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x86/boot: Introduce setup_indirect

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The setup_data is a bit awkward to use for extremely large data objects,
both because the setup_data header has to be adjacent to the data object
and because it has a 32-bit length field. However, it is important that
intermediate stages of the boot process have a way to identify which
chunks of memory are occupied by kernel data. Thus introduce an uniform
way to specify such indirect data as setup_indirect struct and
SETUP_INDIRECT type.

And finally bump setup_header version in arch/x86/boot/header.S.

Suggested-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
Reviewed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: ard.biesheuvel@linaro.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: dave.hansen@linux.intel.com
Cc: eric.snowberg@oracle.com
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Juergen Gross <jgross@suse.com>
Cc: kanth.ghatraju@oracle.com
Cc: linux-doc@vger.kernel.org
Cc: linux-efi <linux-efi@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: rdunlap@infradead.org
Cc: ross.philipson@oracle.com
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Cc: xen-devel@lists.xenproject.org
Link: https://lkml.kernel.org/r/20191112134640.16035-4-daniel.kiper@oracle.com
This commit is contained in:
Daniel Kiper
2019-11-12 14:46:40 +01:00
committed by Borislav Petkov
parent 00cd1c154d
commit b3c72fc9a7
10 changed files with 138 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
Documentation/x86/boot.rst
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@@ -827,6 +827,47 @@ Protocol: 2.09+
sure to consider the case where the linked list already contains
entries.
The setup_data is a bit awkward to use for extremely large data objects,
both because the setup_data header has to be adjacent to the data object
and because it has a 32-bit length field. However, it is important that
intermediate stages of the boot process have a way to identify which
chunks of memory are occupied by kernel data.
Thus setup_indirect struct and SETUP_INDIRECT type were introduced in
protocol 2.15.
struct setup_indirect {
__u32 type;
__u32 reserved; /* Reserved, must be set to zero. */
__u64 len;
__u64 addr;
};
The type member is a SETUP_INDIRECT | SETUP_* type. However, it cannot be
SETUP_INDIRECT itself since making the setup_indirect a tree structure
could require a lot of stack space in something that needs to parse it
and stack space can be limited in boot contexts.
Let's give an example how to point to SETUP_E820_EXT data using setup_indirect.
In this case setup_data and setup_indirect will look like this:
struct setup_data {
__u64 next = 0 or <addr_of_next_setup_data_struct>;
__u32 type = SETUP_INDIRECT;
__u32 len = sizeof(setup_data);
__u8 data[sizeof(setup_indirect)] = struct setup_indirect {
__u32 type = SETUP_INDIRECT | SETUP_E820_EXT;
__u32 reserved = 0;
__u64 len = <len_of_SETUP_E820_EXT_data>;
__u64 addr = <addr_of_SETUP_E820_EXT_data>;
}
}
.. note::
SETUP_INDIRECT | SETUP_NONE objects cannot be properly distinguished
from SETUP_INDIRECT itself. So, this kind of objects cannot be provided
by the bootloaders.
============ ============
Field name: pref_address
Type: read (reloc)
@@ -986,7 +1027,7 @@ Field name: setup_type_max
Offset/size: 0x000c/4
============ ==============
This field contains maximal allowed type for setup_data.
This field contains maximal allowed type for setup_data and setup_indirect structs.
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