| Message ID | 20191024225132.13410-3-samitolvanen@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | add support for Clang's Shadow Call Stack | expand |
On Thu, Oct 24, 2019 at 03:51:17PM -0700, samitolvanen@google.com wrote: > From: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > Register x18 will no longer be used as a caller save register in the > future, so stop using it in the copy_page() code. > > Link: https://patchwork.kernel.org/patch/9836869/ > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > --- > arch/arm64/lib/copy_page.S | 38 +++++++++++++++++++------------------- > 1 file changed, 19 insertions(+), 19 deletions(-) > > diff --git a/arch/arm64/lib/copy_page.S b/arch/arm64/lib/copy_page.S > index bbb8562396af..8b562264c165 100644 > --- a/arch/arm64/lib/copy_page.S > +++ b/arch/arm64/lib/copy_page.S > @@ -34,45 +34,45 @@ alternative_else_nop_endif > ldp x14, x15, [x1, #96] > ldp x16, x17, [x1, #112] > > - mov x18, #(PAGE_SIZE - 128) > + add x0, x0, #256 > add x1, x1, #128 > 1: > - subs x18, x18, #128 > + tst x0, #(PAGE_SIZE - 1) > > alternative_if ARM64_HAS_NO_HW_PREFETCH > prfm pldl1strm, [x1, #384] > alternative_else_nop_endif > > - stnp x2, x3, [x0] > + stnp x2, x3, [x0, #-256] > ldp x2, x3, [x1] > - stnp x4, x5, [x0, #16] > + stnp x4, x5, [x0, #-240] > ldp x4, x5, [x1, #16] For legibility, could we make the offset and bias explicit in the STNPs so that these line up? e.g. stnp x4, x5, [x0, #16 - 256] ldp x4, x5, [x1, #16] ... that'd make it much easier to see by eye that this is sound, much as I trust my mental arithmetic. ;) > - stnp x6, x7, [x0, #32] > + stnp x6, x7, [x0, #-224] > ldp x6, x7, [x1, #32] > - stnp x8, x9, [x0, #48] > + stnp x8, x9, [x0, #-208] > ldp x8, x9, [x1, #48] > - stnp x10, x11, [x0, #64] > + stnp x10, x11, [x0, #-192] > ldp x10, x11, [x1, #64] > - stnp x12, x13, [x0, #80] > + stnp x12, x13, [x0, #-176] > ldp x12, x13, [x1, #80] > - stnp x14, x15, [x0, #96] > + stnp x14, x15, [x0, #-160] > ldp x14, x15, [x1, #96] > - stnp x16, x17, [x0, #112] > + stnp x16, x17, [x0, #-144] > ldp x16, x17, [x1, #112] > > add x0, x0, #128 > add x1, x1, #128 > > - b.gt 1b > + b.ne 1b > > - stnp x2, x3, [x0] > - stnp x4, x5, [x0, #16] > - stnp x6, x7, [x0, #32] > - stnp x8, x9, [x0, #48] > - stnp x10, x11, [x0, #64] > - stnp x12, x13, [x0, #80] > - stnp x14, x15, [x0, #96] > - stnp x16, x17, [x0, #112] > + stnp x2, x3, [x0, #-256] > + stnp x4, x5, [x0, #-240] > + stnp x6, x7, [x0, #-224] > + stnp x8, x9, [x0, #-208] > + stnp x10, x11, [x0, #-192] > + stnp x12, x13, [x0, #-176] > + stnp x14, x15, [x0, #-160] > + stnp x16, x17, [x0, #-144] ... likewise here: stnp xt1, xt2, [x0, #off - 256] I don't see a nicer way to write this sequence without using an additional register, so with those changes: Reviewed-by: Mark Rutland <mark.rutland@arm.com> Thanks, Mark. > > ret > ENDPROC(copy_page) > -- > 2.24.0.rc0.303.g954a862665-goog >
On Fri, Oct 25, 2019 at 2:41 AM Mark Rutland <mark.rutland@arm.com> wrote: > > diff --git a/arch/arm64/lib/copy_page.S b/arch/arm64/lib/copy_page.S > > index bbb8562396af..8b562264c165 100644 > > --- a/arch/arm64/lib/copy_page.S > > +++ b/arch/arm64/lib/copy_page.S > > @@ -34,45 +34,45 @@ alternative_else_nop_endif > > ldp x14, x15, [x1, #96] > > ldp x16, x17, [x1, #112] > > > > - mov x18, #(PAGE_SIZE - 128) > > + add x0, x0, #256 > > add x1, x1, #128 > > 1: > > - subs x18, x18, #128 > > + tst x0, #(PAGE_SIZE - 1) > > > > alternative_if ARM64_HAS_NO_HW_PREFETCH > > prfm pldl1strm, [x1, #384] > > alternative_else_nop_endif > > > > - stnp x2, x3, [x0] > > + stnp x2, x3, [x0, #-256] > > ldp x2, x3, [x1] > > - stnp x4, x5, [x0, #16] > > + stnp x4, x5, [x0, #-240] > > ldp x4, x5, [x1, #16] > > For legibility, could we make the offset and bias explicit in the STNPs > so that these line up? e.g. > > stnp x4, x5, [x0, #16 - 256] > ldp x4, x5, [x1, #16] > > ... that'd make it much easier to see by eye that this is sound, much as > I trust my mental arithmetic. ;) Sure, that makes sense. I'll change this in v3. Sami
diff --git a/arch/arm64/lib/copy_page.S b/arch/arm64/lib/copy_page.S index bbb8562396af..8b562264c165 100644 --- a/arch/arm64/lib/copy_page.S +++ b/arch/arm64/lib/copy_page.S @@ -34,45 +34,45 @@ alternative_else_nop_endif ldp x14, x15, [x1, #96] ldp x16, x17, [x1, #112] - mov x18, #(PAGE_SIZE - 128) + add x0, x0, #256 add x1, x1, #128 1: - subs x18, x18, #128 + tst x0, #(PAGE_SIZE - 1) alternative_if ARM64_HAS_NO_HW_PREFETCH prfm pldl1strm, [x1, #384] alternative_else_nop_endif - stnp x2, x3, [x0] + stnp x2, x3, [x0, #-256] ldp x2, x3, [x1] - stnp x4, x5, [x0, #16] + stnp x4, x5, [x0, #-240] ldp x4, x5, [x1, #16] - stnp x6, x7, [x0, #32] + stnp x6, x7, [x0, #-224] ldp x6, x7, [x1, #32] - stnp x8, x9, [x0, #48] + stnp x8, x9, [x0, #-208] ldp x8, x9, [x1, #48] - stnp x10, x11, [x0, #64] + stnp x10, x11, [x0, #-192] ldp x10, x11, [x1, #64] - stnp x12, x13, [x0, #80] + stnp x12, x13, [x0, #-176] ldp x12, x13, [x1, #80] - stnp x14, x15, [x0, #96] + stnp x14, x15, [x0, #-160] ldp x14, x15, [x1, #96] - stnp x16, x17, [x0, #112] + stnp x16, x17, [x0, #-144] ldp x16, x17, [x1, #112] add x0, x0, #128 add x1, x1, #128 - b.gt 1b + b.ne 1b - stnp x2, x3, [x0] - stnp x4, x5, [x0, #16] - stnp x6, x7, [x0, #32] - stnp x8, x9, [x0, #48] - stnp x10, x11, [x0, #64] - stnp x12, x13, [x0, #80] - stnp x14, x15, [x0, #96] - stnp x16, x17, [x0, #112] + stnp x2, x3, [x0, #-256] + stnp x4, x5, [x0, #-240] + stnp x6, x7, [x0, #-224] + stnp x8, x9, [x0, #-208] + stnp x10, x11, [x0, #-192] + stnp x12, x13, [x0, #-176] + stnp x14, x15, [x0, #-160] + stnp x16, x17, [x0, #-144] ret ENDPROC(copy_page)