From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org
Cc: Mark Brown <broonie@kernel.org>, Will Deacon <will@kernel.org>,
Emanuele Rocca <emanuele.rocca@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Shuah Khan <skhan@linuxfoundation.org>
Subject: Re: [PATCH v2 1/3] arm64: gcs: Do not set PTE_SHARED on GCS mappings if FEAT_LPA2 is enabled
Date: Mon, 23 Feb 2026 20:20:00 +0100 [thread overview]
Message-ID: <a7b9f809-7ce5-418a-90f0-8c4e927cc9c3@kernel.org> (raw)
In-Reply-To: <20260223174533.1478164-2-catalin.marinas@arm.com>
On 2/23/26 18:45, Catalin Marinas wrote:
> When FEAT_LPA2 is enabled, bits 8-9 of the PTE replace the
> shareability attribute with bits 50-51 of the output address. The
> _PAGE_GCS{,_RO} definitions include the PTE_SHARED bits as 0b11 (this
> matches the other _PAGE_* definitions) but using this macro directly
> leads to the following panic when enabling GCS on a system/model with
> LPA2:
>
> Unable to handle kernel paging request at virtual address fffff1ffc32d8008
> Mem abort info:
> ESR = 0x0000000096000004
> EC = 0x25: DABT (current EL), IL = 32 bits
> SET = 0, FnV = 0
> EA = 0, S1PTW = 0
> FSC = 0x04: level 0 translation fault
> Data abort info:
> ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
> CM = 0, WnR = 0, TnD = 0, TagAccess = 0
> GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> swapper pgtable: 4k pages, 52-bit VAs, pgdp=0000000060f4d000
> [fffff1ffc32d8008] pgd=100000006184b003, p4d=0000000000000000
> Internal error: Oops: 0000000096000004 [#1] SMP
> CPU: 0 UID: 0 PID: 513 Comm: gcs_write_fault Tainted: G M 7.0.0-rc1 #1 PREEMPT
> Tainted: [M]=MACHINE_CHECK
> Hardware name: QEMU QEMU Virtual Machine, BIOS 2025.02-8+deb13u1 11/08/2025
> pstate: 03402005 (nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> pc : zap_huge_pmd+0x168/0x468
> lr : zap_huge_pmd+0x2c/0x468
> sp : ffff800080beb660
> x29: ffff800080beb660 x28: fff00000c2058180 x27: ffff800080beb898
> x26: fff00000c2058180 x25: ffff800080beb820 x24: 00c800010b600f41
> x23: ffffc1ffc30af1a8 x22: fff00000c2058180 x21: 0000ffff8dc00000
> x20: fff00000c2bc6370 x19: ffff800080beb898 x18: ffff800080bebb60
> x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000007
> x14: 000000000000000a x13: 0000aaaacbbbffff x12: 0000000000000000
> x11: 0000ffff8ddfffff x10: 00000000000001fe x9 : 0000ffff8ddfffff
> x8 : 0000ffff8de00000 x7 : 0000ffff8da00000 x6 : fff00000c2bc6370
> x5 : 0000ffff8da00000 x4 : 000000010b600000 x3 : ffffc1ffc0000000
> x2 : fff00000c2058180 x1 : fffff1ffc32d8000 x0 : 000000c00010b600
> Call trace:
> zap_huge_pmd+0x168/0x468 (P)
> unmap_page_range+0xd70/0x1560
> unmap_single_vma+0x48/0x80
> unmap_vmas+0x90/0x180
> unmap_region+0x88/0xe4
> vms_complete_munmap_vmas+0xf8/0x1e0
> do_vmi_align_munmap+0x158/0x180
> do_vmi_munmap+0xac/0x160
> __vm_munmap+0xb0/0x138
> vm_munmap+0x14/0x20
> gcs_free+0x70/0x80
> mm_release+0x1c/0xc8
> exit_mm_release+0x28/0x38
> do_exit+0x190/0x8ec
> do_group_exit+0x34/0x90
> get_signal+0x794/0x858
> arch_do_signal_or_restart+0x11c/0x3e0
> exit_to_user_mode_loop+0x10c/0x17c
> el0_da+0x8c/0x9c
> el0t_64_sync_handler+0xd0/0xf0
> el0t_64_sync+0x198/0x19c
> Code: aa1603e2 d34cfc00 cb813001 8b011861 (f9400420)
>
> Similarly to how the kernel handles protection_map[], use a
> gcs_page_prot variable to store the protection bits and clear PTE_SHARED
> if LPA2 is enabled.
>
> Also remove the unused PAGE_GCS{,_RO} macros.
>
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Fixes: 6497b66ba694 ("arm64/mm: Map pages for guarded control stack")
> Reported-by: Emanuele Rocca <emanuele.rocca@arm.com>
> Cc: <stable@vger.kernel.org>
> Cc: Mark Brown <broonie@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> ---
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
next prev parent reply other threads:[~2026-02-23 19:20 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-23 17:45 [PATCH v2 0/3] arm64: Assorted GCS fixes Catalin Marinas
2026-02-23 17:45 ` [PATCH v2 1/3] arm64: gcs: Do not set PTE_SHARED on GCS mappings if FEAT_LPA2 is enabled Catalin Marinas
2026-02-23 19:20 ` David Hildenbrand (Arm) [this message]
2026-02-23 17:45 ` [PATCH v2 2/3] arm64: gcs: Honour mprotect(PROT_NONE) on shadow stack mappings Catalin Marinas
2026-02-23 19:20 ` David Hildenbrand (Arm)
2026-02-23 17:45 ` [PATCH v2 3/3] kselftest: arm64: Check access to GCS after mprotect(PROT_NONE) Catalin Marinas
2026-02-23 18:48 ` Mark Brown
2026-02-26 0:06 ` [PATCH v2 0/3] arm64: Assorted GCS fixes Will Deacon
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