[PATCH v5 21/31] s390: Use arm64 headers

Introduce a flexible system for sharing ARM64 headers with s390 KVM.
Selected arm64 headers or snippet of headers will be reachable by s390
code through asm/header.h.

Add copy-arm64h.awk that detects ARM64_S390_COMMON markers and extracts
marked section into a generated header consumable by s390. Falls back to
full file copy when no markers are found.

Transform copied includes by replacing '#include <asm/...>' with
'#include <arm64/...>' and similar for uapi headers to ensure
correct path resolution on s390 and allow for a clear separation of s390
asm headers and arm64 asm headers.

Integrate this extraction into the s390/kapi target, conditional on (the
not yet existing) CONFIG_KVM_S390_ARM64.

Signed-off-by: Steffen Eiden <[email protected]>
---
 arch/s390/tools/Makefile             | 10 +++-
 arch/s390/tools/Makefile.arm64h      | 57 ++++++++++++++++++++++
 arch/s390/tools/copy-arm64h-full.awk | 47 ++++++++++++++++++
 arch/s390/tools/copy-arm64h.awk      | 72 ++++++++++++++++++++++++++++
 4 files changed, 185 insertions(+), 1 deletion(-)
 create mode 100644 arch/s390/tools/Makefile.arm64h
 create mode 100644 arch/s390/tools/copy-arm64h-full.awk
 create mode 100644 arch/s390/tools/copy-arm64h.awk

diff --git a/arch/s390/tools/Makefile b/arch/s390/tools/Makefile
index f2862364fb42..3e0f21b552da 100644
--- a/arch/s390/tools/Makefile
+++ b/arch/s390/tools/Makefile
@@ -3,12 +3,20 @@
 # Makefile for s390 specific build tools
 #
 
+include $(srctree)/arch/s390/tools/Makefile.arm64h
+
 kapi := arch/$(ARCH)/include/generated/asm
 kapi-hdrs-y := $(kapi)/facility-defs.h $(kapi)/dis-defs.h
 
+targets += $(addprefix ../../../,$(kapi-hdrs-y))
+# Convert ARM64 absolute paths to relative before Kbuild adds $(obj)/ prefix
+targets += $(patsubst $(objtree)/%,../../../%,$(ARM64_TARGETS))
+
+kapi-hdrs-$(CONFIG_KVM_ARM64) += $(ARM64_TARGETS)
+
 PHONY += kapi
 
-kapi:	$(kapi-hdrs-y)
+kapi:	$(kapi-hdrs-y) $(ARM64_TARGETS)
 
 hostprogs		    += gen_facilities
 hostprogs		    += gen_opcode_table
diff --git a/arch/s390/tools/Makefile.arm64h b/arch/s390/tools/Makefile.arm64h
new file mode 100644
index 000000000000..8fbd9cb48695
--- /dev/null
+++ b/arch/s390/tools/Makefile.arm64h
@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Share ARM64 headers with s390 KVM
+#
+
+arm64api := $(objtree)/arch/$(ARCH)/include/generated/arm64
+arm64uapi := $(objtree)/arch/$(ARCH)/include/generated/uapi/arm64
+
+# List of ARM64 headers to share with s390 KVM
+# Format: [uapi:]header.h or header-gen.h
+#
+# * header.h - from arch/arm64/include/asm/ to arm64/
+# * uapi:header.h - from arch/arm64/include/uapi/asm/ to uapi/arm64/
+# * header-gen.h - generated as header-gen.h from ARM64 header header.h
+# If a header contains partial markers (#ifdef ARM64_S390_COMMON) only this part will be copied.
+# If the file does not contain any markers the whole file will be copied.
+ARM64_SHARED_HEADERS := \
+	brk-imm.h \
+	esr.h \
+	kvm_arm.h \
+	kvm_emulate-gen.h \
+	kvm_host.h \
+	ptrace-gen.h \
+	sysreg-gen.h \
+	uapi:hwcap.h \
+	uapi:kvm.h \
+	uapi:ptrace.h \
+	uapi:sve_context.h \
+
+quiet_cmd_gen_arm_hdr = GEN     $@
+      cmd_gen_arm_hdr = mkdir -p $(dir $@); \
+                      $(AWK) -f $(src)/copy-arm64h.awk $< > $@ || \
+                      $(AWK) -f $(src)/copy-arm64h-full.awk -v srcfile="$(subst $(srctree)/,,$(subst $(srctree)/../,,$<))" $< > $@ || \
+		      { echo "Error: Unbalanced ARM64_S390_COMMON markers in $<" >&2; rm -f $@; exit 1; }
+
+arm64-type = $(firstword $(subst :, ,$(1)))
+arm64-base = $(or $(word 2,$(subst :, ,$(1))),$(1))
+arm64-src-base = $(patsubst %-gen.h,%.h,$(call arm64-base,$(1)))
+
+arm64-src = $(srctree)/arch/arm64/include/$(if $(filter uapi,$(call arm64-type,$(1))),uapi/)asm/$(call arm64-src-base,$(1))
+arm64-dst = $(objtree)/$(if $(filter uapi,$(call arm64-type,$(1))),$(arm64uapi),$(arm64api))/$(call arm64-base,$(1))
+
+$(foreach hdr,$(ARM64_SHARED_HEADERS),\
+	$(eval $(call arm64-dst,$(hdr)): $(call arm64-src,$(hdr)) $(src)/copy-arm64h.awk $(src)/copy-arm64h-full.awk))
+
+ARM64_TARGETS := $(sort $(foreach hdr,$(ARM64_SHARED_HEADERS),$(call arm64-dst,$(hdr))))
+
+$(ARM64_TARGETS):
+	$(call cmd,gen_arm_hdr)
+
+quiet_cmd_gen_sysreg_arm64 = GEN     $@
+      cmd_gen_sysreg_arm64 = mkdir -p $(dir $@); $(AWK) -f $(srctree)/arch/arm64/tools/gen-sysreg.awk $(srctree)/arch/arm64/tools/sysreg > $@
+
+$(arm64api)/sysreg-defs.h: $(srctree)/arch/arm64/tools/gen-sysreg.awk $(srctree)/arch/arm64/tools/sysreg FORCE
+	$(call if_changed,gen_sysreg_arm64)
+
+ARM64_TARGETS += $(arm64api)/sysreg-defs.h
diff --git a/arch/s390/tools/copy-arm64h-full.awk b/arch/s390/tools/copy-arm64h-full.awk
new file mode 100644
index 000000000000..a6aaf9cc3332
--- /dev/null
+++ b/arch/s390/tools/copy-arm64h-full.awk
@@ -0,0 +1,47 @@
+#!/usr/bin/awk -f
+# SPDX-License-Identifier: GPL-2.0
+#
+# Process entire ARM64 headers for sharing with s390 KVM
+#
+# Usage: copy-arm64h-full.awk -v srcfile=<source_path> <input_file>
+#
+# This processes the entire file (unlike copy-arm64h.awk which only extracts marked sections)
+
+BEGIN {
+	max_guard_line = 25
+	guard_found = 0
+	header_added = 0
+}
+
+# Find and process the include guard in the first few lines
+NR <= max_guard_line && !guard_found && /^#ifndef [A-Z_0-9]+$/ {
+	guard_name = $2
+	guard_found = 1
+	print "/* This header was copied from " srcfile " */"
+	print ""
+	print
+	header_added = 1
+	next
+}
+
+# Transform include directives
+/^#include <uapi\/asm\// {
+	sub(/<uapi\/asm\//, "<uapi/arm64/")
+	print
+	next
+}
+
+/^#include <asm\// {
+	sub(/<asm\//, "<arm64/")
+	print
+	next
+}
+
+/ARM64_S390_COMMON/ {
+	exit 1
+}
+
+# Pass through all other lines
+{
+	print
+}
diff --git a/arch/s390/tools/copy-arm64h.awk b/arch/s390/tools/copy-arm64h.awk
new file mode 100644
index 000000000000..d74df368c1b5
--- /dev/null
+++ b/arch/s390/tools/copy-arm64h.awk
@@ -0,0 +1,72 @@
+#!/usr/bin/awk -f
+# SPDX-License-Identifier: GPL-2.0
+#
+# Extract marked sections from ARM64 headers for sharing with s390 KVM
+#
+# Usage: share-arm64-header.awk <input_file>
+#
+# Extracts all sections between start/end markers. If no markers found, signals for fallback.
+#TODO verification script or c file for arm to verify the ifdef things keep working
+BEGIN {
+	# Constants
+	start_pattern = "^#ifdef ARM64_S390_COMMON$"
+	end_pattern = "^#endif \\/\\* ARM64_S390_COMMON \\*\\/$"
+	max_guard_line = 25
+
+	# State variables
+	copying = found_marker = 0
+	guard_name = ""
+	file_header_done = 0
+}
+
+NR <= max_guard_line && !guard_name && /^#ifndef [A-Za-z0-9_]+$/ {
+	guard_name = $2
+	filename = FILENAME
+	sub(/^.*arch\/arm64\//, "arch/arm64/", filename)
+	print "/*"
+	print " * This header was automatically generated from " filename
+	print " * Do not modify this file directly."
+	print " */"
+	print "#ifndef " guard_name
+	print "#define " guard_name
+	print ""
+	next
+}
+
+NR > max_guard_line && !guard_name && !file_header_done {
+	print "error: no include guard found in first " max_guard_line " lines" > "/dev/stderr"
+	file_header_done = 1
+	exit 1
+}
+
+!guard_name {
+	print
+	next
+}
+
+$0 ~ start_pattern {
+	if (copying) { exit 1 }
+	copying = found_marker = 1
+	next
+}
+
+guard_name && !found_marker {
+	next
+}
+
+$0 ~ end_pattern { copying = 0; next }
+
+copying {
+	gsub(/#include <asm\//, "#include <arm64/")
+	gsub(/#include <uapi\/asm\//, "#include <uapi/arm64/")
+	print
+	next
+}
+
+END {
+	if (found_marker) {
+		print ""
+		print "#endif /* " guard_name " */"
+	}
+	exit !found_marker || copying
+}
-- 
2.53.0