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| author | Frans Kaashoek <[email protected]> | 2022-08-24 08:57:56 -0400 |
|---|---|---|
| committer | Frans Kaashoek <[email protected]> | 2022-08-24 08:57:56 -0400 |
| commit | cc486ddee0c617ab2a0bd000b4674e1094661386 (patch) | |
| tree | 57aec0596ff7b96a82c2977d2bae0267e94c52e3 | |
| parent | 96047832c62e6a172c92f9ead6715b553d4c2271 (diff) | |
| download | xv6-labs-cc486ddee0c617ab2a0bd000b4674e1094661386.tar.gz xv6-labs-cc486ddee0c617ab2a0bd000b4674e1094661386.tar.bz2 xv6-labs-cc486ddee0c617ab2a0bd000b4674e1094661386.zip | |
Help students read this C syntax
| -rw-r--r-- | kernel/syscall.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/syscall.c b/kernel/syscall.c index ee94696..ed65409 100644 --- a/kernel/syscall.c +++ b/kernel/syscall.c @@ -79,6 +79,7 @@ argstr(int n, char *buf, int max) return fetchstr(addr, buf, max); } +// Prototypes for the functions that handle system calls. extern uint64 sys_fork(void); extern uint64 sys_exit(void); extern uint64 sys_wait(void); @@ -101,6 +102,8 @@ extern uint64 sys_link(void); extern uint64 sys_mkdir(void); extern uint64 sys_close(void); +// An array mapping syscall numbers from syscall.h +// to the function that handles the system call. static uint64 (*syscalls[])(void) = { [SYS_fork] sys_fork, [SYS_exit] sys_exit, @@ -133,6 +136,8 @@ syscall(void) num = p->trapframe->a7; if(num > 0 && num < NELEM(syscalls) && syscalls[num]) { + // Use num to lookup the system call function for num, call it, + // and store its return value in p->trapframe->a0 p->trapframe->a0 = syscalls[num](); } else { printf("%d %s: unknown sys call %d\n", |