kernel.git/arch/arm64/kernel/perf_callchain.c, branch linux-6.3.y

Merge tag 'perf_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-01-13T00:26:58Z

Pull perf updates from Borislav Petkov: "Cleanup of the perf/kvm interaction." * tag 'perf_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: perf: Drop guest callback (un)register stubs KVM: arm64: Drop perf.c and fold its tiny bits of code into arm.c KVM: arm64: Hide kvm_arm_pmu_available behind CONFIG_HW_PERF_EVENTS=y KVM: arm64: Convert to the generic perf callbacks KVM: x86: Move Intel Processor Trace interrupt handler to vmx.c KVM: Move x86's perf guest info callbacks to generic KVM KVM: x86: More precisely identify NMI from guest when handling PMI KVM: x86: Drop current_vcpu for kvm_running_vcpu + kvm_arch_vcpu variable perf/core: Use static_call to optimize perf_guest_info_callbacks perf: Force architectures to opt-in to guest callbacks perf: Add wrappers for invoking guest callbacks perf/core: Rework guest callbacks to prepare for static_call support perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscv perf: Stop pretending that perf can handle multiple guest callbacks KVM: x86: Register Processor Trace interrupt hook iff PT enabled in guest KVM: x86: Register perf callbacks after calling vendor's hardware_setup() perf: Protect perf_guest_cbs with RCU

arm64: Make perf_callchain_kernel() use arch_stack_walk()

2021-12-10T14:06:03Z

To enable RELIABLE_STACKTRACE and LIVEPATCH on arm64, we need to substantially rework arm64's unwinding code. As part of this, we want to minimize the set of unwind interfaces we expose, and avoid open-coding of unwind logic outside of stacktrace.c. Currently perf_callchain_kernel() walks the stack of an interrupted context by calling start_backtrace() with the context's PC and FP, and iterating unwind steps using walk_stackframe(). This is functionally equivalent to calling arch_stack_walk() with the interrupted context's pt_regs, which will start with the PC and FP from the regs. Make perf_callchain_kernel() use arch_stack_walk(). This simplifies perf_callchain_kernel(), and in future will alow us to make walk_stackframe() private to stacktrace.c. At the same time, we update the callchain_trace() callback to check the return value of perf_callchain_store(), which indicates whether there is space for any further entries. When a non-zero value is returned, further calls will be ignored, and are redundant, so we can stop the unwind at this point. We also remove the stale and confusing comment for callchain_trace. There should be no functional change as a result of this patch. Signed-off-by: Madhavan T. Venkataraman Tested-by: Mark Rutland Reviewed-by: Mark Brown Reviewed-by: Mark Rutland [Mark: elaborate commit message, remove comment, fix includes] Signed-off-by: Mark Rutland Link: https://lore.kernel.org/r/20211129142849.3056714-5-mark.rutland@arm.com Signed-off-by: Catalin Marinas

perf: Add wrappers for invoking guest callbacks

2021-11-17T13:49:08Z

Add helpers for the guest callbacks to prepare for burying the callbacks behind a Kconfig (it's a lot easier to provide a few stubs than to #ifdef piles of code), and also to prepare for converting the callbacks to static_call(). perf_instruction_pointer() in particular will have subtle semantics with static_call(), as the "no callbacks" case will return 0 if the callbacks are unregistered between querying guest state and getting the IP. Implement the change now to avoid a functional change when adding static_call() support, and because the new helper needs to return _something_ in this case. Signed-off-by: Sean Christopherson Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Paolo Bonzini Link: https://lore.kernel.org/r/20211111020738.2512932-8-seanjc@google.com

perf/core: Rework guest callbacks to prepare for static_call support

2021-11-17T13:49:07Z

To prepare for using static_calls to optimize perf's guest callbacks, replace ->is_in_guest and ->is_user_mode with a new multiplexed hook ->state, tweak ->handle_intel_pt_intr to play nice with being called when there is no active guest, and drop "guest" from ->get_guest_ip. Return '0' from ->state and ->handle_intel_pt_intr to indicate "not in guest" so that DEFINE_STATIC_CALL_RET0 can be used to define the static calls, i.e. no callback == !guest. [sean: extracted from static_call patch, fixed get_ip() bug, wrote changelog] Suggested-by: Peter Zijlstra (Intel) Originally-by: Peter Zijlstra (Intel) Signed-off-by: Like Xu Signed-off-by: Zhu Lingshan Signed-off-by: Sean Christopherson Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Boris Ostrovsky Reviewed-by: Paolo Bonzini Link: https://lore.kernel.org/r/20211111020738.2512932-7-seanjc@google.com

perf: Protect perf_guest_cbs with RCU

2021-11-17T13:49:06Z

Protect perf_guest_cbs with RCU to fix multiple possible errors. Luckily, all paths that read perf_guest_cbs already require RCU protection, e.g. to protect the callback chains, so only the direct perf_guest_cbs touchpoints need to be modified. Bug #1 is a simple lack of WRITE_ONCE/READ_ONCE behavior to ensure perf_guest_cbs isn't reloaded between a !NULL check and a dereference. Fixed via the READ_ONCE() in rcu_dereference(). Bug #2 is that on weakly-ordered architectures, updates to the callbacks themselves are not guaranteed to be visible before the pointer is made visible to readers. Fixed by the smp_store_release() in rcu_assign_pointer() when the new pointer is non-NULL. Bug #3 is that, because the callbacks are global, it's possible for readers to run in parallel with an unregisters, and thus a module implementing the callbacks can be unloaded while readers are in flight, resulting in a use-after-free. Fixed by a synchronize_rcu() call when unregistering callbacks. Bug #1 escaped notice because it's extremely unlikely a compiler will reload perf_guest_cbs in this sequence. perf_guest_cbs does get reloaded for future derefs, e.g. for ->is_user_mode(), but the ->is_in_guest() guard all but guarantees the consumer will win the race, e.g. to nullify perf_guest_cbs, KVM has to completely exit the guest and teardown down all VMs before KVM start its module unload / unregister sequence. This also makes it all but impossible to encounter bug #3. Bug #2 has not been a problem because all architectures that register callbacks are strongly ordered and/or have a static set of callbacks. But with help, unloading kvm_intel can trigger bug #1 e.g. wrapping perf_guest_cbs with READ_ONCE in perf_misc_flags() while spamming kvm_intel module load/unload leads to: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP CPU: 6 PID: 1825 Comm: stress Not tainted 5.14.0-rc2+ #459 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:perf_misc_flags+0x1c/0x70 Call Trace: perf_prepare_sample+0x53/0x6b0 perf_event_output_forward+0x67/0x160 __perf_event_overflow+0x52/0xf0 handle_pmi_common+0x207/0x300 intel_pmu_handle_irq+0xcf/0x410 perf_event_nmi_handler+0x28/0x50 nmi_handle+0xc7/0x260 default_do_nmi+0x6b/0x170 exc_nmi+0x103/0x130 asm_exc_nmi+0x76/0xbf Fixes: 39447b386c84 ("perf: Enhance perf to allow for guest statistic collection from host") Signed-off-by: Sean Christopherson Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Paolo Bonzini Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211111020738.2512932-2-seanjc@google.com

arm64: stacktrace: Relax frame record alignment requirement to 8 bytes

2021-05-26T19:01:17Z

The AAPCS places no requirements on the alignment of the frame record. In theory it could be placed anywhere, although it seems sensible to require it to be aligned to 8 bytes. With an upcoming enhancement to tag-based KASAN Clang will begin creating frame records located at an address that is only aligned to 8 bytes. Accommodate such frame records in the stack unwinding code. As pointed out by Mark Rutland, the userspace stack unwinding code has the same problem, so fix it there as well. Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/Ia22c375230e67ca055e9e4bb639383567f7ad268 Acked-by: Andrey Konovalov Reviewed-by: Mark Rutland Tested-by: Mark Rutland Link: https://lore.kernel.org/r/20210526174927.2477847-2-pcc@google.com Signed-off-by: Will Deacon

arm64: stacktrace: Make stack walk callback consistent with generic code

2020-09-18T13:24:16Z

As with the generic arch_stack_walk() code the arm64 stack walk code takes a callback that is called per stack frame. Currently the arm64 code always passes a struct stackframe to the callback and the generic code just passes the pc, however none of the users ever reference anything in the struct other than the pc value. The arm64 code also uses a return type of int while the generic code uses a return type of bool though in both cases the return value is a boolean value and the sense is inverted between the two. In order to reduce code duplication when arm64 is converted to use arch_stack_walk() change the signature and return sense of the arm64 specific callback to match that of the generic code. Signed-off-by: Mark Brown Reviewed-by: Miroslav Benes Link: https://lore.kernel.org/r/20200914153409.25097-3-broonie@kernel.org Signed-off-by: Will Deacon

arm64: stacktrace: Factor out backtrace initialisation

2019-07-22T10:44:08Z

Some common code is required by each stacktrace user to initialise struct stackframe before the first call to unwind_frame(). In preparation for adding to the common code, this patch factors it out into a separate function start_backtrace(), and modifies the stacktrace callers appropriately. No functional change. Signed-off-by: Dave Martin [Mark: drop tsk argument, update more callsites] Signed-off-by: Mark Rutland Reviewed-by: James Morse Acked-by: Catalin Marinas Signed-off-by: Will Deacon

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234

2019-06-19T15:09:07Z

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details you should have received a copy of the gnu general public license along with this program if not see http www gnu org licenses extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 503 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Alexios Zavras Reviewed-by: Allison Randal Reviewed-by: Enrico Weigelt Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190602204653.811534538@linutronix.de Signed-off-by: Greg Kroah-Hartman

Remove 'type' argument from access_ok() function

2019-01-04T02:57:57Z

Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument of the user address range verification function since we got rid of the old racy i386-only code to walk page tables by hand. It existed because the original 80386 would not honor the write protect bit when in kernel mode, so you had to do COW by hand before doing any user access. But we haven't supported that in a long time, and these days the 'type' argument is a purely historical artifact. A discussion about extending 'user_access_begin()' to do the range checking resulted this patch, because there is no way we're going to move the old VERIFY_xyz interface to that model. And it's best done at the end of the merge window when I've done most of my merges, so let's just get this done once and for all. This patch was mostly done with a sed-script, with manual fix-ups for the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form. There were a couple of notable cases: - csky still had the old "verify_area()" name as an alias. - the iter_iov code had magical hardcoded knowledge of the actual values of VERIFY_{READ,WRITE} (not that they mattered, since nothing really used it) - microblaze used the type argument for a debug printout but other than those oddities this should be a total no-op patch. I tried to fix up all architectures, did fairly extensive grepping for access_ok() uses, and the changes are trivial, but I may have missed something. Any missed conversion should be trivially fixable, though. Signed-off-by: Linus Torvalds