[PATCH v2 06/16] perf dwarf-regs: Adapt get_dwarf_regnum() for arm64

[Tengda Wu]

The current arm64 DWARF register lookup relies on 'aarch64_regstr_tbl',
a static string table. While this works for kprobe-tracer where register
names start with '%', it is insufficient for parsing register numbers
directly from raw instructions (e.g., extracting '6' from 'x6' or 'w6')
during annotation.

Since get_dwarf_regnum() is currently used only by 'perf annotate' and
does not affect kprobe-tracer, replace the limited table-based lookup
with a programmatic implementation in __get_dwarf_regnum_arm64(). This
allows resolving arm64 register names (x0-x30, w0-w30, sp, etc.) directly
into their corresponding DWARF register numbers.

Signed-off-by: Tengda Wu <wutengda@xxxxxxxxxxxxxxx>
---
 .../util/dwarf-regs-arch/dwarf-regs-arm64.c   | 20 +++++++++++++++++++
 tools/perf/util/dwarf-regs.c                  |  2 +-
 tools/perf/util/include/dwarf-regs.h          |  1 +
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/dwarf-regs-arch/dwarf-regs-arm64.c b/tools/perf/util/dwarf-regs-arch/dwarf-regs-arm64.c
index 593ca7d4fccc..be55fc2a4f38 100644
--- a/tools/perf/util/dwarf-regs-arch/dwarf-regs-arm64.c
+++ b/tools/perf/util/dwarf-regs-arch/dwarf-regs-arm64.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <errno.h>
+#include <ctype.h>
 #include <dwarf-regs.h>
 #include "../../../arch/arm64/include/uapi/asm/perf_regs.h"
 
@@ -10,3 +11,22 @@ int __get_dwarf_regnum_for_perf_regnum_arm64(int perf_regnum)
 
 	return perf_regnum;
 }
+
+int __get_dwarf_regnum_arm64(const char *name)
+{
+	int reg;
+
+	if (!strcmp(name, "sp") || !strcmp(name, "wzr") || !strcmp(name, "xzr"))
+		return 31;
+
+	if (*name != 'x' && *name != 'w')
+		return -ENOENT;
+
+	name++;
+	if (!isdigit(*name))
+		return -ENOENT;
+
+	reg = strtol(name, NULL, 10);
+
+	return reg >= 0 && reg <= 30 ? reg : -ENOENT;
+}
diff --git a/tools/perf/util/dwarf-regs.c b/tools/perf/util/dwarf-regs.c
index 797f455eba0d..bacf5c13c3bc 100644
--- a/tools/perf/util/dwarf-regs.c
+++ b/tools/perf/util/dwarf-regs.c
@@ -114,7 +114,7 @@ int get_dwarf_regnum(const char *name, unsigned int machine, unsigned int flags)
 		reg = _get_dwarf_regnum(arm_regstr_tbl, name);
 		break;
 	case EM_AARCH64:
-		reg = _get_dwarf_regnum(aarch64_regstr_tbl, name);
+		reg = __get_dwarf_regnum_arm64(name);
 		break;
 	case EM_CSKY:
 		reg = __get_csky_regnum(name, flags);
diff --git a/tools/perf/util/include/dwarf-regs.h b/tools/perf/util/include/dwarf-regs.h
index 46a764cf322f..a25f038bbff2 100644
--- a/tools/perf/util/include/dwarf-regs.h
+++ b/tools/perf/util/include/dwarf-regs.h
@@ -105,6 +105,7 @@ int __get_dwarf_regnum_x86_64(const char *name);
 int __get_dwarf_regnum_for_perf_regnum_i386(int perf_regnum);
 int __get_dwarf_regnum_for_perf_regnum_x86_64(int perf_regnum);
 
+int __get_dwarf_regnum_arm64(const char *name);
 int __get_dwarf_regnum_for_perf_regnum_arm(int perf_regnum);
 int __get_dwarf_regnum_for_perf_regnum_arm64(int perf_regnum);
 
-- 
2.34.1