139 lines
3.1 KiB
C
139 lines
3.1 KiB
C
/*
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libco.amd64 (2016-09-14)
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author: byuu
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license: public domain
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*/
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#include "libco.h"
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#include <stdint.h>
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#include <assert.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <emulibc.h>
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// allocations are 16k larger than asked for,
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// and include guard space between the stack and the storage
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typedef struct {
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// used by coswap.s, has to be at the beginning of the struct
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uint64_t jmp_buf[32];
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// points to the lowest address in the stack
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void* stack;
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// length of the stack that we allocated in bytes
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uint64_t stack_size;
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} cothread_impl;
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// the cothread that represents the real host thread we started from
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static cothread_impl co_host_buffer;
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// what cothread are we in right now
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static cothread_impl* co_active_handle;
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static cothread_impl* alloc_thread(uint64_t size)
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{
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cothread_impl* co = calloc(1, sizeof(*co));
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if (!co)
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return NULL;
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// align up to 4k
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size = (size + 4095) & ~4095;
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co->stack = mmap(NULL, size,
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PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_STACK, -1, 0);
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if (co->stack == (void*)(-1))
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{
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free(co);
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return NULL;
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}
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co->stack_size = size;
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return co;
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}
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static void free_thread(cothread_impl* co)
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{
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if (munmap(co->stack, co->stack_size) != 0)
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abort();
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free(co);
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}
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extern void co_swap(cothread_impl*, cothread_impl*);
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static void crash(void)
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{
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__asm__("int3"); // called only if cothread_t entrypoint returns
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}
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ECL_EXPORT void co_clean(void)
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{
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memset(&co_host_buffer, 0, sizeof(co_host_buffer));
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}
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cothread_t co_active(void)
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{
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if (!co_active_handle)
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co_active_handle = &co_host_buffer;
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return co_active_handle;
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}
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cothread_t co_create(unsigned int sz, void (*entrypoint)(void))
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{
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cothread_impl* co;
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if (!co_active_handle)
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co_active_handle = &co_host_buffer;
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if ((co = alloc_thread(sz)))
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{
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uint64_t* p = (uint64_t*)((char*)co->stack + co->stack_size); // seek to top of stack
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*--p = (uint64_t)crash; // crash if entrypoint returns
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*--p = (uint64_t)entrypoint; // start of function
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co->jmp_buf[0] = (uint64_t)p; // stack pointer
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}
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return co;
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}
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void co_delete(cothread_t handle)
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{
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free_thread(handle);
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}
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static uint64_t hoststart;
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static uint64_t hostend;
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void co_switch(cothread_t handle)
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{
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cothread_impl* co = handle;
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uint64_t start;
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uint64_t end;
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if (co_active_handle == &co_host_buffer)
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{
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// migrating off of real thread; save stack params
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__asm__("movq %%gs:0x08, %0": "=r"(end));
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__asm__("movq %%gs:0x10, %0": "=r"(start));
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hoststart = start;
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hostend = end;
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}
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if (handle == &co_host_buffer)
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{
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// migrating onto real thread; load stack params
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start = hoststart;
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end = hostend;
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hoststart = 0;
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hostend = 0;
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}
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else
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{
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// migrating onto cothread; compute its extents we allocated them
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start = (uintptr_t)co->stack;
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end = start + co->stack_size;
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}
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__asm__("movq %0, %%gs:0x08":: "r"(end));
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__asm__("movq %0, %%gs:0x10":: "r"(start));
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register cothread_impl* co_previous_handle = co_active_handle;
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co_swap(co_active_handle = co, co_previous_handle);
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}
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