From: Quentin Perret <qperret@xxxxxxxxxx> The asm entry code in the kernel uses a trick to check if VMAP'd stacks have overflowed by aligning them at THREAD_SHIFT * 2 granularity and checking the SP's THREAD_SHIFT bit. Protected KVM will soon make use of a similar trick to detect stack overflows, so factor out the asm code in a re-usable macro. Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx> [Kalesh - Resolve minor conflicts] Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx> --- arch/arm64/include/asm/assembler.h | 11 +++++++++++ arch/arm64/kernel/entry.S | 7 +------ 2 files changed, 12 insertions(+), 6 deletions(-) diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index e8bd0af0141c..ad40eb0eee83 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -850,4 +850,15 @@ alternative_endif #endif /* GNU_PROPERTY_AARCH64_FEATURE_1_DEFAULT */ +/* + * Test whether the SP has overflowed, without corrupting a GPR. + */ +.macro test_sp_overflow shift, label + add sp, sp, x0 // sp' = sp + x0 + sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp + tbnz x0, #\shift, \label + sub x0, sp, x0 // x0'' = sp' - x0' = (sp + x0) - sp = x0 + sub sp, sp, x0 // sp'' = sp' - x0 = (sp + x0) - x0 = sp +.endm + #endif /* __ASM_ASSEMBLER_H */ diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 772ec2ecf488..ce99ee30c77e 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -53,15 +53,10 @@ alternative_else_nop_endif sub sp, sp, #PT_REGS_SIZE #ifdef CONFIG_VMAP_STACK /* - * Test whether the SP has overflowed, without corrupting a GPR. * Task and IRQ stacks are aligned so that SP & (1 << THREAD_SHIFT) * should always be zero. */ - add sp, sp, x0 // sp' = sp + x0 - sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp - tbnz x0, #THREAD_SHIFT, 0f - sub x0, sp, x0 // x0'' = sp' - x0' = (sp + x0) - sp = x0 - sub sp, sp, x0 // sp'' = sp' - x0 = (sp + x0) - x0 = sp + test_sp_overflow THREAD_SHIFT, 0f b el\el\ht\()_\regsize\()_\label 0: -- 2.35.1.473.g83b2b277ed-goog _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
