On Mon, Apr 18, 2016 at 05:09:42PM +0200, Ard Biesheuvel wrote: > We can simply use a relocated 64-bit literal to store the address of > __secondary_switched(), and the relocation code will ensure that it > holds the correct value at secondary entry time, as long as we make sure > that the literal is not dereferenced until after we have enabled the MMU. > > So jump via a small __secondary_switch() function covered by the ID map > that performs the literal load and branch-to-register. > > Signed-off-by: Ard Biesheuvel <[email protected]>
Neat! Acked-by: Mark Rutland <[email protected]> Mark. > --- > arch/arm64/kernel/head.S | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index ac27d8d937b2..f13276d4ca91 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -468,9 +468,7 @@ __mmap_switched: > str x15, [x11, x23] > b 0b > > -2: adr_l x8, kimage_vaddr // make relocated kimage_vaddr > - dc cvac, x8 // value visible to secondaries > - dsb sy // with MMU off > +2: > #endif > > adr_l sp, initial_sp, x4 > @@ -699,12 +697,9 @@ secondary_startup: > adrp x26, swapper_pg_dir > bl __cpu_setup // initialise processor > > - ldr x8, kimage_vaddr > - ldr w9, 0f > - sub x27, x8, w9, sxtw // address to jump to after > enabling the MMU > + adr_l x27, __secondary_switch // address to jump to after > enabling the MMU > b __enable_mmu > ENDPROC(secondary_startup) > -0: .long (_text - TEXT_OFFSET) - __secondary_switched > > __secondary_switched: > adr_l x5, vectors > @@ -806,3 +801,8 @@ __no_granule_support: > wfi > b 1b > ENDPROC(__no_granule_support) > + > +__secondary_switch: > + ldr x8, =__secondary_switched > + br x8 > +ENDPROC(__secondary_switch) > -- > 2.5.0 >
