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x86, doc: Adding comments about .iommu_table and its neighbors.

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Updating the linker section with comments about .iommu_table and
some other ones that I know of.

CC: Sam Ravnborg <sam@ravnborg.org>
CC: H. Peter Anvin <hpa@zytor.com>
CC: Fujita Tomonori <fujita.tomonori@lab.ntt.co.jp>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
LKML-Reference: <1282933173-19960-1-git-send-email-konrad.wilk@oracle.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2010-08-27 14:19:33 -04:00 committed by H. Peter Anvin
parent ee1f284f38
commit 6f44d0337c
1 changed files with 22 additions and 0 deletions
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22
arch/x86/kernel/vmlinux.lds.S
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@ -242,6 +242,12 @@ SECTIONS
__x86_cpu_dev_end = .; __x86_cpu_dev_end = .;
} }
/*
* start address and size of operations which during runtime
* can be patched with virtualization friendly instructions or
* baremetal native ones. Think page table operations.
* Details in paravirt_types.h
*/
. = ALIGN(8); . = ALIGN(8);
.parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) { .parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) {
__parainstructions = .; __parainstructions = .;
@ -249,6 +255,11 @@ SECTIONS
__parainstructions_end = .; __parainstructions_end = .;
} }
/*
* struct alt_inst entries. From the header (alternative.h):
* "Alternative instructions for different CPU types or capabilities"
* Think locking instructions on spinlocks.
*/
. = ALIGN(8); . = ALIGN(8);
.altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) { .altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
__alt_instructions = .; __alt_instructions = .;
@ -256,10 +267,21 @@ SECTIONS
__alt_instructions_end = .; __alt_instructions_end = .;
} }
/*
* And here are the replacement instructions. The linker sticks
* them as binary blobs. The .altinstructions has enough data to
* get the address and the length of them to patch the kernel safely.
*/
.altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) { .altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) {
*(.altinstr_replacement) *(.altinstr_replacement)
} }
/*
* struct iommu_table_entry entries are injected in this section.
* It is an array of IOMMUs which during run time gets sorted depending
* on its dependency order. After rootfs_initcall is complete
* this section can be safely removed.
*/
.iommu_table : AT(ADDR(.iommu_table) - LOAD_OFFSET) { .iommu_table : AT(ADDR(.iommu_table) - LOAD_OFFSET) {
__iommu_table = .; __iommu_table = .;
*(.iommu_table) *(.iommu_table)