[PATCH 4/5] selftests/kexec: select tests using the target compiler

[Sasha Levin <sashal@kernel.org>]

The kexec Makefile recognizes PowerPC only through the ppc64le spelling
of ARCH, so the canonical ARCH=powerpc used for cross builds omits the
tests. The x86 jump test is selected with IS_64_BIT from
scripts/Makefile.arch, which describes the build host rather than the
compiler being used. On other architectures the Makefile includes no
lib.mk rules at all, so installation and runlist generation fail with
missing targets.

Select x86 and PowerPC from the target ARCH when it is given and from
the host's SUBARCH otherwise, without assigning ARCH, so that lib.mk
keeps choosing the compiler's native clang target. Ask the selected
compiler, including USERCFLAGS, whether it targets a 64-bit x86 ABI
and whether it targets little-endian 64-bit PowerPC. lib.mk expands the
generated program list before it appends USERCFLAGS to CFLAGS, so the
flags are passed explicitly to keep both probes consistent. If the
compiler cannot be run, select the jump test so that the build fails
instead of silently dropping it. Include lib.mk unconditionally so that
unsupported targets build, install and emit an empty runlist.

Fixes: 65e38e32a959 ("selftests/kexec: Enable secureboot tests for PowerPC")
Fixes: 7615b94b6371 ("selftests/kexec: Add x86_64 selftest for kexec-jump and exception handling")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 tools/testing/selftests/kexec/Makefile | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/kexec/Makefile b/tools/testing/selftests/kexec/Makefile
index 874cfdd3b75b3..97d5dd10208a1 100644
--- a/tools/testing/selftests/kexec/Makefile
+++ b/tools/testing/selftests/kexec/Makefile
@@ -1,20 +1,22 @@
 # SPDX-License-Identifier: GPL-2.0-only
 # Makefile for kexec tests
 
-ARCH ?= $(shell uname -m 2>/dev/null || echo not)
-ARCH_PROCESSED := $(shell echo $(ARCH) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
+top_srcdir = ../../../..
+include $(top_srcdir)/scripts/subarch.include
+ARCH_PROCESSED := $(shell echo $(or $(ARCH),$(SUBARCH)) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
 
-ifeq ($(ARCH_PROCESSED),$(filter $(ARCH_PROCESSED),x86 ppc64le))
-TEST_PROGS := test_kexec_load.sh test_kexec_file_load.sh
-TEST_FILES := kexec_common_lib.sh
+PROBE_CC = $(filter-out -fuse-ld=%,$(CC)) $(CFLAGS) $(USERCFLAGS) -E -P -x c -
+CC_IS_64BIT = $(shell echo __SIZEOF_LONG__ | $(PROBE_CC) || echo 8)
+PPC64LE = $(shell printf '\043if defined(__powerpc64__) && __BYTE_ORDER__ == \
+	__ORDER_LITTLE_ENDIAN__\n1\n\043endif\n' | $(PROBE_CC))
 
-include ../../../scripts/Makefile.arch
-
-ifeq ($(IS_64_BIT)$(ARCH_PROCESSED),1x86)
-TEST_PROGS += test_kexec_jump.sh
-TEST_GEN_PROGS := test_kexec_jump
+ifeq ($(ARCH_PROCESSED),x86)
+TEST_PROGS = test_kexec_load.sh test_kexec_file_load.sh \
+	$(if $(filter 8,$(CC_IS_64BIT)),test_kexec_jump.sh)
+TEST_GEN_PROGS = $(if $(filter 8,$(CC_IS_64BIT)),test_kexec_jump)
+else ifneq (,$(filter powerpc ppc64le,$(ARCH_PROCESSED)))
+TEST_PROGS = $(if $(filter 1,$(PPC64LE)),test_kexec_load.sh test_kexec_file_load.sh)
 endif
+TEST_FILES = $(if $(TEST_PROGS),kexec_common_lib.sh)
 
 include ../lib.mk
-
-endif
-- 
2.53.0