work around linux bug in mprotect

per POSIX: The mprotect() function shall change the access protections
to be that specified by prot for those whole pages containing any part
of the address space of the process starting at address addr and
continuing for len bytes.

on the other hand, linux mprotect fails with EINVAL if the base
address and/or length is not page-aligned, so we have to align them
before making the syscall.

diff --git a/src/mman/mprotect.c b/src/mman/mprotect.c
index 1db2aea2f127afeab663822b839981a36e9220f1..5ab2d8b0278896ace8109eed8251a3e72abe8c47 100644 (file)
--- a/src/mman/mprotect.c
+++ b/src/mman/mprotect.c
@@ -1,7 +1,11 @@
 #include <sys/mman.h>
+#include <limits.h>
 #include "syscall.h"
 
 int mprotect(void *addr, size_t len, int prot)
 {
-       return syscall(SYS_mprotect, addr, len, prot);
+       size_t start, end;
+       start = (size_t)addr & -PAGE_SIZE;
+       end = (size_t)((char *)addr + len + PAGE_SIZE-1) & -PAGE_SIZE;
+       return syscall(SYS_mprotect, start, end-start, prot);
 }