linux-kernel - Re: kexec and struct boot

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Date:	Wed, 12 Dec 2012 18:49:27 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kexec and struct boot_params

On Thu, Dec 6, 2012 at 10:57 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> On Wed, Dec 5, 2012 at 7:12 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>> On Wed, Dec 5, 2012 at 5:57 PM, H. Peter Anvin <hpa@...or.com> wrote:
>>> Hi Eric,
>>>
>>> Could you give a list of struct boot_params field which are initialized
>>> properly by kexec?  I think we need to do the sentinel hack, and want to
>>> know what to whitelist.
>>
>> the one with *
>> ? means set only when lfb_depth > 8
>> also
>>    0xa2 to 0x1df is not set
>>
>> struct x86_linux_param_header {
>>         uint8_t  orig_x;                        /* 0x00 */  *
>>         uint8_t  orig_y;                        /* 0x01 */  *
>>         uint16_t ext_mem_k;                     /* 0x02 -- EXT_MEM_K sits here */   *
>>         uint16_t orig_video_page;               /* 0x04 */  *
>>         uint8_t  orig_video_mode;               /* 0x06 */  *
>>         uint8_t  orig_video_cols;               /* 0x07 */  *
>>         uint16_t unused2;                       /* 0x08 */
>>         uint16_t orig_video_ega_bx;             /* 0x0a */  *
>>         uint16_t unused3;                       /* 0x0c */
>>         uint8_t  orig_video_lines;              /* 0x0e */  *
>>         uint8_t  orig_video_isVGA;              /* 0x0f */   *
>>         uint16_t orig_video_points;             /* 0x10 */   *
>>
>>         /* VESA graphic mode -- linear frame buffer */
>>         uint16_t lfb_width;                     /* 0x12 */   *
>>         uint16_t lfb_height;                    /* 0x14 */   *
>>         uint16_t lfb_depth;                     /* 0x16 */   *
>>         uint32_t lfb_base;                      /* 0x18 */   *
>>         uint32_t lfb_size;                      /* 0x1c */   *
>>         uint16_t cl_magic;                      /* 0x20 */   *
>> #define CL_MAGIC_VALUE 0xA33F
>>         uint16_t cl_offset;                     /* 0x22 */   *
>>         uint16_t lfb_linelength;                /* 0x24 */   *
>>         uint8_t  red_size;                      /* 0x26 */   ?
>>         uint8_t  red_pos;                       /* 0x27 */   ?
>>         uint8_t  green_size;                    /* 0x28 */   ?
>>         uint8_t  green_pos;                     /* 0x29 */   ?
>>         uint8_t  blue_size;                     /* 0x2a */   ?
>>         uint8_t  blue_pos;                      /* 0x2b */   ?
>>         uint8_t  rsvd_size;                     /* 0x2c */   ?
>>         uint8_t  rsvd_pos;                      /* 0x2d */   ?
>>         uint16_t vesapm_seg;                    /* 0x2e */   *
>>         uint16_t vesapm_off;                    /* 0x30 */
>>         uint16_t pages;                         /* 0x32 */   *
>>         uint8_t  reserved4[12];                 /* 0x34 -- 0x3f reserved for future expansion */
>>
>>         struct apm_bios_info apm_bios_info;     /* 0x40 */   *
>>         struct drive_info_struct drive_info;    /* 0x80 */   *
>>         struct sys_desc_table sys_desc_table;   /* 0xa0 */   * only .length =
>> 0, aka 0xa2 to 0x1df is not set
>>         uint32_t alt_mem_k;                     /* 0x1e0 */  *
>>         uint8_t  reserved5[4];                  /* 0x1e4 */
>>         uint8_t  e820_map_nr;                   /* 0x1e8 */  *
>>         uint8_t  eddbuf_entries;                /* 0x1e9 */  *
>>         uint8_t  edd_mbr_sig_buf_entries;       /* 0x1ea */  *
>>         uint8_t  reserved6[6];                  /* 0x1eb */
>>         HEADER.....                                         copied and or meset 0 and set.
>>         uint8_t  reserved16[0x290 - 0x248];     /* 0x248 */
>>         uint32_t edd_mbr_sig_buffer[EDD_MBR_SIG_MAX];   /* 0x290 */  *
>> #endif
>>         struct  e820entry e820_map[E820MAX];    /* 0x2d0 */   *
>>         uint8_t _pad8[48];                      /* 0xcd0 */
>>         struct  edd_info eddbuf[EDDMAXNR];      /* 0xd00 */   *
>>                                                 /* 0xeec */
>> #define COMMAND_LINE_SIZE 2048
>> };
>>
>>
>>>
>>> Also, does kexec set a bootloader ID?
>>
>> no, 0xff
>
> Hi, Peter,
>
> What's your decision about this?
>
> Do you mean have one boot_params mask in initdata and AND that with
> boot_params from bootloader
> to clean not used bytes?
>
> So later will not need to check
>     if (boot_params.hdr.xloadflags & USE_EXT_BOOT_PARAMS)
> ?
>
> I worked out other patches that remove kdump 896M limitation.
> would like to post those patches to get more testing.
> those are needed for bigger system with lots of pcie devices.


ping!
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