Imbus/xv6-riscv-kernel
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Initial version of single-cpu xv6 with page tables

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This commit is contained in:
Frans Kaashoek 2010-07-02 14:51:53 -04:00
parent b7a517f227
commit 40889627ba
22 changed files with 307 additions and 152 deletions
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90
exec.c
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@ -11,12 +11,13 @@ exec(char *path, char **argv)
{
char *mem, *s, *last;
int i, argc, arglen, len, off;
uint sz, sp, argp;
uint sz, sp, spoffset, argp;
struct elfhdr elf;
struct inode *ip;
struct proghdr ph;
pde_t *pgdir, *oldpgdir;
mem = 0;
pgdir = 0;
sz = 0;
if((ip = namei(path)) == 0)
@ -29,37 +30,8 @@ exec(char *path, char **argv)
if(elf.magic != ELF_MAGIC)
goto bad;
// Compute memory size of new process.
// Program segments.
for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph))
goto bad;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.memsz < ph.filesz)
goto bad;
sz += ph.memsz;
}
// Arguments.
arglen = 0;
for(argc=0; argv[argc]; argc++)
arglen += strlen(argv[argc]) + 1;
arglen = (arglen+3) & ~3;
sz += arglen;
sz += 4*(argc+1); // argv data
sz += 4; // argv
sz += 4; // argc
// Stack.
sz += PAGE;
// Allocate program memory.
sz = (sz+PAGE-1) & ~(PAGE-1);
mem = kalloc(sz);
if(mem == 0)
if (!(pgdir = setupkvm()))
goto bad;
memset(mem, 0, sz);
// Load program into memory.
for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
@ -67,37 +39,48 @@ exec(char *path, char **argv)
goto bad;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.va + ph.memsz < ph.va || ph.va + ph.memsz > sz)
goto bad;
if(ph.memsz < ph.filesz)
goto bad;
if(readi(ip, mem + ph.va, ph.offset, ph.filesz) != ph.filesz)
if (!allocuvm(pgdir, (char *)ph.va, ph.memsz))
goto bad;
sz += PGROUNDUP(ph.memsz);
if (!loaduvm(pgdir, (char *)ph.va, ip, ph.offset, ph.filesz))
goto bad;
memset(mem + ph.va + ph.filesz, 0, ph.memsz - ph.filesz);
}
iunlockput(ip);
// Initialize stack.
// Allocate and initialize stack at sz
if (!allocuvm(pgdir, (char *)sz, PGSIZE))
goto bad;
mem = uva2ka(pgdir, (char *)sz);
spoffset = sz;
sz += PGSIZE;
arglen = 0;
for(argc=0; argv[argc]; argc++)
arglen += strlen(argv[argc]) + 1;
arglen = (arglen+3) & ~3;
sp = sz;
argp = sz - arglen - 4*(argc+1);
// Copy argv strings and pointers to stack.
*(uint*)(mem+argp + 4*argc) = 0; // argv[argc]
*(uint*)(mem+argp-spoffset + 4*argc) = 0; // argv[argc]
for(i=argc-1; i>=0; i--){
len = strlen(argv[i]) + 1;
sp -= len;
memmove(mem+sp, argv[i], len);
*(uint*)(mem+argp + 4*i) = sp; // argv[i]
memmove(mem+sp-spoffset, argv[i], len);
*(uint*)(mem+argp-spoffset + 4*i) = sp; // argv[i]
}
// Stack frame for main(argc, argv), below arguments.
sp = argp;
sp -= 4;
*(uint*)(mem+sp) = argp;
*(uint*)(mem+sp-spoffset) = argp;
sp -= 4;
*(uint*)(mem+sp) = argc;
*(uint*)(mem+sp-spoffset) = argc;
sp -= 4;
*(uint*)(mem+sp) = 0xffffffff; // fake return pc
*(uint*)(mem+sp-spoffset) = 0xffffffff; // fake return pc
// Save program name for debugging.
for(last=s=path; *s; s++)
@ -105,18 +88,25 @@ exec(char *path, char **argv)
last = s+1;
safestrcpy(proc->name, last, sizeof(proc->name));
// Commit to the new image.
kfree(proc->mem, proc->sz);
proc->mem = mem;
// Commit to the user image.
oldpgdir = proc->pgdir;
proc->pgdir = pgdir;
proc->sz = sz;
proc->tf->eip = elf.entry; // main
proc->tf->esp = sp;
usegment();
// printstack();
loadvm(proc);
freevm(oldpgdir);
// printstack();
return 0;
bad:
if(mem)
kfree(mem, sz);
freevm(pgdir);
iunlockput(ip);
return -1;
}