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author | Robert Morris <[email protected]> | 2010-09-27 16:14:33 -0400 |
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committer | Robert Morris <[email protected]> | 2010-09-27 16:14:33 -0400 |
commit | 4655d42e3b65f906eae8c815fb78331790f6e423 (patch) | |
tree | de5b3e4e74c992fd3cd8fef0a2d37cb805c659ac /exec.c | |
parent | a9183883b88bfccd1c6a62e27621b2c892d50b67 (diff) | |
download | xv6-labs-4655d42e3b65f906eae8c815fb78331790f6e423.tar.gz xv6-labs-4655d42e3b65f906eae8c815fb78331790f6e423.tar.bz2 xv6-labs-4655d42e3b65f906eae8c815fb78331790f6e423.zip |
copyout() copies data to a va in a pagetable, for exec() &c
usertest that passes too many arguments, break exec
Diffstat (limited to 'exec.c')
-rw-r--r-- | exec.c | 93 |
1 files changed, 58 insertions, 35 deletions
@@ -9,16 +9,13 @@ int exec(char *path, char **argv) { - char *mem, *s, *last; - int i, argc, arglen, len, off; - uint sz, sp, spbottom, argp; + char *s, *last; + int i, off; + uint sz = 0; struct elfhdr elf; - struct inode *ip; + struct inode *ip = 0; struct proghdr ph; - pde_t *pgdir, *oldpgdir; - - pgdir = 0; - sz = 0; + pde_t *pgdir = 0, *oldpgdir; if((ip = namei(path)) == 0) return -1; @@ -48,40 +45,65 @@ exec(char *path, char **argv) } iunlockput(ip); - // Allocate and initialize stack at sz - sz = spbottom = PGROUNDUP(sz); + // Allocate a one-page stack at the next page boundary + sz = PGROUNDUP(sz); if(!(sz = allocuvm(pgdir, sz, sz + PGSIZE))) goto bad; - mem = uva2ka(pgdir, (char *)spbottom); - - 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); - - // XXX rtm: does the following code work if the - // arguments &c do not fit in one page? - - // Copy argv strings and pointers to stack. - *(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-spbottom, argv[i], len); - *(uint*)(mem+argp-spbottom + 4*i) = sp; // argv[i] + + // initialize stack content: + + // "argumentN" -- nul-terminated string + // ... + // "argument0" + // 0 -- argv[argc] + // address of argumentN + // ... + // address of argument0 -- argv[0] + // address of address of argument0 -- argv argument to main() + // argc -- argc argument to main() + // ffffffff -- return PC for main() call + + uint sp = sz; + + // count arguments + int argc; + for(argc = 0; argv[argc]; argc++) + ; + if(argc >= MAXARG) + goto bad; + + // push strings and remember where they are + uint strings[MAXARG]; + for(i = argc - 1; i >= 0; --i){ + sp -= strlen(argv[i]) + 1; + strings[i] = sp; + copyout(pgdir, sp, argv[i], strlen(argv[i]) + 1); + } + + // push 0 for argv[argc] + sp -= 4; + int zero = 0; + copyout(pgdir, sp, &zero, 4); + + // push argv[] elements + for(i = argc - 1; i >= 0; --i){ + sp -= 4; + copyout(pgdir, sp, &strings[i], 4); } - // Stack frame for main(argc, argv), below arguments. - sp = argp; + // push argv + uint argvaddr = sp; sp -= 4; - *(uint*)(mem+sp-spbottom) = argp; + copyout(pgdir, sp, &argvaddr, 4); + + // push argc sp -= 4; - *(uint*)(mem+sp-spbottom) = argc; + copyout(pgdir, sp, &argc, 4); + + // push 0 in case main returns sp -= 4; - *(uint*)(mem+sp-spbottom) = 0xffffffff; // fake return pc + uint ffffffff = 0xffffffff; + copyout(pgdir, sp, &ffffffff, 4); // Save program name for debugging. for(last=s=path; *s; s++) @@ -103,6 +125,7 @@ exec(char *path, char **argv) return 0; bad: + cprintf("kernel: exec failed\n"); if(pgdir) freevm(pgdir); iunlockput(ip); return -1; |