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riscv: libstub: Implement KASLR by using generic functions

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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: Alexandre Ghiti <alexghiti@rivosinc.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Song Shuai <songshuaishuai@tinylab.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20230722123850.634544-6-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Alexandre Ghiti 2023-07-22 14:38:50 +02:00 committed by Palmer Dabbelt
parent 3c35d1a03c
commit b7ac4b8ee7
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
4 changed files with 19 additions and 19 deletions
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2
arch/riscv/include/asm/efi.h
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@ -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 */

1
arch/riscv/kernel/image-vars.h
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@ -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

2
drivers/firmware/efi/libstub/Makefile
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@ -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)

33
drivers/firmware/efi/libstub/riscv-stub.c
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@ -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");
}