Messages in this thread | | | Date | Fri, 20 Jan 2023 12:49:33 +0100 | From | "Erhard F." <> | Subject | Re: [bisected] clang 15 built kernel fails to boot, stuck at "Loading Linux 6.1.1 ...", gcc 12 built kernel with same config boots fine |
| |
On Fri, 20 Jan 2023 12:16:26 +0100 Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, Jan 20, 2023 at 11:20:53AM +0530, Sandipan Das wrote: > > > With the combination of defconfig+kvm_guest.config+localyesconfig, the only > > thing that made a difference was the compiler optimization choice. The kernel > > boots up with CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y but not with > > CONFIG_CC_OPTIMIZE_FOR_SIZE=y. Both Clang 15 and 16 kernel builds are affected. > > *groan*.. > > 0000000000000350 <amd_pmu_add_event>: > 350: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 351: R_X86_64_NONE __fentry__-0x4 > 355: 48 83 bf 20 01 00 00 00 cmpq $0x0,0x120(%rdi) > 35d: 0f 85 00 00 00 00 jne 363 <amd_pmu_add_event+0x13> 35f: R_X86_64_PLT32 __SCT__amd_pmu_branch_add-0x4 > 363: e9 00 00 00 00 jmp 368 <amd_pmu_add_event+0x18> 364: R_X86_64_PLT32 __x86_return_thunk-0x4 > > and static_call() can't deal with Jcc, I wonder why we've not seen that > before -- this isn't totally idiotic code-gen and esp. clang is known to > do this (see the retpoline thing). > > Let me see if I can do something about that.
I can confirm that with -O2 I get a booting kernel with netconsole output using the .config I originally posted.
However the machine does not finish booting, even with -O2. In the netconsole dmesg I get to the point "Run /sbin/init as init process" but that's it, no on-screen ouput on the laptop itself... So there seem to be 2 issues.
And sorry for my custom .config! Forgot that it was tailored for my Lenovo Thinkpad A275. Next time I'll try to replicate my issues with a more generic config (hopefully) bootable on a VM.
Regards, Erhard
| |