5ce9751cab
Linux 2.4 box using gcc 3.4.6 don't seem to follow the same
conventions as the i386-jos-elf-gcc compilers.
Can run make 'TOOLPREFIX=' or edit the Makefile.
curproc[cpu()] can now be NULL, indicating that no proc is running.
This seemed safer to me than having curproc[0] and curproc[1]
both pointing at proc[0] potentially.
The old implementation of swtch depended on the stack frame layout
used inside swtch being okay to return from on the other stack
(exactly the V6 you are not expected to understand this).
It also could be called in two contexts: at boot time, to schedule
the very first process, and later, on behalf of a process, to sleep
or schedule some other process.
I split this into two functions: scheduler and swtch.
The scheduler is now a separate never-returning function, invoked
by each cpu once set up. The scheduler looks like:
scheduler() {
setjmp(cpu.context);
pick proc to schedule
blah blah blah
longjmp(proc.context)
}
The new swtch is intended to be called only when curproc[cpu()] is not NULL,
that is, only on behalf of a user proc. It does:
swtch() {
if(setjmp(proc.context) == 0)
longjmp(cpu.context)
}
to save the current proc context and then jump over to the scheduler,
running on the cpu stack.
Similarly the system call stubs are now in assembly in usys.S to avoid
needing to know the details of stack frame layout used by the compiler.
Also various changes in the debugging prints.
111 lines
2.8 KiB
C
111 lines
2.8 KiB
C
#include "types.h"
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#include "param.h"
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#include "mmu.h"
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#include "proc.h"
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#include "defs.h"
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#include "x86.h"
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#include "traps.h"
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#include "syscall.h"
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#include "elf.h"
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#include "param.h"
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extern char edata[], end[];
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extern int acpu;
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extern char _binary_user1_start[], _binary_user1_size[];
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extern char _binary_usertests_start[], _binary_usertests_size[];
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extern char _binary_userfs_start[], _binary_userfs_size[];
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char buf[512];
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int
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main()
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{
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struct proc *p;
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if (acpu) {
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cprintf("an application processor\n");
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release_spinlock(&kernel_lock);
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acquire_spinlock(&kernel_lock);
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idtinit(); // CPU's idt
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lapic_init(cpu());
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scheduler();
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}
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acpu = 1;
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// clear BSS
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memset(edata, 0, end - edata);
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cprintf("\nxV6\n\n");
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pic_init(); // initialize PIC
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mp_init(); // multiprocessor
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kinit(); // physical memory allocator
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tvinit(); // trap vectors
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idtinit(); // CPU's idt
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// create fake process zero
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p = &proc[0];
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memset(p, 0, sizeof *p);
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p->state = WAITING;
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p->sz = 4 * PAGE;
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p->mem = kalloc(p->sz);
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memset(p->mem, 0, p->sz);
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p->kstack = kalloc(KSTACKSIZE);
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p->tf = (struct Trapframe *) (p->kstack + KSTACKSIZE - sizeof(struct Trapframe));
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memset(p->tf, 0, sizeof(struct Trapframe));
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p->tf->tf_es = p->tf->tf_ds = p->tf->tf_ss = (SEG_UDATA << 3) | 3;
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p->tf->tf_cs = (SEG_UCODE << 3) | 3;
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p->tf->tf_eflags = FL_IF;
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p->pid = 0;
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p->ppid = 0;
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setupsegs(p);
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// turn on timer and enable interrupts on the local APIC
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lapic_timerinit();
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lapic_enableintr();
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// init disk device
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ide_init();
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// become interruptable
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write_eflags(read_eflags() | FL_IF);
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p = newproc();
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// load_icode(p, _binary_usertests_start, (unsigned) _binary_usertests_size);
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load_icode(p, _binary_userfs_start, (unsigned) _binary_userfs_size);
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cprintf("loaded userfs\n");
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scheduler();
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return 0;
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}
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void
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load_icode(struct proc *p, uint8_t *binary, unsigned size)
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{
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int i;
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struct Elf *elf;
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struct Proghdr *ph;
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// Check magic number on binary
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elf = (struct Elf*) binary;
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cprintf("elf %x magic %x\n", elf, elf->e_magic);
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if (elf->e_magic != ELF_MAGIC)
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panic("load_icode: not an ELF binary");
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p->tf->tf_eip = elf->e_entry;
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p->tf->tf_esp = p->sz;
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// Map and load segments as directed.
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ph = (struct Proghdr*) (binary + elf->e_phoff);
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for (i = 0; i < elf->e_phnum; i++, ph++) {
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if (ph->p_type != ELF_PROG_LOAD)
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continue;
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cprintf("va %x memsz %d\n", ph->p_va, ph->p_memsz);
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if (ph->p_va + ph->p_memsz < ph->p_va)
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panic("load_icode: overflow in elf header segment");
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if (ph->p_va + ph->p_memsz >= p->sz)
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panic("load_icode: icode wants to be above UTOP");
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// Load/clear the segment
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memcpy(p->mem + ph->p_va, binary + ph->p_offset, ph->p_filesz);
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memset(p->mem + ph->p_va + ph->p_filesz, 0, ph->p_memsz - ph->p_filesz);
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}
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}
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