Use pgb_addr_set to probe for all of the guest addresses,
not just the main executable. Handle the identity map
specially and separately from the search.
If /proc/self/maps is available, utilize the full power
of the interval tree search, rather than a linear search
through the address list.
If /proc/self/maps is not available, increase the skip
between probes so that we do not probe every single page
of the host address space. Choose 1 MiB for 32-bit hosts
(max 4k probes) and 1 GiB for 64-bit hosts (possibly a
large number of probes, but the large step makes it more
likely to find empty space quicker).
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
linux-user/elfload.c | 311 ++++++++++++++++---------------------------
1 file changed, 115 insertions(+), 196 deletions(-)
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 33c74be3af..ffea900308 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2686,220 +2686,143 @@ static void pgb_fixed(const char *image_name,
uintptr_t guest_loaddr,
}
/**
- * pgd_find_hole_fallback: potential mmap address
- * @guest_size: size of available space
- * @brk: location of break
- * @align: memory alignment
+ * pgb_find_fallback:
*
- * This is a fallback method for finding a hole in the host address
- * space if we don't have the benefit of being able to access
- * /proc/self/map. It can potentially take a very long time as we can
- * only dumbly iterate up the host address space seeing if the
- * allocation would work.
+ * This is a fallback method for finding holes in the host address space
+ * if we don't have the benefit of being able to access /proc/self/map.
+ * It can potentially take a very long time as we can only dumbly iterate
+ * up the host address space seeing if the allocation would work.
*/
-static uintptr_t pgd_find_hole_fallback(uintptr_t guest_size, uintptr_t brk,
- long align, uintptr_t offset)
+static uintptr_t pgb_find_fallback(const PGBAddrs *ga, uintptr_t align,
+ uintptr_t brk)
{
- uintptr_t base;
+ /* TODO: come up with a better estimate of how much to skip. */
+ uintptr_t skip = sizeof(uintptr_t) == 4 ? MiB : GiB;
- /* Start (aligned) at the bottom and work our way up */
- base = ROUND_UP(mmap_min_addr, align);
-
- while (true) {
- uintptr_t align_start, end;
- align_start = ROUND_UP(base, align);
- end = align_start + guest_size + offset;
-
- /* if brk is anywhere in the range give ourselves some room to grow. */
- if (align_start <= brk && brk < end) {
- base = brk + (16 * MiB);
- continue;
- } else if (align_start + guest_size < align_start) {
- /* we have run out of space */
+ for (uintptr_t base = skip; ; base += skip) {
+ base = ROUND_UP(base, align);
+ if (pgb_try_mmap_set(ga, base, brk)) {
+ return base;
+ }
+ if (base >= -skip) {
return -1;
- } else {
- int flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE |
- MAP_FIXED_NOREPLACE;
- void * mmap_start = mmap((void *) align_start, guest_size,
- PROT_NONE, flags, -1, 0);
- if (mmap_start != MAP_FAILED) {
- munmap(mmap_start, guest_size);
- if (mmap_start == (void *) align_start) {
- return (uintptr_t) mmap_start + offset;
- }
- }
- base += qemu_host_page_size;
}
}
}
-/* Return value for guest_base, or -1 if no hole found. */
-static uintptr_t pgb_find_hole(uintptr_t guest_loaddr, uintptr_t guest_size,
- long align, uintptr_t offset)
+static uintptr_t pgb_try_itree(const PGBAddrs *ga, uintptr_t base,
+ IntervalTreeRoot *root)
{
- IntervalTreeRoot *maps;
- IntervalTreeNode *iter;
- uintptr_t this_start, this_end, next_start, brk;
- intptr_t ret = -1;
+ for (int i = ga->nbounds - 1; i >= 0; --i) {
+ uintptr_t s = base + ga->bounds[i][0];
+ uintptr_t l = base + ga->bounds[i][1];
+ IntervalTreeNode *n;
+
+ if (l < s) {
+ /* Wraparound. Skip to advance S to 0. */
+ return -s;
+ }
+
+ n = interval_tree_iter_first(root, s, l);
+ if (n != NULL) {
+ /* Conflict. Skip to advance S to LAST + 1. */
+ return n->last - s + 1;
+ }
+ }
+ return 0; /* success */
+}
+
+static uintptr_t pgb_find_itree(const PGBAddrs *ga, IntervalTreeRoot *root,
+ uintptr_t align, uintptr_t brk)
+{
+ uintptr_t last = mmap_min_addr;
+ uintptr_t base, skip;
+
+ while (true) {
+ base = ROUND_UP(last, align);
+ if (base < last) {
+ return -1;
+ }
+
+ skip = pgb_try_itree(ga, base, root);
+ if (skip == 0) {
+ break;
+ }
+
+ last = base + skip;
+ if (last < base) {
+ return -1;
+ }
+ }
+
+ /*
+ * We've chosen 'base' based on holes in the interval tree,
+ * but we don't yet know if it is a valid host address.
+ * Because it is the first matching hole, if the host addresses
+ * are invalid we know there are no further matches.
+ */
+ return pgb_try_mmap_set(ga, base, brk) ? base : -1;
+}
+
+static void pgb_dynamic(const char *image_name, uintptr_t guest_loaddr,
+ uintptr_t guest_hiaddr, uintptr_t align)
+{
+ IntervalTreeRoot *root;
+ uintptr_t brk, ret;
+ PGBAddrs ga;
assert(QEMU_IS_ALIGNED(guest_loaddr, align));
- maps = read_self_maps();
+ /* Try the identity map first. */
+ if (pgb_addr_set(&ga, guest_loaddr, guest_hiaddr, true)) {
+ brk = (uintptr_t)sbrk(0);
+ if (pgb_try_mmap_set(&ga, 0, brk)) {
+ guest_base = 0;
+ return;
+ }
+ }
+
+ /*
+ * Rebuild the address set for non-identity map.
+ * This differs in the mapping of the guest NULL page.
+ */
+ pgb_addr_set(&ga, guest_loaddr, guest_hiaddr, false);
+
+ root = read_self_maps();
/* Read brk after we've read the maps, which will malloc. */
brk = (uintptr_t)sbrk(0);
- if (!maps) {
- return pgd_find_hole_fallback(guest_size, brk, align, offset);
- }
-
- /* The first hole is before the first map entry. */
- this_start = mmap_min_addr;
-
- for (iter = interval_tree_iter_first(maps, 0, -1);
- iter;
- this_start = next_start,
- iter = interval_tree_iter_next(iter, 0, -1)) {
- MapInfo *info = container_of(iter, MapInfo, itree);
- uintptr_t align_start, hole_size;
-
- this_end = info->itree.start;
- next_start = info->itree.last + 1;
- align_start = ROUND_UP(this_start + offset, align);
-
- /* Skip holes that are too small. */
- if (align_start >= this_end) {
- continue;
- }
- hole_size = this_end - align_start;
- if (hole_size < guest_size) {
- continue;
- }
-
- /* If this hole contains brk, give ourselves some room to grow. */
- if (this_start <= brk && brk < this_end) {
- hole_size -= guest_size;
- if (sizeof(uintptr_t) == 8 && hole_size >= 1 * GiB) {
- align_start += 1 * GiB;
- } else if (hole_size >= 16 * MiB) {
- align_start += 16 * MiB;
- } else {
- align_start = (this_end - guest_size) & -align;
- if (align_start < this_start) {
- continue;
- }
- }
- }
-
- /* Record the lowest successful match. */
- if (ret < 0) {
- ret = align_start;
- }
- /* If this hole contains the identity map, select it. */
- if (align_start <= guest_loaddr &&
- guest_loaddr + guest_size <= this_end) {
- ret = 0;
- }
- /* If this hole ends above the identity map, stop looking. */
- if (this_end >= guest_loaddr) {
- break;
- }
- }
- free_self_maps(maps);
- return ret;
-}
-
-static void pgb_static(const char *image_name, abi_ulong orig_loaddr,
- abi_ulong orig_hiaddr, long align)
-{
- uintptr_t loaddr = orig_loaddr;
- uintptr_t hiaddr = orig_hiaddr;
- uintptr_t offset = 0;
- uintptr_t addr;
-
- loaddr &= -align;
- if (HI_COMMPAGE) {
+ if (!root) {
+ ret = pgb_find_fallback(&ga, align, brk);
+ } else {
/*
- * Extend the allocation to include the commpage.
- * For a 64-bit host, this is just 4GiB; for a 32-bit host we
- * need to ensure there is space bellow the guest_base so we
- * can map the commpage in the place needed when the address
- * arithmetic wraps around.
+ * Reserve the area close to the host brk.
+ * This will be freed with the rest of the tree.
*/
- if (sizeof(uintptr_t) == 8 || loaddr >= 0x80000000u) {
- hiaddr = UINT32_MAX;
- } else {
- offset = -(HI_COMMPAGE & -align);
- }
- } else if (LO_COMMPAGE != -1) {
- loaddr = MIN(loaddr, LO_COMMPAGE & -align);
+ IntervalTreeNode *b = g_new0(IntervalTreeNode, 1);
+ b->start = brk;
+ b->last = brk + 16 * MiB - 1;
+ interval_tree_insert(b, root);
+
+ ret = pgb_find_itree(&ga, root, align, brk);
+ free_self_maps(root);
}
- addr = pgb_find_hole(loaddr, hiaddr - loaddr + 1, align, offset);
- if (addr == -1) {
- /*
- * If HI_COMMPAGE, there *might* be a non-consecutive allocation
- * that can satisfy both. But as the normal arm32 link base address
- * is ~32k, and we extend down to include the commpage, making the
- * overhead only ~96k, this is unlikely.
- */
- error_report("%s: Unable to allocate %#zx bytes of "
- "virtual address space", image_name,
- (size_t)(hiaddr - loaddr));
- exit(EXIT_FAILURE);
- }
-
- guest_base = addr;
-}
-
-static void pgb_dynamic(const char *image_name, long align)
-{
- /*
- * The executable is dynamic and does not require a fixed address.
- * All we need is a commpage that satisfies align.
- * If we do not need a commpage, leave guest_base == 0.
- */
- if (HI_COMMPAGE) {
- uintptr_t addr, commpage;
-
- /* 64-bit hosts should have used reserved_va. */
- assert(sizeof(uintptr_t) == 4);
-
- /*
- * By putting the commpage at the first hole, that puts guest_base
- * just above that, and maximises the positive guest addresses.
- */
- commpage = HI_COMMPAGE & -align;
- addr = pgb_find_hole(commpage, -commpage, align, 0);
- assert(addr != -1);
- guest_base = addr;
- }
-}
-
-static void pgb_reserved_va(const char *image_name, abi_ulong guest_loaddr,
- abi_ulong guest_hiaddr, long align)
-{
- int flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE;
- void *addr, *test;
-
- /* Widen the "image" to the entire reserved address space. */
- pgb_static(image_name, 0, reserved_va, align);
-
- /* osdep.h defines this as 0 if it's missing */
- flags |= MAP_FIXED_NOREPLACE;
-
- /* Reserve the memory on the host. */
- assert(guest_base != 0);
- test = g2h_untagged(0);
- addr = mmap(test, reserved_va + 1, PROT_NONE, flags, -1, 0);
- if (addr == MAP_FAILED || addr != test) {
- error_report("Unable to reserve 0x%lx bytes of virtual address "
- "space at %p (%s) for use as guest address space (check
your "
- "virtual memory ulimit setting, mmap_min_addr or reserve
less "
- "using qemu-user's -R option)",
- reserved_va + 1, test, strerror(errno));
+ if (ret == -1) {
+ int w = TARGET_LONG_BITS / 4;
+
+ error_report("%s: Unable to find a guest_base to satisfy all "
+ "guest address mapping requirements", image_name);
+
+ for (int i = 0; i < ga.nbounds; ++i) {
+ error_printf(" %0*" PRIx64 "-%0*" PRIx64 "\n",
+ w, (uint64_t)ga.bounds[i][0],
+ w, (uint64_t)ga.bounds[i][1]);
+ }
exit(EXIT_FAILURE);
}
+ guest_base = ret;
}
void probe_guest_base(const char *image_name, abi_ulong guest_loaddr,
@@ -2927,12 +2850,8 @@ void probe_guest_base(const char *image_name, abi_ulong
guest_loaddr,
if (have_guest_base) {
pgb_fixed(image_name, guest_loaddr, guest_hiaddr, align);
- } else if (reserved_va) {
- pgb_reserved_va(image_name, guest_loaddr, guest_hiaddr, align);
- } else if (guest_loaddr) {
- pgb_static(image_name, guest_loaddr, guest_hiaddr, align);
} else {
- pgb_dynamic(image_name, align);
+ pgb_dynamic(image_name, guest_loaddr, guest_hiaddr, align);
}
/* Reserve and initialize the commpage. */
--
2.34.1
