1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
|
/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Copyright (C) 2026 Richard Qin */
/*
* Context Switch & Kernel Thread Trampoline (RISC-V 64)
*
* context_switch: saves/restores callee-saved registers.
* kthread_entry_trampoline: entry point for newly created kernel threads.
* After context_switch loads the new Context, execution lands here via
* Context.ra = kthread_entry_trampoline. The entry function and argument
* are in s0 and s1 respectively, set by sched_init/create_tcb.
*
* The trampoline calls the MI-layer kthread_entry(entry, arg).
*
* Reference: docs/specs/scheduler.md §6
*/
.section .text
/* ========================================================================
* void context_switch(Context* old_ctx, Context* next_ctx);
* a0 = old_ctx_ptr, a1 = next_ctx_ptr
* ======================================================================== */
.globl context_switch
.align 2
context_switch:
sd ra, 0(a0)
sd sp, 8(a0)
sd s0, 16(a0)
sd s1, 24(a0)
sd s2, 32(a0)
sd s3, 40(a0)
sd s4, 48(a0)
sd s5, 56(a0)
sd s6, 64(a0)
sd s7, 72(a0)
sd s8, 80(a0)
sd s9, 88(a0)
sd s10, 96(a0)
sd s11, 104(a0)
ld ra, 0(a1)
ld sp, 8(a1)
ld s0, 16(a1)
ld s1, 24(a1)
ld s2, 32(a1)
ld s3, 40(a1)
ld s4, 48(a1)
ld s5, 56(a1)
ld s6, 64(a1)
ld s7, 72(a1)
ld s8, 80(a1)
ld s9, 88(a1)
ld s10, 96(a1)
ld s11, 104(a1)
ret
/* ========================================================================
* kthread_entry_trampoline
*
* Reached via context_switch when a new kthread is first scheduled.
* Context was set up by create_tcb():
* s0 = entry function pointer
* s1 = argument pointer
*
* Calls the MI-layer C++ function:
* void kthread_entry(void (*entry)(void*), void* arg);
* ======================================================================== */
.globl kthread_entry_trampoline
.align 2
kthread_entry_trampoline:
mv a0, s0 /* a0 = entry function */
mv a1, s1 /* a1 = argument */
call kthread_entry /* MI-layer C++ function */
/* kthread_entry should never return, but if it does: */
wfi
j kthread_entry_trampoline + 12 /* loop on wfi */
|
