thread.c

Go to the documentation of this file.

/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <thread.h>
 
#if ENV_X86_64
#error COOP_MULTITASKING does not currently support x86_64
#endif
 
/* The stack frame looks like the following after a pushad instruction. */
struct pushad_regs {
        uint32_t edi; /* Offset 0x00 */
        uint32_t esi; /* Offset 0x04 */
        uint32_t ebp; /* Offset 0x08 */
        uint32_t esp; /* Offset 0x0c */
        uint32_t ebx; /* Offset 0x10 */
        uint32_t edx; /* Offset 0x14 */
        uint32_t ecx; /* Offset 0x18 */
        uint32_t eax; /* Offset 0x1c */
};
 
static inline uintptr_t push_stack(uintptr_t cur_stack, uintptr_t value)
{
        uintptr_t *addr;
 
        cur_stack -= sizeof(value);
        addr = (uintptr_t *)cur_stack;
        *addr = value;
        return cur_stack;
}
 
void arch_prepare_thread(struct thread *t,
                        asmlinkage void (*thread_entry)(void *), void *arg)
{
        uintptr_t stack = t->stack_current;
 
        /* Imitate thread_entry(t) with return address of 0. thread_entry()
         * is assumed to never return. */
        stack = push_stack(stack, (uintptr_t)arg);
        stack = push_stack(stack, (uintptr_t)0);
        stack = push_stack(stack, (uintptr_t)thread_entry);
        /* Make room for the registers. Ignore initial values. */
        stack -= sizeof(struct pushad_regs);
 
        t->stack_current = stack;
}