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 <songshuaishuai@tinylab.org> Link: https://lore.kernel.org/r/20230907103304.590739-2-songshuaishuai@tinylab.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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@ -17,27 +17,17 @@ SYM_CODE_START(riscv_kexec_relocate)
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* s1: (const) Phys address to jump to after relocation
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* s2: (const) Phys address of the FDT image
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* s3: (const) The hartid of the current hart
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* s4: Pointer to the destination address for the relocation
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* s5: (const) Number of words per page
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* s6: (const) 1, used for subtraction
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* s7: (const) kernel_map.va_pa_offset, used when switching MMU off
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* s8: (const) Physical address of the main loop
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* s9: (debug) indirection page counter
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* s10: (debug) entry counter
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* s11: (debug) copied words counter
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* s4: (const) kernel_map.va_pa_offset, used when switching MMU off
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* s5: Pointer to the destination address for the relocation
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* s6: (const) Physical address of the main loop
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*/
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mv s0, a0
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mv s1, a1
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mv s2, a2
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mv s3, a3
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mv s4, zero
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li s5, (PAGE_SIZE / RISCV_SZPTR)
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li s6, 1
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mv s7, a4
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mv s8, zero
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mv s9, zero
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mv s10, zero
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mv s11, zero
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mv s4, a4
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mv s5, zero
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mv s6, zero
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/* Disable / cleanup interrupts */
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csrw CSR_SIE, zero
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@ -52,21 +42,27 @@ SYM_CODE_START(riscv_kexec_relocate)
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* the start of the loop below so that we jump there in
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* any case.
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*/
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la s8, 1f
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sub s8, s8, s7
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csrw CSR_STVEC, s8
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la s6, 1f
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sub s6, s6, s4
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csrw CSR_STVEC, s6
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/*
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* With C-extension, here we get 42 Bytes and the next
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* .align directive would pad zeros here up to 44 Bytes.
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* So manually put a nop here to avoid zeros padding.
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*/
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nop
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/* Process entries in a loop */
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.align 2
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1:
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addi s10, s10, 1
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REG_L t0, 0(s0) /* t0 = *image->entry */
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addi s0, s0, RISCV_SZPTR /* image->entry++ */
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/* IND_DESTINATION entry ? -> save destination address */
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andi t1, t0, 0x1
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beqz t1, 2f
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andi s4, t0, ~0x1
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andi s5, t0, ~0x1
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j 1b
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2:
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@ -74,9 +70,8 @@ SYM_CODE_START(riscv_kexec_relocate)
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andi t1, t0, 0x2
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beqz t1, 2f
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andi s0, t0, ~0x2
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addi s9, s9, 1
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csrw CSR_SATP, zero
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jalr zero, s8, 0
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jr s6
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2:
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/* IND_DONE entry ? -> jump to done label */
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@ -92,14 +87,13 @@ SYM_CODE_START(riscv_kexec_relocate)
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andi t1, t0, 0x8
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beqz t1, 1b /* Unknown entry type, ignore it */
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andi t0, t0, ~0x8
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mv t3, s5 /* i = num words per page */
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li t3, (PAGE_SIZE / RISCV_SZPTR) /* i = num words per page */
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3: /* copy loop */
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REG_L t1, (t0) /* t1 = *src_ptr */
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REG_S t1, (s4) /* *dst_ptr = *src_ptr */
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REG_S t1, (s5) /* *dst_ptr = *src_ptr */
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addi t0, t0, RISCV_SZPTR /* stc_ptr++ */
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addi s4, s4, RISCV_SZPTR /* dst_ptr++ */
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sub t3, t3, s6 /* i-- */
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addi s11, s11, 1 /* c++ */
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addi s5, s5, RISCV_SZPTR /* dst_ptr++ */
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addi t3, t3, -0x1 /* i-- */
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beqz t3, 1b /* copy done ? */
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j 3b
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@ -146,7 +140,7 @@ SYM_CODE_START(riscv_kexec_relocate)
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*/
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fence.i
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jalr zero, a2, 0
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jr a2
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SYM_CODE_END(riscv_kexec_relocate)
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riscv_kexec_relocate_end:
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