From ea6eac904f0a5a0c223bcfb133ec880ba9c70ae3 Mon Sep 17 00:00:00 2001 From: Shanker Donthineni Date: Wed, 22 Feb 2017 21:10:48 -0600 Subject: [PATCH] arm64: Avoid clobbering mm in erratum workaround on QDF2400 Commit 38fd94b0275c ("arm64: Work around Falkor erratum 1003") tried to work around a hardware erratum, but actually caused a system crash of its own during switch_mm: cpu_do_switch_mm+0x20/0x40 efi_virtmap_load+0x34/0x40 virt_efi_get_next_variable+0x64/0xc8 efivar_init+0x8c/0x348 efisubsys_init+0xd4/0x270 do_one_initcall+0x80/0x110 kernel_init_freeable+0x19c/0x240 kernel_init+0x10/0x100 ret_from_fork+0x10/0x50 Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b In cpu_do_switch_mm, x1 contains the mm_struct pointer, which needs to be preserved by the pre_ttbr0_update_workaround macro rather than passed as a temporary. This patch clobbers x2 and x3 instead, keeping the mm_struct intact after the workaround has run. Fixes: 38fd94b0275c ("arm64: Work around Falkor erratum 1003") Tested-by: Manoj Iyer Signed-off-by: Shanker Donthineni Signed-off-by: Will Deacon --- arch/arm64/mm/proc.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index cd4d53d7e458..877d42fb0df6 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -138,7 +138,7 @@ ENDPROC(cpu_do_resume) * - pgd_phys - physical address of new TTB */ ENTRY(cpu_do_switch_mm) - pre_ttbr0_update_workaround x0, x1, x2 + pre_ttbr0_update_workaround x0, x2, x3 mmid x1, x1 // get mm->context.id bfi x0, x1, #48, #16 // set the ASID msr ttbr0_el1, x0 // set TTBR0