Bug 251083 - Kernel built WITH_INIT_ALL_ZERO results in exception in UEFI during boot
Summary: Kernel built WITH_INIT_ALL_ZERO results in exception in UEFI during boot
Status: Open
Alias: None
Product: Base System
Classification: Unclassified
Component: misc (show other bugs)
Version: CURRENT
Hardware: amd64 Any
: --- Affects Only Me
Assignee: freebsd-bugs (Nobody)
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-11-12 20:52 UTC by Ed Maste
Modified: 2020-11-16 19:23 UTC (History)
1 user (show)

See Also:


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Description Ed Maste freebsd_committer 2020-11-12 20:52:48 UTC
Building world/kernel on amd64 with WITH_INIT_ALL_ZERO set and booting in QEMU results in this failure to boot:

/boot/entropy size=0x1000
Start @ 0xffffffff80377000 ...
!!!! X64 Exception Type - 06(#UD - Invalid Opcode)  CPU Apic ID - 00000000 !!!!
RIP  - FFFFFFFF819BCAFA, CS  - 0000000000000038, RFLAGS - 0000000000000002
RAX  - FFFFFFFF80376020, RCX - 0000000000000000, RDX - 00000000000018AA
RBX  - 0000000000000000, RSP - FFFFFFFF819BC658, RBP - FFFFFFFF82118000
RSI  - 00000000000058B8, RDI - FFFFFFFF819BC428
R8   - 0000000000000000, R9  - FFFFFFFF80C40A50, R10 - 0000000000005A30
R11  - 0000000000000CF0, R12 - 0000000002122000, R13 - 0211800000000000
R14  - 0000000002122000, R15 - 000F000000000000
DS   - 0000000000000030, ES  - 0000000000000030, FS  - 0000000000000030
GS   - 0000000000000030, SS  - 0000000000000030
CR0  - 0000000080010033, CR2 - 0000000000000000, CR3 - 000000000EA4F000
CR4  - 0000000000000668, CR8 - 0000000000000000
DR0  - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
DR3  - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
GDTR - 000000000FBEEA98 0000000000000047, LDTR - 0000000000000000
IDTR - 000000000F819018 0000000000000FFF,   TR - 0000000000000000
FXSAVE_STATE - FFFFFFFF819BC2B0
!!!! Find image based on IP(0x819BCAFA) /wrkdirs/usr/ports/sysutils/uefi-edk2-qemu/work-x86_64/edk2-edk2-stable201911/Build/OvmfX64/RELEASE_GCC5/X64/MdeModulePkg/Core/Pei/PeiMain/DEBUG/PeiCore.dll (ImageBase=FFFFFFFF4FEED000, EntryPoint=FFFFFFFF4FEF29F8) !!!!
qemu-system-x86_64: terminating on signal 15 from pid 12144 (timeout)
Comment 1 Conrad Meyer freebsd_committer 2020-11-12 21:38:58 UTC
To be clear, the port sysutils/uefi-edk2-qemu was *not* built with INIT_ALL_ZERO, right?
Comment 2 Conrad Meyer freebsd_committer 2020-11-12 21:41:56 UTC
Oh, I think I get it.  It seems like INIT_ALL_ZERO is emitting some instruction qemu doesn't understand?
Comment 3 Conrad Meyer freebsd_committer 2020-11-12 21:44:15 UTC
Can you disassemble your kernel around 0xFFFFFFFF819BCAFA?
Comment 4 Ed Maste freebsd_committer 2020-11-13 01:18:56 UTC
Further experiments confirm this is not reproducible with the kernel forcing INIT_ALL_ZERO off, but leaving on for the loader. I will investigate more later - I have not built with INIT_ALL_ZERO locally, only via Cirrus-CI.
Comment 5 Ed Maste freebsd_committer 2020-11-13 04:26:50 UTC
(In reply to Conrad Meyer from comment #3)

That addr is in:

  [46] .bss              NOBITS           ffffffff819bbb00  017bbaa8
       0000000000444500  0000000000000000  WA       0     0     128
Comment 6 Ed Maste freebsd_committer 2020-11-13 14:19:56 UTC
Using QEMU's `-d exec` option I see last instructions before the exception are in these regions:

Chain 0: 0x18a5f40 [0000000000000000/ffffffff8105176a/0x40c2b0] ^M
Chain 0: 0x18a60c0 [0000000000000000/ffffffff80c40a50/0x40c2b0] ^M
Chain 0: 0x18ae840 [0000000000000000/ffffffff8104dd60/0x40c2b0] ^M
Chain 0: 0x18a6900 [0000000000000000/ffffffff80c40a84/0x40c2b0] ^M
Chain 0: 0x18a6bc0 [0000000000000000/ffffffff81051779/0x40c2b0] ^M
Chain 0: 0x18a74c0 [0000000000000000/ffffffff80c4058a/0x40c2b0] ^M

Symbols associated with these addrs:

ffffffff80c403f0 T link_elf_ireloc
ffffffff80c40a50 t elf_lookup_ifunc
ffffffff810516e0 t elf_reloc_internal
ffffffff8104dd60 t copyout_resolver

the last instructions executed are in link_elf_ireloc()
Comment 7 Ed Maste freebsd_committer 2020-11-13 14:33:52 UTC
Andy pointed out https://reviews.freebsd.org/D23499.
I forgot about this review :(
Comment 8 commit-hook freebsd_committer 2020-11-13 18:35:07 UTC
A commit references this bug:

Author: emaste
Date: Fri Nov 13 18:34:13 UTC 2020
New revision: 367646
URL: https://svnweb.freebsd.org/changeset/base/367646

Log:
  Disable kernel INIT_ALL_ZERO on amd64

  It is currently incompatible with kernel ifunc memset.

  PR:		251083
  MFC with:	r367577
  Sponsored by:	The FreeBSD Foundation

Changes:
  head/sys/conf/kern.opts.mk