| Message ID | 1472049366-10922-9-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
On Wed, Aug 24, 2016 at 04:36:05PM +0200, Ard Biesheuvel wrote: > Instead of stashing the value of the link register in x28 before setting > up the stack and calling into C code, create an ordinary PCS compatible > stack frame so that we can push the return address onto the stack. > > Since exception handlers require a stack as well, assign the stach pointer > register before installing the vector table. Nit: s/stach/stack/ > Note that this accounts for the difference between THREAD_START_SP and > THREAD_SIZE, given that the stack pointer is always decremented before > calling into any C code. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Mark. > --- > arch/arm64/kernel/head.S | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 27f51272de68..ad1dc61d67ac 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -415,13 +415,18 @@ ENDPROC(__create_page_tables) > * > * x0 = __PHYS_OFFSET > */ > - .set initial_sp, init_thread_union + THREAD_START_SP > __primary_switched: > - mov x28, lr // preserve LR > + adrp x4, init_thread_union > + add sp, x4, #THREAD_SIZE > + msr sp_el0, x4 // Save thread_info > + > adr_l x8, vectors // load VBAR_EL1 with virtual > msr vbar_el1, x8 // vector table address > isb > > + stp xzr, x30, [sp, #-16]! > + mov x29, sp > + > str_l x21, __fdt_pointer, x5 // Save FDT pointer > > ldr_l x4, kimage_vaddr // Save the offset between > @@ -436,11 +441,6 @@ __primary_switched: > bl __pi_memset > dsb ishst // Make zero page visible to PTW > > - adr_l sp, initial_sp, x4 > - mov x4, sp > - and x4, x4, #~(THREAD_SIZE - 1) > - msr sp_el0, x4 // Save thread_info > - mov x29, #0 > #ifdef CONFIG_KASAN > bl kasan_early_init > #endif > @@ -452,8 +452,8 @@ __primary_switched: > bl kaslr_early_init // parse FDT for KASLR options > cbz x0, 0f // KASLR disabled? just proceed > orr x23, x23, x0 // record KASLR offset > - ret x28 // we must enable KASLR, return > - // to __primary_switch() > + ldp x29, x30, [sp], #16 // we must enable KASLR, return > + ret // to __primary_switch() > 0: > #endif > b start_kernel > -- > 2.7.4 > _______________________________________________ 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 27f51272de68..ad1dc61d67ac 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -415,13 +415,18 @@ ENDPROC(__create_page_tables) * * x0 = __PHYS_OFFSET */ - .set initial_sp, init_thread_union + THREAD_START_SP __primary_switched: - mov x28, lr // preserve LR + adrp x4, init_thread_union + add sp, x4, #THREAD_SIZE + msr sp_el0, x4 // Save thread_info + adr_l x8, vectors // load VBAR_EL1 with virtual msr vbar_el1, x8 // vector table address isb + stp xzr, x30, [sp, #-16]! + mov x29, sp + str_l x21, __fdt_pointer, x5 // Save FDT pointer ldr_l x4, kimage_vaddr // Save the offset between @@ -436,11 +441,6 @@ __primary_switched: bl __pi_memset dsb ishst // Make zero page visible to PTW - adr_l sp, initial_sp, x4 - mov x4, sp - and x4, x4, #~(THREAD_SIZE - 1) - msr sp_el0, x4 // Save thread_info - mov x29, #0 #ifdef CONFIG_KASAN bl kasan_early_init #endif @@ -452,8 +452,8 @@ __primary_switched: bl kaslr_early_init // parse FDT for KASLR options cbz x0, 0f // KASLR disabled? just proceed orr x23, x23, x0 // record KASLR offset - ret x28 // we must enable KASLR, return - // to __primary_switch() + ldp x29, x30, [sp], #16 // we must enable KASLR, return + ret // to __primary_switch() 0: #endif b start_kernel
Instead of stashing the value of the link register in x28 before setting up the stack and calling into C code, create an ordinary PCS compatible stack frame so that we can push the return address onto the stack. Since exception handlers require a stack as well, assign the stach pointer register before installing the vector table. Note that this accounts for the difference between THREAD_START_SP and THREAD_SIZE, given that the stack pointer is always decremented before calling into any C code. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/kernel/head.S | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) -- 2.7.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel