scripts/sorttable: Allow matches to functions before function entry

ARM 64 uses -fpatchable-function-entry=4,2 which adds padding before the
function and the addresses in the mcount_loc point there instead of the
function entry that is returned by nm. In order to find a function from nm
to make sure it's not an unused weak function, the entries in the
mcount_loc section needs to match the entries from nm. Since it can be an
instruction before the entry, add a before_func variable that ARM 64 can
set to 8, and if the mcount_loc entry is within 8 bytes of the nm function
entry, then it will be considered a match.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: "Arnd Bergmann" <arnd@arndb.de>
Cc: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/20250225182054.815536219@goodmis.org
Fixes: ef378c3b82338 ("scripts/sorttable: Zero out weak functions in mcount_loc table")
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/scripts/sorttable.c b/scripts/sorttable.c
index 07ad8116bc8ddf541b4831b578acf6d0151bcbb5..7b4b3714b1af1aca7301091066f145efd05f6ae9 100644 (file)
--- a/scripts/sorttable.c
+++ b/scripts/sorttable.c
@@ -611,13 +611,16 @@ static int add_field(uint64_t addr, uint64_t size)
        return 0;
 }
 
+/* Used for when mcount/fentry is before the function entry */
+static int before_func;
+
 /* Only return match if the address lies inside the function size */
 static int cmp_func_addr(const void *K, const void *A)
 {
        uint64_t key = *(const uint64_t *)K;
        const struct func_info *a = A;
 
-       if (key < a->addr)
+       if (key + before_func < a->addr)
                return -1;
        return key >= a->addr + a->size;
 }
@@ -1253,6 +1256,8 @@ static int do_file(char const *const fname, void *addr)
 #ifdef MCOUNT_SORT_ENABLED
                sort_reloc = true;
                rela_type = 0x403;
+               /* arm64 uses patchable function entry placing before function */
+               before_func = 8;
 #endif
                /* fallthrough */
        case EM_386: