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authorRichard Henderson <rth@twiddle.net>2010-03-10 15:39:07 -0800
committerPaul Brook <paul@codesourcery.com>2010-03-12 16:29:18 +0000
commit14f24e1465edc44b9b4d89fbbea66e06088154e1 (patch)
treea4d7af58d82337b45a4566a5c3f7d3d15b18a584 /linux-user/mmap.c
parent7bc7b099dfa38a856b1bc892c0f9f3d6fe28e170 (diff)
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linux-user: Fix mmap_find_vma returning invalid addresses.
Don't return addresses that aren't properly aligned for the guest, e.g. when the guest has a larger page size than the host. Don't return addresses that are outside the virtual address space for the target, by paying proper attention to the h2g/g2h macros. At the same time, place the default mapping base for 64-bit guests (on 64-bit hosts) outside the low 4G. Consistently interpret mmap_next_start in the guest address space. Signed-off-by: Richard Henderson <rth@twiddle.net>
Diffstat (limited to 'linux-user/mmap.c')
-rw-r--r--linux-user/mmap.c102
1 files changed, 78 insertions, 24 deletions
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 65fdc33..ad00b6f 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -264,12 +264,15 @@ static int mmap_frag(abi_ulong real_start,
return 0;
}
-#if defined(__CYGWIN__)
+#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64
+# define TASK_UNMAPPED_BASE (1ul << 38)
+#elif defined(__CYGWIN__)
/* Cygwin doesn't have a whole lot of address space. */
-static abi_ulong mmap_next_start = 0x18000000;
+# define TASK_UNMAPPED_BASE 0x18000000
#else
-static abi_ulong mmap_next_start = 0x40000000;
+# define TASK_UNMAPPED_BASE 0x40000000
#endif
+static abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;
unsigned long last_brk;
@@ -281,19 +284,24 @@ unsigned long last_brk;
*/
abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
{
- void *ptr;
+ void *ptr, *prev;
abi_ulong addr;
-
- size = HOST_PAGE_ALIGN(size);
- start &= qemu_host_page_mask;
+ int wrapped, repeat;
/* If 'start' == 0, then a default start address is used. */
- if (start == 0)
+ if (start == 0) {
start = mmap_next_start;
+ } else {
+ start &= qemu_host_page_mask;
+ }
+
+ size = HOST_PAGE_ALIGN(size);
addr = start;
+ wrapped = repeat = 0;
+ prev = 0;
- for(;;) {
+ for (;; prev = ptr) {
/*
* Reserve needed memory area to avoid a race.
* It should be discarded using:
@@ -301,31 +309,77 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
* - mremap() with MREMAP_FIXED flag
* - shmat() with SHM_REMAP flag
*/
- ptr = mmap((void *)(unsigned long)addr, size, PROT_NONE,
+ ptr = mmap(g2h(addr), size, PROT_NONE,
MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
/* ENOMEM, if host address space has no memory */
- if (ptr == MAP_FAILED)
+ if (ptr == MAP_FAILED) {
return (abi_ulong)-1;
+ }
- /* If address fits target address space we've found what we need */
- if ((unsigned long)ptr + size - 1 <= (abi_ulong)-1)
- break;
+ /* Count the number of sequential returns of the same address.
+ This is used to modify the search algorithm below. */
+ repeat = (ptr == prev ? repeat + 1 : 0);
- /* Unmap and try again with new page */
+ if (h2g_valid(ptr + size - 1)) {
+ addr = h2g(ptr);
+
+ if ((addr & ~TARGET_PAGE_MASK) == 0) {
+ /* Success. */
+ if (start == mmap_next_start && addr >= TASK_UNMAPPED_BASE) {
+ mmap_next_start = addr + size;
+ }
+ return addr;
+ }
+
+ /* The address is not properly aligned for the target. */
+ switch (repeat) {
+ case 0:
+ /* Assume the result that the kernel gave us is the
+ first with enough free space, so start again at the
+ next higher target page. */
+ addr = TARGET_PAGE_ALIGN(addr);
+ break;
+ case 1:
+ /* Sometimes the kernel decides to perform the allocation
+ at the top end of memory instead. */
+ addr &= TARGET_PAGE_MASK;
+ break;
+ case 2:
+ /* Start over at low memory. */
+ addr = 0;
+ break;
+ default:
+ /* Fail. This unaligned block must the last. */
+ addr = -1;
+ break;
+ }
+ } else {
+ /* Since the result the kernel gave didn't fit, start
+ again at low memory. If any repetition, fail. */
+ addr = (repeat ? -1 : 0);
+ }
+
+ /* Unmap and try again. */
munmap(ptr, size);
- addr += qemu_host_page_size;
- /* ENOMEM if we check whole of target address space */
- if (addr == start)
+ /* ENOMEM if we checked the whole of the target address space. */
+ if (addr == -1ul) {
return (abi_ulong)-1;
+ } else if (addr == 0) {
+ if (wrapped) {
+ return (abi_ulong)-1;
+ }
+ wrapped = 1;
+ /* Don't actually use 0 when wrapping, instead indicate
+ that we'd truely like an allocation in low memory. */
+ addr = (mmap_min_addr > TARGET_PAGE_SIZE
+ ? TARGET_PAGE_ALIGN(mmap_min_addr)
+ : TARGET_PAGE_SIZE);
+ } else if (wrapped && addr >= start) {
+ return (abi_ulong)-1;
+ }
}
-
- /* Update default start address */
- if (start == mmap_next_start)
- mmap_next_start = (unsigned long)ptr + size;
-
- return h2g(ptr);
}
/* NOTE: all the constants are the HOST ones */