Re: [PATCH] x86/nospec: Unwreck the RSB stuffing

[Daniel Sneddon]

On 8/16/22 05:28, Peter Zijlstra wrote:

> 
> Could you please test this; I've only compiled it.
> 
When booting I get the following BUG:

------------[ cut here ]------------
kernel BUG at arch/x86/kernel/alternative.c:290!
invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.0.0-rc1-00001-gb72b03c96999 #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1
04/01/2014
RIP: 0010:apply_alternatives+0x287/0x2d0
Code: 4c 29 f6 03 74 24 13 89 74 24 13 45 85 c0 0f 85 d2 41 e9 00 41 0f b6 02 83
e0 fd 3c e9 0f 84 46 ff ff ff e9 5e fe ff ff 0f 0b <0f> 0b f7 c6 00 ff ff ff 0f
84 68 ff ff ff 8d 71 fb c6 44 24 12 e9
RSP: 0000:ffffffff82c03d68 EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffffffff83728c24 RCX: 0000000000007fff
RDX: 00000000ffffffea RSI: 0000000000000000 RDI: 000000000000ffff
RBP: ffffffff82c03d7a R08: e800000010c4c749 R09: 0001e8cc00000001
R10: 10c48348cc000000 R11: e8ae0feb75ccff49 R12: ffffffff8372fcf8
R13: 0000000000000000 R14: ffffffff81001a68 R15: 000000000000001f
FS:  0000000000000000(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff88813ffff000 CR3: 0000000002c0c001 CR4: 0000000000770ef0
PKRU: 55555554
Call Trace:
 <TASK>
 ? insn_get_opcode+0xef/0x1c0
 ? ct_nmi_enter+0xb3/0x180
 ? ct_nmi_exit+0xbe/0x1d0
 ? irqentry_exit+0x2d/0x40
 ? asm_common_interrupt+0x22/0x40
 alternative_instructions+0x5b/0xf5
 check_bugs+0xdaf/0xdef
 start_kernel+0x66a/0x6a2
 secondary_startup_64_no_verify+0xe0/0xeb
 </TASK>
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end trace 0000000000000000 ]---
RIP: 0010:apply_alternatives+0x287/0x2d0
Code: 4c 29 f6 03 74 24 13 89 74 24 13 45 85 c0 0f 85 d2 41 e9 00 41 0f b6 02 83
e0 fd 3c e9 0f 84 46 ff ff ff e9 5e fe ff ff 0f 0b <0f> 0b f7 c6 00 ff ff ff 0f
84 68 ff ff ff 8d 71 fb c6 44 24 12 e9
RSP: 0000:ffffffff82c03d68 EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffffffff83728c24 RCX: 0000000000007fff
RDX: 00000000ffffffea RSI: 0000000000000000 RDI: 000000000000ffff
RBP: ffffffff82c03d7a R08: e800000010c4c749 R09: 0001e8cc00000001
R10: 10c48348cc000000 R11: e8ae0feb75ccff49 R12: ffffffff8372fcf8
R13: 0000000000000000 R14: ffffffff81001a68 R15: 000000000000001f
FS:  0000000000000000(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff88813ffff000 CR3: 0000000002c0c001 CR4: 0000000000770ef0
PKRU: 55555554
Kernel panic - not syncing: Attempted to kill the idle task!
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---