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OpenCloudOS-Kernel/Documentation/x86/zero-page.rst

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Documentation: x86: convert zero-page.txt to reST This converts the plain text documentation to reStructuredText format and add it to Sphinx TOC tree. No essential content change. Signed-off-by: Changbin Du <changbin.du@gmail.com> Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-05-08 23:21:22 +08:00
.. SPDX-License-Identifier: GPL-2.0
=========
Zero Page
=========
The additional fields in struct boot_params as a part of 32-bit boot
protocol of kernel. These should be filled by bootloader or 16-bit
real-mode setup code of the kernel. References/settings to it mainly
are in::
arch/x86/include/uapi/asm/bootparam.h
=========== ===== ======================= =================================================
Offset/Size Proto Name Meaning
000/040 ALL screen_info Text mode or frame buffer information
(struct screen_info)
040/014 ALL apm_bios_info APM BIOS information (struct apm_bios_info)
058/008 ALL tboot_addr Physical address of tboot shared page
060/010 ALL ist_info Intel SpeedStep (IST) BIOS support information
(struct ist_info)
x86/boot: Add a pointer to Confidential Computing blob in bootparams The previously defined Confidential Computing blob is provided to the kernel via a setup_data structure or EFI config table entry. Currently, these are both checked for by boot/compressed kernel to access the CPUID table address within it for use with SEV-SNP CPUID enforcement. To also enable that enforcement for the run-time kernel, similar access to the CPUID table is needed early on while it's still using the identity-mapped page table set up by boot/compressed, where global pointers need to be accessed via fixup_pointer(). This isn't much of an issue for accessing setup_data, and the EFI config table helper code currently used in boot/compressed *could* be used in this case as well since they both rely on identity-mapping. However, it has some reliance on EFI helpers/string constants that would need to be accessed via fixup_pointer(), and fixing it up while making it shareable between boot/compressed and run-time kernel is fragile and introduces a good bit of ugliness. Instead, add a boot_params->cc_blob_address pointer that the boot/compressed kernel can initialize so that the run-time kernel can access the CC blob from there instead of re-scanning the EFI config table. Also document these in Documentation/x86/zero-page.rst. While there, add missing documentation for the acpi_rsdp_addr field, which serves a similar purpose in providing the run-time kernel a pointer to the ACPI RSDP table so that it does not need to [re-]scan the EFI configuration table. [ bp: Fix typos, massage commit message. ] Signed-off-by: Michael Roth <michael.roth@amd.com> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lore.kernel.org/r/20220307213356.2797205-34-brijesh.singh@amd.com
2022-02-25 00:56:13 +08:00
070/008 ALL acpi_rsdp_addr Physical address of ACPI RSDP table
Documentation: x86: convert zero-page.txt to reST This converts the plain text documentation to reStructuredText format and add it to Sphinx TOC tree. No essential content change. Signed-off-by: Changbin Du <changbin.du@gmail.com> Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-05-08 23:21:22 +08:00
080/010 ALL hd0_info hd0 disk parameter, OBSOLETE!!
090/010 ALL hd1_info hd1 disk parameter, OBSOLETE!!
0A0/010 ALL sys_desc_table System description table (struct sys_desc_table),
OBSOLETE!!
0B0/010 ALL olpc_ofw_header OLPC's OpenFirmware CIF and friends
0C0/004 ALL ext_ramdisk_image ramdisk_image high 32bits
0C4/004 ALL ext_ramdisk_size ramdisk_size high 32bits
0C8/004 ALL ext_cmd_line_ptr cmd_line_ptr high 32bits
x86/boot: Add a pointer to Confidential Computing blob in bootparams The previously defined Confidential Computing blob is provided to the kernel via a setup_data structure or EFI config table entry. Currently, these are both checked for by boot/compressed kernel to access the CPUID table address within it for use with SEV-SNP CPUID enforcement. To also enable that enforcement for the run-time kernel, similar access to the CPUID table is needed early on while it's still using the identity-mapped page table set up by boot/compressed, where global pointers need to be accessed via fixup_pointer(). This isn't much of an issue for accessing setup_data, and the EFI config table helper code currently used in boot/compressed *could* be used in this case as well since they both rely on identity-mapping. However, it has some reliance on EFI helpers/string constants that would need to be accessed via fixup_pointer(), and fixing it up while making it shareable between boot/compressed and run-time kernel is fragile and introduces a good bit of ugliness. Instead, add a boot_params->cc_blob_address pointer that the boot/compressed kernel can initialize so that the run-time kernel can access the CC blob from there instead of re-scanning the EFI config table. Also document these in Documentation/x86/zero-page.rst. While there, add missing documentation for the acpi_rsdp_addr field, which serves a similar purpose in providing the run-time kernel a pointer to the ACPI RSDP table so that it does not need to [re-]scan the EFI configuration table. [ bp: Fix typos, massage commit message. ] Signed-off-by: Michael Roth <michael.roth@amd.com> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lore.kernel.org/r/20220307213356.2797205-34-brijesh.singh@amd.com
2022-02-25 00:56:13 +08:00
13C/004 ALL cc_blob_address Physical address of Confidential Computing blob
Documentation: x86: convert zero-page.txt to reST This converts the plain text documentation to reStructuredText format and add it to Sphinx TOC tree. No essential content change. Signed-off-by: Changbin Du <changbin.du@gmail.com> Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-05-08 23:21:22 +08:00
140/080 ALL edid_info Video mode setup (struct edid_info)
1C0/020 ALL efi_info EFI 32 information (struct efi_info)
1E0/004 ALL alt_mem_k Alternative mem check, in KB
1E4/004 ALL scratch Scratch field for the kernel setup code
1E8/001 ALL e820_entries Number of entries in e820_table (below)
1E9/001 ALL eddbuf_entries Number of entries in eddbuf (below)
1EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer
(below)
1EB/001 ALL kbd_status Numlock is enabled
1EC/001 ALL secure_boot Secure boot is enabled in the firmware
1EF/001 ALL sentinel Used to detect broken bootloaders
290/040 ALL edd_mbr_sig_buffer EDD MBR signatures
2D0/A00 ALL e820_table E820 memory map table
(array of struct e820_entry)
D00/1EC ALL eddbuf EDD data (array of struct edd_info)
=========== ===== ======================= =================================================