[RFC v5 02/10] build: Implement libnative library and the build machinery for libnative

[Yeqi Fu]

This commit implements a shared library, where native functions are
rewritten as special instructions. At runtime, user programs load
the shared library, and special instructions are executed when
native functions are called.

Signed-off-by: Yeqi Fu <fufuyqqqqqq@gmail.com>
---
 Makefile                            |  2 +
 common-user/native/Makefile.include |  9 ++++
 common-user/native/Makefile.target  | 22 +++++++++
 common-user/native/libnative.S      | 69 +++++++++++++++++++++++++++++
 configure                           | 39 ++++++++++++++++
 5 files changed, 141 insertions(+)
 create mode 100644 common-user/native/Makefile.include
 create mode 100644 common-user/native/Makefile.target
 create mode 100644 common-user/native/libnative.S

diff --git a/Makefile b/Makefile
index 5d48dfac18..6f6147b40f 100644
--- a/Makefile
+++ b/Makefile
@@ -182,6 +182,8 @@ SUBDIR_MAKEFLAGS=$(if $(V),,--no-print-directory --quiet)
 
 include $(SRC_PATH)/tests/Makefile.include
 
+include $(SRC_PATH)/common-user/native/Makefile.include
+
 all: recurse-all
 
 ROMS_RULES=$(foreach t, all clean distclean, $(addsuffix /$(t), $(ROMS)))
diff --git a/common-user/native/Makefile.include 
b/common-user/native/Makefile.include
new file mode 100644
index 0000000000..40d20bcd4c
--- /dev/null
+++ b/common-user/native/Makefile.include
@@ -0,0 +1,9 @@
+.PHONY: build-native
+build-native: $(NATIVE_TARGETS:%=build-native-library-%)
+$(NATIVE_TARGETS:%=build-native-library-%): build-native-library-%:
+       $(call quiet-command, \
+           $(MAKE) -C common-user/native/$* $(SUBDIR_MAKEFLAGS), \
+       "BUILD","$* native library")
+# endif
+
+all: build-native
diff --git a/common-user/native/Makefile.target 
b/common-user/native/Makefile.target
new file mode 100644
index 0000000000..65d90102e2
--- /dev/null
+++ b/common-user/native/Makefile.target
@@ -0,0 +1,22 @@
+# -*- Mode: makefile -*-
+#
+# Library for native calls
+#
+
+all:
+-include ../../../config-host.mak
+-include config-target.mak
+
+CFLAGS+=-shared -D $(TARGET_NAME)
+LDFLAGS+=
+
+SRC = $(SRC_PATH)/common-user/native/libnative.S
+LIBNATIVE = libnative.so
+
+all: $(LIBNATIVE)
+
+$(LIBNATIVE): $(SRC)
+       $(CC) $(CFLAGS) $(EXTRA_CFLAGS) $(EXTRA_NATIVE_CALL_FLAGS) $< -o $@ 
$(LDFLAGS)
+
+clean:
+       rm -f $(LIBNATIVE)
diff --git a/common-user/native/libnative.S b/common-user/native/libnative.S
new file mode 100644
index 0000000000..3692eaa3cf
--- /dev/null
+++ b/common-user/native/libnative.S
@@ -0,0 +1,69 @@
+#if defined(i386) || defined(x86_64)
+/*
+ * An unused instruction is utilized to mark a native call.
+ */
+#define __SPECIAL_INSTR .byte 0x0f, 0xff;
+#define __RET_INSTR ret;
+#endif
+
+#if defined(arm) || defined(aarch64)
+/*
+ * HLT is an invalid instruction for userspace programs,
+ * and is used to mark a native call.
+ */
+#define __SPECIAL_INSTR hlt 0xffff;
+#if defined(aarch64)
+#define __RET_INSTR ret;
+#else
+#define __RET_INSTR bx lr;
+#endif
+#endif
+
+
+#if defined(mips) || defined(mips64)
+/*
+ * The syscall instruction contains 20 unused bits, which are typically
+ * set to 0. These bits can be used to store non-zero data,
+ * distinguishing them from a regular syscall instruction.
+ */
+#define __SPECIAL_INSTR syscall 0xffff;
+#define __RET_INSTR jr $ra;
+#endif
+
+/* Symbols of native functions */
+.section .data
+sym_memset:  .asciz "memset"
+sym_memcpy:  .asciz "memcpy"
+sym_strncpy:  .asciz "strncpy"
+sym_memcmp:  .asciz "memcmp"
+sym_strncmp:  .asciz "strncmp"
+sym_strcpy:  .asciz "strcpy"
+sym_strcat:  .asciz "strcat"
+sym_strcmp:  .asciz "strcmp"
+
+.macro define_function name
+\name:
+#if defined(x86_64) || defined(aarch64)
+    __SPECIAL_INSTR
+    .quad sym_\name
+    __RET_INSTR
+#elif defined(mips64)
+.align 4
+    __SPECIAL_INSTR
+    .quad sym_\name
+    __RET_INSTR
+#elif defined(i386) || defined(mips) || defined(arm)
+    __SPECIAL_INSTR
+    .long sym_\name
+    __RET_INSTR
+#endif
+.endm
+
+define_function memcpy
+define_function strncpy
+define_function memset
+define_function memcmp
+define_function strncmp
+define_function strcpy
+define_function strcat
+define_function strcmp
diff --git a/configure b/configure
index 7a1e463d9c..de533b27a2 100755
--- a/configure
+++ b/configure
@@ -1826,6 +1826,45 @@ if test "$tcg" = "enabled"; then
 fi
 )
 
+# common-user/native configuration
+(mkdir -p common-user/native
+
+native_targets=
+for target in $target_list; do
+  case $target in
+    *-softmmu)
+    continue
+    ;;
+  esac
+
+  # native call is only supported on these architectures
+  arch=${target%%-*}
+  config_target_mak=common-user/native/${target}/config-target.mak
+  case $arch in
+    i386|x86_64|arm|aarch64|mips|mips64)
+      if test -f cross-build/${target}/config-target.mak; then
+        mkdir -p "common-user/native/${target}"
+        ln -srf cross-build/${target}/config-target.mak "$config_target_mak"
+        if test $arch = arm; then
+          echo "EXTRA_NATIVE_CALL_FLAGS=-marm" >> "$config_target_mak"
+        fi
+        if test $arch = $cpu || \
+          { test $arch = i386 && test $cpu = x86_64; } || \
+          { test $arch = arm && test $cpu = aarch64; } || \
+          { test $arch = mips && test $cpu = mips64; }; then
+          echo "LD_PREFIX=/" >> "$config_target_mak"
+        fi
+        echo "LIBNATIVE=$PWD/common-user/native/${target}/libnative.so" >> 
"$config_target_mak"
+        ln -sf ${source_path}/common-user/native/Makefile.target 
common-user/native/${target}/Makefile
+        native_targets="$native_targets ${target}"
+      fi
+    ;;
+  esac
+done
+
+echo "NATIVE_TARGETS=$native_targets" >> config-host.mak
+)
+
 if test "$skip_meson" = no; then
   cross="config-meson.cross.new"
   meson_quote() {
-- 
2.34.1