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Description: x86: only allow real mode to access 32bit without LMA
When we're running in non-64bit mode with qemu-system-x86_64 we can
still end up with virtual addresses that are above the 32bit boundary
if a segment offset is set up.
.
GNU Hurd does exactly that. It sets the segment offset to 0x80000000 and
puts its EIP value to 0x8xxxxxxx to access low memory.
.
This doesn't hit us when we enable paging, as there we just mask away the
unused bits. But with real mode, we assume that vaddr == paddr which is
wrong in this case. Real hardware wraps the virtual address around at the
32bit boundary. So let's do the same.
.
This fixes booting GNU Hurd in qemu-system-x86_64 for me.
Author: Alexander Graf <agraf@suse.de>
Origin: upstream, http://git.qemu.org/?p=qemu.git;a=commitdiff;h=33dfdb56f2f3c8686d218395b871ec12fd5bf30b
Bug-Debian: https://bugs.debian.org/719633
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -512,6 +512,12 @@ int cpu_x86_handle_mmu_fault(CPUX86State
if (!(env->cr[0] & CR0_PG_MASK)) {
pte = addr;
+#ifdef TARGET_X86_64
+ if (!(env->hflags & HF_LMA_MASK)) {
+ /* Without long mode we can only address 32bits in real mode */
+ pte = (uint32_t)pte;
+ }
+#endif
virt_addr = addr & TARGET_PAGE_MASK;
prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
page_size = 4096;
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