From: Catalin Marinas <catalin.marinas@arm.com>
To: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Ard Biesheuvel <ardb@kernel.org>,
Ada Couprie Diaz <ada.coupriediaz@arm.com>,
David Hildenbrand <david@kernel.org>,
Vladimir Murzin <vladimir.murzin@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Mostafa Saleh <smostafa@google.com>,
Lorenzo Stoakes <ljs@kernel.org>,
Oliver Upton <oupton@kernel.org>,
Linus Walleij <linusw@kernel.org>, Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH v2 15/21] arm64: entry: Point SP_EL0 at the overflow stack
Date: Mon, 21 Sep 2026 16:56:47 +0100 [thread overview]
Message-ID: <arFTvxg2FJQUV7qt@arm.com> (raw)
In-Reply-To: <20260918161407.2300-16-will@kernel.org>
On Fri, Sep 18, 2026 at 05:13:59PM +0100, Will Deacon wrote:
> static void __init set_boot_cpu_offset(void)
> {
> - asm volatile("msr tpidr_el1, %0"
> - :: "r" (per_cpu_offset(0)) : "memory");
> + u64 ovf_sp = (u64)raw_cpu_ptr(overflow_stack) + OVERFLOW_STACK_SIZE;
raw_cpu_ptr() is using tpidr_el1 and we haven't initialised it yet.
Actually, I think we get away with it because in head.S we initialise it
to 0 (__per_cpu_offsets[0] is still zero at that point for the boot CPU).
> +
> + asm volatile(
> + " msr tpidr_el1, %1\n"
> + " add %0, %0, %1\n"
> + " msr sp_el0, %0" /* Update the overflow stack pointer */
> + : "+r" (ovf_sp)
> + : "r" (per_cpu_offset(0))
> + : "memory");
Even if this is intentional and we rely in TPIDR_EL1 to be 0, it feels
weird to add the offset to raw_cpu_ptr().
Could we just do (untested):
unsigned long ovf_sp = (unsigned long)per_cpu_ptr(overflow_stack, 0) +
OVERFLOW_STACK_SIZE;
asm volatile(
" msr tpidr_el1, %0\n"
" msr sp_el0, %1"
:
: "r" (per_cpu_offset(0)), "r" (ovf_sp)
: "memory");
with no further arithmetics in asm.
--
Catalin
next prev parent reply other threads:[~2026-09-21 15:56 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-18 16:13 [PATCH v2 00/21] arm64: Move overflow sp into SP_EL1 and kernel sp into SP_EL0 Will Deacon
2026-09-18 16:13 ` [PATCH v2 01/21] arm64: entry: Defer setting of TPIDRRO_EL0 until exit to userspace Will Deacon
2026-09-18 16:13 ` [PATCH v2 02/21] arm64: entry: Only check for stack overflow on exceptions from EL1 Will Deacon
2026-09-18 16:13 ` [PATCH v2 03/21] arm64: stackprotector: Temporarily disable per-task stackprotector Will Deacon
2026-09-18 16:13 ` [PATCH v2 04/21] arm64: bpf: Add support for generating reads of TPIDRRO_EL0 Will Deacon
2026-09-18 16:13 ` [PATCH v2 05/21] KVM: arm64: Protect TPIDRRO_EL0 across guest entry/exit Will Deacon
2026-09-18 16:13 ` [PATCH v2 06/21] arm64: Store 'current' in TPIDRRO_EL0 instead of SP_EL0 Will Deacon
2026-09-18 16:13 ` [PATCH v2 07/21] selftests/bpf: arm64: Use TPIDRRO_EL0 instead of SP_EL0 for 'current' Will Deacon
2026-09-18 16:13 ` [PATCH v2 08/21] scripts/gdb: " Will Deacon
2026-09-18 16:13 ` [PATCH v2 09/21] arm64: stackprotector: Re-enable per-task stackprotector Will Deacon
2026-09-18 16:13 ` [PATCH v2 10/21] arm64: percpu: Specialise set_my_cpu_offset() for the primary CPU Will Deacon
2026-09-18 16:13 ` [PATCH v2 11/21] arm64: percpu: Annotate __kern_my_cpu_offset() as '__always_inline' Will Deacon
2026-09-18 16:13 ` [PATCH v2 12/21] KVM: arm64: Preserve handler/thread bit of EL1 mode in __finalise_el2() Will Deacon
2026-09-18 16:13 ` [PATCH v2 13/21] arm64: sdei: Guard most of asm/sdei.h with CONFIG_ARM_SDE_INTERFACE Will Deacon
2026-09-18 16:13 ` [PATCH v2 14/21] arm64: sdei: Support SDEI events from kernel handler and thread modes Will Deacon
2026-09-18 16:13 ` [PATCH v2 15/21] arm64: entry: Point SP_EL0 at the overflow stack Will Deacon
2026-09-21 15:56 ` Catalin Marinas [this message]
2026-09-18 16:14 ` [PATCH v2 16/21] arm64: entry: Implement EL1t exception handlers for " Will Deacon
2026-09-18 16:14 ` [PATCH v2 17/21] arm64: entry: Use SPSel to switch to " Will Deacon
2026-09-18 16:14 ` [PATCH v2 18/21] arm64: entry: Split up kernel_ventry macro into separate helper macros Will Deacon
2026-09-18 16:14 ` [PATCH v2 19/21] arm64: entry: The great stack switcheroo Will Deacon
2026-09-19 11:41 ` Bradley Morgan
2026-09-22 13:51 ` Catalin Marinas
2026-09-18 16:14 ` [PATCH v2 20/21] arm64: tracing: Advertise a mode of EL1t in synthetic kernel regs Will Deacon
2026-09-22 14:00 ` Catalin Marinas
2026-09-18 16:14 ` [PATCH v2 21/21] arm64: Rename 'overflow_stack' and OVERFLOW_STACK_SIZE Will Deacon
2026-09-22 14:01 ` Catalin Marinas
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