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arm64: Avoid clobbering mm in erratum workaround on QDF2400 

Commit 38fd94b027 ("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: 38fd94b027 ("arm64: Work around Falkor erratum 1003")
Tested-by: Manoj Iyer <manoj.iyer@canonical.com>
Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Shanker Donthineni 2017-02-22 21:10:48 -06:00 committed by Will Deacon
parent ffe7afd171
commit ea6eac904f
1 changed files with 1 additions and 1 deletions
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2
arch/arm64/mm/proc.S
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@ -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