From: Will Deacon <will@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Mark Rutland <mark.rutland@arm.com>,
Vladimir Murzin <vladimir.murzin@arm.com>,
Arnd Bergmann <arnd@arndb.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Linus Walleij <linusw@kernel.org>,
linux-kernel@vger.kernel.org, Mostafa Saleh <smostafa@google.com>,
Marc Zyngier <maz@kernel.org>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
Oliver Upton <oupton@kernel.org>, Will Deacon <will@kernel.org>,
Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH 16/21] arm64: entry: Implement EL1t exception handlers for overflow stack
Date: Mon, 7 Sep 2026 17:42:41 +0100 [thread overview]
Message-ID: <20260907164247.17223-17-will@kernel.org> (raw)
In-Reply-To: <20260907164247.17223-1-will@kernel.org>
In preparation for using EL1t to handle exceptions taken whilst running
on the overflow stack, implement some simple wrappers around the EL1h
handlers which perform a best-effort stack overflow check before
proceeding.
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/kernel/entry-common.c | 43 +++++++++++++++++++++++++++++---
1 file changed, 39 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 72c03ccea59f..9738142780df 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -327,10 +327,45 @@ static void debug_exception_exit(struct pt_regs *regs)
}
NOKPROBE_SYMBOL(debug_exception_exit);
-UNHANDLED(el1t, 64, sync)
-UNHANDLED(el1t, 64, irq)
-UNHANDLED(el1t, 64, fiq)
-UNHANDLED(el1t, 64, error)
+static void noinstr el1t_64_check_overflow_stack(struct pt_regs *regs)
+{
+ unsigned long sp = kernel_stack_pointer(regs) - sizeof(*regs);
+ unsigned long ovf_stack = (unsigned long)this_cpu_ptr(overflow_stack);
+
+ /*
+ * We're in big trouble if we've overflowed the overflow stack
+ * so perform a best-effort check before we proceed. If our SP
+ * is outside of the overflow stack for this CPU then presumably
+ * we're already corrupting memory, so park ourselves here in an
+ * attempt to contain the damage.
+ */
+ if (sp < ovf_stack || sp > ovf_stack + OVERFLOW_STACK_SIZE)
+ cpu_park_loop();
+}
+
+asmlinkage void noinstr el1t_64_sync_handler(struct pt_regs *regs)
+{
+ el1t_64_check_overflow_stack(regs);
+ el1h_64_sync_handler(regs);
+}
+
+asmlinkage void noinstr el1t_64_irq_handler(struct pt_regs *regs)
+{
+ el1t_64_check_overflow_stack(regs);
+ el1h_64_irq_handler(regs);
+}
+
+asmlinkage void noinstr el1t_64_fiq_handler(struct pt_regs *regs)
+{
+ el1t_64_check_overflow_stack(regs);
+ el1h_64_fiq_handler(regs);
+}
+
+asmlinkage void noinstr el1t_64_error_handler(struct pt_regs *regs)
+{
+ el1t_64_check_overflow_stack(regs);
+ el1h_64_error_handler(regs);
+}
static void noinstr el1_abort(struct pt_regs *regs, unsigned long esr)
{
--
2.55.0.979.g7e5102b832-goog
next prev parent reply other threads:[~2026-09-07 16:44 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-07 16:42 [PATCH 00/21] arm64: Move overflow sp into SP_EL1 and kernel sp into SP_EL0 Will Deacon
2026-09-07 16:42 ` [PATCH 01/21] arm64: entry: Defer setting of TPIDRRO_EL0 until exit to userspace Will Deacon
2026-09-11 7:53 ` Jinjie Ruan
2026-09-07 16:42 ` [PATCH 02/21] arm64: entry: Only check for stack overflow on exceptions from EL1 Will Deacon
2026-09-07 16:42 ` [PATCH 03/21] arm64: stackprotector: Temporarily disable per-task stackprotector Will Deacon
2026-09-07 16:42 ` [PATCH 04/21] arm64: bpf: Add support for generating reads of TPIDRRO_EL0 Will Deacon
2026-09-07 16:42 ` [PATCH 05/21] KVM: arm64: Protect TPIDRRO_EL0 across guest entry/exit Will Deacon
2026-09-07 16:42 ` [PATCH 06/21] arm64: Store 'current' in TPIDRRO_EL0 instead of SP_EL0 Will Deacon
2026-09-08 13:19 ` David Laight
2026-09-11 12:57 ` Will Deacon
2026-09-07 16:42 ` [PATCH 07/21] selftests/bpf: arm64: Use TPIDRRO_EL0 instead of SP_EL0 for 'current' Will Deacon
2026-09-07 16:42 ` [PATCH 08/21] scripts/gdb: " Will Deacon
2026-09-07 16:42 ` [PATCH 09/21] arm64: stackprotector: Re-enable per-task stackprotector Will Deacon
2026-09-07 16:42 ` [PATCH 10/21] arm64: percpu: Specialise set_my_cpu_offset() for the primary CPU Will Deacon
2026-09-07 16:42 ` [PATCH 11/21] arm64: percpu: Annotate __kern_my_cpu_offset() as '__always_inline' Will Deacon
2026-09-07 16:42 ` [PATCH 12/21] KVM: arm64: Preserve handler/thread bit of EL1 mode in __finalise_el2() Will Deacon
2026-09-07 16:42 ` [PATCH 13/21] arm64: sdei: Guard most of asm/sdei.h with CONFIG_ARM_SDE_INTERFACE Will Deacon
2026-09-07 16:42 ` [PATCH 14/21] arm64: sdei: Support SDEI events from kernel handler and thread modes Will Deacon
2026-09-07 16:42 ` [PATCH 15/21] arm64: entry: Point SP_EL0 at the overflow stack Will Deacon
2026-09-07 16:42 ` Will Deacon [this message]
2026-09-07 16:42 ` [PATCH 17/21] arm64: entry: Use SPSel to switch to " Will Deacon
2026-09-07 16:42 ` [PATCH 18/21] arm64: entry: Split up kernel_ventry macro into separate helper macros Will Deacon
2026-09-07 16:42 ` [PATCH 19/21] arm64: entry: The great stack switcheroo Will Deacon
2026-09-08 11:30 ` Will Deacon
2026-09-07 16:42 ` [PATCH 20/21] arm64: tracing: Advertise a mode of EL1t in synthetic kernel regs Will Deacon
2026-09-07 16:42 ` [PATCH 21/21] arm64: Rename 'overflow_stack' and OVERFLOW_STACK_SIZE Will Deacon
2026-09-09 10:39 ` [PATCH 00/21] arm64: Move overflow sp into SP_EL1 and kernel sp into SP_EL0 Vladimir Murzin
2026-09-09 11:29 ` Will Deacon
2026-09-10 13:49 ` Vladimir Murzin
2026-09-11 12:57 ` Will Deacon
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