Merge patch series "riscv: kexec: cleanup and fixups"

Song Shuai <songshuaishuai@tinylab.org> says:

This series contains a cleanup for riscv_kexec_relocate() and two fixups
for KEXEC_FILE and had passed the basic kexec test in my 64bit Qemu-virt.

You can use this kexec-tools[3] to test the kexec-file-syscall and these patches.

riscv: kexec: Cleanup riscv_kexec_relocate (patch1)
==================================================

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

riscv: kexec: Align the kexeced kernel entry (patch2)
==================================================

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().

riscv: kexec: Remove -fPIE for PURGATORY_CFLAGS (patch3)
==================================================

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.

 arch/riscv/kernel/elf_kexec.c      |  8 ++++-
 arch/riscv/kernel/kexec_relocate.S | 52 +++++++++++++-----------------
 arch/riscv/purgatory/Makefile      |  4 +++
 3 files changed, 34 insertions(+), 30 deletions(-)

* b4-shazam-merge:
  riscv: kexec: Remove -fPIE for PURGATORY_CFLAGS
  riscv: kexec: Align the kexeced kernel entry
  riscv: kexec: Cleanup riscv_kexec_relocate

Link: https://lore.kernel.org/r/20230907103304.590739-1-songshuaishuai@tinylab.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index f4099059ed8f2507913ecfbb3713249feda33373..e60fbd8660c4a531c6deef3938c45afe2e158839 100644 (file)
--- 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;

diff --git a/arch/riscv/kernel/kexec_relocate.S b/arch/riscv/kernel/kexec_relocate.S
index 059c5e216ae75958750474cc4e49ecc886213b73..de0a4b35d01efcc6b904fadb29eb8ae25da3df7c 100644 (file)
--- 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:

diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile
index 9e6476719abbbb4e9206cd89292be7f25261a5b6..982fc8e771085edc6ba91f40855ec8edca525c13 100644 (file)
--- a/arch/riscv/purgatory/Makefile
+++ b/arch/riscv/purgatory/Makefile
@@ -81,6 +81,10 @@ ifdef CONFIG_CFI_CLANG
 PURGATORY_CFLAGS_REMOVE                += $(CC_FLAGS_CFI)
 endif
 
+ifdef CONFIG_RELOCATABLE
+PURGATORY_CFLAGS_REMOVE                += -fPIE
+endif
+
 CFLAGS_REMOVE_purgatory.o      += $(PURGATORY_CFLAGS_REMOVE)
 CFLAGS_purgatory.o             += $(PURGATORY_CFLAGS)