Re: [PATCH master] RISC-V: boot: uncompress: determine piggy data bounds before relocation

[Sascha Hauer <sha@pengutronix.de>]

On Sat, Apr 03, 2021 at 09:03:32AM +0200, Ahmad Fatoum wrote:
> Like on ARM, the PBL common code does not relocate the piggy data and
> instead keeps pointers into the old image's location.
> 
> For relocate_to_current_adr, this doesn't matter, because both
> destination and source address are the same, but when running from ROM
> or flash relocate_to_adr will only copy up to __bss_start, so
> determining the piggy data bounds _must_ happen before relocation.
> 
> We did so, but input_data_len, which references the image end was
> executed after relocation unearthing two bugs at once:
> 
>   - The compiler cached input_data_end from before relocation, so
>     the runtime offset wasn't being added
> 
>   - Even with runtime offset added, we were pointing at the new
>     address, but the old piggy data wasn't copied there (On erizo,
>     it's still in ROM)
> 
> Fix these by evaluating the bounds before relocation and add a comment,
> why it needs to be there. The same comment will also be added at the
> code's origin in the ARM architecture support.
> 
> Reported-by: Antony Pavlov <antonynpavlov@gmail.com>
> Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
> ---
> Please apply to master.

Did that, thanks

Sascha

> ---
>  arch/riscv/boot/uncompress.c      | 6 +++---
>  arch/riscv/include/asm/sections.h | 4 +++-
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/riscv/boot/uncompress.c b/arch/riscv/boot/uncompress.c
> index 411cefb0e31b..b4e010998a4a 100644
> --- a/arch/riscv/boot/uncompress.c
> +++ b/arch/riscv/boot/uncompress.c
> @@ -32,8 +32,11 @@ void __noreturn barebox_pbl_start(unsigned long membase, unsigned long memsize,
>  	void *pg_start, *pg_end;
>  	unsigned long pc = get_pc();
>  
> +	/* piggy data is not relocated, so determine the bounds now */
>  	pg_start = input_data + get_runtime_offset();
>  	pg_end = input_data_end + get_runtime_offset();
> +	pg_len = pg_end - pg_start;
> +	uncompressed_len = input_data_len();
>  
>  	/*
>  	 * If we run from inside the memory just relocate the binary
> @@ -45,9 +48,6 @@ void __noreturn barebox_pbl_start(unsigned long membase, unsigned long memsize,
>  	else
>  		relocate_to_adr(membase);
>  
> -	pg_len = pg_end - pg_start;
> -	uncompressed_len = input_data_len();
> -
>  	barebox_base = riscv_mem_barebox_image(membase, endmem,
>  					       uncompressed_len + MAX_BSS_SIZE);
>  
> diff --git a/arch/riscv/include/asm/sections.h b/arch/riscv/include/asm/sections.h
> index 725fd8db474e..6673648bcd58 100644
> --- a/arch/riscv/include/asm/sections.h
> +++ b/arch/riscv/include/asm/sections.h
> @@ -15,9 +15,11 @@ extern char __dynsym_end[];
>  extern char input_data[];
>  extern char input_data_end[];
>  
> +unsigned long get_runtime_offset(void);
> +
>  static inline unsigned int input_data_len(void)
>  {
> -	return get_unaligned((const u32 *)(input_data_end - 4));
> +	return get_unaligned((const u32 *)(input_data_end + get_runtime_offset() - 4));
>  }
>  
>  #endif
> -- 
> 2.30.0
> 
> 
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