aboutsummaryrefslogtreecommitdiff
path: root/arch/csky/kernel/perf_callchain.c
AgeCommit message (Collapse)AuthorFilesLines
2021-11-17perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscvSean Christopherson1-12/+0
Drop "support" for guest callbacks from architectures that don't implement the guest callbacks. Future patches will convert the callbacks to static_call; rather than churn a bunch of arch code (that was presumably copy+pasted from x86), remove it wholesale as it's useless and at best wasting cycles. A future patch will also add a Kconfig to force architcture to opt into the callbacks to make it more difficult for uses "support" to sneak in in the future. No functional change intended. Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Link: https://lore.kernel.org/r/20211111020738.2512932-6-seanjc@google.com
2021-11-17perf: Protect perf_guest_cbs with RCUSean Christopherson1-2/+4
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 <seanjc@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211111020738.2512932-2-seanjc@google.com
2020-05-13csky: Fixup perf callchain unwindMao Han1-2/+7
[ 5221.974084] Unable to handle kernel paging request at virtual address 0xfffff000, pc: 0x8002c18e [ 5221.985929] Oops: 00000000 [ 5221.989488] [ 5221.989488] CURRENT PROCESS: [ 5221.989488] [ 5221.992877] COMM=callchain_test PID=11962 [ 5221.995213] TEXT=00008000-000087e0 DATA=00009f1c-0000a018 BSS=0000a018-0000b000 [ 5221.999037] USER-STACK=7fc18e20 KERNEL-STACK=be204680 [ 5221.999037] [ 5222.003292] PC: 0x8002c18e (perf_callchain_kernel+0x3e/0xd4) [ 5222.007957] LR: 0x8002c198 (perf_callchain_kernel+0x48/0xd4) [ 5222.074873] Call Trace: [ 5222.074873] [<800a248e>] get_perf_callchain+0x20a/0x29c [ 5222.074873] [<8009d964>] perf_callchain+0x64/0x80 [ 5222.074873] [<8009dc1c>] perf_prepare_sample+0x29c/0x4b8 [ 5222.074873] [<8009de6e>] perf_event_output_forward+0x36/0x98 [ 5222.074873] [<800497e0>] search_exception_tables+0x20/0x44 [ 5222.074873] [<8002cbb6>] do_page_fault+0x92/0x378 [ 5222.074873] [<80098608>] __perf_event_overflow+0x54/0xdc [ 5222.074873] [<80098778>] perf_swevent_hrtimer+0xe8/0x164 [ 5222.074873] [<8002ddd0>] update_mmu_cache+0x0/0xd8 [ 5222.074873] [<8002c014>] user_backtrace+0x58/0xc4 [ 5222.074873] [<8002c0b4>] perf_callchain_user+0x34/0xd0 [ 5222.074873] [<800a2442>] get_perf_callchain+0x1be/0x29c [ 5222.074873] [<8009d964>] perf_callchain+0x64/0x80 [ 5222.074873] [<8009d834>] perf_output_sample+0x78c/0x858 [ 5222.074873] [<8009dc1c>] perf_prepare_sample+0x29c/0x4b8 [ 5222.074873] [<8009de94>] perf_event_output_forward+0x5c/0x98 [ 5222.097846] [ 5222.097846] [<800a0300>] perf_event_exit_task+0x58/0x43c [ 5222.097846] [<8006c874>] hrtimer_interrupt+0x104/0x2ec [ 5222.097846] [<800a0300>] perf_event_exit_task+0x58/0x43c [ 5222.097846] [<80437bb6>] dw_apb_clockevent_irq+0x2a/0x4c [ 5222.097846] [<8006c770>] hrtimer_interrupt+0x0/0x2ec [ 5222.097846] [<8005f2e4>] __handle_irq_event_percpu+0xac/0x19c [ 5222.097846] [<80437bb6>] dw_apb_clockevent_irq+0x2a/0x4c [ 5222.097846] [<8005f408>] handle_irq_event_percpu+0x34/0x88 [ 5222.097846] [<8005f480>] handle_irq_event+0x24/0x64 [ 5222.097846] [<8006218c>] handle_level_irq+0x68/0xdc [ 5222.097846] [<8005ec76>] __handle_domain_irq+0x56/0xa8 [ 5222.097846] [<80450e90>] ck_irq_handler+0xac/0xe4 [ 5222.097846] [<80029012>] csky_do_IRQ+0x12/0x24 [ 5222.097846] [<8002a3a0>] csky_irq+0x70/0x80 [ 5222.097846] [<800ca612>] alloc_set_pte+0xd2/0x238 [ 5222.097846] [<8002ddd0>] update_mmu_cache+0x0/0xd8 [ 5222.097846] [<800a0340>] perf_event_exit_task+0x98/0x43c The original fp check doesn't base on the real kernal stack region. Invalid fp address may cause kernel panic. Signed-off-by: Mao Han <han_mao@linux.alibaba.com> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
2019-04-22csky: Add perf callchain supportMao Han1-0/+119
This patch add support for perf callchain sampling on csky platform. As fp is used to unwind the stack, the program being sampled and the C library need to be compiled with -mbacktrace for user callchains, kernel callchains require CONFIG_STACKTRACE = y. Changelog: - Coding convention with Christoph's advice for riscv's. Signed-off-by: Mao Han <han_mao@c-sky.com> Signed-off-by: Guo Ren <ren_guo@c-sky.com> Cc: Christoph Hellwig <hch@infradead.org>
Powered by cgit, Gruvboxed by Blaster4385.