Messages in this thread | | | Date | Wed, 16 Nov 2011 17:32:56 +0800 | From | wangyanqing <> | Subject | Re: [PATCH -V1] x86: make executable for video bios area |
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Hi All! Here is the result of my research, hope it is useful to resolve this question.
Notice:trace from up to down 1:pci_arch_init()
2:pci_mmcfg_early_init() ;boot without PCI_PROBE_NOEARLY
3:__pci_mmcfg_init(1);
4:pci_mmcfg_arch_init(); mmcfg need acpi
5:pci_probe = (pci_probe & ~PCI_PROBE_MASK) | PCI_PROBE_MMCONF; <== IMPORTANT: clean PCI_PROBE_BIOS away
6:pci_pcbios_init();
7:pci_probe & PCI_PROBE_BIOS ; it will fail
8:pci_find_bios() will no chance to execute
the result is: 1:pcibios_enabled will always 0 2:set_bios_x will no chance to execute, so from BIOS_BEGIN to BIOS_END is NX
lrmi:linux real mode interface project, http://sourceforge.net/projects/lrmi/ v86d use lrmi lrmi.c:358
if (!map_file((void *)0xc0000, 0x40000, PROT_READ | PROT_EXEC, MAP_FIXED | MAP_SHARED, "/dev/mem", 0xc0000)) { munmap((void *)0, 0x502); munmap((void *)0xa0000, 0x20000); real_mem_deinit(); return 0; } this function to map 000c0000-00100000 with X privilege
00000000-00001000 rw-s 00000000 00:01 822 /dev/mem 00009000-0000a000 r-xp 00001000 00:01 912 /sbin/v86d 00010000-00050000 rwxp 00000000 00:01 818 /dev/zero 000a0000-000c0000 rw-s 000a0000 00:01 822 /dev/mem 000c0000-00100000 r-xs 000c0000 00:01 822 /dev/mem 08048000-0804c000 r-xp 00001000 00:01 912 /sbin/v86d 0804c000-0804d000 rw-p 00004000 00:01 912 /sbin/v86d b779a000-b779b000 r-xp 00000000 00:00 0 [vdso] bfac2000-bfae3000 rw-p 00000000 00:00 0 [stack]
At last we get the reason that my machine hang with black screen The reason is when I boot with ACPI, BIOS_BEGIN to BIOS_END is NX, then v86d try to map 0xc0000 to 0x100000 with executable privilege, it mmap success(mem.c:300, mmap_mem haven't check whether it is illegal), but the pages between BIOS_BEGIN and BIOS_END is NX at all, so it hang!
Question: 1:boot with ACPI make BIOS area NX on X86, is that what we want? 2:mmap_mem haven't check whether it is illegal the mmap target address, right?
Thanks
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