Linux/POSIX-compatible mmap and munmap prototypes

These don't implement anything yet that the old syscalls didn't support, but they give us a place to pass flags and make it easier to share user code between xv6 and Linux.

Linux/POSIX-compatible mmap and munmap prototypes
52040c66 · Austin Clements · 7f3e124e · 52040c66 · 52040c66 · 52040c66
--- a/kernel/sysproc.cc
+++ b/kernel/sysproc.cc
@@ -12,6 +12,8 @@
 #include "kmtrace.hh"
 #include "futex.h"

+#include <uk/mman.h>
+
 //SYSCALL
 int
 sys_fork(int flags)
@@ -98,33 +100,65 @@ sys_uptime(void)
 }

 //SYSCALL
-int
-sys_map(userptr<void> addr, size_t len)
+void *
+sys_mmap(userptr<void> addr, size_t len, int prot, int flags, int fd,
+         off_t offset)
 {
  ANON_REGION(__func__, &perfgroup);

+  mt_ascope ascope("%s(%p,%lu,%#x,%#x,%d,%#lx)",
+                   __func__, addr.unsafe_get(), len, prot, flags, fd, offset);
+
+  if (!(prot & (PROT_READ | PROT_WRITE))) {
+    cprintf("not implemented: !(prot & (PROT_READ | PROT_WRITE))\n");
+    return MAP_FAILED;
+  }
+  if (flags & MAP_SHARED) {
+    cprintf("not implemented: (flags & MAP_SHARED)\n");
+    return MAP_FAILED;
+  }
+  if (!(flags & MAP_ANONYMOUS)) {
+    cprintf("not implemented: !(flags & MAP_ANONYMOUS)\n");
+    return MAP_FAILED;
+  }
+
+  uptr start = PGROUNDDOWN(addr);
+  uptr end = PGROUNDUP(addr + len);
+
+  if ((flags & MAP_FIXED) && start != addr)
+    return MAP_FAILED;
+
 #if MTRACE
-  mt_ascope ascope("%s(%p,%#lx)", __func__, addr.unsafe_get(), len);
-  for (uptr i = addr / PGSIZE; i < PGROUNDUP(addr + len) / PGSIZE; i++)
-    mtwriteavar("pte:%p.%#lx", myproc()->vmap, i);
+  if (addr != 0) {
+    for (uptr i = start / PGSIZE; i < end / PGSIZE; i++)
+      mtwriteavar("pte:%p.%#lx", myproc()->vmap, i);
+  }
 #endif

-  vmnode *vmn = new vmnode(PGROUNDUP(len) / PGSIZE);
+  vmnode *vmn = new vmnode((end - start) / PGSIZE);
  if (vmn == 0)
-    return -1;
+    return MAP_FAILED;

-  long r = myproc()->vmap->insert(vmn, PGROUNDDOWN(addr), 1);
+  uptr r = myproc()->vmap->insert(vmn, start, 1);
  if (r < 0) {
    delete vmn;
-    return -1;
+    return MAP_FAILED;
  }

-  return r;
+  return (void*)r;
+}
+
+//SYSCALL
+uptr
+sys_map(userptr<void> addr, size_t len)
+{
+  // XXX Compatibility
+  return (uptr)sys_mmap(addr, len, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
 }

 //SYSCALL
 int
-sys_unmap(userptr<void> addr, size_t len)
+sys_munmap(userptr<void> addr, size_t len)
 {
  ANON_REGION(__func__, &perfgroup);

@@ -142,6 +176,14 @@ sys_unmap(userptr<void> addr, size_t len)
  return 0;
 }

+//SYSCALL
+int
+sys_unmap(userptr<void> addr, size_t len)
+{
+  // XXX Compatibility
+  return sys_munmap(addr, len);
+}
+
 //SYSCALL NORET
 void
 sys_halt(void)

--- a/stdinc/sys/mman.h
+++ b/stdinc/sys/mman.h
+#pragma once
+
+#include <uk/mman.h>
--- a/stdinc/uk/mman.h
+++ b/stdinc/uk/mman.h
+// User/kernel shared mmap definitions
+#pragma once
+
+#define PROT_NONE  0x0
+#define PROT_READ  0x1
+#define PROT_WRITE 0x2
+#define PROT_EXEC  0x4
+
+#define MAP_SHARED    0x1
+#define MAP_PRIVATE   0x2
+#define MAP_FIXED     0x4
+#define MAP_ANONYMOUS 0x8
+
+#define MAP_FAILED ((void*)-1)