From 04a6a8eb1375c1c1f3a735c5715854ce8a3f3730 Mon Sep 17 00:00:00 2001 From: Song Shuai Date: Thu, 7 Sep 2023 18:33:02 +0800 Subject: [PATCH 1/3] riscv: kexec: Cleanup riscv_kexec_relocate For readability and simplicity, cleanup the riscv_kexec_relocate code: - Re-sort the first 4 `mv` instructions against `riscv_kexec_method()` - Eliminate registers for debugging (s9,s10,s11) and storing const-value (s5,s6) - Replace `jalr` with `jr` for no-link jump I tested this on Qemu virt machine and works as it was. Signed-off-by: Song Shuai Link: https://lore.kernel.org/r/20230907103304.590739-2-songshuaishuai@tinylab.org Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/kexec_relocate.S | 52 +++++++++++++----------------- 1 file changed, 23 insertions(+), 29 deletions(-) diff --git a/arch/riscv/kernel/kexec_relocate.S b/arch/riscv/kernel/kexec_relocate.S index 059c5e216ae7..de0a4b35d01e 100644 --- a/arch/riscv/kernel/kexec_relocate.S +++ b/arch/riscv/kernel/kexec_relocate.S @@ -17,27 +17,17 @@ SYM_CODE_START(riscv_kexec_relocate) * s1: (const) Phys address to jump to after relocation * s2: (const) Phys address of the FDT image * s3: (const) The hartid of the current hart - * s4: Pointer to the destination address for the relocation - * s5: (const) Number of words per page - * s6: (const) 1, used for subtraction - * s7: (const) kernel_map.va_pa_offset, used when switching MMU off - * s8: (const) Physical address of the main loop - * s9: (debug) indirection page counter - * s10: (debug) entry counter - * s11: (debug) copied words counter + * s4: (const) kernel_map.va_pa_offset, used when switching MMU off + * s5: Pointer to the destination address for the relocation + * s6: (const) Physical address of the main loop */ mv s0, a0 mv s1, a1 mv s2, a2 mv s3, a3 - mv s4, zero - li s5, (PAGE_SIZE / RISCV_SZPTR) - li s6, 1 - mv s7, a4 - mv s8, zero - mv s9, zero - mv s10, zero - mv s11, zero + mv s4, a4 + mv s5, zero + mv s6, zero /* Disable / cleanup interrupts */ csrw CSR_SIE, zero @@ -52,21 +42,27 @@ SYM_CODE_START(riscv_kexec_relocate) * the start of the loop below so that we jump there in * any case. */ - la s8, 1f - sub s8, s8, s7 - csrw CSR_STVEC, s8 + la s6, 1f + sub s6, s6, s4 + csrw CSR_STVEC, s6 + + /* + * With C-extension, here we get 42 Bytes and the next + * .align directive would pad zeros here up to 44 Bytes. + * So manually put a nop here to avoid zeros padding. + */ + nop /* Process entries in a loop */ .align 2 1: - addi s10, s10, 1 REG_L t0, 0(s0) /* t0 = *image->entry */ addi s0, s0, RISCV_SZPTR /* image->entry++ */ /* IND_DESTINATION entry ? -> save destination address */ andi t1, t0, 0x1 beqz t1, 2f - andi s4, t0, ~0x1 + andi s5, t0, ~0x1 j 1b 2: @@ -74,9 +70,8 @@ SYM_CODE_START(riscv_kexec_relocate) andi t1, t0, 0x2 beqz t1, 2f andi s0, t0, ~0x2 - addi s9, s9, 1 csrw CSR_SATP, zero - jalr zero, s8, 0 + jr s6 2: /* IND_DONE entry ? -> jump to done label */ @@ -92,14 +87,13 @@ SYM_CODE_START(riscv_kexec_relocate) andi t1, t0, 0x8 beqz t1, 1b /* Unknown entry type, ignore it */ andi t0, t0, ~0x8 - mv t3, s5 /* i = num words per page */ + li t3, (PAGE_SIZE / RISCV_SZPTR) /* i = num words per page */ 3: /* copy loop */ REG_L t1, (t0) /* t1 = *src_ptr */ - REG_S t1, (s4) /* *dst_ptr = *src_ptr */ + REG_S t1, (s5) /* *dst_ptr = *src_ptr */ addi t0, t0, RISCV_SZPTR /* stc_ptr++ */ - addi s4, s4, RISCV_SZPTR /* dst_ptr++ */ - sub t3, t3, s6 /* i-- */ - addi s11, s11, 1 /* c++ */ + addi s5, s5, RISCV_SZPTR /* dst_ptr++ */ + addi t3, t3, -0x1 /* i-- */ beqz t3, 1b /* copy done ? */ j 3b @@ -146,7 +140,7 @@ SYM_CODE_START(riscv_kexec_relocate) */ fence.i - jalr zero, a2, 0 + jr a2 SYM_CODE_END(riscv_kexec_relocate) riscv_kexec_relocate_end: From 767423658d53d147409821e51e6d0bc12425b24f Mon Sep 17 00:00:00 2001 From: Song Shuai Date: Thu, 7 Sep 2023 18:33:03 +0800 Subject: [PATCH 2/3] riscv: kexec: Align the kexeced kernel entry The current riscv boot protocol requires 2MB alignment for RV64 and 4MB alignment for RV32. In KEXEC_FILE path, the elf_find_pbase() function should align the kexeced kernel entry according to the requirement, otherwise the kexeced kernel would silently BUG at the setup_vm(). Fixes: 8acea455fafa ("RISC-V: Support for kexec_file on panic") Signed-off-by: Song Shuai Link: https://lore.kernel.org/r/20230907103304.590739-3-songshuaishuai@tinylab.org Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/elf_kexec.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c index 5372b708fae2..9a81d6926ac6 100644 --- a/arch/riscv/kernel/elf_kexec.c +++ b/arch/riscv/kernel/elf_kexec.c @@ -98,7 +98,13 @@ static int elf_find_pbase(struct kimage *image, unsigned long kernel_len, kbuf.image = image; kbuf.buf_min = lowest_paddr; kbuf.buf_max = ULONG_MAX; - kbuf.buf_align = PAGE_SIZE; + + /* + * Current riscv boot protocol requires 2MB alignment for + * RV64 and 4MB alignment for RV32 + * + */ + kbuf.buf_align = PMD_SIZE; kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; kbuf.memsz = ALIGN(kernel_len, PAGE_SIZE); kbuf.top_down = false; From 0f5f46a869a5e82fde7a208fbde6f3846972c72a Mon Sep 17 00:00:00 2001 From: Song Shuai Date: Thu, 7 Sep 2023 18:33:04 +0800 Subject: [PATCH 3/3] riscv: kexec: Remove -fPIE for PURGATORY_CFLAGS With CONFIG_RELOCATABLE enabled, KBUILD_CFLAGS had a -fPIE option and then the purgatory/string.o was built to reference _ctype symbol via R_RISCV_GOT_HI20 relocations which can't be handled by purgatory. As a consequence, the kernel failed kexec_load_file() with: [ 880.386562] kexec_image: The entry point of kernel at 0x80200000 [ 880.388650] kexec_image: Unknown rela relocation: 20 [ 880.389173] kexec_image: Error loading purgatory ret=-8 So remove the -fPIE option for PURGATORY_CFLAGS to generate R_RISCV_PCREL_HI20 relocations type making puragtory work as it was. Fixes: 39b33072941f ("riscv: Introduce CONFIG_RELOCATABLE") Signed-off-by: Song Shuai Link: https://lore.kernel.org/r/20230907103304.590739-4-songshuaishuai@tinylab.org Signed-off-by: Palmer Dabbelt --- arch/riscv/purgatory/Makefile | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile index dc20e166983e..c2065d63945f 100644 --- a/arch/riscv/purgatory/Makefile +++ b/arch/riscv/purgatory/Makefile @@ -77,6 +77,10 @@ ifdef CONFIG_STACKPROTECTOR_STRONG PURGATORY_CFLAGS_REMOVE += -fstack-protector-strong endif +ifdef CONFIG_RELOCATABLE +PURGATORY_CFLAGS_REMOVE += -fPIE +endif + CFLAGS_REMOVE_purgatory.o += $(PURGATORY_CFLAGS_REMOVE) CFLAGS_purgatory.o += $(PURGATORY_CFLAGS)