Linux 中的 ATA 可信命令

Question

同事，

我正在实现对 ATA 可信命令的支持

0x5C, TRUSTED RECEIVE, 
0x5D, TRUSTED RECEIVE DMA, 
0x5E, TRUSTED SEND
0x5F, TRUSTED SEND DMA, 

用于 Linux（两台主机，Fedora 12 和 14）以支持自加密驱动器。我从这个页面http://www.jukie.net/bart/blog/ata-via-scsi中获取了一个代码作为基本代码。对于可信接收（在这一层，它与 IDENTIFY, 0xEC 相同）：

sg_io.interface_id    = 'S';
sg_io.cmdp            = cdb;
sg_io.cmd_len         = sizeof(cdb);
sg_io.dxferp          = data_in_buffer;
sg_io.dxfer_len       = data_in_length;         // multiple of 512
sg_io.dxfer_direction = SG_DXFER_FROM_DEV;
sg_io.sbp             = sense;
sg_io.mx_sb_len       = sizeof(sense);
sg_io.timeout         = 5000;                   // 5 seconds


cdb[0] = 0x85;           // pass-through ATA16 command (no translation)
cdb[1] = (4 << 1);       // data-in
cdb[2] = 0x2e;           // data-in
cdb[4] = feature_id;     // ATA feature ID
cdb[6] = 1;              // number of sectors
cdb[7] = lba_low >> 8;
cdb[8] = lba_low;
cdb[9] = lba_mid >> 8;
cdb[10] = lba_mid;
cdb[11] = lba_high >> 8;
cdb[12] = lba_high;
cdb[14] = 0x5C;           // TRUSTED RECEIVE

rc = ioctl (fd, SG_IO, &sg_io);

它非常适用于识别和所有其他命令，但不适用于受信任的命令。当我连接协议分析器时，我看到这些命令没有发送到 SATA 总线。适配器能够发送它们，因为它们在 Windows 下运行正常（不是我的代码，但我认为使用 ATA_PASS_THROUGH）。是的，我以 root 身份运行此代码。

请帮助解开这个谜:)

Answer 1

见/usr/src/linux/drivers/ata/libata-scsi.c：

/*
 * Filter TPM commands by default. These provide an
 * essentially uncontrolled encrypted "back door" between
 * applications and the disk. Set libata.allow_tpm=1 if you
 * have a real reason for wanting to use them. This ensures
 * that installed software cannot easily mess stuff up without
 * user intent. DVR type users will probably ship with this enabled
 * for movie content management.
 *
 * Note that for ATA8 we can issue a DCS change and DCS freeze lock
 * for this and should do in future but that it is not sufficient as
 * DCS is an optional feature set. Thus we also do the software filter
 * so that we comply with the TC consortium stated goal that the user
 * can turn off TC features of their system.
 */
if (tf->command >= 0x5C && tf->command <= 0x5F && !libata_allow_tpm)
        goto invalid_fld;