[U-Boot] Problems with Linker Symbols to make HAB on i.MX28 work

[Christopher Preschern]

Hi,

I want to make High Assurance Boot (HAB) for the Freescale i.MX28 with 
U-Boot 04/2012 work. To do that I have to link an Image Vector Table 
(IVT, consists of some boot image addresses which I insert by using 
linker symbols in the C-code) to the u-boot binary. My problem is, that 
the linker symbols are not inserted into the binary correctly (they 
always have the value 0).

Here is my code - I include the following to board/denx/m28evk/m28evk.c

/*IVT DEFINITION */
#define BASE_ADDRESS 0x00000100
extern unsigned int __hab_uboot_data; // defined in u-boot.lds
extern int __hab_uboot_end;           // defined in u-boot.lds
extern void* _start;
struct my_ivt {                       // IVT structur according to
     uint32_t header;                  // some Freescale manuals
     uint32_t *entry;
     uint32_t reserved1;
     uint32_t *dcd;
     uint32_t *boot_data;
     uint32_t *self;
     uint32_t *csf;
     uint32_t reserved2;
     uint32_t img_len;
};
const struct my_ivt input_ivt 
__attribute__((section(".ivt"),aligned(4))) = {
     0x402000d1                       //header
     (uint32_t*) (&_start),           //entry
     0,                               //reserved
     NULL,                            //DCD
     NULL,                            //boot data
     (uint32_t*) (&input_ivt),        //IVT address
     (uint32_t*) (&__hab_uboot_data), //CSF
     0,                               //reserved
     (uint32_t) (&__hab_uboot_end) - BASE_ADDRESS   //image length
};
/*END OF IVT DEFINITION*/

and I modify the linker file (arch/arm/cpu/u-boot.lds)

/*INSERTED RIGHT BEFORE THE BSS SECTION */
   . = ALIGN(4);
   __uboot_ivt = .;
   .ivt : { *(.ivt) }
   __hab_uboot_data = .;
   . = . + 0x2000;
   __hab_uboot_end = .;

With this code, the IVT should be written to the end of u-boot.bin. 
When looking at it with a hex-Editor I do see the IVT (e.g. the 
hard-coded header is there - in little-endian), but the values for the 
linker symbols (e.g. __hab_uboot_data) are 0.
D1002040 00010040 00000000 00000000
00000000 00900640 00000000 00000000
00FFFFFF

However, I think that the linker symbols are correctly included in the 
C-source, because the compiler does not complain that he cannot find the 
extern __hab_uboot_data variable and in all the forums/tutorials I 
googled I found the syntax I use. Also if I put
   printf("HAB-DEBUG: %x \n",(uint32_t)(&__hab_uboot_end));
somewhere in the code (e.g. into the board_init() in m28evk.c), I do get 
an address which is not 0 (although it is also not the address I expect 
– I get the expected address + the U-Boot relocation offset)

I appreciate any kind of help very much!

Best regards,
Christopher