armcm_boot: Introduce application_check_valid()

Move application_check_valid() in bootentry.c to armcm_boot.c and make
the check specific to the ARM cortex-m.  On these ARM machines it is
easier to validate the application stack address.

Also rename jump_to_application() to application_jump().

Also rename flash_read_block() to application_read_flash() and move to
armcm_boot.c .

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/bootentry.c

@@ -44,20 +44,6 @@ check_double_reset(void)
     // No reset, read the key back out to clear it
 }
 
-static uint8_t
-check_application_code(void)
-{
-    // Read the first block of memory, if it
-    // is all 0xFF then no application has been flashed
-    uint8_t buf[CONFIG_BLOCK_SIZE];
-    flash_read_block(CONFIG_APPLICATION_START, (uint32_t*)buf);
-    for (uint8_t i = 0; i < CONFIG_BLOCK_SIZE; i++) {
-        if (buf[i] != 0xFF)
-            return 1;
-    }
-    return 0;
-}
-
 // Check if bootloader or application should be started
 int
 bootentry_check(void)
@@ -66,7 +52,7 @@ bootentry_check(void)
     // - The request signature is set in memory (request from app)
     // - No application code is present
     uint64_t bootup_code = get_bootup_code();
-    if (bootup_code == REQUEST_SIG || !check_application_code()
+    if (bootup_code == REQUEST_SIG || !application_check_valid()
         || check_button_pressed()) {
         // Start bootloader main loop
         set_bootup_code(0);

src/flashcmd.c

@@ -7,7 +7,7 @@
 #include <string.h> // memmove
 #include "autoconf.h" // CONFIG_BLOCK_SIZE
 #include "board/flash.h" // flash_write_page
-#include "board/misc.h" // jump_to_application
+#include "board/misc.h" // application_jump
 #include "byteorder.h" // cpu_to_le32
 #include "command.h" // command_respond_ack
 #include "flashcmd.h" // flashcmd_is_in_transfer
@@ -48,7 +48,7 @@ void
 complete_task(void)
 {
     if (complete && timer_is_before(complete_endtime, timer_read_time()))
-        jump_to_application();
+        application_jump();
 }
 DECL_TASK(complete_task);
 
@@ -85,7 +85,7 @@ command_read_block(uint32_t *data)
     uint32_t block_address = le32_to_cpu(data[1]);
     uint32_t out[CONFIG_BLOCK_SIZE / 4 + 2 + 2];
     out[2] = cpu_to_le32(block_address);
-    flash_read_block(block_address, &out[3]);
+    application_read_flash(block_address, &out[3]);
     command_respond_ack(CMD_REQ_BLOCK, out, ARRAY_SIZE(out));
 }
 

src/generic/armcm_boot.c

@@ -4,6 +4,7 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
+#include <string.h> // memcpy
 #include "armcm_boot.h" // DECL_ARMCM_IRQ
 #include "autoconf.h" // CONFIG_MCU
 #include "board/internal.h" // SysTick
@@ -33,10 +34,26 @@ set_bootup_code(uint64_t code)
     barrier();
 }
 
+// Helper function to read area of flash
+void
+application_read_flash(uint32_t address, uint32_t *dest)
+{
+    memcpy(dest, (void*)address, CONFIG_BLOCK_SIZE);
+}
+
+// Check if the application flash area looks valid
+int
+application_check_valid(void)
+{
+    uint32_t *app = (void*)CONFIG_APPLICATION_START;
+    return *app != 0 && *app != 0xffffffff;
+}
+
 #define REQUEST_START_APP 0x7b06ec45a9a8243d
 
+// Jump to the main application (exiting the bootloader)
 void
-jump_to_application(void)
+application_jump(void)
 {
     irq_disable();
     set_bootup_code(REQUEST_START_APP);

src/generic/misc.h

@@ -10,7 +10,9 @@ void *console_receive_buffer(void);
 
 uint64_t get_bootup_code(void);
 void set_bootup_code(uint64_t code);
-void jump_to_application(void);
+void application_read_flash(uint32_t address, uint32_t *dest);
+int application_check_valid(void);
+void application_jump(void);
 
 void timer_setup(void);
 

src/sched.c

@@ -47,7 +47,7 @@ sched_main(void)
 {
     timer_setup();
     if (!bootentry_check())
-        jump_to_application();
+        application_jump();
 
     // Run all init functions marked with DECL_INIT()
     extern void ctr_run_initfuncs(void);

src/stm32/flash.c

@@ -4,7 +4,6 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
-#include <string.h> // memcpy
 #include "autoconf.h" // CONFIG_MACH_STM32F103
 #include "flash.h" // flash_write_page
 #include "internal.h" // FLASH
@@ -141,9 +140,3 @@ flash_write_page(uint32_t page_address, void *data)
         flash_write_stm32f1xx(page_address, (uint16_t *)data);
     }
 }
-
-void
-flash_read_block(uint32_t block_address, uint32_t *buffer)
-{
-    memcpy(buffer, (void*)block_address, CONFIG_BLOCK_SIZE);
-}

src/stm32/flash.h

@@ -6,6 +6,5 @@
 uint32_t flash_get_page_size(void);
 void flash_complete(void);
 void flash_write_page(uint32_t page_address, void *data);
-void flash_read_block(uint32_t block_address, uint32_t *buffer);
 
 #endif