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kernel: add CONFIG_SRAM_OFFSET

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This adds a new kconfig CONFIG_SRAM_OFFSET to specify the offset
from beginning of SRAM where the kernel begins. On x86 and
PC compatible platforms, the first 1MB of RAM is reserved and
Zephyr should not link anything there. However, this 1MB still
needs to be mapped by the MMU to access various platform related
information. CONFIG_SRAM_OFFSET serves similar function as
CONFIG_KERNEL_VM_OFFSET and is needed for proper phys/virt
address translations.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This commit is contained in:
Daniel Leung 2021-02-20 11:02:17 -08:00 committed by Anas Nashif
parent ec21c0b92f
commit ece9cad858
4 changed files with 19 additions and 3 deletions
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16
Kconfig.zephyr
View file

@ -167,6 +167,22 @@ config LINKER_SORT_BY_ALIGNMENT
in decreasing size of symbols. This helps to minimize
padding between symbols.
config HAS_SRAM_OFFSET
bool
help
This option is selected by targets that require SRAM_OFFSET.
config SRAM_OFFSET
hex "Kernel SRAM offset" if HAS_SRAM_OFFSET
default 0
help
This option specifies the byte offset from the beginning of SRAM
where the kernel begins. Changing this value from zero will affect
the Zephyr image's link, and will decrease the total amount of
SRAM available for use by application code.
If unsure, leave at the default value 0.
endmenu
menu "Compiler Options"

2
arch/Kconfig
View file

@ -608,7 +608,7 @@ config KERNEL_VM_OFFSET
in page tables, the equation:
virt = phys + ((KERNEL_VM_BASE + KERNEL_VM_OFFSET) -
SRAM_BASE_ADDRESS)
(SRAM_BASE_ADDRESS + SRAM_OFFSET))
Will be used to convert between physical and virtual addresses for
memory that is mapped at boot.

2
arch/x86/include/x86_mmu.h
View file

@ -82,7 +82,7 @@
*/
#ifdef CONFIG_MMU
#define Z_X86_VIRT_OFFSET ((CONFIG_KERNEL_VM_BASE + CONFIG_KERNEL_VM_OFFSET) - \
CONFIG_SRAM_BASE_ADDRESS)
(CONFIG_SRAM_BASE_ADDRESS + CONFIG_SRAM_OFFSET))
#else
#define Z_X86_VIRT_OFFSET 0
#endif

2
kernel/include/mmu.h
View file

@ -41,7 +41,7 @@
#define Z_KERNEL_VIRT_SIZE (Z_KERNEL_VIRT_END - Z_KERNEL_VIRT_START)
#define Z_VM_OFFSET ((CONFIG_KERNEL_VM_BASE + CONFIG_KERNEL_VM_OFFSET) - \
CONFIG_SRAM_BASE_ADDRESS)
(CONFIG_SRAM_BASE_ADDRESS + CONFIG_SRAM_OFFSET))
/* Only applies to boot RAM mappings within the Zephyr image that have never
* been remapped or paged out. Never use this unless you know exactly what you