Introduce feature test macro and build options

The feature test macro SEMU_HAS(x) accepts the feature "x" and expands
the predefined entry prefixing with "SEMU_FEATURE_". Then, we can check
certain SEMU feature at build time as following:

  #if RV32_HAS(VIRTIONET)
  /* the operations associated with RV32_FEATURE_VIRTIONET. */
  #endif

Author: jserv

Makefile

@@ -6,14 +6,25 @@ CFLAGS += -include common.h
 
 OBJS_EXTRA :=
 
+# virtio-blk
+ENABLE_VIRTIOBLK ?= 1
+OBJS_EXTRA += virtio-blk.o
+$(call set-feature, VIRTIOBLK)
+
+# virtio-net
+ENABLE_VIRTIONET ?= 1
 ifeq ($(UNAME_S),Linux)
-CFLAGS += -D ENABLE_VIRTIONET
-CFLAGS += -D ENABLE_VIRTIOBLK
 OBJS_EXTRA += virtio-net.o
-OBJS_EXTRA += virtio-blk.o
+else
+ENABLE_VIRTIONET := 0
+endif
+$(call set-feature, VIRTIONET)
+
+# device tree
+# TODO: generate device tree source upon configurations
+ifeq ($(UNAME_S),Linux)
 MINIMAL_DTS = minimal-virtio.dts
 else
-CFLAGS += -D ENABLE_VIRTIOBLK
 MINIMAL_DTS = minimal.dts
 endif
 

common.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include "feature.h"
+
 #define unlikely(x) __builtin_expect((x), 0)
 #define likely(x) __builtin_expect((x), 1)
 

device.h

@@ -72,7 +72,7 @@ void capture_keyboard_input();
 
 /* VirtIO-Net */
 
-#if defined(ENABLE_VIRTIONET)
+#if SEMU_HAS(VIRTIONET)
 #define IRQ_VNET 2
 #define IRQ_VNET_BIT (1 << IRQ_VNET)
 
@@ -115,10 +115,10 @@ void virtio_net_write(vm_t *core,
 void virtio_net_refresh_queue(virtio_net_state_t *vnet);
 
 bool virtio_net_init(virtio_net_state_t *vnet);
-#endif /* ENABLE_VIRTIONET */
+#endif /* SEMU_HAS(VIRTIONET) */
 
 /* VirtIO-Block */
-#if defined(ENABLE_VIRTIOBLK)
+#if SEMU_HAS(VIRTIOBLK)
 
 #define IRQ_VBLK 3
 #define IRQ_VBLK_BIT (1 << IRQ_VBLK)
@@ -162,7 +162,7 @@ void virtio_blk_write(vm_t *vm,
                       uint32_t value);
 
 uint32_t *virtio_blk_init(virtio_blk_state_t *vblk, char *disk_file);
-#endif /* ENABLE_VIRTIOBLK */
+#endif /* SEMU_HAS(VIRTIOBLK) */
 
 /* memory mapping */
 
@@ -172,10 +172,10 @@ typedef struct {
     uint32_t *disk;
     plic_state_t plic;
     u8250_state_t uart;
-#if defined(ENABLE_VIRTIONET)
+#if SEMU_HAS(VIRTIONET)
     virtio_net_state_t vnet;
 #endif
-#if defined(ENABLE_VIRTIOBLK)
+#if SEMU_HAS(VIRTIOBLK)
     virtio_blk_state_t vblk;
 #endif
     uint32_t timer_lo, timer_hi;

feature.h

@@ -0,0 +1,16 @@
+#pragma once
+
+/* enable/disable (compile time) features in this header */
+
+/* virtio-blk */
+#ifndef SEMU_FEATUREVIRTIOBLK
+#define SEMU_FEATUREVIRTIOBLK 1
+#endif
+
+/* virtio-net */
+#ifndef SEMU_FEATUREVIRTIONET
+#define SEMU_FEATUREVIRTIONET 1
+#endif
+
+/* Feature test macro */
+#define SEMU_HAS(x) SEMU_FEATURE_##x

main.c

@@ -46,7 +46,7 @@ static void emu_update_uart_interrupts(vm_t *vm)
     plic_update_interrupts(vm, &data->plic);
 }
 
-#if defined(ENABLE_VIRTIONET)
+#if SEMU_HAS(VIRTIONET)
 static void emu_update_vnet_interrupts(vm_t *vm)
 {
     emu_state_t *data = (emu_state_t *) vm->priv;
@@ -58,7 +58,7 @@ static void emu_update_vnet_interrupts(vm_t *vm)
 }
 #endif
 
-#if defined(ENABLE_VIRTIOBLK)
+#if SEMU_HAS(VIRTIOBLK)
 static void emu_update_vblk_interrupts(vm_t *vm)
 {
     emu_state_t *data = (emu_state_t *) vm->priv;
@@ -92,13 +92,13 @@ static void mem_load(vm_t *vm, uint32_t addr, uint8_t width, uint32_t *value)
             u8250_read(vm, &data->uart, addr & 0xFFFFF, width, value);
             emu_update_uart_interrupts(vm);
             return;
-#if defined(ENABLE_VIRTIONET)
+#if SEMU_HAS(VIRTIONET)
         case 0x41: /* VirtIO-Net */
             virtio_net_read(vm, &data->vnet, addr & 0xFFFFF, width, value);
             emu_update_vnet_interrupts(vm);
             return;
 #endif
-#if defined(ENABLE_VIRTIOBLK)
+#if SEMU_HAS(VIRTIOBLK)
         case 0x42: /* virtio-blk */
             virtio_blk_read(vm, &data->vblk, addr & 0xFFFFF, width, value);
             emu_update_vblk_interrupts(vm);
@@ -131,13 +131,13 @@ static void mem_store(vm_t *vm, uint32_t addr, uint8_t width, uint32_t value)
             u8250_write(vm, &data->uart, addr & 0xFFFFF, width, value);
             emu_update_uart_interrupts(vm);
             return;
-#if defined(ENABLE_VIRTIONET)
+#if SEMU_HAS(VIRTIONET)
         case 0x41: /* VirtIO-Net */
             virtio_net_write(vm, &data->vnet, addr & 0xFFFFF, width, value);
             emu_update_vnet_interrupts(vm);
             return;
 #endif
-#if defined(ENABLE_VIRTIOBLK)
+#if SEMU_HAS(VIRTIOBLK)
         case 0x42: /* virtio-blk */
             virtio_blk_write(vm, &data->vblk, addr & 0xFFFFF, width, value);
             emu_update_vblk_interrupts(vm);
@@ -391,12 +391,12 @@ static int semu_start(int argc, char **argv)
     /* Set up peripherals */
     emu.uart.in_fd = 0, emu.uart.out_fd = 1;
     capture_keyboard_input(); /* set up uart */
-#if defined(ENABLE_VIRTIONET)
+#if SEMU_HAS(VIRTIONET)
     if (!virtio_net_init(&(emu.vnet)))
         fprintf(stderr, "No virtio-net functioned\n");
     emu.vnet.ram = emu.ram;
 #endif
-#if defined(ENABLE_VIRTIOBLK)
+#if SEMU_HAS(VIRTIOBLK)
     emu.vblk.ram = emu.ram;
     emu.disk = virtio_blk_init(&(emu.vblk), disk_file);
 #endif
@@ -411,13 +411,13 @@ static int semu_start(int argc, char **argv)
             if (emu.uart.in_ready)
                 emu_update_uart_interrupts(&vm);
 
-#if defined(ENABLE_VIRTIONET)
+#if SEMU_HAS(VIRTIONET)
             virtio_net_refresh_queue(&emu.vnet);
             if (emu.vnet.InterruptStatus)
                 emu_update_vnet_interrupts(&vm);
 #endif
 
-#if defined(ENABLE_VIRTIOBLK)
+#if SEMU_HAS(VIRTIOBLK)
             if (emu.vblk.InterruptStatus)
                 emu_update_vblk_interrupts(&vm);
 #endif

mk/common.mk

@@ -16,6 +16,17 @@ else
     REDIR = >/dev/null
 endif
 
+# Get specified feature
+POSITIVE_WORDS = 1 true yes
+define has
+$(if $(filter $(firstword $(ENABLE_$(strip $1))), $(POSITIVE_WORDS)),1,0)
+endef
+
+# Set specified feature
+define set-feature
+$(eval CFLAGS += -D SEMU_FEATURE_$(strip $1)=$(call has, $1))
+endef
+
 # Test suite
 PASS_COLOR = \e[32;01m
 NO_COLOR = \e[0m