When using reserved_va, which is the default for a 64-bit host
and a 32-bit guest, set guest_base_signed_addr32 if requested
by TCG_TARGET_SIGNED_ADDR32, and the executable layout allows.
Reviewed-by: Alex Bennée <alex.ben...@linaro.org>
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
include/exec/cpu-all.h | 4 ---
linux-user/elfload.c | 62 ++++++++++++++++++++++++++++++++++--------
2 files changed, 50 insertions(+), 16 deletions(-)
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 26ecd3c886..8bea0e069e 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -269,11 +269,7 @@ extern const TargetPageBits target_page;
#define PAGE_RESET 0x0040
/* For linux-user, indicates that the page is MAP_ANON. */
#define PAGE_ANON 0x0080
-
-#if defined(CONFIG_BSD) && defined(CONFIG_USER_ONLY)
-/* FIXME: Code that sets/uses this is broken and needs to go away. */
#define PAGE_RESERVED 0x0100
-#endif
/* Target-specific bits that will be used via page_get_flags(). */
#define PAGE_TARGET_1 0x0200
#define PAGE_TARGET_2 0x0400
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 9628a38361..5522f9e721 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2482,34 +2482,72 @@ static void pgb_dynamic(const char *image_name, long
align)
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;
+ int flags = (MAP_ANONYMOUS | MAP_PRIVATE |
+ MAP_NORESERVE | MAP_FIXED_NOREPLACE);
+ unsigned long local_rva = reserved_va;
+ bool protect_wrap = false;
void *addr, *test;
- if (guest_hiaddr > reserved_va) {
+ if (guest_hiaddr > local_rva) {
error_report("%s: requires more than reserved virtual "
"address space (0x%" PRIx64 " > 0x%lx)",
- image_name, (uint64_t)guest_hiaddr, reserved_va);
+ image_name, (uint64_t)guest_hiaddr, local_rva);
exit(EXIT_FAILURE);
}
- /* Widen the "image" to the entire reserved address space. */
- pgb_static(image_name, 0, reserved_va, align);
+ if (TCG_TARGET_SIGNED_ADDR32 && TARGET_LONG_BITS == 32) {
+ if (guest_loaddr < 0x80000000u && guest_hiaddr > 0x80000000u) {
+ /*
+ * The executable itself wraps on signed addresses.
+ * Without per-page translation, we must keep the
+ * guest address 0x7fff_ffff adjacent to 0x8000_0000
+ * consecutive in host memory: unsigned addresses.
+ */
+ } else {
+ set_guest_base_signed_addr32();
+ if (local_rva <= 0x80000000u) {
+ /* No guest addresses are "negative": win! */
+ } else {
+ /* Begin by allocating the entire address space. */
+ local_rva = 0xfffffffful + 1;
+ protect_wrap = true;
+ }
+ }
+ }
- /* osdep.h defines this as 0 if it's missing */
- flags |= MAP_FIXED_NOREPLACE;
+ /* Widen the "image" to the entire reserved address space. */
+ pgb_static(image_name, 0, local_rva, align);
+ assert(guest_base != 0);
/* Reserve the memory on the host. */
- assert(guest_base != 0);
test = g2h_untagged(0);
- addr = mmap(test, reserved_va, PROT_NONE, flags, -1, 0);
+ addr = mmap(test, local_rva, PROT_NONE, flags, -1, 0);
if (addr == MAP_FAILED || addr != test) {
+ /*
+ * If protect_wrap, we could try again with the original reserved_va
+ * setting, but the edge case of low ulimit vm setting on a 64-bit
+ * host is probably useless.
+ */
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, min_mmap_addr or reserve
less "
- "using -R option)", reserved_va, test, strerror(errno));
+ "space at %p (%s) for use as guest address space "
+ "(check your virtual memory ulimit setting, "
+ "min_mmap_addr or reserve less using -R option)",
+ local_rva, test, strerror(errno));
exit(EXIT_FAILURE);
}
+ if (protect_wrap) {
+ /*
+ * Prevent the page just before 0x80000000 from being allocated.
+ * This prevents a single guest object/allocation from crossing
+ * the signed wrap, and thus being discontiguous in host memory.
+ */
+ page_set_flags(0x7fffffff & TARGET_PAGE_MASK, 0x80000000u,
+ PAGE_RESERVED);
+ /* Adjust guest_base so that 0 is in the middle of the reservation. */
+ guest_base += 0x80000000ul;
+ }
+
qemu_log_mask(CPU_LOG_PAGE, "%s: base @ %p for %lu bytes\n",
__func__, addr, reserved_va);
}
--
2.25.1
