LoongArch: Add perf events support

The perf events infrastructure of LoongArch is very similar to old MIPS-
based Loongson, so most of the codes are derived from MIPS.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/Kconfig

@@ -97,6 +97,8 @@ config LOONGARCH
 	select HAVE_NMI
 	select HAVE_PCI
 	select HAVE_PERF_EVENTS
+	select HAVE_PERF_REGS
+	select HAVE_PERF_USER_STACK_DUMP
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RSEQ
 	select HAVE_SETUP_PER_CPU_AREA if NUMA

arch/loongarch/include/asm/perf_event.h

@@ -6,5 +6,7 @@
 
 #ifndef __LOONGARCH_PERF_EVENT_H__
 #define __LOONGARCH_PERF_EVENT_H__
-/* Nothing to show here; the file is required by linux/perf_event.h. */
+
+#define perf_arch_bpf_user_pt_regs(regs) (struct user_pt_regs *)regs
+
 #endif /* __LOONGARCH_PERF_EVENT_H__ */

arch/loongarch/include/uapi/asm/perf_regs.h

+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _ASM_LOONGARCH_PERF_REGS_H
+#define _ASM_LOONGARCH_PERF_REGS_H
+
+enum perf_event_loongarch_regs {
+	PERF_REG_LOONGARCH_PC,
+	PERF_REG_LOONGARCH_R1,
+	PERF_REG_LOONGARCH_R2,
+	PERF_REG_LOONGARCH_R3,
+	PERF_REG_LOONGARCH_R4,
+	PERF_REG_LOONGARCH_R5,
+	PERF_REG_LOONGARCH_R6,
+	PERF_REG_LOONGARCH_R7,
+	PERF_REG_LOONGARCH_R8,
+	PERF_REG_LOONGARCH_R9,
+	PERF_REG_LOONGARCH_R10,
+	PERF_REG_LOONGARCH_R11,
+	PERF_REG_LOONGARCH_R12,
+	PERF_REG_LOONGARCH_R13,
+	PERF_REG_LOONGARCH_R14,
+	PERF_REG_LOONGARCH_R15,
+	PERF_REG_LOONGARCH_R16,
+	PERF_REG_LOONGARCH_R17,
+	PERF_REG_LOONGARCH_R18,
+	PERF_REG_LOONGARCH_R19,
+	PERF_REG_LOONGARCH_R20,
+	PERF_REG_LOONGARCH_R21,
+	PERF_REG_LOONGARCH_R22,
+	PERF_REG_LOONGARCH_R23,
+	PERF_REG_LOONGARCH_R24,
+	PERF_REG_LOONGARCH_R25,
+	PERF_REG_LOONGARCH_R26,
+	PERF_REG_LOONGARCH_R27,
+	PERF_REG_LOONGARCH_R28,
+	PERF_REG_LOONGARCH_R29,
+	PERF_REG_LOONGARCH_R30,
+	PERF_REG_LOONGARCH_R31,
+	PERF_REG_LOONGARCH_MAX,
+};
+#endif /* _ASM_LOONGARCH_PERF_REGS_H */

arch/loongarch/kernel/Makefile

@@ -26,4 +26,6 @@ obj-$(CONFIG_NUMA)		+= numa.o
 obj-$(CONFIG_UNWINDER_GUESS)	+= unwind_guess.o
 obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o
 
+obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_regs.o
+
 CPPFLAGS_vmlinux.lds		:= $(KBUILD_CFLAGS)

arch/loongarch/kernel/perf_regs.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ *
+ * Derived from MIPS:
+ * Copyright (C) 2013 Cavium, Inc.
+ */
+
+#include <linux/perf_event.h>
+
+#include <asm/ptrace.h>
+
+#ifdef CONFIG_32BIT
+u64 perf_reg_abi(struct task_struct *tsk)
+{
+	return PERF_SAMPLE_REGS_ABI_32;
+}
+#else /* Must be CONFIG_64BIT */
+u64 perf_reg_abi(struct task_struct *tsk)
+{
+	if (test_tsk_thread_flag(tsk, TIF_32BIT_REGS))
+		return PERF_SAMPLE_REGS_ABI_32;
+	else
+		return PERF_SAMPLE_REGS_ABI_64;
+}
+#endif /* CONFIG_32BIT */
+
+int perf_reg_validate(u64 mask)
+{
+	if (!mask)
+		return -EINVAL;
+	if (mask & ~((1ull << PERF_REG_LOONGARCH_MAX) - 1))
+		return -EINVAL;
+	return 0;
+}
+
+u64 perf_reg_value(struct pt_regs *regs, int idx)
+{
+	if (WARN_ON_ONCE((u32)idx >= PERF_REG_LOONGARCH_MAX))
+		return 0;
+
+	if ((u32)idx == PERF_REG_LOONGARCH_PC)
+		return regs->csr_era;
+
+	return regs->regs[idx];
+}
+
+void perf_get_regs_user(struct perf_regs *regs_user,
+			struct pt_regs *regs)
+{
+	regs_user->regs = task_pt_regs(current);
+	regs_user->abi = perf_reg_abi(current);
+}