perf tools: Support MIPS unwinding and dwarf-regs

Map perf APIs (perf_reg_name/get_arch_regstr/unwind__arch_reg_id) with
MIPS specific registers.

[[e-mail]: repick this patch for unwinding userstack backtrace
by perf and libunwind on MIPS based CPU.]

[[e-mail]: Add sample_reg_masks[] to fix build error,
silence some checkpatch errors and warnings, and also separate the
original patches into two parts (MIPS kernel and perf tools) to merge
easily.]

The original patches:

https://lore.kernel.org/patchwork/patch/1126521/
https://lore.kernel.org/patchwork/patch/1126520/

Committer notes:

Do it as __perf_reg_name() to cope with:

067012974c8ae31a ("perf tools: Fix arm64 build error with gcc-11")

Signed-off-by: Tiezhu Yang <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Archer Yan <[e-mail]>
Cc: David Daney <[e-mail]>
Cc: Jianlin Lv <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Juxin Gao <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Cc: Xuefeng Li <[e-mail]>
Cc: Thomas Bogendoerfer <[e-mail]>
Cc: [e-mail]
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Archer Yan <[e-mail]>
Signed-off-by: David Daney <[e-mail]>
Signed-off-by: Ralf Baechle <[e-mail]>
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Makefile.config

···
   CFLAGS += -fPIC -I$(OUTPUT)arch/s390/include/generated
 endif
 
+ifeq ($(ARCH),mips)
+  NO_PERF_REGS := 0
+  CFLAGS += -I../../arch/mips/include/uapi -I../../arch/mips/include/generated/uapi
+  LIBUNWIND_LIBS = -lunwind -lunwind-mips
+endif
+
 ifeq ($(NO_PERF_REGS),0)
   $(call detected,CONFIG_PERF_REGS)
 endif

tools/perf/arch/mips/Makefile

···
+# SPDX-License-Identifier: GPL-2.0
+ifndef NO_DWARF
+PERF_HAVE_DWARF_REGS := 1
+endif

tools/perf/arch/mips/include/dwarf-regs-table.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * dwarf-regs-table.h : Mapping of DWARF debug register numbers into
+ * register names.
+ *
+ * Copyright (C) 2013 Cavium, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifdef DEFINE_DWARF_REGSTR_TABLE
+#undef REG_DWARFNUM_NAME
+#define REG_DWARFNUM_NAME(reg, idx)	[idx] = "$" #reg
+static const char * const mips_regstr_tbl[] = {
+	"$0", "$1", "$2", "$3", "$4", "$5", "$6", "$7", "$8", "$9",
+	"$10", "$11", "$12", "$13", "$14", "$15", "$16", "$17", "$18", "$19",
+	"$20", "$21", "$22", "$23", "$24", "$25", "$26", "$27", "$28", "%29",
+	"$30", "$31",
+	REG_DWARFNUM_NAME(hi, 64),
+	REG_DWARFNUM_NAME(lo, 65),
+};
+#endif

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

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#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_MAX PERF_REG_MIPS_MAX
+#define PERF_REG_IP PERF_REG_MIPS_PC
+#define PERF_REG_SP PERF_REG_MIPS_R29
+
+#define PERF_REGS_MASK ((1ULL << PERF_REG_MIPS_MAX) - 1)
+
+static inline const char *__perf_reg_name(int id)
+{
+	switch (id) {
+	case PERF_REG_MIPS_PC:
+		return "PC";
+	case PERF_REG_MIPS_R1:
+		return "$1";
+	case PERF_REG_MIPS_R2:
+		return "$2";
+	case PERF_REG_MIPS_R3:
+		return "$3";
+	case PERF_REG_MIPS_R4:
+		return "$4";
+	case PERF_REG_MIPS_R5:
+		return "$5";
+	case PERF_REG_MIPS_R6:
+		return "$6";
+	case PERF_REG_MIPS_R7:
+		return "$7";
+	case PERF_REG_MIPS_R8:
+		return "$8";
+	case PERF_REG_MIPS_R9:
+		return "$9";
+	case PERF_REG_MIPS_R10:
+		return "$10";
+	case PERF_REG_MIPS_R11:
+		return "$11";
+	case PERF_REG_MIPS_R12:
+		return "$12";
+	case PERF_REG_MIPS_R13:
+		return "$13";
+	case PERF_REG_MIPS_R14:
+		return "$14";
+	case PERF_REG_MIPS_R15:
+		return "$15";
+	case PERF_REG_MIPS_R16:
+		return "$16";
+	case PERF_REG_MIPS_R17:
+		return "$17";
+	case PERF_REG_MIPS_R18:
+		return "$18";
+	case PERF_REG_MIPS_R19:
+		return "$19";
+	case PERF_REG_MIPS_R20:
+		return "$20";
+	case PERF_REG_MIPS_R21:
+		return "$21";
+	case PERF_REG_MIPS_R22:
+		return "$22";
+	case PERF_REG_MIPS_R23:
+		return "$23";
+	case PERF_REG_MIPS_R24:
+		return "$24";
+	case PERF_REG_MIPS_R25:
+		return "$25";
+	case PERF_REG_MIPS_R28:
+		return "$28";
+	case PERF_REG_MIPS_R29:
+		return "$29";
+	case PERF_REG_MIPS_R30:
+		return "$30";
+	case PERF_REG_MIPS_R31:
+		return "$31";
+	default:
+		break;
+	}
+	return NULL;
+}
+
+#endif /* ARCH_PERF_REGS_H */

tools/perf/arch/mips/util/Build

···
+perf-y += perf_regs.o
+perf-$(CONFIG_DWARF) += dwarf-regs.o
+perf-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind.o

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

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * dwarf-regs.c : Mapping of DWARF debug register numbers into register names.
+ *
+ * Copyright (C) 2013 Cavium, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <stdio.h>
+#include <dwarf-regs.h>
+
+static const char *mips_gpr_names[32] = {
+	"$0", "$1", "$2", "$3", "$4", "$5", "$6", "$7", "$8", "$9",
+	"$10", "$11", "$12", "$13", "$14", "$15", "$16", "$17", "$18", "$19",
+	"$20", "$21", "$22", "$23", "$24", "$25", "$26", "$27", "$28", "$29",
+	"$30", "$31"
+};
+
+const char *get_arch_regstr(unsigned int n)
+{
+	if (n < 32)
+		return mips_gpr_names[n];
+	if (n == 64)
+		return "hi";
+	if (n == 65)
+		return "lo";
+	return NULL;
+}

tools/perf/arch/mips/util/perf_regs.c

···
+// SPDX-License-Identifier: GPL-2.0
+#include "../../util/perf_regs.h"
+
+const struct sample_reg sample_reg_masks[] = {
+	SMPL_REG_END
+};

tools/perf/arch/mips/util/unwind-libunwind.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include <errno.h>
+#include <libunwind.h>
+#include "perf_regs.h"
+#include "../../util/unwind.h"
+#include "util/debug.h"
+
+int libunwind__arch_reg_id(int regnum)
+{
+	switch (regnum) {
+	case UNW_MIPS_R1 ... UNW_MIPS_R25:
+		return regnum - UNW_MIPS_R1 + PERF_REG_MIPS_R1;
+	case UNW_MIPS_R28 ... UNW_MIPS_R31:
+		return regnum - UNW_MIPS_R28 + PERF_REG_MIPS_R28;
+	case UNW_MIPS_PC:
+		return PERF_REG_MIPS_PC;
+	default:
+		pr_err("unwind: invalid reg id %d\n", regnum);
+		return -EINVAL;
+	}
+}

tools/perf/util/dwarf-regs.c

···
 #include "../arch/s390/include/dwarf-regs-table.h"
 #include "../arch/sparc/include/dwarf-regs-table.h"
 #include "../arch/xtensa/include/dwarf-regs-table.h"
+#include "../arch/mips/include/dwarf-regs-table.h"
 
 #define __get_dwarf_regstr(tbl, n) (((n) < ARRAY_SIZE(tbl)) ? (tbl)[(n)] : NULL)
 
···
 		return __get_dwarf_regstr(sparc_regstr_tbl, n);
 	case EM_XTENSA:
 		return __get_dwarf_regstr(xtensa_regstr_tbl, n);
+	case EM_MIPS:
+		return __get_dwarf_regstr(mips_regstr_tbl, n);
 	default:
 		pr_err("ELF MACHINE %x is not supported.\n", machine);
 	}