Add support for ARM's GCC ARM embedded toolchain.

Based on patches provided by Hanspeter Portner:

http://forums.leaflabs.com/topic.php?id=1717#post-11812
Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

5 files changed, 44 insertions, 22 deletions

diff --git a/Makefile b/Makefile
index 3c36bec..b1f970c 100644
--- a/Makefile
+++ b/Makefile
@@ -58,7 +58,7 @@ GLOBAL_CFLAGS   := -Os -g3 -gdwarf-2  -mcpu=cortex-m3 -mthumb -march=armv7-m \
 GLOBAL_CXXFLAGS := -fno-rtti -fno-exceptions -Wall $(TARGET_FLAGS)
 GLOBAL_ASFLAGS  := -mcpu=cortex-m3 -march=armv7-m -mthumb		     \
 		   -x assembler-with-cpp $(TARGET_FLAGS)
-LDFLAGS  = $(TARGET_LDFLAGS) -mcpu=cortex-m3 -mthumb \
+LDFLAGS  = $(TARGET_LDFLAGS) $(TOOLCHAIN_LDFLAGS) -mcpu=cortex-m3 -mthumb \
            -Xlinker --gc-sections \
            -Xassembler --march=armv7-m -Wall
 #          -Xlinker --print-gc-sections \
diff --git a/support/ld/common.inc b/support/ld/common.inc
index f749b19..f5a0f5b 100644
--- a/support/ld/common.inc
+++ b/support/ld/common.inc
@@ -5,12 +5,20 @@
  */
 
 OUTPUT_FORMAT ("elf32-littlearm", "elf32-bigarm", "elf32-littlearm")
-ENTRY(_start)
 
 /*
- * Link against libgcc, libc, and libm
+ * Configure other libraries we want in the link.
+ *
+ * libgcc, libc, and libm are common across supported toolchains.
+ * However, some toolchains require additional archives which aren't
+ * present everywhere (e.g. ARM's gcc-arm-embedded releases).
+ *
+ * To hack around this, we let the build system specify additional
+ * archives by putting the right extra_libs.inc (in a directory under
+ * toolchains/) in our search path.
  */
 GROUP(libgcc.a libc.a libm.a)
+INCLUDE extra_libs.inc
 
 /*
  * These force the linker to search for vector table symbols.
@@ -35,8 +43,9 @@ EXTERN(__msp_init)
 PROVIDE(__msp_init = ORIGIN(ram) + LENGTH(ram));
 
 /* Reset vector and chip reset entry point */
-EXTERN(_start)
-PROVIDE(__exc_reset = _start);
+EXTERN(__start__)
+ENTRY(__start__)
+PROVIDE(__exc_reset = __start__);
 
 /* Heap boundaries, for libmaple */
 EXTERN(_lm_heap_start);
@@ -44,10 +53,9 @@ EXTERN(_lm_heap_end);
 
 SECTIONS
 {
-    /* TODO pull out rodata and stick into separate sections  */
     .text :
       {
-        _text = .;
+        __text_start__ = .;
         /*
          * STM32 vector table.  Leave this here.  Yes, really.
          */
@@ -107,7 +115,7 @@ SECTIONS
     .text.align :
       {
         . = ALIGN(8);
-        _etext = .;
+        __text_end__ = .;
       } > REGION_TEXT
 
     /*
@@ -126,13 +134,13 @@ SECTIONS
     .data :
       {
         . = ALIGN(8);
-        _data = .;
+        __data_start__ = .;
 
         *(.got.plt) *(.got)
         *(.data .data.* .gnu.linkonce.d.*)
 
         . = ALIGN(8);
-        _edata = .;
+        __data_end__ = .;
       } > REGION_DATA AT> REGION_RODATA
 
     /*
@@ -166,12 +174,12 @@ SECTIONS
     .bss :
       {
         . = ALIGN(8);
-        _bss = .;
+        __bss_start__ = .;
         *(.bss .bss.* .gnu.linkonce.b.*)
         *(COMMON)
         . = ALIGN (8);
-        _ebss = .;
-        _end = _ebss;
+        __bss_end__ = .;
+        _end = __bss_end__;
       } > REGION_BSS
 
     /*
diff --git a/support/make/build-rules.mk b/support/make/build-rules.mk
index 3d541ba..d180c89 100644
--- a/support/make/build-rules.mk
+++ b/support/make/build-rules.mk
@@ -22,6 +22,8 @@ ifndef V
    SILENT_OBJDUMP  = @echo '  [OBJDUMP]  ' $(OBJDUMP);
 endif
 
+# Extra build configuration
+
 BUILDDIRS :=
 TGT_BIN   :=
 
@@ -29,6 +31,17 @@ CFLAGS   = $(GLOBAL_CFLAGS) $(TGT_CFLAGS)
 CXXFLAGS = $(GLOBAL_CXXFLAGS) $(TGT_CXXFLAGS)
 ASFLAGS  = $(GLOBAL_ASFLAGS) $(TGT_ASFLAGS)
 
+# Hacks to determine extra libraries we need to link against based on
+# the toolchain. The default specifies no extra libraries, but it can
+# be overridden.
+LD_TOOLCHAIN_PATH := $(LDDIR)/toolchains/generic
+ifneq ($(findstring ARM/embedded,$(shell $(CC) --version)),)
+# GCC ARM Embedded, https://launchpad.net/gcc-arm-embedded/
+LD_TOOLCHAIN_PATH := $(LDDIR)/toolchains/gcc-arm-embedded
+endif
+# Add toolchain directory to LD search path
+TOOLCHAIN_LDFLAGS := -L $(LD_TOOLCHAIN_PATH)
+
 # General directory independent build rules, generate dependency information
 $(BUILD_PATH)/%.o: %.c
 	$(SILENT_CC) $(CC) $(CFLAGS) -MMD -MP -MF $(@:%.o=%.d) -MT $@ -o $@ -c $<
diff --git a/wirish/start.S b/wirish/start.S
index 2488895..8b181aa 100644
--- a/wirish/start.S
+++ b/wirish/start.S
@@ -44,9 +44,9 @@
         .code 16
         .thumb_func
 
-        .globl _start
-        .type _start, %function
-_start:
+        .globl __start__
+        .type __start__, %function
+__start__:
         .fnstart
         ldr r1,=__msp_init
         mov sp,r1
diff --git a/wirish/start_c.c b/wirish/start_c.c
index 301565c..655fefb 100644
--- a/wirish/start_c.c
+++ b/wirish/start_c.c
@@ -50,8 +50,9 @@ extern int main(int, char**, char**);
 
 extern void exit(int) __attribute__((noreturn, weak));
 
-extern char _data, _edata;
-extern char _bss, _ebss;
+/* The linker must ensure that these are at least 4-byte aligned. */
+extern char __data_start__, __data_end__;
+extern char __bss_start__, __bss_end__;
 
 struct rom_img_cfg {
     int *img_start;
@@ -62,20 +63,20 @@ extern char _lm_rom_img_cfgp;
 void __attribute__((noreturn)) start_c(void) {
     struct rom_img_cfg *img_cfg = (struct rom_img_cfg*)&_lm_rom_img_cfgp;
     int *src = img_cfg->img_start;
-    int *dst = (int*)&_data;
+    int *dst = (int*)&__data_start__;
     int exit_code;
 
     /* Initialize .data, if necessary. */
     if (src != dst) {
-        int *end = (int*)&_edata;
+        int *end = (int*)&__data_end__;
         while (dst < end) {
             *dst++ = *src++;
         }
     }
 
     /* Zero .bss. */
-    dst = (int*)&_bss;
-    while (dst < (int*)&_ebss) {
+    dst = (int*)&__bss_start__;
+    while (dst < (int*)&__bss_end__) {
         *dst++ = 0;
     }