[PATCH 4/4] scripts/sorttable: Allow matches to functions before function entry

[Steven Rostedt <rostedt@goodmis.org>]

From: Steven Rostedt <rostedt@goodmis.org>

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.

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>
---
 scripts/sorttable.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/scripts/sorttable.c b/scripts/sorttable.c
index 07ad8116bc8d..7b4b3714b1af 100644
--- 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:
-- 
2.47.2