linux-kernel - Re: [PATCH 05/29] x86/boot/e820: Print gaps in the E820 table

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aAcwYKtGMDv-AoL1@kernel.org>
Date: Tue, 22 Apr 2025 09:00:00 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, Andy Shevchenko <andy@...nel.org>,
	Arnd Bergmann <arnd@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Juergen Gross <jgross@...e.com>, "H . Peter Anvin" <hpa@...or.com>,
	Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul Menzel <pmenzel@...gen.mpg.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH 05/29] x86/boot/e820: Print gaps in the E820 table

On Mon, Apr 21, 2025 at 08:51:45PM +0200, Ingo Molnar wrote:
> Gaps in the E820 table are not obvious at a glance and can
> easily be overlooked.
> 
> Print out gaps in the E820 table:
> 
> Before:
> 
> 	BIOS-provided physical RAM map:
> 	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
> 	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> 	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> 	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
> 	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
> 	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
> 	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> 	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
> 	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
> 	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
> After:
> 
> 	BIOS-provided physical RAM map:
> 	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
> 	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> 	BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff]
> 	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> 	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
> 	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
> 	BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff]
> 	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
> 	BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff]
> 	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> 	BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff]
> 	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
> 	BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff]
> 	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
> 	BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff]
> 	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
> 
> Also warn about badly ordered E820 table entries:
> 
> 	BUG: out of order E820 entry!
> 
> ( this is printed before the entry is printed, so there's no need to
>   print any additional data with the warning. )
> 
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Cc: Andy Shevchenko <andy@...nel.org>
> Cc: Arnd Bergmann <arnd@...nel.org>
> Cc: David Woodhouse <dwmw@...zon.co.uk>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Mike Rapoport (Microsoft) <rppt@...nel.org>
> ---
>  arch/x86/kernel/e820.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 4244b6d53fd0..a8edfa375fbd 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -201,18 +201,32 @@ static void __init e820_print_type(enum e820_type type)
>  
>  static void __init e820__print_table(const char *who)
>  {
> +	u64 range_end_prev = 0;
>  	int i;
>  
>  	for (i = 0; i < e820_table->nr_entries; i++) {
>  		struct e820_entry *entry = e820_table->entries + i;
> +		u64 range_start, range_end;
>  
> -		pr_info("%s: [mem %#018Lx-%#018Lx] ",
> -			who,
> -			entry->addr,
> -			entry->addr + entry->size-1);
> +		range_start = entry->addr;
> +		range_end   = entry->addr + entry->size;
>  
> +		/* Out of order E820 maps should not happen: */
> +		if (range_start < range_end_prev)
> +			pr_info("BUG: out of order E820 entry!\n");

Maybe "BIOS BUG"?

> +
> +		if (range_start > range_end_prev) {
> +			pr_info("%s: [gap %#018Lx-%#018Lx]\n",
> +				who,
> +				range_end_prev,
> +				range_start-1);

range_start - 1 ;-)

> +		}
> +
> +		pr_info("%s: [mem %#018Lx-%#018Lx] ", who, range_start, range_end-1);
>  		e820_print_type(entry->type);
>  		pr_cont("\n");
> +
> +		range_end_prev = range_end;
>  	}
>  }
>  
> -- 
> 2.45.2
> 

-- 
Sincerely yours,
Mike.