[PATCH] D106056: [CVP] processSwitch: Remove default case when switch cover all possible values.

Wed Aug 18 12:45:06 PDT 2021

nathanchance added subscribers: samitolvanen, nathanchance.
nathanchance added a comment.

I apologize that I do not have a ton of information (I am happy to provide whatever would be useful) but this patch causes an issue with booting an `x86_64_defconfig` Linux kernel build with ThinLTO (initially reported here: https://github.com/ClangBuiltLinux/linux/issues/1440).

  $ make -skj"$(nproc)" LLVM=1 LLVM_IAS=1 distclean defconfig

  $ scripts/config -e LTO_CLANG_THIN

  $ make -skj"$(nproc)" LLVM=1 LLVM_IAS=1 olddefconfig bzImage

  # from https://github.com/ClangBuiltLinux/boot-utils
  $ ../boot-utils/boot-qemu.sh -a x86_64 -k . -t 30s
  ...
  [    3.999233] jump_label: Fatal kernel bug, unexpected op at __mod_timer.llvm.2796501342197355523+0x37f/0x4d0 [ffffffff8a90587f] (eb 02 eb 29 41 != 66 90 0f 1f 00)) size:2 type:1
  [    4.000759] ------------[ cut here ]------------
  [    4.001232] kernel BUG at arch/x86/kernel/jump_label.c:73!
  [    4.001746] invalid opcode: 0000 [#1] SMP NOPTI
  [    4.002174] CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 5.14.0-rc6+ #1
  [    4.002227] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
  [    4.002227] Workqueue: events timer_update_keys
  [    4.002227] RIP: 0010:__jump_label_patch+0x1ab/0x1c0
  [    4.002227] Code: 5d 41 5e 41 5f 5d c3 48 c7 c7 2a 5f b0 8b 4c 89 fe 4c 89 fa 4c 89 f9 49 89 e8 45 89 e1 31 c0 41 56 e8 6c e8 0a 00 48 83 c4 08 <0f> 0b e8 be 54 c7 00 0f 0b 0f 0b 0f 0b 00 00 cc cc 00 00 cc cc 48
  [    4.002227] RSP: 0018:ffff8e5440037d88 EFLAGS: 00010286
  [    4.002227] RAX: 00000000000000a4 RBX: ffffffff8c20f964 RCX: 5fbdcdcfa2eb3900
  [    4.002227] RDX: 0000000000000000 RSI: 0000000000000004 RDI: c0000000ffffbfff
  [    4.002227] RBP: ffffffff8bbd5c11 R08: 0000000000000000 R09: ffff8c86de0a0000
  [    4.002227] R10: 000000000000bffd R11: ffff8e5440037c40 R12: 0000000000000002
  [    4.002227] R13: ffffffff8bbd5c11 R14: 0000000000000001 R15: ffffffff8a90587f
  [    4.002227] FS:  0000000000000000(0000) GS:ffff8c86de200000(0000) knlGS:0000000000000000
  [    4.002227] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [    4.002227] CR2: 0000000000000000 CR3: 000000000e20c000 CR4: 0000000000350ff0
  [    4.002227] Call Trace:
  [    4.002227]  ? __mod_timer.llvm.2796501342197355523+0x37f/0x4d0
  [    4.002227]  ? __mod_timer.llvm.2796501342197355523+0x38e/0x4d0
  [    4.002227]  ? __mod_timer.llvm.2796501342197355523+0x381/0x4d0
  [    4.002227]  ? arch_jump_label_transform_queue+0x26/0x60
  [    4.002227]  ? __jump_label_update+0x9c/0x150
  [    4.002227]  ? static_key_enable_cpuslocked+0x59/0x70
  [    4.002227]  ? timer_update_keys+0x59/0x70
  [    4.002227]  ? process_one_work+0x1cb/0x340
  [    4.002227]  ? worker_thread+0x25d/0x490
  [    4.002227]  ? kthread+0x1b6/0x1d0
  [    4.002227]  ? worker_clr_flags+0x40/0x40
  [    4.002227]  ? kthread_unuse_mm+0x80/0x80
  [    4.002227]  ? ret_from_fork+0x22/0x30
  [    4.002227] Modules linked in:
  [    4.018292] ---[ end trace 15930e2291b4abfa ]---
  [    4.018735] RIP: 0010:__jump_label_patch+0x1ab/0x1c0
  [    4.019229] Code: 5d 41 5e 41 5f 5d c3 48 c7 c7 2a 5f b0 8b 4c 89 fe 4c 89 fa 4c 89 f9 49 89 e8 45 89 e1 31 c0 41 56 e8 6c e8 0a 00 48 83 c4 08 <0f> 0b e8 be 54 c7 00 0f 0b 0f 0b 0f 0b 00 00 cc cc 00 00 cc cc 48
  [    4.021000] RSP: 0018:ffff8e5440037d88 EFLAGS: 00010286
  [    4.021481] RAX: 00000000000000a4 RBX: ffffffff8c20f964 RCX: 5fbdcdcfa2eb3900
  [    4.022178] RDX: 0000000000000000 RSI: 0000000000000004 RDI: c0000000ffffbfff
  [    4.022878] RBP: ffffffff8bbd5c11 R08: 0000000000000000 R09: ffff8c86de0a0000
  [    4.023536] R10: 000000000000bffd R11: ffff8e5440037c40 R12: 0000000000000002
  [    4.024255] R13: ffffffff8bbd5c11 R14: 0000000000000001 R15: ffffffff8a90587f
  [    4.024957] FS:  0000000000000000(0000) GS:ffff8c86de200000(0000) knlGS:0000000000000000
  [    4.025709] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [    4.026307] CR2: 0000000000000000 CR3: 000000000e20c000 CR4: 0000000000350ff0
  ...

I also see

  [    0.108802] **********************************************************
  [    0.109339] **   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
  [    0.109883] **                                                      **
  [    0.110470] ** This system shows unhashed kernel memory addresses   **
  [    0.111011] ** via the console, logs, and other interfaces. This    **
  [    0.111568] ** might reduce the security of your system.            **
  [    0.112145] **                                                      **
  [    0.112710] ** If you see this message and you are not debugging    **
  [    0.113281] ** the kernel, report this immediately to your system   **
  [    0.113841] ** administrator!                                       **
  [    0.114378] **                                                      **
  [    0.114890] **   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
  [    0.115439] **********************************************************

in the boot logs but there are no command line or kernel changes that would cause this, leading me to believe there is something codegen-wise going wrong. I am more than happy to provide more information if need be.

The `BUG()` in question can be viewed on line 73 here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/jump_label.c#n45

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D106056/new/

https://reviews.llvm.org/D106056