MFC r315518

  Avoid unnecessary calls to vm_map_protect() in elf_load_section().

  Typically, when elf_load_section() unconditionally passed VM_PROT_ALL to
  elf_map_insert(), it was needlessly enabling execute access on the
  mapping, and it would later have to call vm_map_protect() to correct the
  mapping's access rights.  Now, instead, elf_load_section() always passes
  its parameter "prot" to elf_map_insert().  So, elf_load_section() must
  only call vm_map_protect() if it needs to remove the write access that
  was temporarily granted to perform a copyout().

Approved by:	re (kib)

1 files changed, 6 insertions, 4 deletions

diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c
index 6ae6d67..f7bbdcf 100644
--- a/sys/kern/imgact_elf.c
+++ b/sys/kern/imgact_elf.c
@@ -596,7 +596,7 @@ __elfN(load_section)(struct image_params *imgp, vm_ooffset_t offset,
 	/* This had damn well better be true! */
 	if (map_len != 0) {
 		rv = __elfN(map_insert)(imgp, map, NULL, 0, map_addr,
-		    map_addr + map_len, VM_PROT_ALL, 0);
+		    map_addr + map_len, prot, 0);
 		if (rv != KERN_SUCCESS)
 			return (EINVAL);
 	}
@@ -617,10 +617,12 @@ __elfN(load_section)(struct image_params *imgp, vm_ooffset_t offset,
 	}
 
 	/*
-	 * set it to the specified protection.
+	 * Remove write access to the page if it was only granted by map_insert
+	 * to allow copyout.
 	 */
-	vm_map_protect(map, trunc_page(map_addr), round_page(map_addr +
-	    map_len), prot, FALSE);
+	if ((prot & VM_PROT_WRITE) == 0)
+		vm_map_protect(map, trunc_page(map_addr), round_page(map_addr +
+		    map_len), prot, FALSE);
 
 	return (0);
 }