Re: [PATCH 10/12] mips: Print the kernel virtual mem layout on debugging

From: Mike Rapoport <rppt@linux.ibm.com>
To: Serge Semin <fancer.lancer@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>,
	Paul Burton <paul.burton@mips.com>,
	James Hogan <jhogan@kernel.org>,
	Matt Redfearn <matt.redfearn@mips.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thomas Bogendoerfer <tbogendoerfer@suse.de>,
	Huacai Chen <chenhc@lemote.com>, Stefan Agner <stefan@agner.ch>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Juergen Gross <jgross@suse.com>,
	linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 10/12] mips: Print the kernel virtual mem layout on debugging
Date: Wed, 24 Apr 2019 16:47:11 +0300	[thread overview]
Message-ID: <20190424134711.GE6278@rapoport-lnx> (raw)
In-Reply-To: <20190423224748.3765-11-fancer.lancer@gmail.com>

On Wed, Apr 24, 2019 at 01:47:46AM +0300, Serge Semin wrote:
> It is useful at least for debugging to have the kernel virtual
> memory layout printed at boot time so to have the full information
> about the booted kernel. Make the printing optional and available
> only when DEBUG_KERNEL config is enabled so not to leak a sensitive
> kernel information.
> 
> Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
> ---
>  arch/mips/mm/init.c | 49 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
> 
> diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
> index bbb196ad5f26..c338bbd03b2a 100644
> --- a/arch/mips/mm/init.c
> +++ b/arch/mips/mm/init.c
> @@ -31,6 +31,7 @@
>  #include <linux/gfp.h>
>  #include <linux/kcore.h>
>  #include <linux/initrd.h>
> +#include <linux/sizes.h>
>  
>  #include <asm/bootinfo.h>
>  #include <asm/cachectl.h>
> @@ -56,6 +57,53 @@ unsigned long empty_zero_page, zero_page_mask;
>  EXPORT_SYMBOL_GPL(empty_zero_page);
>  EXPORT_SYMBOL(zero_page_mask);
>  
> +/*
> + * Print out the kernel virtual memory layout
> + */
> +#define MLK(b, t) (void *)b, (void *)t, ((t) - (b)) >> 10
> +#define MLM(b, t) (void *)b, (void *)t, ((t) - (b)) >> 20
> +#define MLK_ROUNDUP(b, t) (void *)b, (void *)t, DIV_ROUND_UP(((t) - (b)), SZ_1K)
> +static void __init mem_print_kmap_info(void)
> +{
> +#ifdef CONFIG_DEBUG_KERNEL

Maybe CONFIG_DEBUG_VM?

> +	pr_notice("Kernel virtual memory layout:\n"
> +		  "    lowmem  : 0x%px - 0x%px  (%4ld MB)\n"
> +		  "      .text : 0x%px - 0x%px  (%4td kB)\n"
> +		  "      .data : 0x%px - 0x%px  (%4td kB)\n"
> +		  "      .init : 0x%px - 0x%px  (%4td kB)\n"
> +		  "      .bss  : 0x%px - 0x%px  (%4td kB)\n"
> +		  "    vmalloc : 0x%px - 0x%px  (%4ld MB)\n"
> +#ifdef CONFIG_HIGHMEM
> +		  "    pkmap   : 0x%px - 0x%px  (%4ld MB)\n"
> +#endif
> +		  "    fixmap  : 0x%px - 0x%px  (%4ld kB)\n",
> +		  MLM(PAGE_OFFSET, (unsigned long)high_memory),
> +		  MLK_ROUNDUP(_text, _etext),
> +		  MLK_ROUNDUP(_sdata, _edata),
> +		  MLK_ROUNDUP(__init_begin, __init_end),
> +		  MLK_ROUNDUP(__bss_start, __bss_stop),
> +		  MLM(VMALLOC_START, VMALLOC_END),
> +#ifdef CONFIG_HIGHMEM
> +		  MLM(PKMAP_BASE, (PKMAP_BASE) + (LAST_PKMAP)*(PAGE_SIZE)),
> +#endif
> +		  MLK(FIXADDR_START, FIXADDR_TOP));
> +
> +	/* Check some fundamental inconsistencies. May add something else? */
> +#ifdef CONFIG_HIGHMEM
> +	BUILD_BUG_ON(VMALLOC_END < PAGE_OFFSET);
> +	BUG_ON(VMALLOC_END < (unsigned long)high_memory);
> +	BUILD_BUG_ON((PKMAP_BASE) + (LAST_PKMAP)*(PAGE_SIZE) < PAGE_OFFSET);
> +	BUG_ON((PKMAP_BASE) + (LAST_PKMAP)*(PAGE_SIZE) <
> +		(unsigned long)high_memory);
> +#endif
> +	BUILD_BUG_ON(FIXADDR_TOP < PAGE_OFFSET);
> +	BUG_ON(FIXADDR_TOP < (unsigned long)high_memory);
> +#endif /* CONFIG_DEBUG_KERNEL */
> +}
> +#undef MLK
> +#undef MLM
> +#undef MLK_ROUNDUP
> +
>  /*
>   * Not static inline because used by IP27 special magic initialization code
>   */
> @@ -479,6 +527,7 @@ void __init mem_init(void)
>  	setup_zero_pages();	/* Setup zeroed pages.  */
>  	mem_init_free_highmem();
>  	mem_init_print_info(NULL);
> +	mem_print_kmap_info();
>  
>  #ifdef CONFIG_64BIT
>  	if ((unsigned long) &_text > (unsigned long) CKSEG0)
> -- 
> 2.21.0
> 

-- 
Sincerely yours,
Mike.