Date: Wed, 1 May 2019 17:12:50 +0000 (UTC) From: Andrew Turner <andrew@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r346996 - head/sys/arm64/arm64 Message-ID: <201905011712.x41HCoN3028425@repo.freebsd.org>
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Author: andrew Date: Wed May 1 17:12:49 2019 New Revision: 346996 URL: https://svnweb.freebsd.org/changeset/base/346996 Log: Restore x18 in efi_arch_leave. Some UEFI implementations trash this register and, as we use it as a platform register, the kernel doesn't save it before calling into the UEFI runtime services. As we have a copy in tpidr_el1 restore from there when exiting the EFI environment. PR: 237234, 237055 Reviewed by: manu Tested On: Ampere eMAG MFC after: 2 weeks Sponsored by: DARPA, AFRL Sponsored by: Ampere Computing (hardware) Differential Revision: https://reviews.freebsd.org/D20127 Modified: head/sys/arm64/arm64/efirt_machdep.c Modified: head/sys/arm64/arm64/efirt_machdep.c ============================================================================== --- head/sys/arm64/arm64/efirt_machdep.c Wed May 1 15:28:23 2019 (r346995) +++ head/sys/arm64/arm64/efirt_machdep.c Wed May 1 17:12:49 2019 (r346996) @@ -259,6 +259,16 @@ efi_arch_leave(void) { struct thread *td; + /* + * Restore the pcpu pointer. Some UEFI implementations trash it and + * we don't store it before calling into them. To fix this we need + * to restore it after returning to the kernel context. As reading + * curthread will access x18 we need to restore it before loading + * the thread pointer. + */ + __asm __volatile( + "mrs x18, tpidr_el1 \n" + ); td = curthread; __asm __volatile( "msr ttbr0_el1, %0 \n"
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