From: Daniel Dickman <didickman@gmail.com>
Subject: Re: sparc64/ofwboot: initialize BSS before entering
To: OpenBSD tech <tech@openbsd.org>
Date: Mon, 17 Aug 2026 20:02:58 -0400

Shouldn't the fix go into OpenBIOS rather than ofwboot getting a 
work-around?

Does this bug exist on any real sparc64 hardware?


On Tue, 18 Aug 2026, Kirill A. Korinsky 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?
> 
> 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
> 
>