Re: sparc64/ofwboot: initialize BSS before entering

On Tue, 18 Aug 2026 01:34:26 +0200,
Kirill A. Korinsky <[email protected]> wrote:
> 
> tech@,
> 
> OpenBIOS's init-program ELF loader claims p_memsz bytes for each
> segment, but copies only p_filesz bytes and leaves the remaining memory
> untouched. This lets stale firmware memory appear as initialized BSS.
> 
> This became visible after shrinking ofwboot by using not -O2 to build it
> with LLVM toolchain, tested with -Oz, -Os and -O1.
> 
> As result, freelist head moved twelve bytes beyond the file-backed
> PT_LOAD range and contained an unaligned garbage pointer, causing
> T_ALIGN in alloc().
> 
> Ok?
>

I'd like to withdraw this diff.

I haven't found similar code in OpenBOOT, and -Oz binary boots on tested
real hardware. Instead I send to upstream the fix.

https://marc.info/?l=openbios&m=178705636759610&w=2

> Index: sys/arch/sparc64/stand/ofwboot/srt0.s
> ===================================================================
> RCS file: /home/cvs/src/sys/arch/sparc64/stand/ofwboot/srt0.s,v
> diff -u -p -r1.8 srt0.s
> --- sys/arch/sparc64/stand/ofwboot/srt0.s	14 Nov 2025 19:17:13 -0000	1.8
> +++ sys/arch/sparc64/stand/ofwboot/srt0.s	17 Aug 2026 23:23:37 -0000
> @@ -92,6 +92,13 @@ _start:
>  	clr	%g4		! Point %g4 to start of data segment
>  				! only problem is that apparently the
>  				! start of the data segment is 0
> +
> +	/* OpenBIOS init-program does not clear the ELF BSS. */
> +	set	__bss_start, %o0
> +	clr	%o1
> +	set	_end, %o2
> +	call	memset
> +	 sub	%o2, %o0, %o2
>  	
>  	/*
>  	 * XXXXXXXX Need to determine what params are passed
> 
> 
> -- 
> wbr, Kirill
> 

-- 
wbr, Kirill