Date: Thu, 23 Jul 2020 16:22:31 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 247945] Kernel option KERN_TLS leads to an immediate panic while booting on ARM64 (RPi4) Message-ID: <bug-247945-227-bbvoDMMZS6@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-247945-227@https.bugs.freebsd.org/bugzilla/> References: <bug-247945-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=247945 John Baldwin <jhb@FreeBSD.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |kib@FreeBSD.org --- Comment #5 from John Baldwin <jhb@FreeBSD.org> --- This may be a bug in the arm64 fpu interface? Note that the kthread calls fpu_kern_thread() first thing before it's done any work at all. Ah, I think I see the bug. cpu_copy_thread() in vm_machdep.c just blindly copies pcb_flags which means that if the first kthread runs before another one is forked, the newly forked thread will bogusly have PCB_FP_KERN set in pcb_flags. The amd64 version is careful to do this in cpu_copy_thread: clear_pcb_flags(pcb2, PCB_FPUINITDONE | PCB_USERFPUINITDONE | PCB_KERNFPU); cpu_fork() for amd64 does an fpuexit() before copying the pcb which effectively does the same thing. On arm64, cpu_fork() calls vfp_save_state which does not clear any pcb_flags after doing vfp_store/vfp_disable. It also doesn't check pcb_flags to determine if it should store/disable which is probably wrong. cpu_copy_thread() just needs to clear the relevant flags in the new pcb I think. -- You are receiving this mail because: You are the assignee for the bug.help
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