RISC-V: enable XIP
Introduce XIP (eXecute In Place) support for RISC-V platforms.
It allows code to be executed directly from non-volatile storage
directly addressable by the CPU, such as QSPI NOR flash which can
be found on many RISC-V platforms. This makes way for significant
optimization of RAM footprint. The XIP kernel is not compressed
since it has to run directly from flash, so it will occupy more
space on the non-volatile storage. The physical flash address used
to link the kernel object files and for storing it has to be known
at compile time and is represented by a Kconfig option.
XIP on RISC-V will for the time being only work on MMU-enabled
kernels.
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
[Alex: Rebase on top of "Move kernel mapping outside the linear mapping" ]
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
[Palmer: disable XIP for allyesconfig]
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 61514e0..6ddf5a2 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -28,8 +28,8 @@
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_SET_DIRECT_MAP
select ARCH_HAS_SET_MEMORY
- select ARCH_HAS_STRICT_KERNEL_RWX if MMU
- select ARCH_HAS_STRICT_MODULE_RWX if MMU
+ select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
+ select ARCH_HAS_STRICT_MODULE_RWX if MMU && !XIP_KERNEL
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
@@ -468,7 +468,7 @@
config EFI
bool "UEFI runtime support"
- depends on OF
+ depends on OF && !XIP_KERNEL
select LIBFDT
select UCS2_STRING
select EFI_PARAMS_FROM_FDT
@@ -492,11 +492,63 @@
def_bool y
depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS
+config PHYS_RAM_BASE_FIXED
+ bool "Explicitly specified physical RAM address"
+ default n
+
+config PHYS_RAM_BASE
+ hex "Platform Physical RAM address"
+ depends on PHYS_RAM_BASE_FIXED
+ default "0x80000000"
+ help
+ This is the physical address of RAM in the system. It has to be
+ explicitly specified to run early relocations of read-write data
+ from flash to RAM.
+
+config XIP_KERNEL
+ bool "Kernel Execute-In-Place from ROM"
+ depends on MMU && SPARSEMEM
+ # This prevents XIP from being enabled by all{yes,mod}config, which
+ # fail to build since XIP doesn't support large kernels.
+ depends on !COMPILE_TEST
+ select PHYS_RAM_BASE_FIXED
+ help
+ Execute-In-Place allows the kernel to run from non-volatile storage
+ directly addressable by the CPU, such as NOR flash. This saves RAM
+ space since the text section of the kernel is not loaded from flash
+ to RAM. Read-write sections, such as the data section and stack,
+ are still copied to RAM. The XIP kernel is not compressed since
+ it has to run directly from flash, so it will take more space to
+ store it. The flash address used to link the kernel object files,
+ and for storing it, is configuration dependent. Therefore, if you
+ say Y here, you must know the proper physical address where to
+ store the kernel image depending on your own flash memory usage.
+
+ Also note that the make target becomes "make xipImage" rather than
+ "make zImage" or "make Image". The final kernel binary to put in
+ ROM memory will be arch/riscv/boot/xipImage.
+
+ SPARSEMEM is required because the kernel text and rodata that are
+ flash resident are not backed by memmap, then any attempt to get
+ a struct page on those regions will trigger a fault.
+
+ If unsure, say N.
+
+config XIP_PHYS_ADDR
+ hex "XIP Kernel Physical Location"
+ depends on XIP_KERNEL
+ default "0x21000000"
+ help
+ This is the physical address in your flash memory the kernel will
+ be linked for and stored to. This address is dependent on your
+ own flash usage.
+
endmenu
config BUILTIN_DTB
- def_bool n
+ bool
depends on OF
+ default y if XIP_KERNEL
menu "Power management options"