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Message-ID: <f3063c1c-a9c4-336e-2ace-2802f707d3cb@gmail.com>
Date: Wed, 13 Apr 2022 23:26:10 +0200
From: Michael Straube <straube.linux@...il.com>
To: Pavel Skripkin <paskripkin@...il.com>,
Larry Finger <Larry.Finger@...inger.net>
Cc: Phillip Potter <phil@...lpotter.co.uk>,
Greg KH <gregkh@...uxfoundation.org>,
"open list:STAGING SUBSYSTEM" <linux-staging@...ts.linux.dev>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: staging: r8188eu: struct rt_firmware_header issues
On 4/13/22 22:58, Pavel Skripkin wrote:
> Hi Michael,
>
> On 4/13/22 19:27, Michael Straube wrote:
>> Hi all,
>>
>> I think the rt_firmware_hdr structure in rtw_fw.c has some issues.
>>
>>
>> struct rt_firmware_hdr {
>> /* 8-byte alinment required */
>> /* LONG WORD 0 ---- */
>> __le16 Signature; /* 92C0: test chip; 92C,
>> * 88C0: test chip; 88C1: MP A-cut;
>> * 92C1: MP A-cut */
>> u8 Category; /* AP/NIC and USB/PCI */
>> u8 Function; /* Reserved for different FW function
>> * indcation, for further use when
>> * driver needs to download different
>> * FW for different conditions */
>> __le16 Version; /* FW Version */
>> u8 Subversion; /* FW Subversion, default 0x00 */
>> u16 Rsvd1;
>>
>> /* LONG WORD 1 ---- */
>> u8 Month; /* Release time Month field */
>> u8 Date; /* Release time Date field */
>> u8 Hour; /* Release time Hour field */
>> u8 Minute; /* Release time Minute field */
>> __le16 RamCodeSize; /* The size of RAM code */
>> u8 Foundry;
>> u8 Rsvd2;
>>
>> /* LONG WORD 2 ---- */
>> __le32 SvnIdx; /* The SVN entry index */
>> u32 Rsvd3;
>>
>> /* LONG WORD 3 ---- */
>> u32 Rsvd4;
>> u32 Rsvd5;
>> };
>>
>>
>> Then we have in rtl8188e_firmware_download():
>>
>>
>> fwhdr = (struct rt_firmware_hdr *)dvobj->firmware.data;
>>
>> <snip>
>>
>> if (IS_FW_HEADER_EXIST(fwhdr)) {
>> /* Shift 32 bytes for FW header */
>> fw_data = fw_data + 32;
>> fw_size = fw_size - 32;
>> }
>>
>> We add/sub 32 bytes but the size of struct rt_firmware_hdr is actually
>> 33 bytes. I noticed this when I wanted to replace:
>>
>
> Looks like size of that structure is 36
>
> └──$ pahole -C rt_firmware_hdr r8188eu.ko
> struct rt_firmware_hdr {
> __le16 Signature; /* 0 2 */
> u8 Category; /* 2 1 */
> u8 Function; /* 3 1 */
> __le16 Version; /* 4 2 */
> u8 Subversion; /* 6 1 */
>
> /* XXX 1 byte hole, try to pack */
>
> u16 Rsvd1; /* 8 2 */
> u8 Month; /* 10 1 */
> u8 Date; /* 11 1 */
> u8 Hour; /* 12 1 */
> u8 Minute; /* 13 1 */
> __le16 RamCodeSize; /* 14 2 */
> u8 Foundry; /* 16 1 */
> u8 Rsvd2; /* 17 1 */
>
> /* XXX 2 bytes hole, try to pack */
>
> __le32 SvnIdx; /* 20 4 */
> u32 Rsvd3; /* 24 4 */
> u32 Rsvd4; /* 28 4 */
> u32 Rsvd5; /* 32 4 */
>
> /* size: 36, cachelines: 1, members: 17 */
> /* sum members: 33, holes: 2, sum holes: 3 */
> /* last cacheline: 36 bytes */
> };
>
>
> And these comments like 'LONG WORD 1' looks misleading, maybe worth
> removing.
>
>
>> fw_data = fw_data + 32;
>> fw_size = fw_size - 32;
>>
>> with:
>> fw_data = fw_data + sizeof(struct rt_firmware_hdr);
>> fw_size = fw_size - sizeof(struct rt_firmware_hdr);;
>>
>> To me it looks add/sub 32 is correct here but the struct is
>> wrong. I don't know if the firmware for this driver is so much different
>> from firmware for the drivers in drivers/net/wireless/realtek/rtlwifi.
>> They use a struct of size 32.
>>
>
> I am not sure about 32... Why non-packed structures are passed via
> wires? Maybe `__packed` is missing? Is realtek fw open-source?
>
> Just thoughts.
>
>> Also, souldn't the u16 and u32 variables in the struct be __le16 and
>> __le32 ?
>>
>> I wonder if we can just use the rtlwifi_firmware_header structure from
>> drivers/net/wireless/realtek/rtlwifi/wifi.h ?
>>
>
> We _should_ use it, since its size is indeed 32 bytes.
>
> └──$ pahole -s vmlinux | rg rtlwifi_firmware_header
> rtlwifi_firmware_header 32 0
>
>
> Looks like you have found a real bug
>
>
Hi Pavel,
I looked at the hexdump of rtl8188eufw.bin and compared it with
rtl8188efw.bin and rtlwifi_firmware_header.
The comparsion showed that Rsvd1 should be u8 instead of u16:
OFFSET rtl8188eufw.bin
-----------------------------------------------------------
0x00000000 E1 88 10 00 0B 00 01 00 01 21 11 27 30
36 00 00
^ ^ ^ ^ ^ ^
Subversion Rsvd1 Month Date Hour Minute
So rt_firmware_hdr is wrong, but it had no effect because 32 is
hardcoded here:
/* Shift 32 bytes for FW header */
fw_data = fw_data + 32;
fw_size = fw_size - 32;
and all fields after Subversion are not used.
regards,
Michael
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