On Tue, Jul 11, 2023 at 11:37:04AM -0700, Nathan Chancellor wrote:

Masami, thanks for verifying!

Hi Greg and Sasha,

On Tue, Jul 11, 2023 at 10:33:03AM +0900, Masami Hiramatsu wrote:

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On Mon, 10 Jul 2023 08:57:03 -0700 Nathan Chancellor nathan@kernel.org wrote:

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On Mon, Jul 10, 2023 at 09:14:13PM +0900, Masami Hiramatsu (Google) wrote:

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I just build tested, since I could not boot the kernel with CFI_CLANG=y. Would anyone know something about this error?

[ 0.141030] MMIO Stale Data: Unknown: No mitigations [ 0.153511] SMP alternatives: Using kCFI [ 0.164593] Freeing SMP alternatives memory: 36K [ 0.165053] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: start_kernel+0x472/0x48b [ 0.166028] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.2-00002-g12b1b2fca8ef #126 [ 0.166028] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 [ 0.166028] Call Trace: [ 0.166028] <TASK> [ 0.166028] dump_stack_lvl+0x6e/0xb0 [ 0.166028] panic+0x146/0x2f0 [ 0.166028] ? start_kernel+0x472/0x48b [ 0.166028] __stack_chk_fail+0x14/0x20 [ 0.166028] start_kernel+0x472/0x48b [ 0.166028] x86_64_start_reservations+0x24/0x30 [ 0.166028] x86_64_start_kernel+0xa6/0xbb [ 0.166028] secondary_startup_64_no_verify+0x106/0x11b [ 0.166028] </TASK> [ 0.166028] ---[ end Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: start_kernel+0x472/0x48b ]---

This looks like https://github.com/ClangBuiltLinux/linux/issues/1815 to me. What version of LLVM are you using? This was fixed in 16.0.4. Commit 514ca14ed544 ("start_kernel: Add __no_stack_protector function attribute") should resolve it on the Linux side, it looks like that is in 6.5-rc1. Not sure if we should backport it or just let people upgrade their toolchains on older releases.

Thanks for the info. I confirmed that the commit fixed the boot issue. So I think it should be backported to the stable tree.

Would you please apply commit 514ca14ed544 ("start_kernel: Add __no_stack_protector function attribute") to linux-6.4.y? The series ending with commit 611d4c716db0 ("x86/hyperv: Mark hv_ghcb_terminate() as noreturn") that shipped in 6.4 exposes an LLVM issue that affected 16.0.0 and 16.0.1, which was resolved in 16.0.2. When using those affected LLVM releases, the following crash at boot occurs:

[ 0.181667] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: start_kernel+0x3cf/0x3d0 [ 0.182621] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.3 #1 [ 0.182621] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [ 0.182621] Call Trace: [ 0.182621] <TASK> [ 0.182621] dump_stack_lvl+0x6a/0xa0 [ 0.182621] panic+0x124/0x2f0 [ 0.182621] ? start_kernel+0x3cf/0x3d0 [ 0.182621] ? acpi_enable+0x64/0xc0 [ 0.182621] __stack_chk_fail+0x14/0x20 [ 0.182621] start_kernel+0x3cf/0x3d0 [ 0.182621] x86_64_start_reservations+0x24/0x30 [ 0.182621] x86_64_start_kernel+0xab/0xb0 [ 0.182621] secondary_startup_64_no_verify+0x107/0x10b [ 0.182621] </TASK> [ 0.182621] ---[ end Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: start_kernel+0x3cf/0x3d0 ]---

514ca14ed544 aims to avoid this on the Linux side. I have verified that it applies to 6.4.3 cleanly and resolves the issue there, as has Masami.

If there are any issues or questions, please let me know.

Now queued up, thanks.

greg k-h