From 264447c195a612abd95f28d75bdcbb48ee3b2bd2 Mon Sep 17 00:00:00 2001
From: Igor Svilenkov Bozic <svilenkov@gmail.com>
Date: Thu, 14 Aug 2025 14:39:52 +0200
Subject: [PATCH] compel: gcs: add opt-in GCS test support for AArch64

Introduce an opt-in mode for building and running compel tests
with Guarded Control Stack (GCS) enabled on AArch64.

Changes:
 - Extend compel/test/infect to support `GCS_ENABLE=1` builds,
   adding `-mbranch-protection=standard` and
   `-z experimental-gcs=check` to CFLAGS/LDFLAGS.
 - Export required GLIBC_TUNABLES at runtime via `TEST_ENV`.

Usage:
    make -C compel/test/infect GCS_ENABLE=1
    make -C compel/test/infect GCS_ENABLE=1 run

By default (`GCS_ENABLE` unset or 0), builds and runs are unchanged.

Signed-off-by: Igor Svilenkov Bozic <svilenkov@gmail.com>
---
 compel/test/infect/Makefile | 7 ++++++-
 compel/test/infect/spy.c    | 3 +++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/compel/test/infect/Makefile b/compel/test/infect/Makefile
index bacfad962..85efa5fd9 100644
--- a/compel/test/infect/Makefile
+++ b/compel/test/infect/Makefile
@@ -3,6 +3,11 @@ CFLAGS	?= -O2 -g -Wall -Werror
 
 COMPEL		:= ../../../compel/compel-host
 
+ifeq ($(GCS_ENABLE),1)
+CFLAGS  += -mbranch-protection=standard -DGCS_TEST_ENABLE=1
+LDFLAGS += -z experimental-gcs=check
+endif
+
 all: victim spy
 
 run:
@@ -17,7 +22,7 @@ clean:
 	rm -f parasite.o
 
 victim: victim.c
-	$(CC) $(CFLAGS) -o $@ $^
+	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
 spy: spy.c parasite.h
 	$(CC) $(CFLAGS) $(shell $(COMPEL) includes) -o $@ $< $(shell $(COMPEL) --static libs)
diff --git a/compel/test/infect/spy.c b/compel/test/infect/spy.c
index 840dfa220..da9b2d729 100644
--- a/compel/test/infect/spy.c
+++ b/compel/test/infect/spy.c
@@ -112,6 +112,9 @@ int main(int argc, char **argv)
 		return -1;
 	}
 
+#ifdef GCS_TEST_ENABLE
+	setenv("GLIBC_TUNABLES", "glibc.cpu.aarch64_gcs=1:glibc.cpu.aarch64_gcs_policy=2", 1);
+#endif
 	pid = vfork();
 	if (pid == 0) {
 		close(p_in[1]);