On 07/25/2018 11:21 PM, Kirill A. Shutemov wrote:
On Wed, Jul 25, 2018 at 05:26:02PM +0000, Dmitry Malkin wrote:there may be some other reasons which may cause undefined behavior (reboot for example): in arch/x86/boot/compressed/pgtable_64.c in function paging_prepare(): 1. structure "paging_config" allocated on stack without setting default value for flag "l5_required":struct paging_config paging_config = {};l5_required is set only if CONFIG_X86_5LEVEL is definedHm? C99 initializer zeros the structure.
https://elixir.bootlin.com/linux/latest/source/Makefile#L366 Here I only see std=gnu89.
Sure, here it is (please note than not both pages are reserved but only second one: 0x9e000-0x9ffff):2. reading from memory which may be reserved in case of EFI systems:ebda_start = *(unsigned short *)0x40e << 4; bios_start = *(unsigned short *)0x413 << 10;Also, on EFI system without CSM it will results in all zeros. Which will place trampoline_start to 0x9d000. And it also may be reserved memory. In fact I have such system and it is causes instant reboot (when code starts copying to "trampoline_start").Could you show dmesg from such system?
[ 0.000000] Linux version 4.17.9-1.el7.elrepo.x86_64 (mockbuild@Build64R7) (gcc version 4.8.5 20150623 (Red Hat 4.8.5-28) (GCC)) #1 SMP Sun Jul 22 11:57:51 EDT 2018 [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-4.17.9-1.el7.elrepo.x86_64 root=UUID=51cc5f87-2bb2-45b5-a0ee-691970f9cf06 ro crashkernel=auto rhgb quiet [ 0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers' [ 0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'[ 0.000000] x86/fpu: Supporting XSAVE feature 0x008: 'MPX bounds registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x010: 'MPX CSR' [ 0.000000] x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256 [ 0.000000] x86/fpu: xstate_offset[3]: 832, xstate_sizes[3]: 64 [ 0.000000] x86/fpu: xstate_offset[4]: 896, xstate_sizes[4]: 64[ 0.000000] x86/fpu: Enabled xstate features 0x1f, context size is 960 bytes, using 'compacted' format.
[ 0.000000] e820: BIOS-provided physical RAM map: [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x0000000000057fff] usable[ 0.000000] BIOS-e820: [mem 0x0000000000058000-0x0000000000058fff] reserved
[ 0.000000] BIOS-e820: [mem 0x0000000000059000-0x000000000009dfff] usable[ 0.000000] BIOS-e820: [mem 0x000000000009e000-0x000000000009ffff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000e0fff] reserved
[ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000c4a14fff] usable[ 0.000000] BIOS-e820: [mem 0x00000000c4a15000-0x00000000c4a15fff] ACPI NVS [ 0.000000] BIOS-e820: [mem 0x00000000c4a16000-0x00000000c4a3ffff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000c4a40000-0x00000000c91acfff] usable[ 0.000000] BIOS-e820: [mem 0x00000000c91ad000-0x00000000c9749fff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000c974a000-0x00000000c9776fff] ACPI data [ 0.000000] BIOS-e820: [mem 0x00000000c9777000-0x00000000cba86fff] ACPI NVS [ 0.000000] BIOS-e820: [mem 0x00000000cba87000-0x00000000cbefdfff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000cbefe000-0x00000000cbefefff] usable[ 0.000000] BIOS-e820: [mem 0x00000000cbf00000-0x00000000cbffffff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000f8000000-0x00000000fbffffff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000fe000000-0x00000000fe010fff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000fec00000-0x00000000fec00fff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000ff000000-0x00000000ffffffff] reserved
[ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000022f7fffff] usable [ 0.000000] NX (Execute Disable) protection: active [ 0.000000] e820: update [mem 0xc42c9018-0xc4321057] usable ==> usable [ 0.000000] e820: update [mem 0xc42c9018-0xc4321057] usable ==> usable [ 0.000000] e820: update [mem 0xc42b9018-0xc42c8c57] usable ==> usable [ 0.000000] e820: update [mem 0xc42b9018-0xc42c8c57] usable ==> usable [ 0.000000] e820: update [mem 0xc42a8018-0xc42b8257] usable ==> usable [ 0.000000] e820: update [mem 0xc42a8018-0xc42b8257] usable ==> usable [ 0.000000] extended physical RAM map:[ 0.000000] reserve setup_data: [mem 0x0000000000000000-0x0000000000057fff] usable [ 0.000000] reserve setup_data: [mem 0x0000000000058000-0x0000000000058fff] reserved [ 0.000000] reserve setup_data: [mem 0x0000000000059000-0x000000000009dfff] usable [ 0.000000] reserve setup_data: [mem 0x000000000009e000-0x000000000009ffff] reserved [ 0.000000] reserve setup_data: [mem 0x00000000000e0000-0x00000000000e0fff] reserved [ 0.000000] reserve setup_data: [mem 0x0000000000100000-0x00000000c42a8017] usable [ 0.000000] reserve setup_data: [mem 0x00000000c42a8018-0x00000000c42b8257] usable [ 0.000000] reserve setup_data: [mem 0x00000000c42b8258-0x00000000c42b9017] usable [ 0.000000] reserve setup_data: [mem 0x00000000c42b9018-0x00000000c42c8c57] usable [ 0.000000] reserve setup_data: [mem 0x00000000c42c8c58-0x00000000c42c9017] usable [ 0.000000] reserve setup_data: [mem 0x00000000c42c9018-0x00000000c4321057] usable [ 0.000000] reserve setup_data: [mem 0x00000000c4321058-0x00000000c4a14fff] usable [ 0.000000] reserve setup_data: [mem 0x00000000c4a15000-0x00000000c4a15fff] ACPI NVS [ 0.000000] reserve setup_data: [mem 0x00000000c4a16000-0x00000000c4a3ffff] reserved [ 0.000000] reserve setup_data: [mem 0x00000000c4a40000-0x00000000c91acfff] usable [ 0.000000] reserve setup_data: [mem 0x00000000c91ad000-0x00000000c9749fff] reserved [ 0.000000] reserve setup_data: [mem 0x00000000c974a000-0x00000000c9776fff] ACPI data [ 0.000000] reserve setup_data: [mem 0x00000000c9777000-0x00000000cba86fff] ACPI NVS [ 0.000000] reserve setup_data: [mem 0x00000000cba87000-0x00000000cbefdfff] reserved [ 0.000000] reserve setup_data: [mem 0x00000000cbefe000-0x00000000cbefefff] usable [ 0.000000] reserve setup_data: [mem 0x00000000cbf00000-0x00000000cbffffff] reserved [ 0.000000] reserve setup_data: [mem 0x00000000f8000000-0x00000000fbffffff] reserved [ 0.000000] reserve setup_data: [mem 0x00000000fe000000-0x00000000fe010fff] reserved [ 0.000000] reserve setup_data: [mem 0x00000000fec00000-0x00000000fec00fff] reserved [ 0.000000] reserve setup_data: [mem 0x00000000fee00000-0x00000000fee00fff] reserved [ 0.000000] reserve setup_data: [mem 0x00000000ff000000-0x00000000ffffffff] reserved [ 0.000000] reserve setup_data: [mem 0x0000000100000000-0x000000022f7fffff] usable
[ 0.000000] efi: EFI v2.40 by American Megatrends[ 0.000000] efi: ESRT=0xcbd9de18 ACPI=0xc974f000 ACPI 2.0=0xc974f000 SMBIOS=0xcbd99000 SMBIOS 3.0=0xcbd98000
[ 0.000000] SMBIOS 3.0.0 present.[ 0.000000] DMI: SIEMENS AG RackPC_547G_HG-B.2.0/D3445-S1, BIOS V5.0.0.11 R1.11.0 for D3445-S1x 02/24/2016
3. paging_prepare(void) returns "struct paging_config". Copy by value. Is it really specified by ABI or GCC itself that the second field (which is flag "l5_required") will go to RDX register?https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-1.0.pdf 3.2.3 Parameter Passing ... Returning of Values The returning of values is done according to the following algorithm: ... 3. If the class is INTEGER, the next available register of the sequence %rax, %rdx is used.
Got it, thank you.
Attachment:
smime.p7s
Description: S/MIME Cryptographic Signature
