• Shanker Donthineni's avatar
    arm64: Avoid clobbering mm in erratum workaround on QDF2400 · ea6eac90
    Shanker Donthineni authored
    Commit 38fd94b0 ("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: 38fd94b0 ("arm64: Work around Falkor erratum 1003")
    Tested-by: default avatarManoj Iyer <manoj.iyer@canonical.com>
    Signed-off-by: default avatarShanker Donthineni <shankerd@codeaurora.org>
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    ea6eac90
proc.S 6.43 KB