ 1] = pt->r1;
293 dest[ 2] = pt->r2;
294 dest[ 3] = pt->r3;
295 dest[ 4] = pt->r4;
296 dest[ 5] = pt->r5;
297 dest[ 6] = pt->r6;
298 dest[ 7] = pt->r7;
299 dest[ 8] = pt->r8;
300 dest[ 9] = sw->r9;
301 dest[10] = sw->r10;
302 dest[11] = sw->r11;
303 dest[12] = sw->r12;
304 dest[13] = sw->r13;
305 dest[14] = sw->r14;
306 dest[15] = sw->r15;
307 dest[16] = pt->r16;
308 dest[17] = pt->r17;
309 dest[18] = pt->r18;
310 dest[19] = pt->r19;
311 dest[20] = pt->r20;
312 dest[21] = pt->r21;
313 dest[22] = pt->r22;
314 dest[23] = pt->r23;
315 dest[24] = pt->r24;
316 dest[25] = pt->r25;
317 dest[26] = pt->r26;
318 dest[27] = pt->r27;
319 dest[28] = pt->r28;
320 dest[29] = pt->gp;
321 dest[30] = ti == current_thread_info() ? rdusp() : ti->pcb.usp;
322 dest[31] = pt->pc;
323
324 /* Once upon a time this was the PS value. Which is stupid
325 since that is always 8 for usermode. Usurped for the more
326 useful value of the thread's UNIQUE field. */
327 dest[32] = ti->pcb.unique;
328}
329EXPORT_SYMBOL(dump_elf_thread);
330
331int
332dump_elf_task(elf_greg_t *dest, struct task_struct *task)
333{
334 dump_elf_thread(dest, task_pt_regs(task), task_thread_info(task));
335 return 1;
336}
337EXPORT_SYMBOL(dump_elf_task);
338
339int elf_core_copy_task_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
340{
341 memcpy(fpu, task_thread_info(t)->fp, 32 * 8);
342 return 1;
343}
344
345/*
346 * Return saved PC of a blocked thread. This assumes the frame
347 * pointer is the 6th saved long on the kernel stack and that the
348 * saved return address is the first long in the frame. This all
349 * holds provided the thread blocked through a call to schedule() ($15
350 * is the frame pointer in schedule() and $15 is saved at offset 48 by
351 * entry.S:do_switch_stack).
352 *
353 * Under heavy swap load I've seen this lose in an ugly way. So do
354 * some extra sanity checking on the ranges we expect these pointers
355 * to be in so that we can fail gracefully. This is just for ps after
356 * all. -- r~
357 */
358
359static unsigned long
360thread_saved_pc(struct task_struct *t)
361{
362 unsigned long base = (unsigned long)task_stack_page(t);
363 unsigned long fp, sp = task_thread_info(t)->pcb.ksp;
364
365 if (sp > base && sp+6*8 < base + 16*1024) {
366 fp = ((unsigned long*)sp)[6];
367 if (fp > sp && fp < base + 16*1024)
368 return *(unsigned long *)fp;
369 }
370
371 return 0;
372}
373
374unsigned long
375__get_wchan(struct task_struct *p)
376{
377 unsigned long schedule_frame;
378 unsigned long pc;
379
380 /*
381 * This one depends on the frame size of schedule(). Do a
382 * "disass schedule" in gdb to find the frame size. Also, the
383 * code assumes that sleep_on() follows immediately after
384 * interruptible_sleep_on() and that add_timer() follows
385 * immediately after interruptible_sleep(). Ugly, isn't it?
386 * Maybe adding a wchan field to task_struct would be better,
387 * after all...
388 */
389
390 pc = thread_saved_pc(p);
391 if (in_sched_functions(pc)) {
392 schedule_frame = ((unsigned long *)task_thread_info(p)->pcb.ksp)[6];
393 return ((unsigned long *)schedule_frame)[12];
394 }
395 return pc;
396}