Author: alc
Date: Sat Mar 18 23:37:00 2017
New Revision: 315518
URL: https://svnweb.freebsd.org/changeset/base/315518
Log:
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().
Reviewed by: kib
MFC after: 1 week
Modified:
head/sys/kern/imgact_elf.c
Modified: head/sys/kern/imgact_elf.c
==============================================================================
--- head/sys/kern/imgact_elf.c Sat Mar 18 23:24:52 2017 (r315517)
+++ head/sys/kern/imgact_elf.c Sat Mar 18 23:37:00 2017 (r315518)
@@ -582,7 +582,7 @@ __elfN(load_section)(struct image_params
/* 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);
}
@@ -603,10 +603,12 @@ __elfN(load_section)(struct image_params
}
/*
- * 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);
}
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