[PATCH] armv8a: Set -mbranch-protection more specifically

[Frank Zhang <rmxpzlb@gmail.com>]

GCC-15 enable gcs in standard branch protection, which is support by armv9.
Openssl don't support this feature in assemble code, caused ld warning.
Moeover, other recipes will fail when link with openssl.
This patch set armv8a branch protection based on extension version.

Signed-off-by: Frank Zhang <rmxpzlb@gmail.com>
---
 meta/conf/machine/include/arm/arch-arm64.inc | 21 +++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/meta/conf/machine/include/arm/arch-arm64.inc b/meta/conf/machine/include/arm/arch-arm64.inc
index 832d0000ac..938dee4798 100644
--- a/meta/conf/machine/include/arm/arch-arm64.inc
+++ b/meta/conf/machine/include/arm/arch-arm64.inc
@@ -41,4 +41,23 @@ TARGET_FPU = "${@bb.utils.contains('TUNE_FEATURES', 'aarch64', '${TARGET_FPU_64}
 # Emit branch protection (PAC/BTI) instructions.  On hardware that doesn't
 # support these they're meaningless NOP instructions, so there's very little
 # reason not to.
-TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'aarch64', ' -mbranch-protection=standard', '', d)}"
+def arm64_get_branch_protection(d):
+    import re
+    bp = "standard"
+    tunes = d.getVar('AVAILTUNES')
+    if "armv8a" in tunes.split():
+        bp = "none"
+        subver = 0
+        for tune in tunes.split():
+            arch = re.match('armv8-[1-9]a', tune)
+            if arch:
+                subver = int(tune[6:7])
+                break
+
+        if subver >= 5:
+            bp = "bti+pac-ret"
+        elif subver >= 3:
+            bp = "pac-ret"
+    return bp
+
+TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'aarch64', ' -mbranch-protection=%s' % (arm64_get_branch_protection(d)), '', d)}"