Check if an address is readable in Rockbox

tryread.diff

diff --git a/firmware/drivers/tuner/si4700.c b/firmware/drivers/tuner/si4700.c
index a5b004a..f3bac29 100644
--- a/firmware/drivers/tuner/si4700.c
+++ b/firmware/drivers/tuner/si4700.c
@@ -355,6 +355,7 @@ static void si4700_sleep(int snooze)
 
 bool si4700_detect(void)
 {
+    panicf("read: %d", safe_read8(0x40000000, NULL));
     if (!tuner_present) {
         tuner_power(true);
         tuner_present = (si4700_read_reg(DEVICEID) == 0x1242);
diff --git a/firmware/target/arm/imx233/crt0.S b/firmware/target/arm/imx233/crt0.S
index 4ae083c..37f04c7 100644
--- a/firmware/target/arm/imx233/crt0.S
+++ b/firmware/target/arm/imx233/crt0.S
@@ -188,11 +188,6 @@ prefetch_abort_handler:
     mov    r1, #1
     b      UIE
 
-data_abort_handler:
-    sub    r0, lr, #8 
-    mov    r1, #2
-    b      UIE
-
 /* 256 words of IRQ stack */
     .space 256*4
 irq_stack:
diff --git a/firmware/target/arm/system-arm.c b/firmware/target/arm/system-arm.c
index c4692bb..a550056 100644
--- a/firmware/target/arm/system-arm.c
+++ b/firmware/target/arm/system-arm.c
@@ -36,6 +36,15 @@ static const char* const uiename[] = {
     "SWI"
 };
 
+void __attribute__((weak,naked)) data_abort_handler(void)
+{
+    asm volatile(
+        "sub    r0, lr, #8  \r\n"
+        "mov    r1, #2      \r\n"
+        "b      UIE         \r\n"
+        );
+}
+
 /* Unexpected Interrupt or Exception handler. Currently only deals with
    exceptions, but will deal with interrupts later.
  */
@@ -98,7 +107,7 @@ void NORETURN_ATTR UIE(unsigned int pc, unsigned int num)
     if (!triggered)
     {
         triggered = true;
-        backtrace(pc, __get_sp(), &line);
+        //backtrace(pc, __get_sp(), &line);
     }
 
     lcd_update();
diff --git a/lib/unwarminder/SOURCES b/lib/unwarminder/SOURCES
index 055e6d0..b060e29 100644
--- a/lib/unwarminder/SOURCES
+++ b/lib/unwarminder/SOURCES
@@ -5,3 +5,4 @@ unwarm.c
 unwarminder.c
 unwarmmem.c
 unwarm_thumb.c
+safe_read.S
\ No newline at end of file
diff --git a/lib/unwarminder/backtrace.c b/lib/unwarminder/backtrace.c
index 4e16091..2cb50ee 100644
--- a/lib/unwarminder/backtrace.c
+++ b/lib/unwarminder/backtrace.c
@@ -23,6 +23,7 @@
  ***************************************************************************/
 
 #include "backtrace.h"
+#include "symtable.h"
 
 /***************************************************************************
  * Prototypes
diff --git a/lib/unwarminder/safe_read.S b/lib/unwarminder/safe_read.S
new file mode 100644
index 0000000..520c767
--- /dev/null
+++ b/lib/unwarminder/safe_read.S
@@ -0,0 +1,75 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2012 by Amaury Pouly
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+.data
+was_aborted:
+    .word   0
+
+.section    .text.safe_read8,"ax",%progbits
+.global     safe_read8
+@ bool safe_read8(uint8_t *addr, uint8_t *value)
+safe_read8:
+    @ was_aborted = 0
+    ldr     r2, =was_aborted
+    mov     r3, #0
+    str     r3, [r2]
+    @ r0=*addr
+safe_read8_faulty_addr:
+    ldrb    r0, [r0]
+    @ if(was_aborted)
+    ldr     r2, [r2]
+    cmp     r2, #1
+    @   return false;
+    moveq   r0, #0
+    bxeq    lr
+    @ if(value != NULL)
+    cmp     r1, #0
+    @   *value = r0
+    streqb  r0, [r1]
+    @ return true;
+    mov     r0, #1
+    bx      lr
+
+.section    .text.data_abort_handler,"ax",%progbits
+.global     data_abort_handler
+data_abort_handler:
+    @ store minimal amount of registers
+    stmfd   sp!, {r0-r1}
+    @ compute faulty address
+    sub     r0, lr, #8
+    @ compare to safe_read8
+    ldr     r1, =safe_read8_faulty_addr
+    cmp     r0, r1
+    @ if equal, special treatment
+    beq     1f
+    @ otherwise just normally to UIE
+    mov     r0, r1
+    mov     r1, #2
+    b       UIE
+1:
+    @ set was_aborted
+    ldr     r1, =was_aborted
+    mov     r0, #1
+    str     r0, [r1]
+    @ restore registers
+    ldmfd   sp!, {r0-r1}
+    @ restore mode and jump back to the *next* instruction
+    subs    pc, lr, #-4
diff --git a/lib/unwarminder/safe_read.h b/lib/unwarminder/safe_read.h
new file mode 100644
index 0000000..0ad23e6
--- /dev/null
+++ b/lib/unwarminder/safe_read.h
@@ -0,0 +1,33 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2012 by Amaury Pouly
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#ifndef __SAFE_READ__
+#define __SAFE_READ__
+
+#include "system.h"
+
+/* Try to read an X-bit unsigned integer. If the address is not readable,
+ * returns false. Otherwise returns true and store the result in *value
+ * if value is not NULL */
+bool safe_read8(uint8_t *addr, uint8_t *value);
+bool safe_read16(uint16_t *addr, uint16_t *value);
+bool safe_read32(uint32_t *addr, uint32_t *value);
+
+#endif /* __SAFE_READ__ */
\ No newline at end of file
diff --git a/tools/configure b/tools/configure
index ffded7e..b6152cc 100755
--- a/tools/configure
+++ b/tools/configure
@@ -3695,6 +3695,11 @@ if test -n "$ccache"; then
   CC="$ccache $CC"
 fi
 
+if test "$arch" = "arm"; then
+  extradefines="$extradefines -DPOKE_FUNCTION_NAMES"
+  GCCOPTS="$GCCOPTS -mpoke-function-name"
+fi
+
 if test "$ARG_ARM_THUMB" = "1"; then
   extradefines="$extradefines -DUSE_THUMB"
   CC="$toolsdir/thumb-cc.py $CC"