[PATCH 0/3] Add some perf support for mips

[PATCH 0/3] Add some perf support for mips

[Tiezhu Yang]

Tiezhu Yang (3):
  MIPS: kernel: Support extracting off-line stack traces from user-space
    with perf
  perf tools: Support mips unwinding and dwarf-regs
  perf tools: Generate mips syscalls_n64.c syscall table

 arch/mips/Kconfig                                  |   2 +
 arch/mips/include/uapi/asm/perf_regs.h             |  42 +++
 arch/mips/kernel/Makefile                          |   2 +-
 arch/mips/kernel/perf_regs.c                       |  68 ++++
 tools/perf/Makefile.config                         |   9 +-
 tools/perf/arch/mips/Makefile                      |  22 ++
 tools/perf/arch/mips/entry/syscalls/mksyscalltbl   |  32 ++
 .../perf/arch/mips/entry/syscalls/syscall_n64.tbl  | 358 +++++++++++++++++++++
 tools/perf/arch/mips/include/dwarf-regs-table.h    |  31 ++
 tools/perf/arch/mips/include/perf_regs.h           |  84 +++++
 tools/perf/arch/mips/util/Build                    |   3 +
 tools/perf/arch/mips/util/dwarf-regs.c             |  38 +++
 tools/perf/arch/mips/util/perf_regs.c              |   6 +
 tools/perf/arch/mips/util/unwind-libunwind.c       |  22 ++
 tools/perf/check-headers.sh                        |   1 +
 tools/perf/util/dwarf-regs.c                       |   3 +
 tools/perf/util/syscalltbl.c                       |   4 +
 17 files changed, 725 insertions(+), 2 deletions(-)
 create mode 100644 arch/mips/include/uapi/asm/perf_regs.h
 create mode 100644 arch/mips/kernel/perf_regs.c
 create mode 100644 tools/perf/arch/mips/Makefile
 create mode 100644 tools/perf/arch/mips/entry/syscalls/mksyscalltbl
 create mode 100644 tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl
 create mode 100644 tools/perf/arch/mips/include/dwarf-regs-table.h
 create mode 100644 tools/perf/arch/mips/include/perf_regs.h
 create mode 100644 tools/perf/arch/mips/util/Build
 create mode 100644 tools/perf/arch/mips/util/dwarf-regs.c
 create mode 100644 tools/perf/arch/mips/util/perf_regs.c
 create mode 100644 tools/perf/arch/mips/util/unwind-libunwind.c

-- 
2.1.0

[PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Tiezhu Yang]

Add perf_event_mips_regs/perf_reg_value/perf_reg_validate to support
features HAVE_PERF_REGS/HAVE_PERF_USER_STACK_DUMP in kernel.

[ayan@wavecomp.com: Repick this patch for unwinding userstack backtrace
 by perf and libunwind on MIPS based CPU.]

[ralf@linux-mips.org: Add perf_get_regs_user() which is required after
'commit 88a7c26af8da ("perf: Move task_pt_regs sampling into arch code")'.]

[yangtiezhu@loongson.cn: Fix build error about perf_get_regs_user() after
commit 76a4efa80900 ("perf/arch: Remove perf_sample_data::regs_user_copy"),
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/

Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Archer Yan <ayan@wavecomp.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/mips/Kconfig                      |  2 +
 arch/mips/include/uapi/asm/perf_regs.h | 42 +++++++++++++++++++++
 arch/mips/kernel/Makefile              |  2 +-
 arch/mips/kernel/perf_regs.c           | 68 ++++++++++++++++++++++++++++++++++
 4 files changed, 113 insertions(+), 1 deletion(-)
 create mode 100644 arch/mips/include/uapi/asm/perf_regs.h
 create mode 100644 arch/mips/kernel/perf_regs.c

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 0a17bed..092c876 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -76,6 +76,8 @@ config MIPS
 	select HAVE_NMI
 	select HAVE_OPROFILE
 	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_SPARSE_SYSCALL_NR
diff --git a/arch/mips/include/uapi/asm/perf_regs.h b/arch/mips/include/uapi/asm/perf_regs.h
new file mode 100644
index 0000000..f3cef08
--- /dev/null
+++ b/arch/mips/include/uapi/asm/perf_regs.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _ASM_MIPS_PERF_REGS_H
+#define _ASM_MIPS_PERF_REGS_H
+
+enum perf_event_mips_regs {
+	PERF_REG_MIPS_PC,
+	PERF_REG_MIPS_R1,
+	PERF_REG_MIPS_R2,
+	PERF_REG_MIPS_R3,
+	PERF_REG_MIPS_R4,
+	PERF_REG_MIPS_R5,
+	PERF_REG_MIPS_R6,
+	PERF_REG_MIPS_R7,
+	PERF_REG_MIPS_R8,
+	PERF_REG_MIPS_R9,
+	PERF_REG_MIPS_R10,
+	PERF_REG_MIPS_R11,
+	PERF_REG_MIPS_R12,
+	PERF_REG_MIPS_R13,
+	PERF_REG_MIPS_R14,
+	PERF_REG_MIPS_R15,
+	PERF_REG_MIPS_R16,
+	PERF_REG_MIPS_R17,
+	PERF_REG_MIPS_R18,
+	PERF_REG_MIPS_R19,
+	PERF_REG_MIPS_R20,
+	PERF_REG_MIPS_R21,
+	PERF_REG_MIPS_R22,
+	PERF_REG_MIPS_R23,
+	PERF_REG_MIPS_R24,
+	PERF_REG_MIPS_R25,
+	/*
+	 * 26 and 27 are k0 and k1, they are always clobbered thus not
+	 * stored.
+	 */
+	PERF_REG_MIPS_R28,
+	PERF_REG_MIPS_R29,
+	PERF_REG_MIPS_R30,
+	PERF_REG_MIPS_R31,
+	PERF_REG_MIPS_MAX = PERF_REG_MIPS_R31 + 1,
+};
+#endif /* _ASM_MIPS_PERF_REGS_H */
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 2a05b92..120075a 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -104,7 +104,7 @@ obj-$(CONFIG_MIPSR2_TO_R6_EMULATOR)	+= mips-r2-to-r6-emul.o
 
 CFLAGS_cpu-bugs64.o	= $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/null -x c /dev/null >/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)
 
-obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o
+obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_regs.o
 obj-$(CONFIG_HW_PERF_EVENTS)	+= perf_event_mipsxx.o
 
 obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
diff --git a/arch/mips/kernel/perf_regs.c b/arch/mips/kernel/perf_regs.c
new file mode 100644
index 0000000..e686780
--- /dev/null
+++ b/arch/mips/kernel/perf_regs.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Some parts derived from x86 version of this file.
+ *
+ * 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_MIPS_MAX) - 1))
+		return -EINVAL;
+	return 0;
+}
+
+u64 perf_reg_value(struct pt_regs *regs, int idx)
+{
+	long v;
+
+	switch (idx) {
+	case PERF_REG_MIPS_PC:
+		v = regs->cp0_epc;
+		break;
+	case PERF_REG_MIPS_R1 ... PERF_REG_MIPS_R25:
+		v = regs->regs[idx - PERF_REG_MIPS_R1 + 1];
+		break;
+	case PERF_REG_MIPS_R28 ... PERF_REG_MIPS_R31:
+		v = regs->regs[idx - PERF_REG_MIPS_R28 + 28];
+		break;
+
+	default:
+		WARN_ON_ONCE(1);
+		return 0;
+	}
+
+	return (s64)v; /* Sign extend if 32-bit. */
+}
+
+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);
+}
-- 
2.1.0

[PATCH 2/3] perf tools: Support mips unwinding and dwarf-regs

[Tiezhu Yang]

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

[ayan@wavecomp.com: repick this patch for unwinding userstack
backtrace by perf and libunwind on MIPS based CPU.]

[yangtiezhu@loongson.cn: 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/

Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Archer Yan <ayan@wavecomp.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 tools/perf/Makefile.config                      |  6 ++
 tools/perf/arch/mips/Makefile                   |  4 ++
 tools/perf/arch/mips/include/dwarf-regs-table.h | 31 +++++++++
 tools/perf/arch/mips/include/perf_regs.h        | 84 +++++++++++++++++++++++++
 tools/perf/arch/mips/util/Build                 |  3 +
 tools/perf/arch/mips/util/dwarf-regs.c          | 38 +++++++++++
 tools/perf/arch/mips/util/perf_regs.c           |  6 ++
 tools/perf/arch/mips/util/unwind-libunwind.c    | 22 +++++++
 tools/perf/util/dwarf-regs.c                    |  3 +
 9 files changed, 197 insertions(+)
 create mode 100644 tools/perf/arch/mips/Makefile
 create mode 100644 tools/perf/arch/mips/include/dwarf-regs-table.h
 create mode 100644 tools/perf/arch/mips/include/perf_regs.h
 create mode 100644 tools/perf/arch/mips/util/Build
 create mode 100644 tools/perf/arch/mips/util/dwarf-regs.c
 create mode 100644 tools/perf/arch/mips/util/perf_regs.c
 create mode 100644 tools/perf/arch/mips/util/unwind-libunwind.c

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index ce8516e..e378add 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -87,6 +87,12 @@ ifeq ($(ARCH),s390)
   CFLAGS += -fPIC -I$(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)
   $(call detected,CONFIG_PERF_REGS)
 endif
diff --git a/tools/perf/arch/mips/Makefile b/tools/perf/arch/mips/Makefile
new file mode 100644
index 0000000..6e1106f
--- /dev/null
+++ b/tools/perf/arch/mips/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+ifndef NO_DWARF
+PERF_HAVE_DWARF_REGS := 1
+endif
diff --git a/tools/perf/arch/mips/include/dwarf-regs-table.h b/tools/perf/arch/mips/include/dwarf-regs-table.h
new file mode 100644
index 0000000..5badbcd
--- /dev/null
+++ b/tools/perf/arch/mips/include/dwarf-regs-table.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * dwarf-regs-table.h : Mapping of DWARF debug register numbers into
+ * register names.
+ *
+ * Copyright (C) 2013 Cavium, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifdef DEFINE_DWARF_REGSTR_TABLE
+#undef REG_DWARFNUM_NAME
+#define REG_DWARFNUM_NAME(reg, idx)	[idx] = "$" #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
diff --git a/tools/perf/arch/mips/include/perf_regs.h b/tools/perf/arch/mips/include/perf_regs.h
new file mode 100644
index 0000000..7a7908b
--- /dev/null
+++ b/tools/perf/arch/mips/include/perf_regs.h
@@ -0,0 +1,84 @@
+/* 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 "$31";
+	default:
+		break;
+	}
+	return NULL;
+}
+
+#endif /* ARCH_PERF_REGS_H */
diff --git a/tools/perf/arch/mips/util/Build b/tools/perf/arch/mips/util/Build
new file mode 100644
index 0000000..51c8900
--- /dev/null
+++ b/tools/perf/arch/mips/util/Build
@@ -0,0 +1,3 @@
+perf-y += perf_regs.o
+perf-$(CONFIG_DWARF) += dwarf-regs.o
+perf-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind.o
diff --git a/tools/perf/arch/mips/util/dwarf-regs.c b/tools/perf/arch/mips/util/dwarf-regs.c
new file mode 100644
index 0000000..25c13a9
--- /dev/null
+++ b/tools/perf/arch/mips/util/dwarf-regs.c
@@ -0,0 +1,38 @@
+// 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;
+}
diff --git a/tools/perf/arch/mips/util/perf_regs.c b/tools/perf/arch/mips/util/perf_regs.c
new file mode 100644
index 0000000..2864e2e
--- /dev/null
+++ b/tools/perf/arch/mips/util/perf_regs.c
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "../../util/perf_regs.h"
+
+const struct sample_reg sample_reg_masks[] = {
+	SMPL_REG_END
+};
diff --git a/tools/perf/arch/mips/util/unwind-libunwind.c b/tools/perf/arch/mips/util/unwind-libunwind.c
new file mode 100644
index 0000000..0d8c99c
--- /dev/null
+++ b/tools/perf/arch/mips/util/unwind-libunwind.c
@@ -0,0 +1,22 @@
+// 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;
+	}
+}
diff --git a/tools/perf/util/dwarf-regs.c b/tools/perf/util/dwarf-regs.c
index 1b49ece..3fa4486 100644
--- a/tools/perf/util/dwarf-regs.c
+++ b/tools/perf/util/dwarf-regs.c
@@ -24,6 +24,7 @@
 #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)
 
@@ -53,6 +54,8 @@ const char *get_dwarf_regstr(unsigned int n, unsigned int machine)
 		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);
 	}
-- 
2.1.0

[PATCH 3/3] perf tools: Generate mips syscalls_n64.c syscall table

[Tiezhu Yang]

Grab a copy of arch/mips/kernel/syscalls/syscall_n64.tbl and use it to
generate tools/perf/arch/mips/include/generated/asm/syscalls_n64.c file,
this is similar with commit 1b700c997500 ("perf tools: Build syscall table
.c header from kernel's syscall_64.tbl")

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 tools/perf/Makefile.config                         |   3 +-
 tools/perf/arch/mips/Makefile                      |  18 ++
 tools/perf/arch/mips/entry/syscalls/mksyscalltbl   |  32 ++
 .../perf/arch/mips/entry/syscalls/syscall_n64.tbl  | 358 +++++++++++++++++++++
 tools/perf/check-headers.sh                        |   1 +
 tools/perf/util/syscalltbl.c                       |   4 +
 6 files changed, 415 insertions(+), 1 deletion(-)
 create mode 100644 tools/perf/arch/mips/entry/syscalls/mksyscalltbl
 create mode 100644 tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index e378add..3280366 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -32,7 +32,7 @@ ifneq ($(NO_SYSCALL_TABLE),1)
       NO_SYSCALL_TABLE := 0
     endif
   else
-    ifeq ($(SRCARCH),$(filter $(SRCARCH),powerpc arm64 s390))
+    ifeq ($(SRCARCH),$(filter $(SRCARCH),powerpc arm64 s390 mips))
       NO_SYSCALL_TABLE := 0
     endif
   endif
@@ -89,6 +89,7 @@ endif
 
 ifeq ($(ARCH),mips)
   NO_PERF_REGS := 0
+  CFLAGS += -I$(OUTPUT)arch/mips/include/generated
   CFLAGS += -I../../arch/mips/include/uapi -I../../arch/mips/include/generated/uapi
   LIBUNWIND_LIBS = -lunwind -lunwind-mips
 endif
diff --git a/tools/perf/arch/mips/Makefile b/tools/perf/arch/mips/Makefile
index 6e1106f..8bc0907 100644
--- a/tools/perf/arch/mips/Makefile
+++ b/tools/perf/arch/mips/Makefile
@@ -2,3 +2,21 @@
 ifndef NO_DWARF
 PERF_HAVE_DWARF_REGS := 1
 endif
+
+# Syscall table generation for perf
+out    := $(OUTPUT)arch/mips/include/generated/asm
+header := $(out)/syscalls_n64.c
+sysprf := $(srctree)/tools/perf/arch/mips/entry/syscalls
+sysdef := $(sysprf)/syscall_n64.tbl
+systbl := $(sysprf)/mksyscalltbl
+
+# Create output directory if not already present
+_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
+
+$(header): $(sysdef) $(systbl)
+	$(Q)$(SHELL) '$(systbl)' $(sysdef) > $@
+
+clean::
+	$(call QUIET_CLEAN, mips) $(RM) $(header)
+
+archheaders: $(header)
diff --git a/tools/perf/arch/mips/entry/syscalls/mksyscalltbl b/tools/perf/arch/mips/entry/syscalls/mksyscalltbl
new file mode 100644
index 0000000..fb1f494
--- /dev/null
+++ b/tools/perf/arch/mips/entry/syscalls/mksyscalltbl
@@ -0,0 +1,32 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Generate system call table for perf. Derived from
+# s390 script.
+#
+# Author(s):  Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
+# Changed by: Tiezhu Yang <yangtiezhu@loongson.cn>
+
+SYSCALL_TBL=$1
+
+if ! test -r $SYSCALL_TBL; then
+	echo "Could not read input file" >&2
+	exit 1
+fi
+
+create_table()
+{
+	local max_nr nr abi sc discard
+
+	echo 'static const char *syscalltbl_mips_n64[] = {'
+	while read nr abi sc discard; do
+		printf '\t[%d] = "%s",\n' $nr $sc
+		max_nr=$nr
+	done
+	echo '};'
+	echo "#define SYSCALLTBL_MIPS_N64_MAX_ID $max_nr"
+}
+
+grep -E "^[[:digit:]]+[[:space:]]+(n64)" $SYSCALL_TBL	\
+	|sort -k1 -n					\
+	|create_table
diff --git a/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl b/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl
new file mode 100644
index 0000000..9164969
--- /dev/null
+++ b/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl
@@ -0,0 +1,358 @@
+# SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
+#
+# system call numbers and entry vectors for mips
+#
+# The format is:
+# <number> <abi> <name> <entry point>
+#
+# The <abi> is always "n64" for this file.
+#
+0	n64	read				sys_read
+1	n64	write				sys_write
+2	n64	open				sys_open
+3	n64	close				sys_close
+4	n64	stat				sys_newstat
+5	n64	fstat				sys_newfstat
+6	n64	lstat				sys_newlstat
+7	n64	poll				sys_poll
+8	n64	lseek				sys_lseek
+9	n64	mmap				sys_mips_mmap
+10	n64	mprotect			sys_mprotect
+11	n64	munmap				sys_munmap
+12	n64	brk				sys_brk
+13	n64	rt_sigaction			sys_rt_sigaction
+14	n64	rt_sigprocmask			sys_rt_sigprocmask
+15	n64	ioctl				sys_ioctl
+16	n64	pread64				sys_pread64
+17	n64	pwrite64			sys_pwrite64
+18	n64	readv				sys_readv
+19	n64	writev				sys_writev
+20	n64	access				sys_access
+21	n64	pipe				sysm_pipe
+22	n64	_newselect			sys_select
+23	n64	sched_yield			sys_sched_yield
+24	n64	mremap				sys_mremap
+25	n64	msync				sys_msync
+26	n64	mincore				sys_mincore
+27	n64	madvise				sys_madvise
+28	n64	shmget				sys_shmget
+29	n64	shmat				sys_shmat
+30	n64	shmctl				sys_old_shmctl
+31	n64	dup				sys_dup
+32	n64	dup2				sys_dup2
+33	n64	pause				sys_pause
+34	n64	nanosleep			sys_nanosleep
+35	n64	getitimer			sys_getitimer
+36	n64	setitimer			sys_setitimer
+37	n64	alarm				sys_alarm
+38	n64	getpid				sys_getpid
+39	n64	sendfile			sys_sendfile64
+40	n64	socket				sys_socket
+41	n64	connect				sys_connect
+42	n64	accept				sys_accept
+43	n64	sendto				sys_sendto
+44	n64	recvfrom			sys_recvfrom
+45	n64	sendmsg				sys_sendmsg
+46	n64	recvmsg				sys_recvmsg
+47	n64	shutdown			sys_shutdown
+48	n64	bind				sys_bind
+49	n64	listen				sys_listen
+50	n64	getsockname			sys_getsockname
+51	n64	getpeername			sys_getpeername
+52	n64	socketpair			sys_socketpair
+53	n64	setsockopt			sys_setsockopt
+54	n64	getsockopt			sys_getsockopt
+55	n64	clone				__sys_clone
+56	n64	fork				__sys_fork
+57	n64	execve				sys_execve
+58	n64	exit				sys_exit
+59	n64	wait4				sys_wait4
+60	n64	kill				sys_kill
+61	n64	uname				sys_newuname
+62	n64	semget				sys_semget
+63	n64	semop				sys_semop
+64	n64	semctl				sys_old_semctl
+65	n64	shmdt				sys_shmdt
+66	n64	msgget				sys_msgget
+67	n64	msgsnd				sys_msgsnd
+68	n64	msgrcv				sys_msgrcv
+69	n64	msgctl				sys_old_msgctl
+70	n64	fcntl				sys_fcntl
+71	n64	flock				sys_flock
+72	n64	fsync				sys_fsync
+73	n64	fdatasync			sys_fdatasync
+74	n64	truncate			sys_truncate
+75	n64	ftruncate			sys_ftruncate
+76	n64	getdents			sys_getdents
+77	n64	getcwd				sys_getcwd
+78	n64	chdir				sys_chdir
+79	n64	fchdir				sys_fchdir
+80	n64	rename				sys_rename
+81	n64	mkdir				sys_mkdir
+82	n64	rmdir				sys_rmdir
+83	n64	creat				sys_creat
+84	n64	link				sys_link
+85	n64	unlink				sys_unlink
+86	n64	symlink				sys_symlink
+87	n64	readlink			sys_readlink
+88	n64	chmod				sys_chmod
+89	n64	fchmod				sys_fchmod
+90	n64	chown				sys_chown
+91	n64	fchown				sys_fchown
+92	n64	lchown				sys_lchown
+93	n64	umask				sys_umask
+94	n64	gettimeofday			sys_gettimeofday
+95	n64	getrlimit			sys_getrlimit
+96	n64	getrusage			sys_getrusage
+97	n64	sysinfo				sys_sysinfo
+98	n64	times				sys_times
+99	n64	ptrace				sys_ptrace
+100	n64	getuid				sys_getuid
+101	n64	syslog				sys_syslog
+102	n64	getgid				sys_getgid
+103	n64	setuid				sys_setuid
+104	n64	setgid				sys_setgid
+105	n64	geteuid				sys_geteuid
+106	n64	getegid				sys_getegid
+107	n64	setpgid				sys_setpgid
+108	n64	getppid				sys_getppid
+109	n64	getpgrp				sys_getpgrp
+110	n64	setsid				sys_setsid
+111	n64	setreuid			sys_setreuid
+112	n64	setregid			sys_setregid
+113	n64	getgroups			sys_getgroups
+114	n64	setgroups			sys_setgroups
+115	n64	setresuid			sys_setresuid
+116	n64	getresuid			sys_getresuid
+117	n64	setresgid			sys_setresgid
+118	n64	getresgid			sys_getresgid
+119	n64	getpgid				sys_getpgid
+120	n64	setfsuid			sys_setfsuid
+121	n64	setfsgid			sys_setfsgid
+122	n64	getsid				sys_getsid
+123	n64	capget				sys_capget
+124	n64	capset				sys_capset
+125	n64	rt_sigpending			sys_rt_sigpending
+126	n64	rt_sigtimedwait			sys_rt_sigtimedwait
+127	n64	rt_sigqueueinfo			sys_rt_sigqueueinfo
+128	n64	rt_sigsuspend			sys_rt_sigsuspend
+129	n64	sigaltstack			sys_sigaltstack
+130	n64	utime				sys_utime
+131	n64	mknod				sys_mknod
+132	n64	personality			sys_personality
+133	n64	ustat				sys_ustat
+134	n64	statfs				sys_statfs
+135	n64	fstatfs				sys_fstatfs
+136	n64	sysfs				sys_sysfs
+137	n64	getpriority			sys_getpriority
+138	n64	setpriority			sys_setpriority
+139	n64	sched_setparam			sys_sched_setparam
+140	n64	sched_getparam			sys_sched_getparam
+141	n64	sched_setscheduler		sys_sched_setscheduler
+142	n64	sched_getscheduler		sys_sched_getscheduler
+143	n64	sched_get_priority_max		sys_sched_get_priority_max
+144	n64	sched_get_priority_min		sys_sched_get_priority_min
+145	n64	sched_rr_get_interval		sys_sched_rr_get_interval
+146	n64	mlock				sys_mlock
+147	n64	munlock				sys_munlock
+148	n64	mlockall			sys_mlockall
+149	n64	munlockall			sys_munlockall
+150	n64	vhangup				sys_vhangup
+151	n64	pivot_root			sys_pivot_root
+152	n64	_sysctl				sys_ni_syscall
+153	n64	prctl				sys_prctl
+154	n64	adjtimex			sys_adjtimex
+155	n64	setrlimit			sys_setrlimit
+156	n64	chroot				sys_chroot
+157	n64	sync				sys_sync
+158	n64	acct				sys_acct
+159	n64	settimeofday			sys_settimeofday
+160	n64	mount				sys_mount
+161	n64	umount2				sys_umount
+162	n64	swapon				sys_swapon
+163	n64	swapoff				sys_swapoff
+164	n64	reboot				sys_reboot
+165	n64	sethostname			sys_sethostname
+166	n64	setdomainname			sys_setdomainname
+167	n64	create_module			sys_ni_syscall
+168	n64	init_module			sys_init_module
+169	n64	delete_module			sys_delete_module
+170	n64	get_kernel_syms			sys_ni_syscall
+171	n64	query_module			sys_ni_syscall
+172	n64	quotactl			sys_quotactl
+173	n64	nfsservctl			sys_ni_syscall
+174	n64	getpmsg				sys_ni_syscall
+175	n64	putpmsg				sys_ni_syscall
+176	n64	afs_syscall			sys_ni_syscall
+# 177 reserved for security
+177	n64	reserved177			sys_ni_syscall
+178	n64	gettid				sys_gettid
+179	n64	readahead			sys_readahead
+180	n64	setxattr			sys_setxattr
+181	n64	lsetxattr			sys_lsetxattr
+182	n64	fsetxattr			sys_fsetxattr
+183	n64	getxattr			sys_getxattr
+184	n64	lgetxattr			sys_lgetxattr
+185	n64	fgetxattr			sys_fgetxattr
+186	n64	listxattr			sys_listxattr
+187	n64	llistxattr			sys_llistxattr
+188	n64	flistxattr			sys_flistxattr
+189	n64	removexattr			sys_removexattr
+190	n64	lremovexattr			sys_lremovexattr
+191	n64	fremovexattr			sys_fremovexattr
+192	n64	tkill				sys_tkill
+193	n64	reserved193			sys_ni_syscall
+194	n64	futex				sys_futex
+195	n64	sched_setaffinity		sys_sched_setaffinity
+196	n64	sched_getaffinity		sys_sched_getaffinity
+197	n64	cacheflush			sys_cacheflush
+198	n64	cachectl			sys_cachectl
+199	n64	sysmips				__sys_sysmips
+200	n64	io_setup			sys_io_setup
+201	n64	io_destroy			sys_io_destroy
+202	n64	io_getevents			sys_io_getevents
+203	n64	io_submit			sys_io_submit
+204	n64	io_cancel			sys_io_cancel
+205	n64	exit_group			sys_exit_group
+206	n64	lookup_dcookie			sys_lookup_dcookie
+207	n64	epoll_create			sys_epoll_create
+208	n64	epoll_ctl			sys_epoll_ctl
+209	n64	epoll_wait			sys_epoll_wait
+210	n64	remap_file_pages		sys_remap_file_pages
+211	n64	rt_sigreturn			sys_rt_sigreturn
+212	n64	set_tid_address			sys_set_tid_address
+213	n64	restart_syscall			sys_restart_syscall
+214	n64	semtimedop			sys_semtimedop
+215	n64	fadvise64			sys_fadvise64_64
+216	n64	timer_create			sys_timer_create
+217	n64	timer_settime			sys_timer_settime
+218	n64	timer_gettime			sys_timer_gettime
+219	n64	timer_getoverrun		sys_timer_getoverrun
+220	n64	timer_delete			sys_timer_delete
+221	n64	clock_settime			sys_clock_settime
+222	n64	clock_gettime			sys_clock_gettime
+223	n64	clock_getres			sys_clock_getres
+224	n64	clock_nanosleep			sys_clock_nanosleep
+225	n64	tgkill				sys_tgkill
+226	n64	utimes				sys_utimes
+227	n64	mbind				sys_mbind
+228	n64	get_mempolicy			sys_get_mempolicy
+229	n64	set_mempolicy			sys_set_mempolicy
+230	n64	mq_open				sys_mq_open
+231	n64	mq_unlink			sys_mq_unlink
+232	n64	mq_timedsend			sys_mq_timedsend
+233	n64	mq_timedreceive			sys_mq_timedreceive
+234	n64	mq_notify			sys_mq_notify
+235	n64	mq_getsetattr			sys_mq_getsetattr
+236	n64	vserver				sys_ni_syscall
+237	n64	waitid				sys_waitid
+# 238 was sys_setaltroot
+239	n64	add_key				sys_add_key
+240	n64	request_key			sys_request_key
+241	n64	keyctl				sys_keyctl
+242	n64	set_thread_area			sys_set_thread_area
+243	n64	inotify_init			sys_inotify_init
+244	n64	inotify_add_watch		sys_inotify_add_watch
+245	n64	inotify_rm_watch		sys_inotify_rm_watch
+246	n64	migrate_pages			sys_migrate_pages
+247	n64	openat				sys_openat
+248	n64	mkdirat				sys_mkdirat
+249	n64	mknodat				sys_mknodat
+250	n64	fchownat			sys_fchownat
+251	n64	futimesat			sys_futimesat
+252	n64	newfstatat			sys_newfstatat
+253	n64	unlinkat			sys_unlinkat
+254	n64	renameat			sys_renameat
+255	n64	linkat				sys_linkat
+256	n64	symlinkat			sys_symlinkat
+257	n64	readlinkat			sys_readlinkat
+258	n64	fchmodat			sys_fchmodat
+259	n64	faccessat			sys_faccessat
+260	n64	pselect6			sys_pselect6
+261	n64	ppoll				sys_ppoll
+262	n64	unshare				sys_unshare
+263	n64	splice				sys_splice
+264	n64	sync_file_range			sys_sync_file_range
+265	n64	tee				sys_tee
+266	n64	vmsplice			sys_vmsplice
+267	n64	move_pages			sys_move_pages
+268	n64	set_robust_list			sys_set_robust_list
+269	n64	get_robust_list			sys_get_robust_list
+270	n64	kexec_load			sys_kexec_load
+271	n64	getcpu				sys_getcpu
+272	n64	epoll_pwait			sys_epoll_pwait
+273	n64	ioprio_set			sys_ioprio_set
+274	n64	ioprio_get			sys_ioprio_get
+275	n64	utimensat			sys_utimensat
+276	n64	signalfd			sys_signalfd
+277	n64	timerfd				sys_ni_syscall
+278	n64	eventfd				sys_eventfd
+279	n64	fallocate			sys_fallocate
+280	n64	timerfd_create			sys_timerfd_create
+281	n64	timerfd_gettime			sys_timerfd_gettime
+282	n64	timerfd_settime			sys_timerfd_settime
+283	n64	signalfd4			sys_signalfd4
+284	n64	eventfd2			sys_eventfd2
+285	n64	epoll_create1			sys_epoll_create1
+286	n64	dup3				sys_dup3
+287	n64	pipe2				sys_pipe2
+288	n64	inotify_init1			sys_inotify_init1
+289	n64	preadv				sys_preadv
+290	n64	pwritev				sys_pwritev
+291	n64	rt_tgsigqueueinfo		sys_rt_tgsigqueueinfo
+292	n64	perf_event_open			sys_perf_event_open
+293	n64	accept4				sys_accept4
+294	n64	recvmmsg			sys_recvmmsg
+295	n64	fanotify_init			sys_fanotify_init
+296	n64	fanotify_mark			sys_fanotify_mark
+297	n64	prlimit64			sys_prlimit64
+298	n64	name_to_handle_at		sys_name_to_handle_at
+299	n64	open_by_handle_at		sys_open_by_handle_at
+300	n64	clock_adjtime			sys_clock_adjtime
+301	n64	syncfs				sys_syncfs
+302	n64	sendmmsg			sys_sendmmsg
+303	n64	setns				sys_setns
+304	n64	process_vm_readv		sys_process_vm_readv
+305	n64	process_vm_writev		sys_process_vm_writev
+306	n64	kcmp				sys_kcmp
+307	n64	finit_module			sys_finit_module
+308	n64	getdents64			sys_getdents64
+309	n64	sched_setattr			sys_sched_setattr
+310	n64	sched_getattr			sys_sched_getattr
+311	n64	renameat2			sys_renameat2
+312	n64	seccomp				sys_seccomp
+313	n64	getrandom			sys_getrandom
+314	n64	memfd_create			sys_memfd_create
+315	n64	bpf				sys_bpf
+316	n64	execveat			sys_execveat
+317	n64	userfaultfd			sys_userfaultfd
+318	n64	membarrier			sys_membarrier
+319	n64	mlock2				sys_mlock2
+320	n64	copy_file_range			sys_copy_file_range
+321	n64	preadv2				sys_preadv2
+322	n64	pwritev2			sys_pwritev2
+323	n64	pkey_mprotect			sys_pkey_mprotect
+324	n64	pkey_alloc			sys_pkey_alloc
+325	n64	pkey_free			sys_pkey_free
+326	n64	statx				sys_statx
+327	n64	rseq				sys_rseq
+328	n64	io_pgetevents			sys_io_pgetevents
+# 329 through 423 are reserved to sync up with other architectures
+424	n64	pidfd_send_signal		sys_pidfd_send_signal
+425	n64	io_uring_setup			sys_io_uring_setup
+426	n64	io_uring_enter			sys_io_uring_enter
+427	n64	io_uring_register		sys_io_uring_register
+428	n64	open_tree			sys_open_tree
+429	n64	move_mount			sys_move_mount
+430	n64	fsopen				sys_fsopen
+431	n64	fsconfig			sys_fsconfig
+432	n64	fsmount				sys_fsmount
+433	n64	fspick				sys_fspick
+434	n64	pidfd_open			sys_pidfd_open
+435	n64	clone3				__sys_clone3
+436	n64	close_range			sys_close_range
+437	n64	openat2				sys_openat2
+438	n64	pidfd_getfd			sys_pidfd_getfd
+439	n64	faccessat2			sys_faccessat2
+440	n64	process_madvise			sys_process_madvise
+441	n64	epoll_pwait2			sys_epoll_pwait2
diff --git a/tools/perf/check-headers.sh b/tools/perf/check-headers.sh
index dded93a..39eada9 100755
--- a/tools/perf/check-headers.sh
+++ b/tools/perf/check-headers.sh
@@ -146,6 +146,7 @@ check arch/x86/lib/insn.c             '-I "^#include [\"<]\(../include/\)*asm/in
 check_2 tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl
 check_2 tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl
 check_2 tools/perf/arch/s390/entry/syscalls/syscall.tbl arch/s390/kernel/syscalls/syscall.tbl
+check_2 tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl arch/mips/kernel/syscalls/syscall_n64.tbl
 
 for i in $BEAUTY_FILES; do
   beauty_check $i -B
diff --git a/tools/perf/util/syscalltbl.c b/tools/perf/util/syscalltbl.c
index 03bd99d..a2e9068 100644
--- a/tools/perf/util/syscalltbl.c
+++ b/tools/perf/util/syscalltbl.c
@@ -34,6 +34,10 @@ static const char **syscalltbl_native = syscalltbl_powerpc_32;
 #include <asm/syscalls.c>
 const int syscalltbl_native_max_id = SYSCALLTBL_ARM64_MAX_ID;
 static const char **syscalltbl_native = syscalltbl_arm64;
+#elif defined(__mips__)
+#include <asm/syscalls_n64.c>
+const int syscalltbl_native_max_id = SYSCALLTBL_MIPS_N64_MAX_ID;
+static const char **syscalltbl_native = syscalltbl_mips_n64;
 #endif
 
 struct syscall {
-- 
2.1.0

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Peter Zijlstra]

On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
> +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;
> +}

So we recently changed this on x86 to not rely on TIF flags. IIRC the
problem is that on x86 you can change the mode of a task without the
kernel being aware of it. Is something like that possible on MIPS as
well?

The thing x86 does today is look at it's pt_regs state to determine the
actual state.

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Jiaxun Yang]

在 2021/1/4 下午6:59, Peter Zijlstra 写道:
> On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
>> +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;
>> +}
> So we recently changed this on x86 to not rely on TIF flags. IIRC the
> problem is that on x86 you can change the mode of a task without the
> kernel being aware of it. Is something like that possible on MIPS as
> well?

Hi all,

In MIPS world it's impossible to raise a thread to 64bit without kernel 
aware.
Without STATUS.UX set it will trigger reserved instruction exception 
when trying
to run 64bit instructions.

However it may be possible to run with 32bit ABI without TIF_32BIT_REGS 
if user
program didn't get ELF ABI right. I think that's out of our current 
consideration.

> The thing x86 does today is look at it's pt_regs state to determine the
> actual state.
It is possible to look at pt_regs Status.UX bit on MIPS. But it seems 
unnecessary
as user can't change it.

Thanks.

- Jiaxun

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Peter Zijlstra]

On Tue, Jan 05, 2021 at 11:45:37AM +0800, Jiaxun Yang wrote:
> 在 2021/1/4 下午6:59, Peter Zijlstra 写道:
> > On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
> > > +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;
> > > +}
> > So we recently changed this on x86 to not rely on TIF flags. IIRC the
> > problem is that on x86 you can change the mode of a task without the
> > kernel being aware of it. Is something like that possible on MIPS as
> > well?
> 
> Hi all,
> 
> In MIPS world it's impossible to raise a thread to 64bit without kernel
> aware.
> Without STATUS.UX set it will trigger reserved instruction exception when
> trying
> to run 64bit instructions.

The other way around is the case on x86, a 64bit program can create and
execute 32bit code sections without the kernel being aware. But if
clearing STATUS.UX has the same issue as setting it, that should not be
a problem for you.

> However it may be possible to run with 32bit ABI without
> TIF_32BIT_REGS if user program didn't get ELF ABI right. I think
> that's out of our current consideration.

Fair enough.

> > The thing x86 does today is look at it's pt_regs state to determine the
> > actual state.
> It is possible to look at pt_regs Status.UX bit on MIPS. But it seems
> unnecessary
> as user can't change it.

Ok, good. Then no objection, proceed! :-)

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Thomas Bogendoerfer]

On Tue, Jan 05, 2021 at 11:18:06AM +0100, Peter Zijlstra wrote:
> On Tue, Jan 05, 2021 at 11:45:37AM +0800, Jiaxun Yang wrote:
> > 在 2021/1/4 下午6:59, Peter Zijlstra 写道:
> > > On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
> > > > +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;
> > > > +}
> > > So we recently changed this on x86 to not rely on TIF flags. IIRC the
> > > problem is that on x86 you can change the mode of a task without the
> > > kernel being aware of it. Is something like that possible on MIPS as
> > > well?
> > 
> > Hi all,
> > 
> > In MIPS world it's impossible to raise a thread to 64bit without kernel
> > aware.
> > Without STATUS.UX set it will trigger reserved instruction exception when
> > trying
> > to run 64bit instructions.
> 
> The other way around is the case on x86, a 64bit program can create and
> execute 32bit code sections without the kernel being aware. But if
> clearing STATUS.UX has the same issue as setting it, that should not be
> a problem for you.
> 
> > However it may be possible to run with 32bit ABI without
> > TIF_32BIT_REGS if user program didn't get ELF ABI right. I think
> > that's out of our current consideration.
> 
> Fair enough.
> 
> > > The thing x86 does today is look at it's pt_regs state to determine the
> > > actual state.
> > It is possible to look at pt_regs Status.UX bit on MIPS. But it seems
> > unnecessary
> > as user can't change it.
> 
> Ok, good. Then no objection, proceed! :-)

this patch aims more to mips-next, while patch 2 and 3 are targeting
tools/perf. Should I take them into mips-next, too ?

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Tiezhu Yang]

On 01/28/2021 05:15 AM, Thomas Bogendoerfer wrote:
> On Tue, Jan 05, 2021 at 11:18:06AM +0100, Peter Zijlstra wrote:
>> On Tue, Jan 05, 2021 at 11:45:37AM +0800, Jiaxun Yang wrote:
>>> 在 2021/1/4 下午6:59, Peter Zijlstra 写道:
>>>> On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
>>>>> +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;
>>>>> +}
>>>> So we recently changed this on x86 to not rely on TIF flags. IIRC the
>>>> problem is that on x86 you can change the mode of a task without the
>>>> kernel being aware of it. Is something like that possible on MIPS as
>>>> well?
>>> Hi all,
>>>
>>> In MIPS world it's impossible to raise a thread to 64bit without kernel
>>> aware.
>>> Without STATUS.UX set it will trigger reserved instruction exception when
>>> trying
>>> to run 64bit instructions.
>> The other way around is the case on x86, a 64bit program can create and
>> execute 32bit code sections without the kernel being aware. But if
>> clearing STATUS.UX has the same issue as setting it, that should not be
>> a problem for you.
>>
>>> However it may be possible to run with 32bit ABI without
>>> TIF_32BIT_REGS if user program didn't get ELF ABI right. I think
>>> that's out of our current consideration.
>> Fair enough.
>>
>>>> The thing x86 does today is look at it's pt_regs state to determine the
>>>> actual state.
>>> It is possible to look at pt_regs Status.UX bit on MIPS. But it seems
>>> unnecessary
>>> as user can't change it.
>> Ok, good. Then no objection, proceed! :-)
> this patch aims more to mips-next, while patch 2 and 3 are targeting
> tools/perf. Should I take them into mips-next, too ?

If it is possible, I prefer to merge this three patches together
through mips-next tree.

Thanks,
Tiezhu

>
> Thomas.
>

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Arnaldo Carvalho de Melo]

Em Fri, Jan 29, 2021 at 10:48:52AM +0800, Tiezhu Yang escreveu:
> On 01/28/2021 05:15 AM, Thomas Bogendoerfer wrote:
> > On Tue, Jan 05, 2021 at 11:18:06AM +0100, Peter Zijlstra wrote:
> > > On Tue, Jan 05, 2021 at 11:45:37AM +0800, Jiaxun Yang wrote:
> > > > 在 2021/1/4 下午6:59, Peter Zijlstra 写道:
> > > > > On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
> > > > > > +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;
> > > > > > +}
> > > > > So we recently changed this on x86 to not rely on TIF flags. IIRC the
> > > > > problem is that on x86 you can change the mode of a task without the
> > > > > kernel being aware of it. Is something like that possible on MIPS as
> > > > > well?
> > > > Hi all,
> > > > 
> > > > In MIPS world it's impossible to raise a thread to 64bit without kernel
> > > > aware.
> > > > Without STATUS.UX set it will trigger reserved instruction exception when
> > > > trying
> > > > to run 64bit instructions.
> > > The other way around is the case on x86, a 64bit program can create and
> > > execute 32bit code sections without the kernel being aware. But if
> > > clearing STATUS.UX has the same issue as setting it, that should not be
> > > a problem for you.
> > > 
> > > > However it may be possible to run with 32bit ABI without
> > > > TIF_32BIT_REGS if user program didn't get ELF ABI right. I think
> > > > that's out of our current consideration.
> > > Fair enough.
> > > 
> > > > > The thing x86 does today is look at it's pt_regs state to determine the
> > > > > actual state.
> > > > It is possible to look at pt_regs Status.UX bit on MIPS. But it seems
> > > > unnecessary
> > > > as user can't change it.
> > > Ok, good. Then no objection, proceed! :-)
> > this patch aims more to mips-next, while patch 2 and 3 are targeting
> > tools/perf. Should I take them into mips-next, too ?
> 
> If it is possible, I prefer to merge this three patches together
> through mips-next tree.

The kernel part should go via the mips-next tree, the tooling I can
process, that is how these things go in other cases where kernel and
tooling changes for some new feature are needed.

This helps making sure tooling is not in lockstep with the kernel, one
should be able to use a new tool in an old kernel and vice-versa.

- Arnaldo

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Arnaldo Carvalho de Melo]

Em Wed, Jan 27, 2021 at 10:15:06PM +0100, Thomas Bogendoerfer escreveu:
> On Tue, Jan 05, 2021 at 11:18:06AM +0100, Peter Zijlstra wrote:
> > On Tue, Jan 05, 2021 at 11:45:37AM +0800, Jiaxun Yang wrote:
> > > 在 2021/1/4 下午6:59, Peter Zijlstra 写道:
> > > > On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
> > > > > +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;
> > > > > +}
> > > > So we recently changed this on x86 to not rely on TIF flags. IIRC the
> > > > problem is that on x86 you can change the mode of a task without the
> > > > kernel being aware of it. Is something like that possible on MIPS as
> > > > well?
> > > 
> > > Hi all,
> > > 
> > > In MIPS world it's impossible to raise a thread to 64bit without kernel
> > > aware.
> > > Without STATUS.UX set it will trigger reserved instruction exception when
> > > trying
> > > to run 64bit instructions.
> > 
> > The other way around is the case on x86, a 64bit program can create and
> > execute 32bit code sections without the kernel being aware. But if
> > clearing STATUS.UX has the same issue as setting it, that should not be
> > a problem for you.
> > 
> > > However it may be possible to run with 32bit ABI without
> > > TIF_32BIT_REGS if user program didn't get ELF ABI right. I think
> > > that's out of our current consideration.
> > 
> > Fair enough.
> > 
> > > > The thing x86 does today is look at it's pt_regs state to determine the
> > > > actual state.
> > > It is possible to look at pt_regs Status.UX bit on MIPS. But it seems
> > > unnecessary
> > > as user can't change it.
> > 
> > Ok, good. Then no objection, proceed! :-)
> 
> this patch aims more to mips-next, while patch 2 and 3 are targeting
> tools/perf. Should I take them into mips-next, too ?

I'll process the tools/perf ones, if you took the time to actually
review them, please say so and I'll add a Reviewed-by tag stating that.

I've replied to another message in this thread with reasoning about the
value of processing kernel bits in the relevant arch tree while the
tooling one via my perf/core branch.

- Arnaldo

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Thomas Bogendoerfer]

On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
> +++ b/arch/mips/include/uapi/asm/perf_regs.h
> @@ -0,0 +1,42 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +#ifndef _ASM_MIPS_PERF_REGS_H
> +#define _ASM_MIPS_PERF_REGS_H
> +
> +enum perf_event_mips_regs {
> +	PERF_REG_MIPS_PC,
> +	PERF_REG_MIPS_R1,
> +	PERF_REG_MIPS_R2,
> +	PERF_REG_MIPS_R3,
> +	PERF_REG_MIPS_R4,
> +	PERF_REG_MIPS_R5,
> +	PERF_REG_MIPS_R6,
> +	PERF_REG_MIPS_R7,
> +	PERF_REG_MIPS_R8,
> +	PERF_REG_MIPS_R9,
> +	PERF_REG_MIPS_R10,
> +	PERF_REG_MIPS_R11,
> +	PERF_REG_MIPS_R12,
> +	PERF_REG_MIPS_R13,
> +	PERF_REG_MIPS_R14,
> +	PERF_REG_MIPS_R15,
> +	PERF_REG_MIPS_R16,
> +	PERF_REG_MIPS_R17,
> +	PERF_REG_MIPS_R18,
> +	PERF_REG_MIPS_R19,
> +	PERF_REG_MIPS_R20,
> +	PERF_REG_MIPS_R21,
> +	PERF_REG_MIPS_R22,
> +	PERF_REG_MIPS_R23,
> +	PERF_REG_MIPS_R24,
> +	PERF_REG_MIPS_R25,
> +	/*
> +	 * 26 and 27 are k0 and k1, they are always clobbered thus not
> +	 * stored.
> +	 */

haveing this hole here make all code more complicated. Does it hurt
to have R26 and R27 in the list ?

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Tiezhu Yang]

On 02/01/2021 06:43 PM, Thomas Bogendoerfer wrote:
> On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
>> +++ b/arch/mips/include/uapi/asm/perf_regs.h
>> @@ -0,0 +1,42 @@
>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
>> +#ifndef _ASM_MIPS_PERF_REGS_H
>> +#define _ASM_MIPS_PERF_REGS_H
>> +
>> +enum perf_event_mips_regs {
>> +	PERF_REG_MIPS_PC,
>> +	PERF_REG_MIPS_R1,
>> +	PERF_REG_MIPS_R2,
>> +	PERF_REG_MIPS_R3,
>> +	PERF_REG_MIPS_R4,
>> +	PERF_REG_MIPS_R5,
>> +	PERF_REG_MIPS_R6,
>> +	PERF_REG_MIPS_R7,
>> +	PERF_REG_MIPS_R8,
>> +	PERF_REG_MIPS_R9,
>> +	PERF_REG_MIPS_R10,
>> +	PERF_REG_MIPS_R11,
>> +	PERF_REG_MIPS_R12,
>> +	PERF_REG_MIPS_R13,
>> +	PERF_REG_MIPS_R14,
>> +	PERF_REG_MIPS_R15,
>> +	PERF_REG_MIPS_R16,
>> +	PERF_REG_MIPS_R17,
>> +	PERF_REG_MIPS_R18,
>> +	PERF_REG_MIPS_R19,
>> +	PERF_REG_MIPS_R20,
>> +	PERF_REG_MIPS_R21,
>> +	PERF_REG_MIPS_R22,
>> +	PERF_REG_MIPS_R23,
>> +	PERF_REG_MIPS_R24,
>> +	PERF_REG_MIPS_R25,
>> +	/*
>> +	 * 26 and 27 are k0 and k1, they are always clobbered thus not
>> +	 * stored.
>> +	 */
> haveing this hole here make all code more complicated. Does it hurt
> to have R26 and R27 in the list ?

I think there is no effect if have R26 and R27 in the list.

In the perf_reg_value(), PERF_REG_MIPS_R{26,27} are default case.

+u64 perf_reg_value(struct pt_regs *regs, int idx)
+{
+ long v;
+
+ switch (idx) {
+ case PERF_REG_MIPS_PC:
+ v = regs->cp0_epc;
+ break;
+ case PERF_REG_MIPS_R1 ... PERF_REG_MIPS_R25:
+ v = regs->regs[idx - PERF_REG_MIPS_R1 + 1];
+ break;
+ case PERF_REG_MIPS_R28 ... PERF_REG_MIPS_R31:
+ v = regs->regs[idx - PERF_REG_MIPS_R28 + 28];
+ break;
+
+ default:
+ WARN_ON_ONCE(1);
+ return 0;
+ }
+
+ return (s64)v; /* Sign extend if 32-bit. */
+} Should I modify enum perf_event_mips_regs to add R26 and R27,
and then send v2?

Thanks,
Tiezhu

>
> Thomas.
>

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Thomas Bogendoerfer]

On Mon, Feb 01, 2021 at 08:56:06PM +0800, Tiezhu Yang wrote:
> On 02/01/2021 06:43 PM, Thomas Bogendoerfer wrote:
> > On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
> > > +++ b/arch/mips/include/uapi/asm/perf_regs.h
> > > @@ -0,0 +1,42 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > > +#ifndef _ASM_MIPS_PERF_REGS_H
> > > +#define _ASM_MIPS_PERF_REGS_H
> > > +
> > > +enum perf_event_mips_regs {
> > > +	PERF_REG_MIPS_PC,
> > > +	PERF_REG_MIPS_R1,
> > > +	PERF_REG_MIPS_R2,
> > > +	PERF_REG_MIPS_R3,
> > > +	PERF_REG_MIPS_R4,
> > > +	PERF_REG_MIPS_R5,
> > > +	PERF_REG_MIPS_R6,
> > > +	PERF_REG_MIPS_R7,
> > > +	PERF_REG_MIPS_R8,
> > > +	PERF_REG_MIPS_R9,
> > > +	PERF_REG_MIPS_R10,
> > > +	PERF_REG_MIPS_R11,
> > > +	PERF_REG_MIPS_R12,
> > > +	PERF_REG_MIPS_R13,
> > > +	PERF_REG_MIPS_R14,
> > > +	PERF_REG_MIPS_R15,
> > > +	PERF_REG_MIPS_R16,
> > > +	PERF_REG_MIPS_R17,
> > > +	PERF_REG_MIPS_R18,
> > > +	PERF_REG_MIPS_R19,
> > > +	PERF_REG_MIPS_R20,
> > > +	PERF_REG_MIPS_R21,
> > > +	PERF_REG_MIPS_R22,
> > > +	PERF_REG_MIPS_R23,
> > > +	PERF_REG_MIPS_R24,
> > > +	PERF_REG_MIPS_R25,
> > > +	/*
> > > +	 * 26 and 27 are k0 and k1, they are always clobbered thus not
> > > +	 * stored.
> > > +	 */
> > haveing this hole here make all code more complicated. Does it hurt
> > to have R26 and R27 in the list ?
> 
> I think there is no effect if have R26 and R27 in the list.
> 
> In the perf_reg_value(), PERF_REG_MIPS_R{26,27} are default case.

why make them special ? After all they are real registers and are only
defined special by current ABIs.

> Should I modify enum perf_event_mips_regs to add R26 and R27,
> and then send v2?

yes please.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Tiezhu Yang]

On 2/3/21 6:40 PM, Thomas Bogendoerfer wrote:
> On Mon, Feb 01, 2021 at 08:56:06PM +0800, Tiezhu Yang wrote:
>> On 02/01/2021 06:43 PM, Thomas Bogendoerfer wrote:
>>> On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
>>>> +++ b/arch/mips/include/uapi/asm/perf_regs.h
>>>> @@ -0,0 +1,42 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
>>>> +#ifndef _ASM_MIPS_PERF_REGS_H
>>>> +#define _ASM_MIPS_PERF_REGS_H
>>>> +
>>>> +enum perf_event_mips_regs {
>>>> +	PERF_REG_MIPS_PC,
>>>> +	PERF_REG_MIPS_R1,
>>>> +	PERF_REG_MIPS_R2,
>>>> +	PERF_REG_MIPS_R3,
>>>> +	PERF_REG_MIPS_R4,
>>>> +	PERF_REG_MIPS_R5,
>>>> +	PERF_REG_MIPS_R6,
>>>> +	PERF_REG_MIPS_R7,
>>>> +	PERF_REG_MIPS_R8,
>>>> +	PERF_REG_MIPS_R9,
>>>> +	PERF_REG_MIPS_R10,
>>>> +	PERF_REG_MIPS_R11,
>>>> +	PERF_REG_MIPS_R12,
>>>> +	PERF_REG_MIPS_R13,
>>>> +	PERF_REG_MIPS_R14,
>>>> +	PERF_REG_MIPS_R15,
>>>> +	PERF_REG_MIPS_R16,
>>>> +	PERF_REG_MIPS_R17,
>>>> +	PERF_REG_MIPS_R18,
>>>> +	PERF_REG_MIPS_R19,
>>>> +	PERF_REG_MIPS_R20,
>>>> +	PERF_REG_MIPS_R21,
>>>> +	PERF_REG_MIPS_R22,
>>>> +	PERF_REG_MIPS_R23,
>>>> +	PERF_REG_MIPS_R24,
>>>> +	PERF_REG_MIPS_R25,
>>>> +	/*
>>>> +	 * 26 and 27 are k0 and k1, they are always clobbered thus not
>>>> +	 * stored.
>>>> +	 */
>>> haveing this hole here make all code more complicated. Does it hurt
>>> to have R26 and R27 in the list ?
>> I think there is no effect if have R26 and R27 in the list.
>>
>> In the perf_reg_value(), PERF_REG_MIPS_R{26,27} are default case.
> why make them special ? After all they are real registers and are only
> defined special by current ABIs.


By convention, $26 and $27 are k registers which are reserved for use
by the OS kernel.

Here is an explanation [1]:

"An interrupt handler must save any general - purpose registers that
it is going to use (to be restored at return). But to do so requires
you to modify at least one register first (something like sw $t0, saved_t0
expands to two machine instructions using $at).

This situation is resolved by forbidding user programs from using
two general - purpose registers, $k0 and $k1 (The k stands for kernel,
which an exception handler is part of). The interrupt handler is allowed
to use $k0 and $k1 without having to save or restore their values.
This allows just enough leeway to start saving registers, as well as
making returning from the interrupt handler possible."

[1] 
https://stackoverflow.com/questions/27922315/how-to-use-mips-k0-and-k1-registers


>
>> Should I modify enum perf_event_mips_regs to add R26 and R27,
>> and then send v2?
> yes please.
>
> Thomas.
>

Re: [PATCH 1/3] MIPS: kernel: Support extracting off-line stack traces from user-space with perf

[Thomas Bogendoerfer]

On Wed, Feb 03, 2021 at 09:12:28PM +0800, Tiezhu Yang wrote:
> On 2/3/21 6:40 PM, Thomas Bogendoerfer wrote:
> > On Mon, Feb 01, 2021 at 08:56:06PM +0800, Tiezhu Yang wrote:
> > > On 02/01/2021 06:43 PM, Thomas Bogendoerfer wrote:
> > > > On Tue, Dec 29, 2020 at 08:55:59PM +0800, Tiezhu Yang wrote:
> > > > > +++ b/arch/mips/include/uapi/asm/perf_regs.h
> > > > > @@ -0,0 +1,42 @@
> > > > > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > > > > +#ifndef _ASM_MIPS_PERF_REGS_H
> > > > > +#define _ASM_MIPS_PERF_REGS_H
> > > > > +
> > > > > +enum perf_event_mips_regs {
> > > > > +	PERF_REG_MIPS_PC,
> > > > > +	PERF_REG_MIPS_R1,
> > > > > +	PERF_REG_MIPS_R2,
> > > > > +	PERF_REG_MIPS_R3,
> > > > > +	PERF_REG_MIPS_R4,
> > > > > +	PERF_REG_MIPS_R5,
> > > > > +	PERF_REG_MIPS_R6,
> > > > > +	PERF_REG_MIPS_R7,
> > > > > +	PERF_REG_MIPS_R8,
> > > > > +	PERF_REG_MIPS_R9,
> > > > > +	PERF_REG_MIPS_R10,
> > > > > +	PERF_REG_MIPS_R11,
> > > > > +	PERF_REG_MIPS_R12,
> > > > > +	PERF_REG_MIPS_R13,
> > > > > +	PERF_REG_MIPS_R14,
> > > > > +	PERF_REG_MIPS_R15,
> > > > > +	PERF_REG_MIPS_R16,
> > > > > +	PERF_REG_MIPS_R17,
> > > > > +	PERF_REG_MIPS_R18,
> > > > > +	PERF_REG_MIPS_R19,
> > > > > +	PERF_REG_MIPS_R20,
> > > > > +	PERF_REG_MIPS_R21,
> > > > > +	PERF_REG_MIPS_R22,
> > > > > +	PERF_REG_MIPS_R23,
> > > > > +	PERF_REG_MIPS_R24,
> > > > > +	PERF_REG_MIPS_R25,
> > > > > +	/*
> > > > > +	 * 26 and 27 are k0 and k1, they are always clobbered thus not
> > > > > +	 * stored.
> > > > > +	 */
> > > > haveing this hole here make all code more complicated. Does it hurt
> > > > to have R26 and R27 in the list ?
> > > I think there is no effect if have R26 and R27 in the list.
> > > 
> > > In the perf_reg_value(), PERF_REG_MIPS_R{26,27} are default case.
> > why make them special ? After all they are real registers and are only
> > defined special by current ABIs.
> 
> 
> By convention, $26 and $27 are k registers which are reserved for use
> by the OS kernel.

believe me, I knew that already. But from a CPU standpoint they are
just registers.

Anyway I'm fine with just adding R26 and R27 to the enum.

Thomas.

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