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x86: add CONFIG_X86_KERNEL_OFFSET

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Previously, DTS specification of physical RAM bounds did not
correspond to the actual bounds of system RAM as the first
megabyte was being skipped.

There were reasons for this - the first 1MB on PC-like systems
is a no-man's-land of reserved memory regions, but we need DTS
to accurately capture physical memory bounds.

Instead, we introduce a config option which can apply an offset
to the beginning of physical memory, and apply this to the "RAM"
region defined in the linker scripts.

This also fixes a problem where an extra megabyte was being
added to the size of system RAM.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
This commit is contained in:
Andrew Boie 2020-06-17 12:20:17 -07:00 • committed by Carles Cufí
commit 87dd0492db
9 changed files with 38 additions and 15 deletions
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4
include/arch/x86/ia32/linker.ld
View file

@ -340,11 +340,11 @@ SECTIONS
__data_ram_end = .;
/* All unused memory also owned by the kernel for heaps */
__kernel_ram_end = PHYS_RAM_ADDR + PHYS_RAM_SIZE;
__kernel_ram_end = KERNEL_BASE_ADDR + KERNEL_RAM_SIZE;
__kernel_ram_size = __kernel_ram_end - __kernel_ram_start;
_image_ram_end = .;
_image_ram_all = (PHYS_RAM_ADDR + PHYS_RAM_SIZE) - _image_ram_start;
_image_ram_all = (KERNEL_BASE_ADDR + KERNEL_RAM_SIZE) - _image_ram_start;
_end = .; /* end of image */

2
include/arch/x86/intel64/linker.ld
View file

@ -180,7 +180,7 @@ SECTIONS
_end = .;
/* All unused memory also owned by the kernel for heaps */
__kernel_ram_end = PHYS_RAM_ADDR + PHYS_RAM_SIZE;
__kernel_ram_end = KERNEL_BASE_ADDR + KERNEL_RAM_SIZE;
__kernel_ram_size = __kernel_ram_end - __kernel_ram_start;
#include <linker/debug-sections.ld>