diff options
Diffstat (limited to 'kc/core/cpu/cpu_task.S')
| -rw-r--r-- | kc/core/cpu/cpu_task.S | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/kc/core/cpu/cpu_task.S b/kc/core/cpu/cpu_task.S new file mode 100644 index 0000000..f2fb473 --- /dev/null +++ b/kc/core/cpu/cpu_task.S @@ -0,0 +1,45 @@ +/* thread switching routines for x86_64 +* adapted from: +* https://wiki.osdev.org/Brendan%27s_Multi-tasking_Tutorial +* +* +*/ + +.hidden cpu_set_thread +.global cpu_set_thread +.type cpu_set_thread, @function +cpu_set_thread: + /* x86_64 SysV ABI + * must save the following registers to the stack: + * rbx, rsp, rbp, r12, r13, r14, r15 + * the following are the parameters for switching tasks + * rdi: pointer to control block of thread being switched to + * rsi: pointer to control block of the current thread + * rdx: pointer to this cpu's task state segment esp0 field + */ + push %rbx + push %r12 + push %r13 + push %r14 + push %r15 + push %rbp + /* the current task will be in rsi */ + mov %esp, 0(%rsi) // save the stack pointer for the current task + mov 0(%rdi),%rsp // new stack is the next's task's stack + mov 8(%rdi),%rbx // top of the next task's kernel stack + mov %rbx,0(%rdx) // save the esp0 to the tss + mov 16(%rdi),%rax // page map for the next task + mov %cr3, %rcx // in case we need to change the page map + cmp %rax,%rcx + je .Lfinish + mov %rax,%cr3 // if the page maps are not the same, reload +.Lfinish: + pop %rbp // get all the registers off the new task's stack + pop %r15 + pop %r14 + pop %r13 + pop %r12 + pop %rbx + ret // leave into the new task +.size cpu_set_thread, . - cpu_set_thread + |