From 33dfdb56f2f3c8686d218395b871ec12fd5bf30b Mon Sep 17 00:00:00 2001 From: Alexander Graf Date: Fri, 6 Dec 2013 13:52:24 +0100 Subject: [PATCH] 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. Reported-by: Michael Tokarev Signed-off-by: Alexander Graf Reviewed-by: Richard Henderson Signed-off-by: Michael Tokarev --- target-i386/helper.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/target-i386/helper.c b/target-i386/helper.c index 7c196ffc42..ed965d634d 100644 --- a/target-i386/helper.c +++ b/target-i386/helper.c @@ -531,6 +531,12 @@ int cpu_x86_handle_mmu_fault(CPUX86State *env, target_ulong addr, 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;