| Message ID | 1459781544-14310-2-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Mon, Apr 04, 2016 at 04:52:17PM +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 value is visible to the secondaries before they enable > their MMUs. So place the literal next to kimage_vaddr, and set the alignment > so that it is covered by the same cacheline that we already have to clean > for a similar purpose. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > --- > 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 4203d5f257bc..69b33535911e 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -471,7 +471,8 @@ __mmap_switched: > b 0b > > 2: adr_l x8, kimage_vaddr // make relocated kimage_vaddr > - dc cvac, x8 // value visible to secondaries > + // and __secondary_switched > + dc cvac, x8 // values visible to secondaries > dsb sy // with MMU off > #endif > > @@ -506,10 +507,12 @@ ENDPROC(__mmap_switched) > * end early head section, begin head code that is also used for > * hotplug and needs to have the same protections as the text region > */ > - .section ".text","ax" > - > + .section ".text","ax" > + .align 4 > ENTRY(kimage_vaddr) Since ENTRY already has a .align 4, can you drop the explicit directive here? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 7 April 2016 at 11:38, Will Deacon <will.deacon@arm.com> wrote: > On Mon, Apr 04, 2016 at 04:52:17PM +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 value is visible to the secondaries before they enable >> their MMUs. So place the literal next to kimage_vaddr, and set the alignment >> so that it is covered by the same cacheline that we already have to clean >> for a similar purpose. >> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >> --- >> 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 4203d5f257bc..69b33535911e 100644 >> --- a/arch/arm64/kernel/head.S >> +++ b/arch/arm64/kernel/head.S >> @@ -471,7 +471,8 @@ __mmap_switched: >> b 0b >> >> 2: adr_l x8, kimage_vaddr // make relocated kimage_vaddr >> - dc cvac, x8 // value visible to secondaries >> + // and __secondary_switched >> + dc cvac, x8 // values visible to secondaries >> dsb sy // with MMU off >> #endif >> >> @@ -506,10 +507,12 @@ ENDPROC(__mmap_switched) >> * end early head section, begin head code that is also used for >> * hotplug and needs to have the same protections as the text region >> */ >> - .section ".text","ax" >> - >> + .section ".text","ax" >> + .align 4 >> ENTRY(kimage_vaddr) > > Since ENTRY already has a .align 4, can you drop the explicit directive > here? > Sure, I hadn't realised that. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 4203d5f257bc..69b33535911e 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -471,7 +471,8 @@ __mmap_switched: b 0b 2: adr_l x8, kimage_vaddr // make relocated kimage_vaddr - dc cvac, x8 // value visible to secondaries + // and __secondary_switched + dc cvac, x8 // values visible to secondaries dsb sy // with MMU off #endif @@ -506,10 +507,12 @@ ENDPROC(__mmap_switched) * end early head section, begin head code that is also used for * hotplug and needs to have the same protections as the text region */ - .section ".text","ax" - + .section ".text","ax" + .align 4 ENTRY(kimage_vaddr) .quad _text - TEXT_OFFSET +.L__secondary_switched: + .quad __secondary_switched /* * If we're fortunate enough to boot at EL2, ensure that the world is @@ -701,12 +704,9 @@ ENTRY(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 + ldr x27, .L__secondary_switched b __enable_mmu ENDPROC(secondary_startup) -0: .long (_text - TEXT_OFFSET) - __secondary_switched ENTRY(__secondary_switched) adr_l x5, vectors
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 value is visible to the secondaries before they enable their MMUs. So place the literal next to kimage_vaddr, and set the alignment so that it is covered by the same cacheline that we already have to clean for a similar purpose. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/kernel/head.S | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) -- 2.5.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel