The __LINE__ macro creates challenges for binary diffing. When a .patch
file adds or removes lines, it shifts the line numbers for all code
below it.
This can cause the code generation of functions using __LINE__ to change
due to the line number constant being embedded in a MOV instruction,
despite there being no semantic difference.
Avoid such false positives by adding a fix-patch-lines script which can
be used to insert a #line directive in each patch hunk affecting the
line numbering. This script will be used by klp-build, which will be
introduced in a subsequent patch.
Signed-off-by: Josh Poimboeuf <jpoim...@kernel.org>
---
MAINTAINERS | 1 +
scripts/livepatch/fix-patch-lines | 79 +++++++++++++++++++++++++++++++
2 files changed, 80 insertions(+)
create mode 100755 scripts/livepatch/fix-patch-lines
diff --git a/MAINTAINERS b/MAINTAINERS
index 0298d9570ca8..dd622368d74b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14006,6 +14006,7 @@ F: include/linux/livepatch*.h
F: kernel/livepatch/
F: kernel/module/livepatch.c
F: samples/livepatch/
+F: scripts/livepatch/
F: tools/testing/selftests/livepatch/
LLC (802.2)
diff --git a/scripts/livepatch/fix-patch-lines
b/scripts/livepatch/fix-patch-lines
new file mode 100755
index 000000000000..73c5e3dea46e
--- /dev/null
+++ b/scripts/livepatch/fix-patch-lines
@@ -0,0 +1,79 @@
+#!/usr/bin/awk -f
+# SPDX-License-Identifier: GPL-2.0
+#
+# Use #line directives to preserve original __LINE__ numbers across patches to
+# avoid unwanted compilation changes.
+
+BEGIN {
+ in_hunk = 0
+ skip = 0
+}
+
+/^--- / {
+ skip = $2 !~ /\.(c|h)$/
+ print
+ next
+}
+
+/^@@/ {
+ if (skip) {
+ print
+ next
+ }
+
+ in_hunk = 1
+
+ # for @@ -1,3 +1,4 @@:
+ # 1: line number in old file
+ # 3: how many lines the hunk covers in old file
+ # 1: line number in new file
+ # 4: how many lines the hunk covers in new file
+
+ match($0, /^@@ -([0-9]+)(,([0-9]+))? \+([0-9]+)(,([0-9]+))? @@/, m)
+
+ # Set 'cur' to the old file's line number at the start of the hunk. It
+ # gets incremented for every context line and every line removal, so
+ # that it always represents the old file's current line number.
+ cur = m[1]
+
+ # last = last line number of current hunk
+ last = cur + (m[3] ? m[3] : 1) - 1
+
+ need_line_directive = 0
+
+ print
+ next
+}
+
+{
+ if (skip || !in_hunk || $0 ~ /^\\ No newline at end of file/) {
+ print
+ next
+ }
+
+ # change line
+ if ($0 ~ /^[+-]/) {
+ # inject #line after this group of changes
+ need_line_directive = 1
+
+ if ($0 ~ /^-/)
+ cur++
+
+ print
+ next
+ }
+
+ # If this is the first context line after a group of changes, inject
+ # the #line directive to force the compiler to correct the line
+ # numbering to match the original file.
+ if (need_line_directive) {
+ print "+#line " cur
+ need_line_directive = 0
+ }
+
+ if (cur == last)
+ in_hunk = 0
+
+ cur++
+ print
+}
--
2.49.0
