[PATCH v2 4/4] riscv: libstub: Implement KASLR by using generic functions

[Alexandre Ghiti]

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 at rivosinc.com>
---
 arch/riscv/kernel/image-vars.h                |  1 +
 drivers/firmware/efi/libstub/arm64.c          |  5 ++++
 .../firmware/efi/libstub/efi-stub-helper.c    |  2 +-
 drivers/firmware/efi/libstub/efistub.h        |  2 ++
 drivers/firmware/efi/libstub/riscv-stub.c     | 28 +++++++------------
 drivers/firmware/efi/libstub/riscv.c          |  5 ++++
 6 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/arch/riscv/kernel/image-vars.h b/arch/riscv/kernel/image-vars.h
index 15616155008c..ea1a10355ce9 100644
--- a/arch/riscv/kernel/image-vars.h
+++ b/arch/riscv/kernel/image-vars.h
@@ -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
diff --git a/drivers/firmware/efi/libstub/arm64.c b/drivers/firmware/efi/libstub/arm64.c
index 399770266372..48bc7428d6df 100644
--- a/drivers/firmware/efi/libstub/arm64.c
+++ b/drivers/firmware/efi/libstub/arm64.c
@@ -108,3 +108,8 @@ void __noreturn efi_enter_kernel(unsigned long entrypoint,
 	enter_kernel = (void *)entrypoint + primary_entry_offset();
 	enter_kernel(fdt_addr, 0, 0, 0);
 }
+
+void efi_icache_sync(unsigned long start, unsigned long end)
+{
+	caches_clean_inval_pou(start, end);
+}
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 40ac2625949c..63c7275d42e7 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -865,7 +865,7 @@ efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
 	memcpy((void *)*reserve_addr, (void *)*image_addr, kernel_size);
 	*image_addr = *reserve_addr;
 
-	caches_clean_inval_pou(*image_addr, *image_addr + kernel_codesize);
+	efi_icache_sync(*image_addr, *image_addr + kernel_codesize);
 
 	return status;
 }
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 64273371ce96..9ce114e04b23 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -1107,4 +1107,6 @@ efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
 				       u32 phys_seed);
 u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle);
 
+void efi_icache_sync(unsigned long start, unsigned long end);
+
 #endif
diff --git a/drivers/firmware/efi/libstub/riscv-stub.c b/drivers/firmware/efi/libstub/riscv-stub.c
index 145c9f0ba217..7af07b33a993 100644
--- a/drivers/firmware/efi/libstub/riscv-stub.c
+++ b/drivers/firmware/efi/libstub/riscv-stub.c
@@ -30,32 +30,24 @@ 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;
 }
diff --git a/drivers/firmware/efi/libstub/riscv.c b/drivers/firmware/efi/libstub/riscv.c
index 8022b104c3e6..365f891e598f 100644
--- a/drivers/firmware/efi/libstub/riscv.c
+++ b/drivers/firmware/efi/libstub/riscv.c
@@ -96,3 +96,8 @@ void __noreturn efi_enter_kernel(unsigned long entrypoint, unsigned long fdt,
 	csr_write(CSR_SATP, 0);
 	jump_kernel(hartid, fdt);
 }
+
+void efi_icache_sync(unsigned long start, unsigned long end)
+{
+	asm volatile ("fence.i" ::: "memory");
+}
-- 
2.37.2