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/* uctx.h - assembly stack switching
*
* Copyright (C) 2009 Timo Teräs <timo.teras@iki.fi>
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 or later as
* published by the Free Software Foundation.
*
* See http://www.gnu.org/ for details.
*/
#include <libtf/fiber.h>
#include <stdio.h>
#include <stdlib.h>
#ifdef VALGRIND
#include <valgrind/valgrind.h>
#else
#define VALGRIND_STACK_REGISTER(stack_base, size) 0
#define VALGRIND_STACK_DEREGISTER(stack_id)
#endif
#define STACK_GUARD 0xbad57ac4
struct tf_uctx {
int *stack_guard;
void *alloc;
void *current_sp;
unsigned int stack_id;
};
#if defined(__i386__)
#define switch_fiber(prev, next) \
do { \
unsigned eax, ebx, ecx, edx, esi, edi; \
__asm__ __volatile__ ( \
"push %%ebp \n" \
"call 1f \n" \
"1: \n" \
"addl $2f-1b, (%%esp) \n" \
"movl %%esp, %[prev_sp] \n" \
"movl %[next_sp], %%esp \n" \
"ret \n" \
"2: \n" \
"pop %%ebp \n" \
: [prev_sp] "=m"(prev->current_sp), \
"=a"(eax), "=b"(ebx), "=c"(ecx), \
"=d"(edx), "=S"(esi), "=D"(edi) \
: [next_sp] "m"(next->current_sp) \
: "memory", "cc"); \
} while (0)
#define STACK_GROWS_UP
#else
#error Your architecture is not supported. Contact timo.teras@iki.fi.
#endif
#if defined(STACK_GROWS_UP)
static inline void *stack_pointer(void *base, size_t size)
{
return base + size;
}
static inline void *stack_guard(void *base, size_t size)
{
return base;
}
static inline void *stack_push(void **stackptr, size_t size)
{
(*stackptr) -= size;
return (*stackptr);
}
#else
#error Stack growing direction undefined.
#endif
static inline void stack_push_ptr(void **stackptr, void *ptr)
{
*(void**) stack_push(stackptr, sizeof(ptr)) = ptr;
}
static inline void tf_uctx_create_self(struct tf_uctx *uctx)
{
static int dummy_guard = STACK_GUARD;
*uctx = (struct tf_uctx) {
.stack_guard = &dummy_guard,
};
}
static inline void *
tf_uctx_create_embedded(
size_t stack_size,
size_t private_size,
off_t uctx_offset,
void (*stack_frame_main)(void*), off_t main_argument_offset,
void (*stack_frame_return)(void))
{
size_t size = TF_STACK_SIZE;
void *user_data;
struct tf_uctx *uctx;
void *stack, *stack_base;
/* Allocate new stack */
stack_base = malloc(size);
if (stack_base == NULL)
return NULL;
/* Create initial stack frame (cdecl convention) */
stack = stack_pointer(stack_base, size);
user_data = stack_push(&stack, TF_ALIGN(private_size, 64));
stack_push_ptr(&stack, NULL);
stack_push_ptr(&stack, NULL);
stack_push_ptr(&stack, NULL);
stack_push_ptr(&stack, NULL);
stack_push_ptr(&stack, user_data + main_argument_offset);
stack_push_ptr(&stack, stack_frame_return);
stack_push_ptr(&stack, stack_frame_main);
uctx = user_data + uctx_offset;
*uctx = (struct tf_uctx) {
.stack_guard = stack_guard(stack_base, size),
.alloc = stack_base,
.current_sp = stack,
.stack_id = VALGRIND_STACK_REGISTER(stack_base, size),
};
*uctx->stack_guard = STACK_GUARD;
return user_data;
}
static inline
void tf_uctx_destroy(struct tf_uctx *uctx)
{
if (uctx->alloc != NULL) {
VALGRIND_STACK_DEREGISTER(uctx->stack_id);
free(uctx->alloc);
}
}
static inline
void tf_uctx_transfer(struct tf_uctx *from, struct tf_uctx *to)
{
/* Switch stack pointers */
TF_BUG_ON(*from->stack_guard != STACK_GUARD);
switch_fiber(from, to);
}
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