d0f7acf9eb
An x86-64 operating system built from xv6, now largely rewritten: SMP, a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF rasteriser, and a Linux-numbered syscall ABI. No history before this point -- the tree was never under version control. This commit exists so the rename that follows has something to undo to.
141 lines
3.6 KiB
C
141 lines
3.6 KiB
C
#include "types.h"
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#include "defs.h"
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#include "param.h"
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#include "memlayout.h"
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#include "mmu.h"
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#include "traps.h"
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#include "proc.h"
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#include "x86.h"
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#include "syscall.h"
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#include "uaccess.h"
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#include "errno.h"
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#include "posix.h"
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// -----------------------------------------------------------------------
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// Argument helpers — read syscall args from the saved register frame.
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// x86-64 SysV ABI: rdi, rsi, rdx, r10, r8, r9
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// -----------------------------------------------------------------------
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// Note: address validation goes through uaccess.h (page-table presence +
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// user bit on every page of the range). There is deliberately no
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// `addr < myproc()->sz` check: that would assume every valid user pointer
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// lives in the heap — false for stack addresses and mmap()'d buffers
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// (both live above myproc()->sz), which made syscalls fail whenever a
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// Linux-ABI program passed a string/pointer from either region.
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//
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// Validated pointers are returned as raw user VAs — the process page
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// table is live in kernel mode, so they dereference correctly across
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// page boundaries (unlike a uva2ka() alias, which is only good within
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// the one page it translated).
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int
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fetchint(addr_t addr, int *ip)
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{
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return copy_from_user(ip, addr, sizeof(*ip)) ? -1 : 0;
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}
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int
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fetchaddr(addr_t addr, addr_t *ip)
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{
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return copy_from_user(ip, addr, sizeof(*ip)) ? -1 : 0;
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}
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int
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fetchstr(addr_t addr, char **pp)
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{
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long len = strlen_user(addr);
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if (len < 0)
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return -1;
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*pp = (char*)addr;
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return len;
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}
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static addr_t
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fetcharg(int n)
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{
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switch (n) {
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case 0: return myproc()->tf->rdi;
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case 1: return myproc()->tf->rsi;
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case 2: return myproc()->tf->rdx;
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case 3: return myproc()->tf->r10;
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case 4: return myproc()->tf->r8;
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case 5: return myproc()->tf->r9;
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}
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panic("fetcharg: bad n");
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return 0;
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}
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int argint(int n, int *ip) { *ip = (int)fetcharg(n); return 0; }
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int argaddr(int n, addr_t *ip) { *ip = fetcharg(n); return 0; }
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int
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argptr(int n, char **pp, int size)
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{
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addr_t i;
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if (argaddr(n, &i) < 0)
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return -1;
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if (size < 0)
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return -1;
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char *p = user_ptr(i, (uint64)size);
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if (!p)
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return -1;
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*pp = p;
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return 0;
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}
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int
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argstr(int n, char **pp)
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{
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addr_t addr;
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if (argaddr(n, &addr) < 0)
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return -1;
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return fetchstr(addr, pp);
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}
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// -----------------------------------------------------------------------
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// Dispatch table — auto-generated from table.inc
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// -----------------------------------------------------------------------
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#define SYSCALL(nr, lnr, name) extern addr_t sys_##name(void);
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#define SYSCALL_ALIAS(lnr, name)
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#include "table.inc"
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#undef SYSCALL
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#undef SYSCALL_ALIAS
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static addr_t (*syscalls[NSYSCALLS])(void) = {
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#define SYSCALL(nr, lnr, name) [SYS_##name] = sys_##name,
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#define SYSCALL_ALIAS(lnr, name)
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#include "table.inc"
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#undef SYSCALL
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#undef SYSCALL_ALIAS
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};
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// -----------------------------------------------------------------------
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// Main entry point called from trap.c
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// -----------------------------------------------------------------------
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void
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syscall(struct trapframe *tf)
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{
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kstack_check_canary("syscall entry");
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myproc()->tf = tf;
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uint64 orig = myproc()->tf->rax;
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uint64 num = orig;
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if (myproc()->syscall_map) {
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num = (num < (uint64)myproc()->map_size) ? myproc()->syscall_map[num] : 0;
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}
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if (num > 0 && num < NSYSCALLS && syscalls[num]) {
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tf->rax = syscalls[num]();
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} else {
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tf->rax = -ENOSYS;
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}
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if (myproc()->killed)
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exit(W_EXITCODE(0, myproc()->killsig ? myproc()->killsig : SIGKILL));
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deliver_signals(tf);
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kstack_check_canary("syscall exit");
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}
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