kernel/linux.git/arch/arm64/include/asm/assembler.h, branch v6.12.80

arm64/entry: Mask DAIF in cpu_switch_to(), call_on_irq_stack()

2025-08-01T08:48:43+00:00

commit d42e6c20de6192f8e4ab4cf10be8c694ef27e8cb upstream. `cpu_switch_to()` and `call_on_irq_stack()` manipulate SP to change to different stacks along with the Shadow Call Stack if it is enabled. Those two stack changes cannot be done atomically and both functions can be interrupted by SErrors or Debug Exceptions which, though unlikely, is very much broken : if interrupted, we can end up with mismatched stacks and Shadow Call Stack leading to clobbered stacks. In `cpu_switch_to()`, it can happen when SP_EL0 points to the new task, but x18 stills points to the old task's SCS. When the interrupt handler tries to save the task's SCS pointer, it will save the old task SCS pointer (x18) into the new task struct (pointed to by SP_EL0), clobbering it. In `call_on_irq_stack()`, it can happen when switching from the task stack to the IRQ stack and when switching back. In both cases, we can be interrupted when the SCS pointer points to the IRQ SCS, but SP points to the task stack. The nested interrupt handler pushes its return addresses on the IRQ SCS. It then detects that SP points to the task stack, calls `call_on_irq_stack()` and clobbers the task SCS pointer with the IRQ SCS pointer, which it will also use ! This leads to tasks returning to addresses on the wrong SCS, or even on the IRQ SCS, triggering kernel panics via CONFIG_VMAP_STACK or FPAC if enabled. This is possible on a default config, but unlikely. However, when enabling CONFIG_ARM64_PSEUDO_NMI, DAIF is unmasked and instead the GIC is responsible for filtering what interrupts the CPU should receive based on priority. Given the goal of emulating NMIs, pseudo-NMIs can be received by the CPU even in `cpu_switch_to()` and `call_on_irq_stack()`, possibly *very* frequently depending on the system configuration and workload, leading to unpredictable kernel panics. Completely mask DAIF in `cpu_switch_to()` and restore it when returning. Do the same in `call_on_irq_stack()`, but restore and mask around the branch. Mask DAIF even if CONFIG_SHADOW_CALL_STACK is not enabled for consistency of behaviour between all configurations. Introduce and use an assembly macro for saving and masking DAIF, as the existing one saves but only masks IF. Cc: Signed-off-by: Ada Couprie Diaz Reported-by: Cristian Prundeanu Fixes: 59b37fe52f49 ("arm64: Stash shadow stack pointer in the task struct on interrupt") Tested-by: Cristian Prundeanu Acked-by: Will Deacon Link: https://lore.kernel.org/r/20250718142814.133329-1-ada.coupriediaz@arm.com Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman

arm64/mm: Override PARange for !LPA2 and use it consistently

2025-02-17T09:05:05+00:00

commit 62cffa496aac0c2c4eeca00d080058affd7a0172 upstream. When FEAT_LPA{,2} are not implemented, the ID_AA64MMFR0_EL1.PARange and TCR.IPS values corresponding with 52-bit physical addressing are reserved. Setting the TCR.IPS field to 0b110 (52-bit physical addressing) has side effects, such as how the TTBRn_ELx.BADDR fields are interpreted, and so it is important that disabling FEAT_LPA2 (by overriding the ID_AA64MMFR0.TGran fields) also presents a PARange field consistent with that. So limit the field to 48 bits unless LPA2 is enabled, and update existing references to use the override consistently. Fixes: 352b0395b505 ("arm64: Enable 52-bit virtual addressing for 4k and 16k granule configs") Cc: stable@vger.kernel.org Signed-off-by: Ard Biesheuvel Acked-by: Marc Zyngier Link: https://lore.kernel.org/r/20241212081841.2168124-10-ardb+git@google.com Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman

Merge branch 'for-next/perf' into for-next/core

2024-05-09T14:56:10+00:00

* for-next/perf: (41 commits) arm64: Add USER_STACKTRACE support drivers/perf: hisi: hns3: Actually use devm_add_action_or_reset() drivers/perf: hisi: hns3: Fix out-of-bound access when valid event group drivers/perf: hisi_pcie: Fix out-of-bound access when valid event group perf/arm-spe: Assign parents for event_source device perf/arm-smmuv3: Assign parents for event_source device perf/arm-dsu: Assign parents for event_source device perf/arm-dmc620: Assign parents for event_source device perf/arm-ccn: Assign parents for event_source device perf/arm-cci: Assign parents for event_source device perf/alibaba_uncore: Assign parents for event_source device perf/arm_pmu: Assign parents for event_source devices perf/imx_ddr: Assign parents for event_source devices perf/qcom: Assign parents for event_source devices Documentation: qcom-pmu: Use /sys/bus/event_source/devices paths perf/riscv: Assign parents for event_source devices perf/thunderx2: Assign parents for event_source devices Documentation: thunderx2-pmu: Use /sys/bus/event_source/devices paths perf/xgene: Assign parents for event_source devices Documentation: xgene-pmu: Use /sys/bus/event_source/devices paths ...

arm64: defer clearing DAIF.D

2024-04-28T07:40:35+00:00

For historical reasons we unmask debug exceptions in __cpu_setup(), but it's not necessary to unmask debug exceptions this early in the boot/idle entry paths. It would be better to unmask debug exceptions later in C code as this simplifies the current code and will make it easier to rework exception masking logic to handle non-DAIF bits in future (e.g. PSTATE.{ALLINT,PM}). We started clearing DAIF.D in __cpu_setup() in commit: 2ce39ad15182604b ("arm64: debug: unmask PSTATE.D earlier") At the time, we needed to ensure that DAIF.D was clear on the primary CPU before scheduling and preemption were possible, and chose to do this in __cpu_setup() so that this occurred in the same place for primary and secondary CPUs. As we cannot handle debug exceptions this early, we placed an ISB between initializing MDSCR_EL1 and clearing DAIF.D so that no exceptions should be triggered. Subsequently we rewrote the return-from-{idle,suspend} paths to use __cpu_setup() in commit: cabe1c81ea5be983 ("arm64: Change cpu_resume() to enable mmu early then access sleep_sp by va") ... which allowed for earlier use of the MMU and had the desirable property of using the same code to reset the CPU in the cold and warm boot paths. This introduced a bug: DAIF.D was clear while cpu_do_resume() restored MDSCR_EL1 and other control registers (e.g. breakpoint/watchpoint control/value registers), and so we could unexpectedly take debug exceptions. We fixed that in commit: 744c6c37cc18705d ("arm64: kernel: Fix unmasked debug exceptions when restoring mdscr_el1") ... by having cpu_do_resume() use the `disable_dbg` macro to set DAIF.D before restoring MDSCR_EL1 and other control registers. This relies on DAIF.D being subsequently cleared again in cpu_resume(). Subsequently we reworked DAIF masking in commit: 0fbeb318754860b3 ("arm64: explicitly mask all exceptions") ... where we began enforcing a policy that DAIF.D being set implies all other DAIF bits are set, and so e.g. we cannot take an IRQ while DAIF.D is set. As part of this the use of `disable_dbg` in cpu_resume() was replaced with `disable_daif` for consistency with the rest of the kernel. These days, there's no need to clear DAIF.D early within __cpu_setup(): * setup_arch() clears DAIF.DA before scheduling and preemption are possible on the primary CPU, avoiding the problem we we originally trying to work around. Note: DAIF.IF get cleared later when interrupts are enabled for the first time. * secondary_start_kernel() clears all DAIF bits before scheduling and preemption are possible on secondary CPUs. Note: with pseudo-NMI, the PMR is initialized here before any DAIF bits are cleared. Similar will be necessary for the architectural NMI. * cpu_suspend() restores all DAIF bits when returning from idle, ensuring that we don't unexpectedly leave DAIF.D clear or set. Note: with pseudo-NMI, the PMR is initialized here before DAIF is cleared. Similar will be necessary for the architectural NMI. This patch removes the unmasking of debug exceptions from __cpu_setup(), relying on the above locations to initialize DAIF. This allows some other cleanups: * It is no longer necessary for cpu_resume() to explicitly mask debug (or other) exceptions, as it is always called with all DAIF bits set. Thus we drop the use of `disable_daif`. * The `enable_dbg` macro is no longer used, and so is dropped. * It is no longer necessary to have an ISB immediately after initializing MDSCR_EL1 in __cpu_setup(), and we can revert to relying on the context synchronization that occurs when the MMU is enabled between __cpu_setup() and code which clears DAIF.D Comments are added to setup_arch() and secondary_start_kernel() to explain the initial unmasking of the DAIF bits. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Mark Brown Cc: Will Deacon Link: https://lore.kernel.org/r/20240422113523.4070414-3-mark.rutland@arm.com Signed-off-by: Will Deacon

arm64: assembler: update stale comment for disable_step_tsk

2024-04-28T07:40:35+00:00

A comment in the disable_step_tsk macro refers to synchronising with enable_dbg, as historically the entry used enable_dbg to unmask debug exceptions after disabling single-stepping. These days the unmasking happens in entry-common.c via local_daif_restore() or local_daif_inherit(), so the comment is stale. This logic is likely to chang in future, so it would be best to avoid referring to those macros specifically. Update the comment to take this into account, and describe it in terms of clearing DAIF.D so that it doesn't macro where this logic lives nor what it is called. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Mark Brown Cc: Will Deacon Reviewed-by: Mark Brown Link: https://lore.kernel.org/r/20240422113523.4070414-2-mark.rutland@arm.com Signed-off-by: Will Deacon

arm64: arm_pmuv3: Correctly extract and check the PMUVer

2024-04-12T11:54:55+00:00

Currently we're using "sbfx" to extract the PMUVer from ID_AA64DFR0_EL1 and skip the init/reset if no PMU present when the extracted PMUVer is negative or is zero. However for PMUv3p8 the PMUVer will be 0b1000 and PMUVer extracted by "sbfx" will always be negative and we'll skip the init/reset in __init_el2_debug/reset_pmuserenr_el0 unexpectedly. So this patch use "ubfx" instead of "sbfx" to extract the PMUVer. If the PMUVer is implementation defined (0b1111) or not implemented(0b0000) then skip the reset/init. Previously we'll also skip the init/reset if the PMUVer is higher than the version we known (currently PMUv3p9), with this patch we'll only skip if the PMU is not implemented or implementation defined. This keeps consistence with how we probe the PMU in the driver with pmuv3_implemented(). Signed-off-by: Yicong Yang Link: https://lore.kernel.org/r/20240411123030.7201-1-yangyicong@huawei.com Signed-off-by: Will Deacon

Merge branch 'for-next/stage1-lpa2' into for-next/core

2024-03-07T19:05:29+00:00

* for-next/stage1-lpa2: (48 commits) : Add support for LPA2 and WXN and stage 1 arm64/mm: Avoid ID mapping of kpti flag if it is no longer needed arm64/mm: Use generic __pud_free() helper in pud_free() implementation arm64: gitignore: ignore relacheck arm64: Use Signed/Unsigned enums for TGRAN{4,16,64} and VARange arm64: mm: Make PUD folding check in set_pud() a runtime check arm64: mm: add support for WXN memory translation attribute mm: add arch hook to validate mmap() prot flags arm64: defconfig: Enable LPA2 support arm64: Enable 52-bit virtual addressing for 4k and 16k granule configs arm64: kvm: avoid CONFIG_PGTABLE_LEVELS for runtime levels arm64: ptdump: Deal with translation levels folded at runtime arm64: ptdump: Disregard unaddressable VA space arm64: mm: Add support for folding PUDs at runtime arm64: kasan: Reduce minimum shadow alignment and enable 5 level paging arm64: mm: Add 5 level paging support to fixmap and swapper handling arm64: Enable LPA2 at boot if supported by the system arm64: mm: add LPA2 and 5 level paging support to G-to-nG conversion arm64: mm: Add definitions to support 5 levels of paging arm64: mm: Add LPA2 support to phys<->pte conversion routines arm64: mm: Wire up TCR.DS bit to PTE shareability fields ...

arm64: Remove enable_daif macro

2024-03-01T17:41:37+00:00

Since commit bb8e93a287a5 ("arm64: entry: convert SError handlers to C"), the enable_daif assembler macro is no longer used anywhere, so remove it. Signed-off-by: Jinjie Ruan Reviewed-by: Mark Brown Acked-by: Mark Rutland Link: https://lore.kernel.org/r/20240229132802.1682026-2-ruanjinjie@huawei.com Signed-off-by: Catalin Marinas

arm64: Enable LPA2 at boot if supported by the system

2024-02-16T12:42:40+00:00

Update the early kernel mapping code to take 52-bit virtual addressing into account based on the LPA2 feature. This is a bit more involved than LVA (which is supported with 64k pages only), given that some page table descriptor bits change meaning in this case. To keep the handling in asm to a minimum, the initial ID map is still created with 48-bit virtual addressing, which implies that the kernel image must be loaded into 48-bit addressable physical memory. This is currently required by the boot protocol, even though we happen to support placement outside of that for LVA/64k based configurations. Enabling LPA2 involves more than setting TCR.T1SZ to a lower value, there is also a DS bit in TCR that needs to be set, and which changes the meaning of bits [9:8] in all page table descriptors. Since we cannot enable DS and every live page table descriptor at the same time, let's pivot through another temporary mapping. This avoids the need to reintroduce manipulations of the page tables with the MMU and caches disabled. To permit the LPA2 feature to be overridden on the kernel command line, which may be necessary to work around silicon errata, or to deal with mismatched features on heterogeneous SoC designs, test for CPU feature overrides first, and only then enable LPA2. Signed-off-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20240214122845.2033971-78-ardb+git@google.com Signed-off-by: Catalin Marinas

arm64: mm: Add LPA2 support to phys<->pte conversion routines

2024-02-16T12:42:38+00:00

In preparation for enabling LPA2 support, introduce the mask values for converting between physical addresses and their representations in a page table descriptor. While at it, move the pte_to_phys asm macro into its only user, so that we can freely modify it to use its input value register as a temp register. For LPA2, the PTE_ADDR_MASK contains two non-adjacent sequences of zero bits, which means it no longer fits into the immediate field of an ordinary ALU instruction. So let's redefine it to include the bits in between as well, and only use it when converting from physical address to PTE representation, where the distinction does not matter. Also update the name accordingly to emphasize this. Signed-off-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20240214122845.2033971-75-ardb+git@google.com Signed-off-by: Catalin Marinas