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authorRobert Morris <[email protected]>2010-09-27 16:14:33 -0400
committerRobert Morris <[email protected]>2010-09-27 16:14:33 -0400
commit4655d42e3b65f906eae8c815fb78331790f6e423 (patch)
treede5b3e4e74c992fd3cd8fef0a2d37cb805c659ac /exec.c
parenta9183883b88bfccd1c6a62e27621b2c892d50b67 (diff)
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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.c93
1 files changed, 58 insertions, 35 deletions
diff --git a/exec.c b/exec.c
index 0a9ca59..2e2ced4 100644
--- a/exec.c
+++ b/exec.c
@@ -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;