From 5ab7dba3fad68fdedb3aa513e86ca9fa35de7c8b Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi.kivity@gmail.com>
Date: Wed, 9 Jan 2013 13:37:47 +0200
Subject: [PATCH] mmu: add reserve()
Reserves a vma range for later use. Can be useful to implement mmap() hints
with a two-step algorithm - reserve a range, then overwrite it with the real
mmap.
---
mmu.cc | 47 +++++++++++++++++++++++++++++++++++++++++++++--
mmu.hh | 1 +
2 files changed, 46 insertions(+), 2 deletions(-)
diff --git a/mmu.cc b/mmu.cc
index 34ae0abc0..f9fee0587 100644
--- a/mmu.cc
+++ b/mmu.cc
@@ -21,13 +21,25 @@ namespace mmu {
}
};
- boost::intrusive::set<vma,
+ typedef boost::intrusive::set<vma,
bi::compare<vma_compare>,
bi::member_hook<vma,
bi::set_member_hook<>,
&vma::_vma_list_hook>,
bi::optimize_size<true>
- > vma_list;
+ > vma_list_base;
+
+ struct vma_list_type : vma_list_base {
+ vma_list_type() {
+ // insert markers for the edges of allocatable area
+ // simplifies searches
+ insert(*new vma(0, 0));
+ uintptr_t e = 0x800000000000;
+ insert(*new vma(e, e));
+ }
+ };
+
+ vma_list_type vma_list;
typedef uint64_t pt_element;
const unsigned nlevels = 4;
@@ -111,6 +123,37 @@ namespace mmu {
}
}
+ uintptr_t find_hole(uintptr_t start, uintptr_t size)
+ {
+ // FIXME: use lower_bound or something
+ auto p = vma_list.begin();
+ auto n = std::next(p);
+ while (n != vma_list.end()) {
+ if (start >= p->end() && start + size <= n->start()) {
+ return start;
+ }
+ if (p->end() >= start && n->start() - p->end() >= size) {
+ return p->end();
+ }
+ p = n;
+ ++n;
+ }
+ abort();
+ }
+
+ vma* reserve(void* hint, size_t size)
+ {
+ // look for a hole around 'hint'
+ auto start = reinterpret_cast<uintptr_t>(hint);
+ if (!start) {
+ start = 0x200000000000ul;
+ }
+ start = find_hole(start, size);
+ auto v = new vma(start, start + size);
+ vma_list.insert(*v);
+ return v;
+ }
+
vma* map_anon_dontzero(uintptr_t start, uintptr_t end, unsigned perm)
{
vma* ret = new vma(start, end);
diff --git a/mmu.hh b/mmu.hh
index 718a2c895..10f90b053 100644
--- a/mmu.hh
+++ b/mmu.hh
@@ -32,6 +32,7 @@ namespace mmu {
boost::intrusive::set_member_hook<> _vma_list_hook;
};
+ vma* reserve(void* hint, size_t size);
vma* map_file(void* addr, size_t size, unsigned perm,
file& file, f_offset offset);
vma* map_anon(void* addr, size_t size, unsigned perm);
--
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