process.h

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#ifndef WEENSYOS_PROCESS_H
#define WEENSYOS_PROCESS_H
#include "lib.h"
#include "x86-64.h"
#if WEENSYOS_KERNEL
#error "process.h should not be used by kernel code."
#endif

// process.h
//
//    Support code for WeensyOS processes.


// SYSTEM CALLS

// sys_getpid
//    Return current process ID.
static inline pid_t sys_getpid(void) {
    pid_t result;
    asm volatile ("int %1" : "=a" (result)
                  : "i" (INT_SYS_GETPID)
                  : "cc", "memory");
    return result;
}

// sys_yield
//    Yield control of the CPU to the kernel. The kernel will pick another
//    process to run, if possible.
static inline void sys_yield(void) {
    asm volatile ("int %0" : /* no result */
                  : "i" (INT_SYS_YIELD)
                  : "cc", "memory");
}

// sys_page_alloc(addr)
//    Allocate a page of memory at address `addr`. `Addr` must be page-aligned
//    (i.e., a multiple of PAGESIZE == 4096). Returns 0 on success and -1
//    on failure.
static inline int sys_page_alloc(void* addr) {
    int result;
    asm volatile ("int %1" : "=a" (result)
                  : "i" (INT_SYS_PAGE_ALLOC), "D" /* %rdi */ (addr)
                  : "cc", "memory");
    return result;
}

// sys_fork()
//    Fork the current process. On success, return the child's process ID to
//    the parent, and return 0 to the child. On failure, return -1.
static inline pid_t sys_fork(void) {
    pid_t result;
    asm volatile ("int %1" : "=a" (result)
                  : "i" (INT_SYS_FORK)
                  : "cc", "memory");
    return result;
}

// sys_exit()
//    Exit this process. Does not return.
static inline void sys_exit(void) __attribute__((noreturn));
static inline void sys_exit(void) {
    asm volatile ("int %0" : /* no result */
                  : "i" (INT_SYS_EXIT)
                  : "cc", "memory");
 spinloop: goto spinloop;       // should never get here
}

// sys_panic(msg)
//    Panic.
static inline pid_t __attribute__((noreturn)) sys_panic(const char* msg) {
    asm volatile ("int %0" : /* no result */
                  : "i" (INT_SYS_PANIC), "D" (msg)
                  : "cc", "memory");
 loop: goto loop;
}


// OTHER HELPER FUNCTIONS

// app_printf(format, ...)
//    Calls console_printf() (see lib.h). The cursor position is read from
//    `cursorpos`, a shared variable defined by the kernel, and written back
//    into that variable. The initial color is based on the current process ID.
void app_printf(int colorid, const char* format, ...);

#endif