raspberry BSP: Maybe there is a bug in the linker file?

[Christian Mauderer]

On 20/12/2019 19:19, Niteesh wrote:
> How do you test a patch? Do you checkout that particular commit and
> build and the BSP again?.

Basically yes: You check out the version that you want fixed and apply
the patch. In that case I have gone back and forward a few times to find
the commit that introduced the second bug.

> @Christian Mauderer <mailto:list at c-mauderer.de>  how did you build it
> for the rpi1? Did you follow the steps as in previous threads?

Basically the same steps like for every BSP:
1. Build a recent toolchain using RSB.
2. Build the BSP.
3. Test it on the board.

For the rpi1 the BSP is "raspberrypi" instead of "raspberrypi2". And I
didn't install the BSP because I only wanted the tests and no extra
application.

For testing it I used the guide that you found: Objcopy into a binary
file and replace the kernel.img with it.

> and how did you come to the conclusion that these changes cause the
> exceptions,

I had a look at the history of the raspberry BSP (`gitk
bsps/arm/raspberrypi` or `git log bsps/arm/raspberrypi`) and looked for
suspicious patches. For the raspberry there are not much patches in the
last year so that was quite easy. Then I just tested before and after
some of the patches to find the ones that introduced the bugs.

Again: In this case it was necessary to backport Sebastians patch so
that I have been able to test before / after the one that introduces the
exception.

I haven't had a detailled look at the exception yet but I assume it's
some problem that the wrong variant is used or that my RPi1 is an early
model with less RAM or something like that.

> as a beginner these ideas
> will help in the future.
> On Fri, Dec 20, 2019 at 2:46 PM Christian Mauderer <list at c-mauderer.de
> <mailto:list at c-mauderer.de>> wrote:
> 
>     On 20/12/2019 09:22, Christian Mauderer wrote:
>     > On 20/12/2019 07:33, Sebastian Huber wrote:
>     >> On 19/12/2019 15:28, Niteesh wrote:
>     >>> As far as I know, 0x8000 is a fixed address where the bootloader
>     jumps
>     >>> to after loading the application assuming the CPU is in 32bit mode.
>     >>> For 64bit mode, it jumps to 0x80000.
>     >>
>     >> Would you mind testing this patch:
>     >>
>     >> https://lists.rtems.org/pipermail/devel/2019-December/056551.html
>     >>
>     >
>     > On the Pi 1 now the binary has three time the size (with a lot of 0x00
>     > in it) and at least RTEMS starts. But it runs into an exception quite
>     > fast. I'll investigate that a bit.
>     >
>     > @Niteesh: For the Pi 3 I would expect that it still doesn't print
>     > anything on the console due to the different UART pins.
>     >
>     > The output on the Pi 1 is:
>     >
>     > executing�
>     > *** FATAL ***
>     > fatal source: 9 (RTEMS_FATAL_SOURCE_EXCEPTION)
>     >
>     > R0   = 0xfc037f80 R8  = 0x00000000
>     > R1   = 0xfc345980 R9  = 0x00000010
>     > R2   = 0x00000001 R10 = 0xfc037f8a
>     > R3   = 0x03fc8080 R11 = 0x0030da00
>     > R4   = 0xfc037f80 R12 = 0xfc345988
>     > R5   = 0x00000008 SP  = 0x00300ba8
>     > R6   = 0x0030d9fe LR  = 0x00205a78
>     > R7   = 0x00305218 PC  = 0x00205ac8
>     > CPSR = 0x600001d3 VEC = 0x00000004
>     > RTEMS version: 5.0.0.254f38583fe68c3e17dfe274a2deeb00a5a538d6
>     > RTEMS tools: 7.5.0 20191114 (RTEMS 5, RSB 5 (6c65fc237b9e modified),
>     > Newlib d14714c69)
> 
>     The exception seems to be caused by some of the changes in bspstart.c
>     and bspgetworkarea.c in patch a4d7e4cee77d16b0e34ef543f0804e7eb2954137.
>     So the fix for the linker command file is fine.
>