kernel.git/arch/arm64/kernel/ptrace.c, branch linux-5.16.y

arm64/sve: Put system wide vector length information into structs

2021-10-21T09:18:17Z

With the introduction of SME we will have a second vector length in the system, enumerated and configured in a very similar fashion to the existing SVE vector length. While there are a few differences in how things are handled this is a relatively small portion of the overall code so in order to avoid code duplication we factor out We create two structs, one vl_info for the static hardware properties and one vl_config for the runtime configuration, with an array instantiated for each and update all the users to reference these. Some accessor functions are provided where helpful for readability, and the write to set the vector length is put into a function since the system register being updated needs to be chosen at compile time. This is a mostly mechanical replacement, further work will be required to actually make things generic, ensuring that we handle those places where there are differences properly. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20211019172247.3045838-8-broonie@kernel.org Signed-off-by: Will Deacon

arm64/sve: Use accessor functions for vector lengths in thread_struct

2021-10-21T09:18:17Z

In a system with SME there are parallel vector length controls for SVE and SME vectors which function in much the same way so it is desirable to share the code for handling them as much as possible. In order to prepare for doing this add a layer of accessor functions for the various VL related operations on tasks. Since almost all current interactions are actually via task->thread rather than directly with the thread_info the accessors use that. Accessors are provided for both generic and SVE specific usage, the generic accessors should be used for cases where register state is being manipulated since the registers are shared between streaming and regular SVE so we know that when SME support is implemented we will always have to be in the appropriate mode already and hence can generalise now. Since we are using task_struct and we don't want to cause widespread inclusion of sched.h the acessors are all out of line, it is hoped that none of the uses are in a sufficiently critical path for this to be an issue. Those that are most likely to present an issue are in the same translation unit so hopefully the compiler may be able to inline anyway. This is purely adding the layer of abstraction, additional work will be needed to support tasks using SME. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20211019172247.3045838-7-broonie@kernel.org Signed-off-by: Will Deacon

Merge remote-tracking branch 'tip/sched/arm64' into for-next/core

2021-08-31T08:10:00Z

* tip/sched/arm64: (785 commits) Documentation: arm64: describe asymmetric 32-bit support arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 arm64: Advertise CPUs capable of running 32-bit applications in sysfs arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 arm64: Implement task_cpu_possible_mask() sched: Introduce dl_task_check_affinity() to check proposed affinity sched: Allow task CPU affinity to be restricted on asymmetric systems sched: Split the guts of sched_setaffinity() into a helper function sched: Introduce task_struct::user_cpus_ptr to track requested affinity sched: Reject CPU affinity changes based on task_cpu_possible_mask() cpuset: Cleanup cpuset_cpus_allowed_fallback() use in select_fallback_rq() cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 sched: Introduce task_cpu_possible_mask() to limit fallback rq selection sched: Cgroup SCHED_IDLE support sched/topology: Skip updating masks for non-online nodes Linux 5.14-rc6 lib: use PFN_PHYS() in devmem_is_allowed() ...

arm64/sve: Better handle failure to allocate SVE register storage

2021-08-24T15:44:30Z

Currently we "handle" failure to allocate the SVE register storage by doing a BUG_ON() and hoping for the best. This is obviously not great and the memory allocation failure will already be loud enough without the BUG_ON(). As the comment says it is a corner case but let's try to do a bit better, remove the BUG_ON() and add code to handle the failure in the callers. For the ptrace and signal code we can return -ENOMEM gracefully however we have no real error reporting path available to us for the SVE access trap so instead generate a SIGKILL if the allocation fails there. This at least means that we won't try to soldier on and end up trying to access the nonexistant state and while it's obviously not ideal for userspace SIGKILL doesn't allow any handling so minimises the ABI impact, making it easier to improve the interface later if we come up with a better idea. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20210824153417.18371-1-broonie@kernel.org Signed-off-by: Catalin Marinas

arm64: fix compat syscall return truncation

2021-08-03T09:35:03Z

Due to inconsistencies in the way we manipulate compat GPRs, we have a few issues today: * For audit and tracing, where error codes are handled as a (native) long, negative error codes are expected to be sign-extended to the native 64-bits, or they may fail to be matched correctly. Thus a syscall which fails with an error may erroneously be identified as failing. * For ptrace, *all* compat return values should be sign-extended for consistency with 32-bit arm, but we currently only do this for negative return codes. * As we may transiently set the upper 32 bits of some compat GPRs while in the kernel, these can be sampled by perf, which is somewhat confusing. This means that where a syscall returns a pointer above 2G, this will be sign-extended, but will not be mistaken for an error as error codes are constrained to the inclusive range [-4096, -1] where no user pointer can exist. To fix all of these, we must consistently use helpers to get/set the compat GPRs, ensuring that we never write the upper 32 bits of the return code, and always sign-extend when reading the return code. This patch does so, with the following changes: * We re-organise syscall_get_return_value() to always sign-extend for compat tasks, and reimplement syscall_get_error() atop. We update syscall_trace_exit() to use syscall_get_return_value(). * We consistently use syscall_set_return_value() to set the return value, ensureing the upper 32 bits are never set unexpectedly. * As the core audit code currently uses regs_return_value() rather than syscall_get_return_value(), we special-case this for compat_user_mode(regs) such that this will do the right thing. Going forward, we should try to move the core audit code over to syscall_get_return_value(). Cc: Reported-by: He Zhe Reported-by: weiyuchen Cc: Catalin Marinas Cc: Will Deacon Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20210802104200.21390-1-mark.rutland@arm.com Signed-off-by: Will Deacon

arm64: Change the on_*stack functions to take a size argument

2021-05-26T19:01:17Z

unwind_frame() was previously implicitly checking that the frame record is in bounds of the stack by enforcing that FP is both aligned to 16 and in bounds of the stack. Once the FP alignment requirement is relaxed to 8 this will not be sufficient because it does not account for the case where FP points to 8 bytes before the end of the stack. Make the check explicit by changing the on_*stack functions to take a size argument and adjusting the callers to pass the appropriate sizes. Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/Ib7a3eb3eea41b0687ffaba045ceb2012d077d8b4 Reviewed-by: Mark Rutland Tested-by: Mark Rutland Link: https://lore.kernel.org/r/20210526174927.2477847-1-pcc@google.com Signed-off-by: Will Deacon

arm64: Introduce prctl(PR_PAC_{SET,GET}_ENABLED_KEYS)

2021-04-13T16:31:44Z

This change introduces a prctl that allows the user program to control which PAC keys are enabled in a particular task. The main reason why this is useful is to enable a userspace ABI that uses PAC to sign and authenticate function pointers and other pointers exposed outside of the function, while still allowing binaries conforming to the ABI to interoperate with legacy binaries that do not sign or authenticate pointers. The idea is that a dynamic loader or early startup code would issue this prctl very early after establishing that a process may load legacy binaries, but before executing any PAC instructions. This change adds a small amount of overhead to kernel entry and exit due to additional required instruction sequences. On a DragonBoard 845c (Cortex-A75) with the powersave governor, the overhead of similar instruction sequences was measured as 4.9ns when simulating the common case where IA is left enabled, or 43.7ns when simulating the uncommon case where IA is disabled. These numbers can be seen as the worst case scenario, since in more realistic scenarios a better performing governor would be used and a newer chip would be used that would support PAC unlike Cortex-A75 and would be expected to be faster than Cortex-A75. On an Apple M1 under a hypervisor, the overhead of the entry/exit instruction sequences introduced by this patch was measured as 0.3ns in the case where IA is left enabled, and 33.0ns in the case where IA is disabled. Signed-off-by: Peter Collingbourne Reviewed-by: Dave Martin Link: https://linux-review.googlesource.com/id/Ibc41a5e6a76b275efbaa126b31119dc197b927a5 Link: https://lore.kernel.org/r/d6609065f8f40397a4124654eb68c9f490b4d477.1616123271.git.pcc@google.com Signed-off-by: Catalin Marinas

arm64: ptrace: Fix seccomp of traced syscall -1 (NO_SYSCALL)

2021-02-25T10:27:43Z

Since commit f086f67485c5 ("arm64: ptrace: add support for syscall emulation"), if system call number -1 is called and the process is being traced with PTRACE_SYSCALL, for example by strace, the seccomp check is skipped and -ENOSYS is returned unconditionally (unless altered by the tracer) rather than carrying out action specified in the seccomp filter. The consequence of this is that it is not possible to reliably strace a seccomp based implementation of a foreign system call interface in which r7/x8 is permitted to be -1 on entry to a system call. Also trace_sys_enter and audit_syscall_entry are skipped if a system call is skipped. Fix by removing the in_syscall(regs) check restoring the previous behaviour which is like AArch32, x86 (which uses generic code) and everything else. Cc: Oleg Nesterov Cc: Catalin Marinas Cc: Fixes: f086f67485c5 ("arm64: ptrace: add support for syscall emulation") Reviewed-by: Kees Cook Reviewed-by: Sudeep Holla Tested-by: Sudeep Holla Signed-off-by: Timothy E Baldwin Link: https://lore.kernel.org/r/90edd33b-6353-1228-791f-0336d94d5f8c@majoroak.me.uk Signed-off-by: Will Deacon

arm64: ptrace: Fix missing return in hw breakpoint code

2021-02-02T21:07:56Z

When delivering a hw-breakpoint SIGTRAP to a compat task via ptrace, the lack of a 'return' statement means we fallthrough to the native case, which differs in its handling of 'si_errno'. Although this looks to be harmless because the subsequent signal is effectively ignored, it's confusing and unintentional, so add the missing 'return'. Signed-off-by: Keno Fischer Link: https://lore.kernel.org/r/20210202002109.GA624440@juliacomputing.com Signed-off-by: Will Deacon

arm64: expose FAR_EL1 tag bits in siginfo

2020-11-23T18:17:39Z

The kernel currently clears the tag bits (i.e. bits 56-63) in the fault address exposed via siginfo.si_addr and sigcontext.fault_address. However, the tag bits may be needed by tools in order to accurately diagnose memory errors, such as HWASan [1] or future tools based on the Memory Tagging Extension (MTE). Expose these bits via the arch_untagged_si_addr mechanism, so that they are only exposed to signal handlers with the SA_EXPOSE_TAGBITS flag set. [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html Signed-off-by: Peter Collingbourne Reviewed-by: Catalin Marinas Link: https://linux-review.googlesource.com/id/Ia8876bad8c798e0a32df7c2ce1256c4771c81446 Link: https://lore.kernel.org/r/0010296597784267472fa13b39f8238d87a72cf8.1605904350.git.pcc@google.com Signed-off-by: Catalin Marinas