fix(l0dables): Fix vector table alignment

The vector table's alignment requirements depend on the number of
interrupts [1].  In our case, we have 0x6E(=110) interrupts and thus an
alignment requirement of 0x80(=128).

To satisfy this requirement, this commit moves the IVT to the beginning
of .text and enforces a 128 byte alignment.  Please note that the
headers which come before .text will push the IVT to 0x100 instead of
having it directly in the beginning at 0x00.

[1]: https://developer.arm.com/docs/dui0553/a/cortex-m4-peripherals/system-control-block/vector-table-offset-register



Signed-off-by: Rahix <rahix@rahix.de>

l0dables/lib/crt.s

@@ -18,10 +18,10 @@
 		 *
 		 * All of the following (apart from Reset_Handler, which calls main())
 		 * are backed by weak referenced symbols, which you can override just
-         * by defining them in C code.
+		 * by defining them in C code.
 		 */
-		.section .data
-		.align 2
+		.section .text.isr_vector
+		.align 7
 		.globl __isr_vector
 __isr_vector:
 		.long    0                             /* Top of Stack, overriden by l0der at load time */

l0dables/lib/l0dable.ld

@@ -33,6 +33,9 @@ SECTIONS {
 
     .text :
     {
+        /* The vector table needs 128 byte alignment */
+        . = ALIGN(128);
+        KEEP(*(.text.isr_vector))
         *(.text*)
         *(.rodata*)
 

l0dables/lib/meson.build

@@ -3,7 +3,7 @@ l0dable_startup_lib = static_library(
   'crt.s',
   'hardware.c',
   dependencies: [api_caller],
-  pic: true,
+  c_args: ['-fpie'],
 )
 
 l0dable_startup = declare_dependency(