void syscall(void) { int num; struct proc *curproc = myproc (); num = curproc->tf->eax; if(num > e && num < NELEM(syscalls) && syscalls[num]) { curproc->tf->eax syscalls[num] (); } else { cprintf("%d %s: unknown sys call %d\n", curproc->pid, curproc->name, num); curproc->tf->eax = -1; } }
void syscall(void) { int num; struct proc *curproc = myproc (); num = curproc->tf->eax; if(num > e && num < NELEM(syscalls) && syscalls[num]) { curproc->tf->eax syscalls[num] (); } else { cprintf("%d %s: unknown sys call %d\n", curproc->pid, curproc->name, num); curproc->tf->eax = -1; } }
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
Related questions
Question
![void
syscall(void)
{
int num;
struct proc *curproc = myproc ();
num = curproc->tf->eax;
if(num > 0 && num < NELEM(syscalls) && syscalls[num]) {
curproc->tf->eax = syscalls[num]();
} else {
cprintf("%d %s: unknown sys call %d\n",
curproc->pid, curproc->name, num);
curproc->tf->eax = -1;
}
How is the system call number (read into num) first loaded into curproc->tf->eax?
O the kernel copies it there as a result of a preceding call to argint
O the kernel saves all the general purpose registers onto the kernel stack as part of the trap frame, after an interrupt
O it is saved onto the kernel stack by the hardware as part of the int instruction behavior
O the user places the argument to the system call here before calling int](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F3de854aa-ec1c-4dd9-b455-e29d0496ab9e%2F61fd4a91-a461-4304-9e80-935a35e5ed95%2F77bl7s_processed.png&w=3840&q=75)
Transcribed Image Text:void
syscall(void)
{
int num;
struct proc *curproc = myproc ();
num = curproc->tf->eax;
if(num > 0 && num < NELEM(syscalls) && syscalls[num]) {
curproc->tf->eax = syscalls[num]();
} else {
cprintf("%d %s: unknown sys call %d\n",
curproc->pid, curproc->name, num);
curproc->tf->eax = -1;
}
How is the system call number (read into num) first loaded into curproc->tf->eax?
O the kernel copies it there as a result of a preceding call to argint
O the kernel saves all the general purpose registers onto the kernel stack as part of the trap frame, after an interrupt
O it is saved onto the kernel stack by the hardware as part of the int instruction behavior
O the user places the argument to the system call here before calling int
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