From cfa4d93b977a1b1129e7207d11b5daecdf0c56c4 Mon Sep 17 00:00:00 2001 From: Mao Han Date: Thu, 21 Feb 2019 21:41:26 +0800 Subject: [PATCH] csky: Add perf callchain support 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 Signed-off-by: Guo Ren Cc: Christoph Hellwig --- arch/csky/kernel/Makefile | 1 + arch/csky/kernel/perf_callchain.c | 119 ++++++++++++++++++++++++++++++ 2 files changed, 120 insertions(+) create mode 100644 arch/csky/kernel/perf_callchain.c diff --git a/arch/csky/kernel/Makefile b/arch/csky/kernel/Makefile index 484e6d3a3647..4c462f584dd1 100644 --- a/arch/csky/kernel/Makefile +++ b/arch/csky/kernel/Makefile @@ -9,6 +9,7 @@ obj-$(CONFIG_SMP) += smp.o obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o obj-$(CONFIG_STACKTRACE) += stacktrace.o obj-$(CONFIG_CSKY_PMU_V1) += perf_event.o +obj-$(CONFIG_PERF_EVENTS) += perf_callchain.o ifdef CONFIG_FUNCTION_TRACER CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE) diff --git a/arch/csky/kernel/perf_callchain.c b/arch/csky/kernel/perf_callchain.c new file mode 100644 index 000000000000..e68ff375c8f8 --- /dev/null +++ b/arch/csky/kernel/perf_callchain.c @@ -0,0 +1,119 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. + +#include +#include + +/* Kernel callchain */ +struct stackframe { + unsigned long fp; + unsigned long lr; +}; + +static int unwind_frame_kernel(struct stackframe *frame) +{ + if (kstack_end((void *)frame->fp)) + return -EPERM; + if (frame->fp & 0x3 || frame->fp < TASK_SIZE) + return -EPERM; + + *frame = *(struct stackframe *)frame->fp; + if (__kernel_text_address(frame->lr)) { + int graph = 0; + + frame->lr = ftrace_graph_ret_addr(NULL, &graph, frame->lr, + NULL); + } + return 0; +} + +static void notrace walk_stackframe(struct stackframe *fr, + struct perf_callchain_entry_ctx *entry) +{ + do { + perf_callchain_store(entry, fr->lr); + } while (unwind_frame_kernel(fr) >= 0); +} + +/* + * Get the return address for a single stackframe and return a pointer to the + * next frame tail. + */ +static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry, + unsigned long fp, unsigned long reg_lr) +{ + struct stackframe buftail; + unsigned long lr = 0; + unsigned long *user_frame_tail = (unsigned long *)fp; + + /* Check accessibility of one struct frame_tail beyond */ + if (!access_ok(user_frame_tail, sizeof(buftail))) + return 0; + if (__copy_from_user_inatomic(&buftail, user_frame_tail, + sizeof(buftail))) + return 0; + + if (reg_lr != 0) + lr = reg_lr; + else + lr = buftail.lr; + + fp = buftail.fp; + perf_callchain_store(entry, lr); + + return fp; +} + +/* + * This will be called when the target is in user mode + * This function will only be called when we use + * "PERF_SAMPLE_CALLCHAIN" in + * kernel/events/core.c:perf_prepare_sample() + * + * How to trigger perf_callchain_[user/kernel] : + * $ perf record -e cpu-clock --call-graph fp ./program + * $ perf report --call-graph + * + * On C-SKY platform, the program being sampled and the C library + * need to be compiled with * -mbacktrace, otherwise the user + * stack will not contain function frame. + */ +void perf_callchain_user(struct perf_callchain_entry_ctx *entry, + struct pt_regs *regs) +{ + unsigned long fp = 0; + + /* C-SKY does not support virtualization. */ + if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) + return; + + fp = regs->regs[4]; + perf_callchain_store(entry, regs->pc); + + /* + * While backtrace from leaf function, lr is normally + * not saved inside frame on C-SKY, so get lr from pt_regs + * at the sample point. However, lr value can be incorrect if + * lr is used as temp register + */ + fp = user_backtrace(entry, fp, regs->lr); + + while (fp && !(fp & 0x3) && entry->nr < entry->max_stack) + fp = user_backtrace(entry, fp, 0); +} + +void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, + struct pt_regs *regs) +{ + struct stackframe fr; + + /* C-SKY does not support virtualization. */ + if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) { + pr_warn("C-SKY does not support perf in guest mode!"); + return; + } + + fr.fp = regs->regs[4]; + fr.lr = regs->lr; + walk_stackframe(&fr, entry); +} -- 2.30.2