summaryrefslogtreecommitdiff
path: root/kernel/exec.c
diff options
context:
space:
mode:
authorFrans Kaashoek <[email protected]>2022-08-15 19:02:19 -0400
committerFrans Kaashoek <[email protected]>2022-08-15 19:02:19 -0400
commitcef1b57d4a97f15e9858804e368f7928b579b88e (patch)
tree8f59e7986c6b69e08f2a8d4a3f5449a83e4cf7ea /kernel/exec.c
parent2175c6b0b667b13e09c710c36e4a3ae8fc7c97dc (diff)
downloadxv6-labs-cef1b57d4a97f15e9858804e368f7928b579b88e.tar.gz
xv6-labs-cef1b57d4a97f15e9858804e368f7928b579b88e.tar.bz2
xv6-labs-cef1b57d4a97f15e9858804e368f7928b579b88e.zip
Compile user binary to map text without W and data without X
Use the flags in elf header to set vm permissions Modify pgbug() so that usertests text segment is without W Add test to check app cannot write text segment
Diffstat (limited to 'kernel/exec.c')
-rw-r--r--kernel/exec.c27
1 files changed, 20 insertions, 7 deletions
diff --git a/kernel/exec.c b/kernel/exec.c
index 3c468e1..aee9345 100644
--- a/kernel/exec.c
+++ b/kernel/exec.c
@@ -7,7 +7,17 @@
#include "defs.h"
#include "elf.h"
-static int loadseg(pde_t *pgdir, uint64 addr, struct inode *ip, uint offset, uint sz);
+static int loadseg(pde_t *, uint64, uint, struct inode *, uint, uint);
+
+int flags2perm(int flags)
+{
+ int perm = 0;
+ if(flags & 0x1)
+ perm = PTE_X;
+ if(flags & 0x2)
+ perm |= PTE_W;
+ return perm;
+}
int
exec(char *path, char **argv)
@@ -32,6 +42,7 @@ exec(char *path, char **argv)
// Check ELF header
if(readi(ip, 0, (uint64)&elf, 0, sizeof(elf)) != sizeof(elf))
goto bad;
+
if(elf.magic != ELF_MAGIC)
goto bad;
@@ -48,13 +59,15 @@ exec(char *path, char **argv)
goto bad;
if(ph.vaddr + ph.memsz < ph.vaddr)
goto bad;
+ if(ph.align != PGSIZE)
+ goto bad;
+ uint64 e = PGROUNDUP(ph.vaddr + ph.memsz);
uint64 sz1;
- if((sz1 = uvmalloc(pagetable, sz, ph.vaddr + ph.memsz, PTE_X|PTE_W)) == 0)
+ if((sz1 = uvmalloc(pagetable, sz, e, flags2perm(ph.flags))) == 0)
goto bad;
sz = sz1;
- if((ph.vaddr % PGSIZE) != 0)
- goto bad;
- if(loadseg(pagetable, ph.vaddr, ip, ph.off, ph.filesz) < 0)
+ uint64 s = PGROUNDDOWN(ph.vaddr);
+ if(loadseg(pagetable, s, ph.vaddr - s, ip, ph.off, ph.filesz) < 0)
goto bad;
}
iunlockput(ip);
@@ -134,7 +147,7 @@ exec(char *path, char **argv)
// and the pages from va to va+sz must already be mapped.
// Returns 0 on success, -1 on failure.
static int
-loadseg(pagetable_t pagetable, uint64 va, struct inode *ip, uint offset, uint sz)
+loadseg(pagetable_t pagetable, uint64 va, uint poff, struct inode *ip, uint offset, uint sz)
{
uint i, n;
uint64 pa;
@@ -147,7 +160,7 @@ loadseg(pagetable_t pagetable, uint64 va, struct inode *ip, uint offset, uint sz
n = sz - i;
else
n = PGSIZE;
- if(readi(ip, 0, (uint64)pa, offset+i, n) != n)
+ if(readi(ip, 0, (uint64)pa+poff, offset+i, n) != n)
return -1;
}