linux-kernel - Re: [PATCH v7 1/8] efi: Export boot-services code and data as debugfs-blobs

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Message-ID: <20191014091133.GY16384@42.do-not-panic.com>
Date:   Mon, 14 Oct 2019 09:11:33 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Jonathan Corbet <corbet@....net>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Peter Jones <pjones@...hat.com>,
        Dave Olsthoorn <dave@...aar.me>, x86@...nel.org,
        platform-driver-x86@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-input@...r.kernel.org
Subject: Re: [PATCH v7 1/8] efi: Export boot-services code and data as
 debugfs-blobs

On Fri, Oct 04, 2019 at 04:50:49PM +0200, Hans de Goede wrote:
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 8d3e778e988b..abba49c4c46d 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -314,6 +315,55 @@ static __init int efivar_ssdt_load(void)
>  static inline int efivar_ssdt_load(void) { return 0; }
>  #endif
>  
> +#ifdef CONFIG_DEBUG_FS
> +
> +#define EFI_DEBUGFS_MAX_BLOBS 32
> +
> +static struct debugfs_blob_wrapper debugfs_blob[EFI_DEBUGFS_MAX_BLOBS];
> +
> +static void __init efi_debugfs_init(void)
> +{
> +	struct dentry *efi_debugfs;
> +	efi_memory_desc_t *md;
> +	char name[32];
> +	int type_count[EFI_BOOT_SERVICES_DATA + 1] = {};
> +	int i = 0;
> +
> +	efi_debugfs = debugfs_create_dir("efi", NULL);
> +	if (IS_ERR_OR_NULL(efi_debugfs))
> +		return;
> +
> +	for_each_efi_memory_desc(md) {
> +		switch (md->type) {
> +		case EFI_BOOT_SERVICES_CODE:
> +			snprintf(name, sizeof(name), "boot_services_code%d",
> +				 type_count[md->type]++);
> +			break;
> +		case EFI_BOOT_SERVICES_DATA:
> +			snprintf(name, sizeof(name), "boot_services_data%d",
> +				 type_count[md->type]++);
> +			break;
> +		default:
> +			continue;
> +		}
> +
> +		debugfs_blob[i].size = md->num_pages << EFI_PAGE_SHIFT;
> +		debugfs_blob[i].data = memremap(md->phys_addr,
> +						debugfs_blob[i].size,
> +						MEMREMAP_WB);
> +		if (!debugfs_blob[i].data)
> +			continue;
> +
> +		debugfs_create_blob(name, 0400, efi_debugfs, &debugfs_blob[i]);
> +		i++;
> +		if (i == EFI_DEBUGFS_MAX_BLOBS)
> +			break;

Why do we silently ignore more entries ? And could documentation be
added for ways in which this could be used in practice?

  Luis