From: Tom Hughes <tom@compton.nu>
Date: Fri, 16 Jul 2004 15:36:45 +0000 (+0000)
Subject: Add comments to explain the address space padding technology.
X-Git-Tag: svn/VALGRIND_2_1_2~20
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=29a3645022c3edf77be5854fee94210c98800860;p=thirdparty%2Fvalgrind.git

Add comments to explain the address space padding technology.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@2487
---

diff --git a/coregrind/vg_memory.c b/coregrind/vg_memory.c
index 06586e4460..016ed781f9 100644
--- a/coregrind/vg_memory.c
+++ b/coregrind/vg_memory.c
@@ -545,6 +545,17 @@ Addr VG_(find_map_space)(Addr addr, UInt len, Bool for_client)
    return ret;
 }
 
+/* Pad the entire process address space, from VG_(client_base)
+   to VG_(valgrind_end) by creating an anonymous and inaccessible
+   mapping over any part of the address space which is not covered
+   by an entry in the segment list.
+
+   This is designed for use around system calls which allocate
+   memory in the process address space without providing a way to
+   control it's location such as io_setup. By choosing a suitable
+   address with VG_(find_map_space) and then adding a segment for
+   it and padding the address space valgrind can ensure that the
+   kernel has no choice but to put the memory where we want it. */
 void VG_(pad_address_space)(void)
 {
    Addr addr = VG_(client_base);
@@ -579,6 +590,8 @@ void VG_(pad_address_space)(void)
    return;
 }
 
+/* Removed the address space padding added by VG_(pad_address_space)
+   by removing any mappings that it created. */
 void VG_(unpad_address_space)(void)
 {
    Addr addr = VG_(client_base);