flâneur

Program startup details | Pintos Documentation

cs162.org · 512 words · saved by 1 readers

The Pintos C library for user programs designates _start(), in lib/user/entry.c, as the entry point for user programs. This function is a wrapper around main() that calls exit() if main() returns: The kernel must put the arguments for the initial function on the stack before it allows the user program to begin executing. The arguments are passed in the same way as the normal calling convention (see 80x86 Calling Convention). Consider how to handle arguments for the following example command: /bin/ls -l foo bar. First, break the command into words: /bin/ls, -l, foo, bar. Place the words at the top of the stack. Order doesn’t matter, because they will be referenced through pointers. Then, push the address of each string plus a null pointer sentinel, on the stack, in right-to-left order. These are the elements of argv. The null pointer sentinel ensures that argv[argc] is a null pointer, as required by the C standard. The order ensures that argv[0] is at the lowest virtual address. The x86

Program startup details | Pintos Documentation Skip to main content Menu Expand (external link) Document Search Copy Copied Pintos Documentation Program startup details The Pintos C library for user programs designates _start() , in lib/user/entry.c , as the entry point for user programs. This function is a wrapper around main() that calls exit() if main() returns: void _start (int argc, char *argv[]) { exit (main (argc, argv)); } The kernel must put the arguments for the initial function on the stack before it allows the user program to begin executing. The arguments are passed in the same wa

related reading