Unverified Commit b7ac4b8e authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Palmer Dabbelt
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riscv: libstub: Implement KASLR by using generic functions 



We can now use arm64 functions to handle the move of the kernel physical
mapping: if KASLR is enabled, we will try to get a random seed from the
firmware, if not possible, the kernel will be moved to a location that
suits its alignment constraints.

Signed-off-by: default avatarAlexandre Ghiti <alexghiti@rivosinc.com>
Tested-by: default avatarConor Dooley <conor.dooley@microchip.com>
Tested-by: default avatarSong Shuai <songshuaishuai@tinylab.org>
Reviewed-by: default avatarSami Tolvanen <samitolvanen@google.com>
Tested-by: default avatarSami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20230722123850.634544-6-alexghiti@rivosinc.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 3c35d1a0

arch/riscv/include/asm/efi.h

+2 −0
Original line number Diff line number Diff line
@@ -51,4 +51,6 @@ void efi_virtmap_unload(void); 


unsigned long stext_offset(void);



void efi_icache_sync(unsigned long start, unsigned long end);



#endif /* _ASM_EFI_H */

arch/riscv/kernel/image-vars.h

+1 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ __efistub__start = _start; 
__efistub__start_kernel		= _start_kernel;

__efistub__end			= _end;

__efistub__edata		= _edata;

__efistub___init_text_end	= __init_text_end;

__efistub_screen_info		= screen_info;



#endif

drivers/firmware/efi/libstub/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -88,7 +88,7 @@ lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \ 
lib-$(CONFIG_ARM)		+= arm32-stub.o

lib-$(CONFIG_ARM64)		+= kaslr.o arm64.o arm64-stub.o smbios.o

lib-$(CONFIG_X86)		+= x86-stub.o

lib-$(CONFIG_RISCV)		+= riscv.o riscv-stub.o

lib-$(CONFIG_RISCV)		+= kaslr.o riscv.o riscv-stub.o

lib-$(CONFIG_LOONGARCH)		+= loongarch.o loongarch-stub.o



CFLAGS_arm32-stub.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)

drivers/firmware/efi/libstub/riscv-stub.c

+15 −18
Original line number Diff line number Diff line
@@ -30,32 +30,29 @@ efi_status_t handle_kernel_image(unsigned long *image_addr, 
				 efi_loaded_image_t *image,

				 efi_handle_t image_handle)

{

	unsigned long kernel_size = 0;

	unsigned long preferred_addr;

	unsigned long kernel_size, kernel_codesize, kernel_memsize;

	efi_status_t status;



	kernel_size = _edata - _start;

	kernel_codesize = __init_text_end - _start;

	kernel_memsize = kernel_size + (_end - _edata);

	*image_addr = (unsigned long)_start;

	*image_size = kernel_size + (_end - _edata);



	/*

	 * RISC-V kernel maps PAGE_OFFSET virtual address to the same physical

	 * address where kernel is booted. That's why kernel should boot from

	 * as low as possible to avoid wastage of memory. Currently, dram_base

	 * is occupied by the firmware. So the preferred address for kernel to

	 * boot is next aligned address. If preferred address is not available,

	 * relocate_kernel will fall back to efi_low_alloc_above to allocate

	 * lowest possible memory region as long as the address and size meets

	 * the alignment constraints.

	 */

	preferred_addr = EFI_KIMG_PREFERRED_ADDRESS;

	status = efi_relocate_kernel(image_addr, kernel_size, *image_size,

				     preferred_addr, efi_get_kimg_min_align(),

				     0x0);

	*image_size = kernel_memsize;

	*reserve_size = *image_size;



	status = efi_kaslr_relocate_kernel(image_addr,

					   reserve_addr, reserve_size,

					   kernel_size, kernel_codesize, kernel_memsize,

					   efi_kaslr_get_phys_seed(image_handle));

	if (status != EFI_SUCCESS) {

		efi_err("Failed to relocate kernel\n");

		*image_size = 0;

	}



	return status;

}



void efi_icache_sync(unsigned long start, unsigned long end)

{

	asm volatile ("fence.i" ::: "memory");

}