[PATCH v4 2/3] scripts/faddr2line: Use LLVM addr2line and readelf if LLVM=1

[Will Deacon <will@kernel.org>]

GNU utilities cannot necessarily parse objects built by LLVM, which can
result in confusing errors when using 'faddr2line':

$ CROSS_COMPILE=aarch64-linux-gnu- ./scripts/faddr2line vmlinux do_one_initcall+0xf4/0x260
aarch64-linux-gnu-addr2line: vmlinux: unknown type [0x13] section `.relr.dyn'
aarch64-linux-gnu-addr2line: DWARF error: invalid or unhandled FORM value: 0x25
do_one_initcall+0xf4/0x260:
aarch64-linux-gnu-addr2line: vmlinux: unknown type [0x13] section `.relr.dyn'
aarch64-linux-gnu-addr2line: DWARF error: invalid or unhandled FORM value: 0x25
$x.73 at main.c:?

Although this can be worked around by setting CROSS_COMPILE to "llvm=-",
it's cleaner to follow the same syntax as the top-level Makefile and
accept LLVM= as an indication to use the llvm- tools, optionally
specifying their location or specific version number.

Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: John Stultz <jstultz@google.com>
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
 scripts/faddr2line | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/scripts/faddr2line b/scripts/faddr2line
index a35a420d0f26..6b8206802157 100755
--- a/scripts/faddr2line
+++ b/scripts/faddr2line
@@ -58,8 +58,21 @@ die() {
 	exit 1
 }
 
-READELF="${CROSS_COMPILE:-}readelf"
-ADDR2LINE="${CROSS_COMPILE:-}addr2line"
+UTIL_SUFFIX=""
+if [[ "${LLVM:-}" == "" ]]; then
+	UTIL_PREFIX=${CROSS_COMPILE:-}
+else
+	UTIL_PREFIX=llvm-
+
+	if [[ "${LLVM}" == *"/" ]]; then
+		UTIL_PREFIX=${LLVM}${UTIL_PREFIX}
+	elif [[ "${LLVM}" == "-"* ]]; then
+		UTIL_SUFFIX=${LLVM}
+	fi
+fi
+
+READELF="${UTIL_PREFIX}readelf${UTIL_SUFFIX}"
+ADDR2LINE="${UTIL_PREFIX}addr2line${UTIL_SUFFIX}"
 AWK="awk"
 GREP="grep"
 
-- 
2.42.0.283.g2d96d420d3-goog