riscv: Add support for libdw

This patch adds support for DWARF register mappings and libdw registers
initialization, which is used by perf callchain analyzing when
--call-graph=dwarf is given.

Signed-off-by: Mao Han <[e-mail]>
Cc: Paul Walmsley <[e-mail]>
Cc: Greentime Hu <[e-mail]>
Cc: Palmer Dabbelt <[e-mail]>
Cc: linux-riscv <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Guo Ren <[e-mail]>
Tested-by: Greentime Hu <[e-mail]>
Signed-off-by: Paul Walmsley <[e-mail]>

tools/arch/riscv/include/uapi/asm/perf_regs.h

···
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */
+
+#ifndef _ASM_RISCV_PERF_REGS_H
+#define _ASM_RISCV_PERF_REGS_H
+
+enum perf_event_riscv_regs {
+	PERF_REG_RISCV_PC,
+	PERF_REG_RISCV_RA,
+	PERF_REG_RISCV_SP,
+	PERF_REG_RISCV_GP,
+	PERF_REG_RISCV_TP,
+	PERF_REG_RISCV_T0,
+	PERF_REG_RISCV_T1,
+	PERF_REG_RISCV_T2,
+	PERF_REG_RISCV_S0,
+	PERF_REG_RISCV_S1,
+	PERF_REG_RISCV_A0,
+	PERF_REG_RISCV_A1,
+	PERF_REG_RISCV_A2,
+	PERF_REG_RISCV_A3,
+	PERF_REG_RISCV_A4,
+	PERF_REG_RISCV_A5,
+	PERF_REG_RISCV_A6,
+	PERF_REG_RISCV_A7,
+	PERF_REG_RISCV_S2,
+	PERF_REG_RISCV_S3,
+	PERF_REG_RISCV_S4,
+	PERF_REG_RISCV_S5,
+	PERF_REG_RISCV_S6,
+	PERF_REG_RISCV_S7,
+	PERF_REG_RISCV_S8,
+	PERF_REG_RISCV_S9,
+	PERF_REG_RISCV_S10,
+	PERF_REG_RISCV_S11,
+	PERF_REG_RISCV_T3,
+	PERF_REG_RISCV_T4,
+	PERF_REG_RISCV_T5,
+	PERF_REG_RISCV_T6,
+	PERF_REG_RISCV_MAX,
+};
+#endif /* _ASM_RISCV_PERF_REGS_H */

tools/perf/Makefile.config

···
   LIBUNWIND_LIBS = -lunwind -lunwind-aarch64
 endif
 
+ifeq ($(SRCARCH),riscv)
+  NO_PERF_REGS := 0
+endif
+
 ifeq ($(SRCARCH),csky)
   NO_PERF_REGS := 0
 endif
···
 # Disable it on all other architectures in case libdw unwind
 # support is detected in system. Add supported architectures
 # to the check.
-ifneq ($(SRCARCH),$(filter $(SRCARCH),x86 arm arm64 powerpc s390 csky))
+ifneq ($(SRCARCH),$(filter $(SRCARCH),x86 arm arm64 powerpc s390 csky riscv))
   NO_LIBDW_DWARF_UNWIND := 1
 endif
 

tools/perf/arch/riscv/Build

···
+perf-y += util/

tools/perf/arch/riscv/Makefile

···
+ifndef NO_DWARF
+PERF_HAVE_DWARF_REGS := 1
+endif
+PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET := 1

tools/perf/arch/riscv/include/perf_regs.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */
+
+#ifndef ARCH_PERF_REGS_H
+#define ARCH_PERF_REGS_H
+
+#include <stdlib.h>
+#include <linux/types.h>
+#include <asm/perf_regs.h>
+
+#define PERF_REGS_MASK	((1ULL << PERF_REG_RISCV_MAX) - 1)
+#define PERF_REGS_MAX	PERF_REG_RISCV_MAX
+#if __riscv_xlen == 64
+#define PERF_SAMPLE_REGS_ABI    PERF_SAMPLE_REGS_ABI_64
+#else
+#define PERF_SAMPLE_REGS_ABI	PERF_SAMPLE_REGS_ABI_32
+#endif
+
+#define PERF_REG_IP	PERF_REG_RISCV_PC
+#define PERF_REG_SP	PERF_REG_RISCV_SP
+
+static inline const char *perf_reg_name(int id)
+{
+	switch (id) {
+	case PERF_REG_RISCV_PC:
+		return "pc";
+	case PERF_REG_RISCV_RA:
+		return "ra";
+	case PERF_REG_RISCV_SP:
+		return "sp";
+	case PERF_REG_RISCV_GP:
+		return "gp";
+	case PERF_REG_RISCV_TP:
+		return "tp";
+	case PERF_REG_RISCV_T0:
+		return "t0";
+	case PERF_REG_RISCV_T1:
+		return "t1";
+	case PERF_REG_RISCV_T2:
+		return "t2";
+	case PERF_REG_RISCV_S0:
+		return "s0";
+	case PERF_REG_RISCV_S1:
+		return "s1";
+	case PERF_REG_RISCV_A0:
+		return "a0";
+	case PERF_REG_RISCV_A1:
+		return "a1";
+	case PERF_REG_RISCV_A2:
+		return "a2";
+	case PERF_REG_RISCV_A3:
+		return "a3";
+	case PERF_REG_RISCV_A4:
+		return "a4";
+	case PERF_REG_RISCV_A5:
+		return "a5";
+	case PERF_REG_RISCV_A6:
+		return "a6";
+	case PERF_REG_RISCV_A7:
+		return "a7";
+	case PERF_REG_RISCV_S2:
+		return "s2";
+	case PERF_REG_RISCV_S3:
+		return "s3";
+	case PERF_REG_RISCV_S4:
+		return "s4";
+	case PERF_REG_RISCV_S5:
+		return "s5";
+	case PERF_REG_RISCV_S6:
+		return "s6";
+	case PERF_REG_RISCV_S7:
+		return "s7";
+	case PERF_REG_RISCV_S8:
+		return "s8";
+	case PERF_REG_RISCV_S9:
+		return "s9";
+	case PERF_REG_RISCV_S10:
+		return "s10";
+	case PERF_REG_RISCV_S11:
+		return "s11";
+	case PERF_REG_RISCV_T3:
+		return "t3";
+	case PERF_REG_RISCV_T4:
+		return "t4";
+	case PERF_REG_RISCV_T5:
+		return "t5";
+	case PERF_REG_RISCV_T6:
+		return "t6";
+	default:
+		return NULL;
+	}
+
+	return NULL;
+}
+
+#endif /* ARCH_PERF_REGS_H */

tools/perf/arch/riscv/util/Build

···
+perf-$(CONFIG_DWARF) += dwarf-regs.o
+perf-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o

tools/perf/arch/riscv/util/dwarf-regs.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd.
+ * Mapping of DWARF debug register numbers into register names.
+ */
+
+#include <stddef.h>
+#include <errno.h> /* for EINVAL */
+#include <string.h> /* for strcmp */
+#include <dwarf-regs.h>
+
+struct pt_regs_dwarfnum {
+	const char *name;
+	unsigned int dwarfnum;
+};
+
+#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num}
+#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0}
+
+struct pt_regs_dwarfnum riscv_dwarf_regs_table[] = {
+	REG_DWARFNUM_NAME("%zero", 0),
+	REG_DWARFNUM_NAME("%ra", 1),
+	REG_DWARFNUM_NAME("%sp", 2),
+	REG_DWARFNUM_NAME("%gp", 3),
+	REG_DWARFNUM_NAME("%tp", 4),
+	REG_DWARFNUM_NAME("%t0", 5),
+	REG_DWARFNUM_NAME("%t1", 6),
+	REG_DWARFNUM_NAME("%t2", 7),
+	REG_DWARFNUM_NAME("%s0", 8),
+	REG_DWARFNUM_NAME("%s1", 9),
+	REG_DWARFNUM_NAME("%a0", 10),
+	REG_DWARFNUM_NAME("%a1", 11),
+	REG_DWARFNUM_NAME("%a2", 12),
+	REG_DWARFNUM_NAME("%a3", 13),
+	REG_DWARFNUM_NAME("%a4", 14),
+	REG_DWARFNUM_NAME("%a5", 15),
+	REG_DWARFNUM_NAME("%a6", 16),
+	REG_DWARFNUM_NAME("%a7", 17),
+	REG_DWARFNUM_NAME("%s2", 18),
+	REG_DWARFNUM_NAME("%s3", 19),
+	REG_DWARFNUM_NAME("%s4", 20),
+	REG_DWARFNUM_NAME("%s5", 21),
+	REG_DWARFNUM_NAME("%s6", 22),
+	REG_DWARFNUM_NAME("%s7", 23),
+	REG_DWARFNUM_NAME("%s8", 24),
+	REG_DWARFNUM_NAME("%s9", 25),
+	REG_DWARFNUM_NAME("%s10", 26),
+	REG_DWARFNUM_NAME("%s11", 27),
+	REG_DWARFNUM_NAME("%t3", 28),
+	REG_DWARFNUM_NAME("%t4", 29),
+	REG_DWARFNUM_NAME("%t5", 30),
+	REG_DWARFNUM_NAME("%t6", 31),
+	REG_DWARFNUM_END,
+};
+
+#define RISCV_MAX_REGS ((sizeof(riscv_dwarf_regs_table) / \
+		 sizeof(riscv_dwarf_regs_table[0])) - 1)
+
+const char *get_arch_regstr(unsigned int n)
+{
+	return (n < RISCV_MAX_REGS) ? riscv_dwarf_regs_table[n].name : NULL;
+}
+
+int regs_query_register_offset(const char *name)
+{
+	const struct pt_regs_dwarfnum *roff;
+
+	for (roff = riscv_dwarf_regs_table; roff->name; roff++)
+		if (!strcmp(roff->name, name))
+			return roff->dwarfnum;
+	return -EINVAL;
+}

tools/perf/arch/riscv/util/unwind-libdw.c

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */
+
+#include <elfutils/libdwfl.h>
+#include "../../util/unwind-libdw.h"
+#include "../../util/perf_regs.h"
+#include "../../util/event.h"
+
+bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
+{
+	struct unwind_info *ui = arg;
+	struct regs_dump *user_regs = &ui->sample->user_regs;
+	Dwarf_Word dwarf_regs[32];
+
+#define REG(r) ({						\
+	Dwarf_Word val = 0;					\
+	perf_reg_value(&val, user_regs, PERF_REG_RISCV_##r);	\
+	val;							\
+})
+
+	dwarf_regs[0]  = 0;
+	dwarf_regs[1]  = REG(RA);
+	dwarf_regs[2]  = REG(SP);
+	dwarf_regs[3]  = REG(GP);
+	dwarf_regs[4]  = REG(TP);
+	dwarf_regs[5]  = REG(T0);
+	dwarf_regs[6]  = REG(T1);
+	dwarf_regs[7]  = REG(T2);
+	dwarf_regs[8]  = REG(S0);
+	dwarf_regs[9]  = REG(S1);
+	dwarf_regs[10] = REG(A0);
+	dwarf_regs[11] = REG(A1);
+	dwarf_regs[12] = REG(A2);
+	dwarf_regs[13] = REG(A3);
+	dwarf_regs[14] = REG(A4);
+	dwarf_regs[15] = REG(A5);
+	dwarf_regs[16] = REG(A6);
+	dwarf_regs[17] = REG(A7);
+	dwarf_regs[18] = REG(S2);
+	dwarf_regs[19] = REG(S3);
+	dwarf_regs[20] = REG(S4);
+	dwarf_regs[21] = REG(S5);
+	dwarf_regs[22] = REG(S6);
+	dwarf_regs[23] = REG(S7);
+	dwarf_regs[24] = REG(S8);
+	dwarf_regs[25] = REG(S9);
+	dwarf_regs[26] = REG(S10);
+	dwarf_regs[27] = REG(S11);
+	dwarf_regs[28] = REG(T3);
+	dwarf_regs[29] = REG(T4);
+	dwarf_regs[30] = REG(T5);
+	dwarf_regs[31] = REG(T6);
+	dwfl_thread_state_register_pc(thread, REG(PC));
+
+	return dwfl_thread_state_registers(thread, 0, PERF_REG_RISCV_MAX,
+					   dwarf_regs);
+}