perf: Fix const qualifier warnings in libbpf.c

Fix compilation warnings when building perf with -Werror where const
qualifiers are discarded from pointers returned by strstr() and
strchr() functions in libbpf.c.

Both strstr() and strchr() return 'const char *' when given
'const char *' input parameters. The receiving variables must
preserve this const qualification to maintain const-correctness
and avoid compiler warnings.

Errors fixed:
  libbpf.c:8179:13: error: assignment discards 'const' qualifier
    from pointer target type [-Werror=discarded-qualifiers]
  libbpf.c:11967:35: error: assignment discards 'const' qualifier
    from pointer target type [-Werror=discarded-qualifiers]

This is a workaround for kernel 6.12.x. The issue is already fixed
upstream in kernel 6.13+ and can be removed when the kernel is updated.

Signed-off-by: Yogesh Tyagi <yogesh.tyagi@intel.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/recipes-kernel/perf/perf.bbappend b/recipes-kernel/perf/perf.bbappend
new file mode 100644
index 00000000..54ad4dd9
--- /dev/null
+++ b/recipes-kernel/perf/perf.bbappend
@@ -0,0 +1,17 @@
+# Fix const qualifier warnings in libbpf.c when building with -Werror
+# This is a workaround for older kernel versions (6.12.x) that don't have
+# the upstream fix yet. The issue is already fixed in kernel 6.13+.
+
+# remove at next version upgrade or when output changes
+PR = "r3"
+HASHEQUIV_HASH_VERSION .= ".3"
+
+do_configure:prepend () {
+    # Apply libbpf const qualifier fixes
+    if [ -e "${S}/tools/lib/bpf/libbpf.c" ]; then
+        # Fix kallsyms_cb function - change 'char *res' to 'const char *res'
+        sed -i 's/^\(\s*\)char \*res;/\1const char *res;/' "${S}/tools/lib/bpf/libbpf.c"
+        # Fix resolve_full_path function - change 'char *next_path' to 'const char *next_path'
+        sed -i 's/^\(\s*\)char \*next_path;/\1const char *next_path;/' "${S}/tools/lib/bpf/libbpf.c"
+    fi
+}