jump_label: Don't warn on __exit jump entries

On architectures that discard .exit.* sections at runtime, a
warning is printed for each jump label that is used within an
in-kernel __exit annotated function:

can't patch jump_label at ehci_hcd_cleanup+0x8/0x3c
WARNING: CPU: 0 PID: 1 at kernel/jump_label.c:410 __jump_label_update+0x12c/0x138

As these functions will never get executed (they are free'd along
with the rest of initmem) - we do not need to patch them and should
not display any warnings.

The warning is displayed because the test required to satisfy
jump_entry_is_init is based on init_section_contains (__init_begin to
__init_end) whereas the test in __jump_label_update is based on
init_kernel_text (_sinittext to _einittext) via kernel_text_address).

Fixes: 1948367 ("jump_label: Annotate entries that operate on __init code earlier")
Signed-off-by: Andrew Murray <andrew.murray@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

Author: Andrew Murray

kernel/jump_label.c

@@ -407,7 +407,9 @@ static bool jump_label_can_update(struct jump_entry *entry, bool init)
 		return false;
 
 	if (!kernel_text_address(jump_entry_code(entry))) {
-		WARN_ONCE(1, "can't patch jump_label at %pS", (void *)jump_entry_code(entry));
+		WARN_ONCE(!jump_entry_is_init(entry),
+			  "can't patch jump_label at %pS",
+			  (void *)jump_entry_code(entry));
 		return false;
 	}