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authorMao Han <han_mao@c-sky.com>2019-02-21 21:41:26 +0800
committerGuo Ren <ren_guo@c-sky.com>2019-04-22 13:44:57 +0800
commitcfa4d93b977a1b1129e7207d11b5daecdf0c56c4 (patch)
tree819c1af5ddde73eb5683c992565f3ed79ae1be64 /arch
parent28bb030f93334495ddc64ade0bff18721bf7023d (diff)
downloadlinux-sh-cfa4d93b977a1b1129e7207d11b5daecdf0c56c4.tar.gz
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 <han_mao@c-sky.com> Signed-off-by: Guo Ren <ren_guo@c-sky.com> Cc: Christoph Hellwig <hch@infradead.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/csky/kernel/Makefile1
-rw-r--r--arch/csky/kernel/perf_callchain.c119
2 files changed, 120 insertions, 0 deletions
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 <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)
+{
+ 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);
+}