[PATCH] arm64/kexec-arm64: add support for R_AARCH64_LDST128_ABS_LO12_NC rela

[Pingfan Liu]

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On Thu, Mar 31, 2022 at 9:18 AM Pingfan Liu <piliu at redhat.com> wrote:
>
> GCC 12 has some changes, which affects the generated AArch64 code of kexec-tools.
> Accordingly, a new rel type R_AARCH64_LDST128_ABS_LO12_NC is confronted
> by machine_apply_elf_rel() on AArch64. This fails the load of kernel
> with the message "machine_apply_elf_rel: ERROR Unknown type: 299"
>
> Citing from objdump -rDSl purgatory/purgatory.ro
>
> 0000000000000f80 <sha256_starts>:
> sha256_starts():
>      f80:       90000001        adrp    x1, 0 <verify_sha256_digest>
>                         f80: R_AARCH64_ADR_PREL_PG_HI21 .text+0xfa0
>      f84:       a9007c1f        stp     xzr, xzr, [x0]
>      f88:       3dc00021        ldr     q1, [x1]
>                         f88: R_AARCH64_LDST128_ABS_LO12_NC      .text+0xfa0
>      f8c:       90000001        adrp    x1, 0 <verify_sha256_digest>
>                         f8c: R_AARCH64_ADR_PREL_PG_HI21 .text+0xfb0
>      f90:       3dc00020        ldr     q0, [x1]
>                         f90: R_AARCH64_LDST128_ABS_LO12_NC      .text+0xfb0
>      f94:       ad008001        stp     q1, q0, [x0, #16]
>      f98:       d65f03c0        ret
>      f9c:       d503201f        nop
>      fa0:       6a09e667        .inst   0x6a09e667 ; undefined
>      fa4:       bb67ae85        .inst   0xbb67ae85 ; undefined
>      fa8:       3c6ef372        .inst   0x3c6ef372 ; undefined
>      fac:       a54ff53a        ld3w    {z26.s-z28.s}, p5/z, [x9, #-3, mul vl]
>      fb0:       510e527f        sub     wsp, w19, #0x394
>      fb4:       9b05688c        madd    x12, x4, x5, x26
>      fb8:       1f83d9ab        .inst   0x1f83d9ab ; undefined
>      fbc:       5be0cd19        .inst   0x5be0cd19 ; undefined
>
> Here, gcc generates codes, which make loads and stores carried out using
> the 128-bits floating-point registers. And a new rel type
> R_AARCH64_LDST128_ABS_LO12_NC should be handled.
>
> Make machine_apply_elf_rel() coped with this new reloc, so kexec-tools
> can work smoothly.
>
> Signed-off-by: Pingfan Liu <piliu at redhat.com>
> Cc: Geoff Levand <geoff at infradead.org>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Simon Horman <horms at verge.net.au>
> ---
>  kexec/arch/arm64/kexec-arm64.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> index 9dd072c..e25f600 100644
> --- a/kexec/arch/arm64/kexec-arm64.c
> +++ b/kexec/arch/arm64/kexec-arm64.c
> @@ -1248,6 +1248,10 @@ void machine_apply_elf_rel(struct mem_ehdr *ehdr, struct mem_sym *UNUSED(sym),
>
>  #if !defined(R_AARCH64_LDST64_ABS_LO12_NC)
>  # define R_AARCH64_LDST64_ABS_LO12_NC 286
> +#endif
> +
> +#if !defined(R_AARCH64_LDST128_ABS_LO12_NC)
> +# define R_AARCH64_LDST128_ABS_LO12_NC 299
>  #endif
>
>         uint64_t *loc64;
> @@ -1309,6 +1313,7 @@ void machine_apply_elf_rel(struct mem_ehdr *ehdr, struct mem_sym *UNUSED(sym),
>                 *loc32 = cpu_to_le32(le32_to_cpu(*loc32)
>                         + (((value - address) >> 2) & 0x3ffffff));
>                 break;
> +       /* encode imm field with bits [11:3] of value */
>         case R_AARCH64_LDST64_ABS_LO12_NC:
>                 if (value & 7)
>                         die("%s: ERROR Unaligned value: %lx\n", __func__,
> @@ -1318,6 +1323,17 @@ void machine_apply_elf_rel(struct mem_ehdr *ehdr, struct mem_sym *UNUSED(sym),
>                 *loc32 = cpu_to_le32(le32_to_cpu(*loc32)
>                         + ((value & 0xff8) << (10 - 3)));
>                 break;
> +
> +       /* encode imm field with bits [11:4] of value */
> +       case R_AARCH64_LDST128_ABS_LO12_NC:
> +               if (value & 15)
> +                       die("%s: ERROR Unaligned value: %lx\n", __func__,
> +                               value);
> +               type = "LDST128_ABS_LO12_NC";
> +               loc32 = ptr;
> +               imm = value & 0xff0;
> +               *loc32 = cpu_to_le32(le32_to_cpu(*loc32) + (imm << (10 - 4)));
> +               break;
>         default:
>                 die("%s: ERROR Unknown type: %lu\n", __func__, r_type);
>                 break;
> --
> 2.31.1
>