Probably "MIPS: don't overlay relocation data with BSS" sounds a bit more
human-like :)
Regards,
Peter
On Wed, Jan 29, 2020 at 06:27:37AM +0100, Oleksij Rempel wrote:
> .bss __rel_start (OVERLAY) was used to optimize RAM size used by
> barebox. Since .bss and __rel_start overlap, we should clear bss only
> after __rel_start was used. Following patch changed initialization
> sequence to clear .bss before __rel_start:
> 1e5aef61fc6a444 ("MIPS: reloc: init bss and cpu")
>
> This make relocation buffer unusable and broke relocation with different
> symptoms reported by Antony Pavlov <antonynpavlov@xxxxxxxxx>:
> * iomem output has no information on sdram regions, so memtest is unusable;
> * pc = 0xa081232c, relocation does not work, barebox is located with 8M offset
> from start of RAM. The board has 256M and relocation routine
> should move barebox code much higher;
> * pc = 0xa081232c, so barebox code works from KSEG1 not from KSEG0 as MMU=y option implies.
>
> There is a choice of moving .bss clear sequence after __rel_start or
> remove this optimization. Since the use of this optimization is minimal
> and danger to trap in to similar issue is still high, i prefer to remove
> this optimization.
>
> As result of this change, we need to fix calculation of relocation are
> size:
> relocate_code() calculates relocation area size as a sum (barebox_image_size +
> bss_len). barebox_image_size and bss_len are calculated as (__image_end -
> __image_start) and (__bss_stop - __bss_start) respectively. This doesn't take
> into account relocation data placed between __image_end and __bss_start.
> However relocation preserves BSS position relative to image start, as if
> relocation data is still there. This causes RAM overflow during BSS
> initialization in main_entry(). This problem may be hidden due to the alignment
> of the `relocaddr`.
>
> Reported-by: Antony Pavlov <antonynpavlov@xxxxxxxxx>
> Fixes: 1e5aef61fc6a444 ("MIPS: reloc: init bss and cpu")
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> Signed-off-by: Peter Mamonov <pmamonov@xxxxxxxxx>
> ---
> arch/mips/lib/barebox.lds.S | 2 +-
> arch/mips/lib/reloc.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/lib/barebox.lds.S b/arch/mips/lib/barebox.lds.S
> index 693a778980..c954df41f3 100644
> --- a/arch/mips/lib/barebox.lds.S
> +++ b/arch/mips/lib/barebox.lds.S
> @@ -59,7 +59,7 @@ SECTIONS
>
> _end = .;
>
> - .bss __rel_start (OVERLAY) : {
> + .bss : {
> __bss_start = .;
> *(.sbss.*)
> *(.bss.*)
> diff --git a/arch/mips/lib/reloc.c b/arch/mips/lib/reloc.c
> index df9760e38c..4b0e252352 100644
> --- a/arch/mips/lib/reloc.c
> +++ b/arch/mips/lib/reloc.c
> @@ -118,7 +118,7 @@ void relocate_code(void *fdt, u32 fdt_size, u32 ram_size)
> memset(__bss_start, 0, bss_len);
> cpu_probe();
>
> - length = barebox_image_size + bss_len;
> + length = __bss_stop - __image_start;
> relocaddr = ALIGN_DOWN(ram_size - length, SZ_64K);
> relocaddr = KSEG0ADDR(relocaddr);
> new_stack = relocaddr - MALLOC_SIZE - 16;
> --
> 2.25.0
>
_______________________________________________
barebox mailing list
barebox@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/barebox
