d0f7acf9eb
An x86-64 operating system built from xv6, now largely rewritten: SMP, a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF rasteriser, and a Linux-numbered syscall ABI. No history before this point -- the tree was never under version control. This commit exists so the rename that follows has something to undo to.
241 lines
6.9 KiB
C
241 lines
6.9 KiB
C
#include "types.h"
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#include "traps.h"
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#include "param.h"
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#include "memlayout.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 "elf.h"
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#include "fcntl.h"
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#include "errno.h"
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// Binaries with entry points at 0x100000+ are musl/Linux-ABI.
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// Schunix-native binaries (init) are linked at 0x4000.
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#define LINUX_ABI_ENTRY_THRESHOLD 0x100000UL
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extern int linux_syscall_map[];
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extern int linux_syscall_map_size;
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int
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exec(char *path, char **argv)
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{
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char *s, *last;
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int i, off;
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uint64 argc, sz, sp, ustack[MAXARG+1];
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struct elfhdr elf;
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struct inode *ip;
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struct proghdr ph;
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pml4e_t *pgdir, *oldpgdir;
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uint64 stack_slots[MAXARG + 32];
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int slot;
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uint64 max_sz = 0;
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uint64 rand_va = 0;
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begin_op();
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if((ip = namei(path)) == 0){
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end_op();
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// Must be ENOENT, not a bare -1: execvp() relies on this exact errno to
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// know it should try the next $PATH component rather than give up.
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return -ENOENT;
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}
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ilock(ip);
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pgdir = 0;
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if(readi(ip, 0, (uint64)&elf, 0, sizeof(elf)) != sizeof(elf))
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goto bad;
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if(elf.magic != ELF_MAGIC)
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goto bad;
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if((pgdir = setupkvm()) == 0)
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goto bad;
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for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=elf.phentsize){
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if(readi(ip, 0, (uint64)&ph, off, sizeof(ph)) != sizeof(ph))
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goto bad;
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if(ph.type != ELF_PROG_LOAD)
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continue;
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if(ph.memsz < ph.filesz)
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goto bad;
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if(ph.vaddr + ph.memsz < ph.vaddr)
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goto bad;
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uint64 start = ph.vaddr & ~0xFFF;
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uint64 end = ph.vaddr + ph.memsz;
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if(allocuvm(pgdir, start, end) == 0)
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goto bad;
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if(loaduvm(pgdir, (char*)ph.vaddr, ip, ph.off, ph.filesz) < 0)
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goto bad;
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if(end > max_sz)
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max_sz = end;
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}
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iunlockput(ip);
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end_op();
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ip = 0;
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sz = PGROUNDUP(max_sz);
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if((sz = allocuvm(pgdir, sz, sz + 64*PGSIZE)) == 0)
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goto bad;
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clearpteu(pgdir, (char*)(sz - 64*PGSIZE));
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sp = sz;
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for(argc = 0; argv[argc]; argc++) {
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if(argc >= MAXARG)
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goto bad;
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sp -= strlen(argv[argc]) + 1;
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sp &= ~7;
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if(copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
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goto bad;
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ustack[argc] = sp;
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}
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// Push 16 pseudo-random bytes for AT_RANDOM.
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{
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uint8 randbuf[16];
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uint rseed = (uint)(uintptr_t)myproc() ^ (uint)myproc()->pid;
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for(int ri = 0; ri < 16; ri++){
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rseed = rseed * 1664525u + 1013904223u;
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randbuf[ri] = (uint8)(rseed >> 16);
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}
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sp -= 16; sp &= ~0xFUL;
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rand_va = sp;
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if(copyout(pgdir, rand_va, (char*)randbuf, 16) < 0) goto bad;
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}
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slot = 0;
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stack_slots[slot++] = argc;
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for(i = 0; i < argc; i++) {
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stack_slots[slot++] = ustack[i];
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}
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stack_slots[slot++] = 0; // end of argv
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stack_slots[slot++] = 0; // end of envp (no environment)
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// Auxiliary vector — musl reads these for page size, clock, etc.
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stack_slots[slot++] = 6; // AT_PAGESZ
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stack_slots[slot++] = 4096;
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stack_slots[slot++] = 17; // AT_CLKTCK
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stack_slots[slot++] = 100;
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stack_slots[slot++] = 23; // AT_SECURE = 0 (not setuid)
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stack_slots[slot++] = 0;
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stack_slots[slot++] = 11; // AT_UID
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stack_slots[slot++] = 0;
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stack_slots[slot++] = 12; // AT_EUID
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stack_slots[slot++] = 0;
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stack_slots[slot++] = 13; // AT_GID
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stack_slots[slot++] = 0;
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stack_slots[slot++] = 14; // AT_EGID
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stack_slots[slot++] = 0;
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stack_slots[slot++] = 16; // AT_HWCAP
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stack_slots[slot++] = 0;
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stack_slots[slot++] = 25; // AT_RANDOM
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stack_slots[slot++] = rand_va;
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stack_slots[slot++] = 0; // AT_NULL
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stack_slots[slot++] = 0;
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sp -= slot * sizeof(uint64);
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sp &= ~0xF;
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if(copyout(pgdir, sp, (char*)stack_slots, slot * sizeof(uint64)) < 0)
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goto bad;
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for(last=s=path; *s; s++)
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if(*s == '/')
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last = s+1;
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safestrcpy(myproc()->name, last, sizeof(myproc()->name));
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safestrcpy(myproc()->exe, path, sizeof(myproc()->exe));
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for(int i = 0; i < NOFILE; i++){
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if(myproc()->ofile[i] && (myproc()->ofile_flags[i] & FD_CLOEXEC)){
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fileclose(myproc()->ofile[i]);
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myproc()->ofile[i] = 0;
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myproc()->ofile_flags[i] = 0;
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}
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}
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// Auto-select syscall ABI: musl binaries have entry >= 0x100000;
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// Schunix-native binaries (init) are linked at 0x4000.
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if (elf.entry >= LINUX_ABI_ENTRY_THRESHOLD) {
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myproc()->syscall_map = linux_syscall_map;
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myproc()->map_size = linux_syscall_map_size;
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} else {
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myproc()->syscall_map = 0;
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myproc()->map_size = 0;
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}
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// Detach shared segments before anything forgets which mappings they were.
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//
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// This has to happen while myproc()->pgdir and myproc()->vma[] still describe the
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// *old* image: the memset below erases the bookkeeping, and freevm() at the
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// end would then free a shared memory segment's pages as though they were
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// ordinary heap. Doing it here rather than there is the difference between
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// detaching a segment and corrupting whoever else has it mapped.
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proc_release_shared(myproc());
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oldpgdir = myproc()->pgdir;
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myproc()->pgdir = pgdir;
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myproc()->sz = sz;
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// New address space: reset all per-process mmap/signal/TLS state.
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// sig_handler/sig_restorer point into the *old* image — POSIX resets
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// handled signals to default on exec, and keeping them would make the
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// first delivered signal jump to a stale address in the new image.
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// mmap_next likewise belongs to the old address space; left alone it
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// could hand out mmap ranges overlapping the new image's layout.
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memset(myproc()->vma, 0, sizeof(myproc()->vma));
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memset(myproc()->sig_handler, 0, sizeof(myproc()->sig_handler));
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memset(myproc()->sig_restorer, 0, sizeof(myproc()->sig_restorer));
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myproc()->fs_base = 0;
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myproc()->signal_mask = 0;
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myproc()->pending_signals = 0;
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myproc()->in_signal = 0;
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myproc()->sigsusp_active = 0;
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myproc()->mmap_next = 0;
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myproc()->tf->rax = 0;
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myproc()->tf->rbx = 0;
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myproc()->tf->rdx = 0;
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myproc()->tf->rbp = 0;
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myproc()->tf->r8 = 0;
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myproc()->tf->r9 = 0;
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myproc()->tf->r10 = 0;
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myproc()->tf->r11 = 0x200; // RFLAGS for sysretq: IF=1 (bit 9) so user gets timer IRQs
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myproc()->tf->r12 = 0;
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myproc()->tf->r13 = 0;
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myproc()->tf->r14 = 0;
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myproc()->tf->r15 = 0;
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myproc()->tf->rdi = argc;
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myproc()->tf->rsi = sp + 8;
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myproc()->tf->rip = elf.entry;
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myproc()->tf->rcx = elf.entry;
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myproc()->tf->rsp = sp;
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// syscall_entry saves user RSP at kstack+PGSIZE-16 (not in the trapframe).
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// sysretq reads RSP from that slot, so update it to the new stack pointer.
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// Without this, sysretq returns with the old parent's RSP, causing lksh to
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// start with an invalid/wrong stack pointer.
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*(uint64*)((char*)myproc()->kstack + PGSIZE - 16) = sp;
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// Userspace is running now, so the splash has done its job and the display
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// becomes a terminal. Only the first exec does anything; every later one
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// finds the console already in charge.
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console_takeover();
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switchuvm(myproc());
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freevm(oldpgdir);
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return 0;
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bad:
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if(pgdir)
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freevm(pgdir);
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if(ip){
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iunlockput(ip);
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end_op();
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}
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return -1;
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}
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