Imbus/xv6-riscv-kernel
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Simplify allocuvm/deallocuvm to operate in a contiguous memory model. This makes their interface match up better with proc->sz and also simplifies the callers (it even gets the main body of exec on one page).

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This commit is contained in:
Austin Clements 2010-09-02 18:28:36 -04:00
parent d49d31381d
commit 79cd8b3eed
4 changed files with 44 additions and 51 deletions
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26
exec.c
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@ -11,7 +11,7 @@ exec(char *path, char **argv)
{
char *mem, *s, *last;
int i, argc, arglen, len, off;
uint sz, sp, spoffset, argp;
uint sz, sp, spbottom, argp;
struct elfhdr elf;
struct inode *ip;
struct proghdr ph;
@ -41,22 +41,18 @@ exec(char *path, char **argv)
continue;
if(ph.memsz < ph.filesz)
goto bad;
if(!allocuvm(pgdir, (char *)ph.va, ph.memsz))
if(!(sz = allocuvm(pgdir, sz, ph.va + ph.memsz)))
goto bad;
if(ph.va + ph.memsz > sz)
sz = ph.va + ph.memsz;
if(!loaduvm(pgdir, (char *)ph.va, ip, ph.offset, ph.filesz))
goto bad;
}
iunlockput(ip);
// Allocate and initialize stack at sz
sz = PGROUNDUP(sz);
if(!allocuvm(pgdir, (char *)sz, PGSIZE))
sz = spbottom = PGROUNDUP(sz);
if(!(sz = allocuvm(pgdir, sz, sz + PGSIZE)))
goto bad;
mem = uva2ka(pgdir, (char *)sz);
spoffset = sz;
sz += PGSIZE;
mem = uva2ka(pgdir, (char *)spbottom);
arglen = 0;
for(argc=0; argv[argc]; argc++)
@ -67,22 +63,22 @@ exec(char *path, char **argv)
argp = sz - arglen - 4*(argc+1);
// Copy argv strings and pointers to stack.
*(uint*)(mem+argp-spoffset + 4*argc) = 0; // argv[argc]
*(uint*)(mem+argp-spbottom + 4*argc) = 0; // argv[argc]
for(i=argc-1; i>=0; i--){
len = strlen(argv[i]) + 1;
sp -= len;
memmove(mem+sp-spoffset, argv[i], len);
*(uint*)(mem+argp-spoffset + 4*i) = sp; // argv[i]
memmove(mem+sp-spbottom, argv[i], len);
*(uint*)(mem+argp-spbottom + 4*i) = sp; // argv[i]
}
// Stack frame for main(argc, argv), below arguments.
sp = argp;
sp -= 4;
*(uint*)(mem+sp-spoffset) = argp;
*(uint*)(mem+sp-spbottom) = argp;
sp -= 4;
*(uint*)(mem+sp-spoffset) = argc;
*(uint*)(mem+sp-spbottom) = argc;
sp -= 4;
*(uint*)(mem+sp-spoffset) = 0xffffffff; // fake return pc
*(uint*)(mem+sp-spbottom) = 0xffffffff; // fake return pc
// Save program name for debugging.
for(last=s=path; *s; s++)