kernel/linux.git/arch/arm/vfp, branch v6.3.6

ARM: 9297/1: vfp: avoid unbalanced stack on 'success' return path

2023-05-24T16:30:24+00:00

[ Upstream commit 2b951b0efbaa6c805854b60c11f08811054d50cd ] Commit c76c6c4ecbec0deb5 ("ARM: 9294/2: vfp: Fix broken softirq handling with instrumentation enabled") updated the VFP exception entry logic to go via a C function, so that we get the compiler's version of local_bh_disable(), which may be instrumented, and isn't generally callable from assembler. However, this assumes that passing an alternative 'success' return address works in C as it does in asm, and this is only the case if the C calls in question are tail calls, as otherwise, the stack will need some unwinding as well. I have already sent patches to the list that replace most of the asm logic with C code, and so it is preferable to have a minimal fix that addresses the issue and can be backported along with the commit that it fixes to v6.3 from v6.4. Hopefully, we can land the C conversion for v6.5. So instead of passing the 'success' return address as a function argument, pass the stack address from where to pop it so that both LR and SP have the expected value. Fixes: c76c6c4ecbec0deb5 ("ARM: 9294/2: vfp: Fix broken softirq handling with ...") Reported-by: syzbot+d4b00edc2d0c910d4bf4@syzkaller.appspotmail.com Tested-by: syzbot+d4b00edc2d0c910d4bf4@syzkaller.appspotmail.com Reviewed-by: Linus Walleij Tested-by: Andrew Lunn Signed-off-by: Ard Biesheuvel Tested-by: Andre Przywara Signed-off-by: Russell King (Oracle) Signed-off-by: Sasha Levin

ARM: 9294/2: vfp: Fix broken softirq handling with instrumentation enabled

2023-05-24T16:30:24+00:00

[ Upstream commit c76c6c4ecbec0deb56a4f9e932b26866024a508f ] Commit 62b95a7b44d1 ("ARM: 9282/1: vfp: Manipulate task VFP state with softirqs disabled") replaced the en/disable preemption calls inside the VFP state handling code with en/disabling of soft IRQs, which is necessary to allow kernel use of the VFP/SIMD unit when handling a soft IRQ. Unfortunately, when lockdep is enabled (or other instrumentation that enables TRACE_IRQFLAGS), the disable path implemented in asm fails to perform the lockdep and RCU related bookkeeping, resulting in spurious warnings and other badness. Set let's rework the VFP entry code a little bit so we can make the local_bh_disable() call from C, with all the instrumentations that happen to have been configured. Calling local_bh_enable() can be done from asm, as it is a simple wrapper around __local_bh_enable_ip(), which is always a callable function. Link: https://lore.kernel.org/all/ZBBYCSZUJOWBg1s8@localhost.localdomain/ Fixes: 62b95a7b44d1 ("ARM: 9282/1: vfp: Manipulate task VFP state with softirqs disabled") Signed-off-by: Ard Biesheuvel Reviewed-by: Linus Walleij Tested-by: Guenter Roeck Signed-off-by: Russell King (Oracle) Signed-off-by: Sasha Levin

ARM: 9293/1: vfp: Pass successful return address via register R3

2023-05-11T14:16:56+00:00

[ Upstream commit 3a2bdad0b46649cc73fb3b3f9e2b91ef97a7fa63 ] In preparation for reimplementing the do_vfp()->vfp_support_entry() handover in C code, switch to using R3 to pass the 'success' return address, rather than R9, as it cannot be used for parameter passing. Signed-off-by: Ard Biesheuvel Reviewed-by: Linus Walleij Tested-by: Guenter Roeck Signed-off-by: Russell King (Oracle) Stable-dep-of: c76c6c4ecbec ("ARM: 9294/2: vfp: Fix broken softirq handling with instrumentation enabled") Signed-off-by: Sasha Levin

ARM: 9292/1: vfp: Pass thread_info pointer to vfp_support_entry

2023-05-11T14:16:56+00:00

[ Upstream commit dae904d96ad6a5fa79bd9d99a3decf93685d398b ] Instead of dereferencing thread_info in do_vfp, pass the thread_info pointer to vfp_support_entry via R1. That way, we only use a single caller save register, which makes it easier to convert do_vfp to C code in a subsequent patch. Note that, unlike the CPU number, which can change due to preemption, passing the thread_info pointer can safely be done with preemption enabled. Signed-off-by: Ard Biesheuvel Reviewed-by: Linus Walleij Tested-by: Guenter Roeck Signed-off-by: Russell King (Oracle) Stable-dep-of: c76c6c4ecbec ("ARM: 9294/2: vfp: Fix broken softirq handling with instrumentation enabled") Signed-off-by: Sasha Levin

ARM: 9283/1: permit non-nested kernel mode NEON in softirq context

2023-01-11T16:21:21+00:00

We currently only permit kernel mode NEON in process context, to avoid the need to preserve/restore the NEON register file when taking an exception while running in the kernel. Like we did on arm64, we can relax this restriction substantially, by permitting kernel mode NEON from softirq context, while ensuring that softirq processing is disabled when the NEON is being used in task context. This guarantees that only NEON context belonging to user space needs to be preserved and restored, which is already taken care of. This is especially relevant for network encryption, where incoming frames are typically handled in softirq context, and deferring software decryption to a kernel thread or falling back to C code are both undesirable from a performance PoV. Tested-by: Martin Willi Reviewed-by: Linus Walleij Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King (Oracle)

ARM: 9282/1: vfp: Manipulate task VFP state with softirqs disabled

2023-01-11T16:21:20+00:00

In a subsequent patch, we will relax the kernel mode NEON policy, and permit kernel mode NEON to be used not only from task context, as is permitted today, but also from softirq context. Given that softirqs may trigger over the back of any IRQ unless they are explicitly disabled, we need to address the resulting races in the VFP state handling, by disabling softirq processing in two distinct but related cases: - kernel mode NEON will leave the FPU disabled after it completes, so any kernel code sequence that enables the FPU and subsequently accesses its registers needs to disable softirqs until it completes; - kernel_neon_begin() will preserve the userland VFP state in memory, and if it interrupts the ordinary VFP state preserve sequence, the latter will resume execution with the VFP registers corrupted, and happily continue saving them to memory. Given that disabling softirqs also disables preemption, we can replace the existing preempt_disable/enable occurrences in the VFP state handling asm code with new macros that dis/enable softirqs instead. In the VFP state handling C code, add local_bh_disable/enable() calls in those places where the VFP state is preserved. One thing to keep in mind is that, once we allow NEON use in softirq context, the result of any such interruption is that the FPEXC_EN bit in the FPEXC register will be cleared, and vfp_current_hw_state[cpu] will be NULL. This means that any sequence that [conditionally] clears FPEXC_EN and/or sets vfp_current_hw_state[cpu] to NULL does not need to run with softirqs disabled, as the result will be the same. Furthermore, the handling of THREAD_NOTIFY_SWITCH is guaranteed to run with IRQs disabled, and so it does not need protection from softirq interruptions either. Tested-by: Martin Willi Reviewed-by: Linus Walleij Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King (Oracle)

ARM: 9272/1: vfp: Add hwcap for FEAT_AA32I8MM

2022-11-28T11:57:34+00:00

Int8 matrix multiplication (FEAT_AA32I8MM) is a feature present in AArch32 state for Armv8 and is represented by ISAR6.I8MM identification register. This feature denotes the presence of VSMMLA, VSUDOT, VUMMLA, VUSMMLA and VUSDOT instructions and hence adding a hwcap will enable the userspace to check it before trying to use those instructions. Reviewed-by: Linus Walleij Signed-off-by: Amit Daniel Kachhap Signed-off-by: Russell King (Oracle)

ARM: 9271/1: vfp: Add hwcap for FEAT_AA32BF16

2022-11-28T11:57:33+00:00

Advanced SIMD BFloat16 (FEAT_AA32BF16) is a feature present in AArch32 state for Armv8 and is represented by ISAR6.BF16 identification register. This feature denotes the presence of VCVT, VCVTB, VCVTT, VDOT, VFMAB, VFMAT and VMMLA instructions and hence adding a hwcap will enable the userspace to check it before trying to use those instructions. Reviewed-by: Linus Walleij Signed-off-by: Amit Daniel Kachhap Signed-off-by: Russell King (Oracle)

ARM: 9270/1: vfp: Add hwcap for FEAT_FHM

2022-11-28T11:57:33+00:00

Floating-point half-precision multiplication (FHM) is a feature present in AArch32 state for Armv8 and is represented by ISAR6.FHM identification register. This feature denotes the presence of VFMAL and VMFSL instructions and hence adding a hwcap will enable the userspace to check it before trying to use those instructions. Reviewed-by: Linus Walleij Signed-off-by: Amit Daniel Kachhap Signed-off-by: Russell King (Oracle)

ARM: 9269/1: vfp: Add hwcap for FEAT_DotProd

2022-11-28T11:57:32+00:00

Advanced Dot product is a feature present in AArch32 state for Armv8 and is represented by ISAR6 identification register. This feature denotes the presence of UDOT and SDOT instructions and hence adding a hwcap will enable the userspace to check it before trying to use those instructions. Reviewed-by: Linus Walleij Signed-off-by: Amit Daniel Kachhap Signed-off-by: Russell King (Oracle)