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Message-Id: <20190221134126.930-1-han_mao@c-sky.com>
Date: Thu, 21 Feb 2019 21:41:26 +0800
From: Mao Han <han_mao@...ky.com>
To: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: guoren@...nel.org, Mao Han <han_mao@...ky.com>
Subject: [PATCH] csky: Add perf callchin 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.
Signed-off-by: Mao Han <han_mao@...ky.com>
---
arch/csky/kernel/Makefile | 1 +
arch/csky/kernel/perf_callchain.c | 133 ++++++++++++++++++++++++++++++
2 files changed, 134 insertions(+)
create mode 100644 arch/csky/kernel/perf_callchain.c
diff --git a/arch/csky/kernel/Makefile b/arch/csky/kernel/Makefile
index 484e6d3a3..4c462f584 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 000000000..0a7a546e9
--- /dev/null
+++ b/arch/csky/kernel/perf_callchain.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd.
+
+#include <linux/perf_event.h>
+#include <linux/uaccess.h>
+
+/* Kernel callchain */
+struct stackframe {
+ unsigned long fp;
+ unsigned long lr;
+};
+
+static int
+unwind_frame_kernel(struct stackframe *frame)
+{
+ int graph = 0;
+
+ /* 0x3 means misalignment */
+ if (!kstack_end((void *)frame->fp) &&
+ !((unsigned long)frame->fp & 0x3) &&
+ ((unsigned long)frame->fp >= TASK_SIZE)) {
+ frame->lr = ((struct stackframe *)frame->fp)->lr;
+ frame->fp = ((struct stackframe *)frame->fp)->fp;
+ /* make sure CONFIG_FUNCTION_GRAPH_TRACER is turned on */
+ if (__kernel_text_address(frame->lr))
+ frame->lr = ftrace_graph_ret_addr
+ (NULL, &graph, frame->lr, NULL);
+ return 0;
+ } else {
+ return -EPERM;
+ }
+}
+
+static void notrace
+walk_stackframe(struct stackframe *fr,
+ struct perf_callchain_entry_ctx *entry)
+{
+ while (1) {
+ int ret;
+
+ perf_callchain_store(entry, fr->lr);
+
+ ret = unwind_frame_kernel(fr);
+ if (ret < 0)
+ break;
+ }
+}
+
+/*
+ * 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[2];
+ 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 ((entry->nr < entry->max_stack) &&
+ fp && !((unsigned long)fp & 0x3))
+ 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);
+}
--
2.21.0.rc2
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