selftests: vDSO: unconditionally build chacha test

Rather than using symlinks to find the vgetrandom-chacha.S file for each
arch, store this in a file that uses the compiler to determine
architecture, and then make use of weak symbols to skip the test on
architectures that don't provide the code.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/arch/arm64/vdso

-../../../arch/arm64/kernel/vdso
\ No newline at end of file

tools/arch/loongarch/vdso

-../../../arch/loongarch/vdso
\ No newline at end of file

tools/arch/powerpc/vdso

-../../../arch/powerpc/kernel/vdso
\ No newline at end of file

tools/arch/s390/vdso

-../../../arch/s390/kernel/vdso64
\ No newline at end of file

tools/arch/x86/vdso

-../../../arch/x86/entry/vdso/
\ No newline at end of file

tools/testing/selftests/vDSO/Makefile

@@ -11,8 +11,8 @@ endif
 TEST_GEN_PROGS += vdso_test_correctness
 ifeq ($(ARCH)$(CONFIG_X86_32),$(filter $(ARCH)$(CONFIG_X86_32),x86 x86_64 loongarch arm64 powerpc s390))
 TEST_GEN_PROGS += vdso_test_getrandom
-TEST_GEN_PROGS += vdso_test_chacha
 endif
+TEST_GEN_PROGS += vdso_test_chacha
 
 CFLAGS := -std=gnu99 -O2
 
@@ -37,9 +37,9 @@ $(OUTPUT)/vdso_test_getrandom: CFLAGS += -isystem $(top_srcdir)/tools/include \
                                          $(KHDR_INCLUDES) \
                                          -isystem $(top_srcdir)/include/uapi
 
-$(OUTPUT)/vdso_test_chacha: $(top_srcdir)/tools/arch/$(SRCARCH)/vdso/vgetrandom-chacha.S
+$(OUTPUT)/vdso_test_chacha: vgetrandom-chacha.S
 $(OUTPUT)/vdso_test_chacha: CFLAGS += -idirafter $(top_srcdir)/tools/include \
                                       -idirafter $(top_srcdir)/tools/include/generated \
                                       -idirafter $(top_srcdir)/arch/$(SRCARCH)/include \
                                       -idirafter $(top_srcdir)/include \
-                                      -D__ASSEMBLY__ -Wa,--noexecstack
+                                      -Wa,--noexecstack

tools/testing/selftests/vDSO/vdso_test_chacha.c

@@ -3,6 +3,7 @@
  * Copyright (C) 2022-2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
  */
 
+#include <linux/compiler.h>
 #include <tools/le_byteshift.h>
 #include <sys/random.h>
 #include <sys/auxv.h>
@@ -73,10 +74,10 @@ static void reference_chacha20_blocks(uint8_t *dst_bytes, const uint32_t *key, u
 	counter[1] = s[13];
 }
 
-typedef uint8_t u8;
-typedef uint32_t u32;
-typedef uint64_t u64;
-#include <vdso/getrandom.h>
+void __weak __arch_chacha20_blocks_nostack(uint8_t *dst_bytes, const uint32_t *key, uint32_t *counter, size_t nblocks)
+{
+	ksft_exit_skip("Not implemented on architecture\n");
+}
 
 int main(int argc, char *argv[])
 {

tools/testing/selftests/vDSO/vgetrandom-chacha.S

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#define __ASSEMBLY__
+
+#if defined(__aarch64__)
+#include "../../../../arch/arm64/kernel/vdso/vgetrandom-chacha.S"
+#elif defined(__loongarch__)
+#include "../../../../arch/loongarch/vdso/vgetrandom-chacha.S"
+#elif defined(__powerpc__) || defined(__powerpc64__)
+#include "../../../../arch/powerpc/kernel/vdso/vgetrandom-chacha.S"
+#elif defined(__s390x__)
+#include "../../../../arch/s390/kernel/vdso64/vgetrandom-chacha.S"
+#elif defined(__x86_64__)
+#include "../../../../arch/x86/entry/vdso/vgetrandom-chacha.S"
+#endif