libubacktrace: Add arm implementation

Arm has a different mechanism of getting
_Unwind_GetIP. Therefore we provide arch
specific backtrace file.

Signed-off-by: Khem Raj <raj.khem@gmail.com>

libubacktrace/Makefile.in

@@ -6,7 +6,7 @@
 # Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
 #
 
-subdirs += libubacktrace
+subdirs += libubacktrace libubacktrace/$(TARGET_ARCH)
 
 CFLAGS-libubacktrace := -DNOT_IN_libc -DIS_IN_libubacktrace $(SSP_ALL_CFLAGS)
 
@@ -23,22 +23,36 @@ libubacktrace_FULL_NAME := libubacktrace-$(VERSION).so
 libubacktrace_DIR := $(top_srcdir)libubacktrace
 libubacktrace_OUT := $(top_builddir)libubacktrace
 
+libubacktrace_ARCH_DIR:=$(libubacktrace_DIR)/$(TARGET_ARCH)
+libubacktrace_ARCH_OUT:=$(libubacktrace_OUT)/$(TARGET_ARCH)
+
+-include $(libubacktrace_ARCH_DIR)/Makefile.arch
+
 libubacktrace_SRC-y :=
 libubacktrace_SRC-$(UCLIBC_HAS_BACKTRACE) := backtrace.c backtracesyms.c backtracesymsfd.c
 
+# remove generic sources, if arch specific version is present
+ifneq ($(strip $(libubacktrace_ARCH_SRC-y)),)
+libubacktrace_SRC-y := $(filter-out $(notdir $(libubacktrace_ARCH_SRC-y)),$(libubacktrace_SRC-y))
+endif
+
 # -fasynchronous-unwind-tables is required for backtrace to work using dwarf2
 CFLAGS-backtrace.c := -fasynchronous-unwind-tables
 
+# pass common flags to arch dirs
+ifneq ($(strip $(libubacktrace_ARCH_OBJS)),)
+CFLAGS-libubacktrace/$(TARGET_ARCH)/ := $(CFLAGS-libubacktrace)
+endif
 
-libubacktrace_SRCS := $(addprefix $(libubacktrace_DIR)/,$(libubacktrace_SRC-y))
+libubacktrace_SRCS := $(patsubst %.c,$(libubacktrace_DIR)/%.c,$(libubacktrace_SRC-y))
 libubacktrace_OBJS := $(patsubst $(libubacktrace_DIR)/%.c,$(libubacktrace_OUT)/%.o,$(libubacktrace_SRCS))
 
 ifeq ($(DOPIC),y)
-libubacktrace-a-y := $(libubacktrace_OBJS:.o=.os)
+libubacktrace-a-y += $(libubacktrace_OBJS:.o=.os)
 else
-libubacktrace-a-y := $(libubacktrace_OBJS)
+libubacktrace-a-y += $(libubacktrace_OBJS)
 endif
-libubacktrace-so-y := $(libubacktrace_OBJS:.o=.os)
+libubacktrace-so-y += $(libubacktrace_OBJS:.o=.os)
 
 lib-a-$(UCLIBC_HAS_BACKTRACE) += $(top_builddir)lib/libubacktrace.a
 lib-so-$(UCLIBC_HAS_BACKTRACE) += $(top_builddir)lib/libubacktrace.so
@@ -61,7 +75,7 @@ $(libubacktrace_OUT)/libubacktrace_so.a: $(libubacktrace-so-y)
 	$(Q)$(RM) $@
 	$(do_ar)
 
-$(libubacktrace_OUT)/libubacktrace.oS: $(libubacktrace_SRCS)
+$(libubacktrace_OUT)/libubacktrace.oS: $(libubacktrace_SRCS) $(libubacktrace_ARCH_SRCS)
 	$(Q)$(RM) $@
 	$(compile-m)
 

libubacktrace/arm/Makefile.arch

@@ -0,0 +1,21 @@
+# Makefile for uClibc (libubacktrace)
+#
+# Author: Khem Raj <raj.khem@gmail.com>
+
+# Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
+#
+
+libubacktrace_ARCH_SRC-$(UCLIBC_HAS_BACKTRACE) := backtrace.c
+libubacktrace_ARCH_SRCS := $(addprefix $(libubacktrace_ARCH_DIR)/,$(libubacktrace_ARCH_SRC-y))
+libubacktrace_ARCH_OBJS := $(patsubst $(libubacktrace_ARCH_DIR)/%.c,$(libubacktrace_ARCH_OUT)/%.o,$(libubacktrace_ARCH_SRCS))
+
+ifeq ($(DOPIC),y)
+libubacktrace-a-y+=$(libubacktrace_ARCH_OBJS:.o=.os)
+else
+libubacktrace-a-y+=$(libubacktrace_ARCH_OBJS)
+endif
+libubacktrace-so-y+=$(libubacktrace_ARCH_OBJS:.o=.os)
+
+ifeq ($(CONFIG_ARM_EABI),y)
+LIBGCC += $(shell $(CC) -print-file-name=libgcc_eh.a)
+endif

libubacktrace/arm/backtrace.c

@@ -0,0 +1,90 @@
+/*
+ * Perform stack unwinding by using the _Unwind_Backtrace.
+ *
+ * User application that wants to use backtrace needs to be
+ * compiled with -fasynchronous-unwid-tables option and -rdynamic i
+ * to get full symbols printed.
+ *
+ * Author(s): Khem Raj <raj.khem@gmail.com>
+ * - ARM specific implementation of backtrace
+ *
+ * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
+ *
+ */
+
+#include <execinfo.h>
+#include <dlfcn.h>
+#include <stdlib.h>
+#include <unwind.h>
+#include <assert.h>
+#include <stdio.h>
+
+struct trace_arg
+{
+  void **array;
+  int cnt, size;
+};
+
+static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
+static _Unwind_VRS_Result (*unwind_vrs_get) (_Unwind_Context *,
+					     _Unwind_VRS_RegClass,
+					     _uw,
+					     _Unwind_VRS_DataRepresentation,
+					     void *);
+
+static void backtrace_init (void)
+{
+	void *handle = dlopen ("libgcc_s.so.1", RTLD_LAZY);
+	if (handle == NULL
+		|| ((unwind_backtrace = dlsym (handle, "_Unwind_Backtrace")) == NULL)
+		|| ((unwind_vrs_get = dlsym (handle, "_Unwind_VRS_Get")) == NULL)) {
+		printf("libgcc_s.so.1 must be installed for backtrace to work\n");
+		abort();
+	}
+}
+/* This function is identical to "_Unwind_GetGR", except that it uses
+   "unwind_vrs_get" instead of "_Unwind_VRS_Get".  */
+static inline _Unwind_Word
+unwind_getgr (_Unwind_Context *context, int regno)
+{
+  _uw val;
+  unwind_vrs_get (context, _UVRSC_CORE, regno, _UVRSD_UINT32, &val);
+  return val;
+}
+
+/* This macro is identical to the _Unwind_GetIP macro, except that it
+   uses "unwind_getgr" instead of "_Unwind_GetGR".  */
+#define unwind_getip(context) \
+ (unwind_getgr (context, 15) & ~(_Unwind_Word)1)
+
+static _Unwind_Reason_Code
+backtrace_helper (struct _Unwind_Context *ctx, void *a)
+{
+	struct trace_arg *arg = a;
+
+	assert (unwind_getip != NULL);
+
+	/* We are first called with address in the __backtrace function. Skip it. */
+	if (arg->cnt != -1)
+		arg->array[arg->cnt] = (void *) unwind_getip (ctx);
+	if (++arg->cnt == arg->size)
+		return _URC_END_OF_STACK;
+	return _URC_NO_REASON;
+}
+
+/*
+ * Perform stack unwinding by using the _Unwind_Backtrace.
+ *
+ */
+int backtrace (void **array, int size)
+{
+	struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
+
+	if (unwind_backtrace == NULL)
+		backtrace_init();
+
+	if (size >= 1)
+		unwind_backtrace (backtrace_helper, &arg);
+
+	return arg.cnt != -1 ? arg.cnt : 0;
+}

libubacktrace/backtrace.c

@@ -66,9 +66,6 @@ backtrace_helper (struct _Unwind_Context *ctx, void *a)
 /*
  * Perform stack unwinding by using the _Unwind_Backtrace.
  *
- * User application that wants to use backtrace needs to be
- * compiled with -fexceptions option and -rdynamic to get full
- * symbols printed.
  */
 int backtrace (void **array, int size)
 {