Re: [PATCH DO NOT REVIEW v4 4/7] riscv: errata: andes: Fix auipc-jalr addresses in patched alternatives

[Guo Ren]

On Fri, Nov 25, 2022 at 1:22 AM Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
>
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
>
> This patch is added just for building purpose, as patch [0] will export
> this in its next version.
>
> https://patchwork.kernel.org/project/linux-riscv/patch/20221110164924.529386-6-heiko@xxxxxxxxx/
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> ---
> Note, as Heiko will be exporting riscv_alternative_fix_auipc_jalr() function
> so that it can be used other erratas Ive just included for compilation.
> ---
>  arch/riscv/errata/andes/errata.c | 71 ++++++++++++++++++++++++++++++++
>  1 file changed, 71 insertions(+)
>
> diff --git a/arch/riscv/errata/andes/errata.c b/arch/riscv/errata/andes/errata.c
> index ec3e052ca8c7..4061ad4983bc 100644
> --- a/arch/riscv/errata/andes/errata.c
> +++ b/arch/riscv/errata/andes/errata.c
> @@ -13,9 +13,80 @@
>  #include <asm/alternative.h>
>  #include <asm/cacheflush.h>
>  #include <asm/errata_list.h>
> +#include <asm/parse_asm.h>
>  #include <asm/patch.h>
> +#include <asm/sbi.h>
>  #include <asm/vendorid_list.h>
>
> +/* Copy of Heiko's code from patch [0]
> + * [0] https://patchwork.kernel.org/project/linux-riscv/patch/20221110164924.529386-6-heiko@xxxxxxxxx/
Move it to commit-msg. No link in the code.

> + */
> +DECLARE_INSN(jalr, MATCH_JALR, MASK_JALR)
> +DECLARE_INSN(auipc, MATCH_AUIPC, MASK_AUIPC)
> +
> +static inline bool is_auipc_jalr_pair(long insn1, long insn2)
> +{
> +       return is_auipc_insn(insn1) && is_jalr_insn(insn2);
> +}
> +
> +#define JALR_SIGN_MASK         BIT(I_IMM_SIGN_OPOFF - I_IMM_11_0_OPOFF)
> +#define JALR_OFFSET_MASK       I_IMM_11_0_MASK
> +#define AUIPC_OFFSET_MASK      U_IMM_31_12_MASK
> +#define AUIPC_PAD              (0x00001000)
> +#define JALR_SHIFT             I_IMM_11_0_OPOFF
> +
> +#define to_jalr_imm(offset)                                            \
> +       ((offset & I_IMM_11_0_MASK) << I_IMM_11_0_OPOFF)
> +
> +#define to_auipc_imm(offset)                                           \
> +       ((offset & JALR_SIGN_MASK) ?                                    \
> +       ((offset & AUIPC_OFFSET_MASK) + AUIPC_PAD) :                    \
> +       (offset & AUIPC_OFFSET_MASK))
> +
> +static void riscv_alternative_fix_auipc_jalr(unsigned int *alt_ptr,
> +                                            unsigned int len, int patch_offset)
> +{
> +       int num_instr = len / sizeof(u32);
> +       unsigned int call[2];
> +       int i;
> +       int imm1;
> +       u32 rd1;
> +
> +       for (i = 0; i < num_instr; i++) {
> +               /* is there a further instruction? */
> +               if (i + 1 >= num_instr)
> +                       continue;
> +
> +               if (!is_auipc_jalr_pair(*(alt_ptr + i), *(alt_ptr + i + 1)))
> +                       continue;
> +
> +               /* call will use ra register */
> +               rd1 = EXTRACT_RD_REG(*(alt_ptr + i));
> +               if (rd1 != 1)
> +                       continue;
> +
> +               /* get and adjust new target address */
> +               imm1 = EXTRACT_UTYPE_IMM(*(alt_ptr + i));
> +               imm1 += EXTRACT_ITYPE_IMM(*(alt_ptr + i + 1));
> +               imm1 -= patch_offset;
> +
> +               /* pick the original auipc + jalr */
> +               call[0] = *(alt_ptr + i);
> +               call[1] = *(alt_ptr + i + 1);
> +
> +               /* drop the old IMMs */
> +               call[0] &= ~(U_IMM_31_12_MASK);
> +               call[1] &= ~(I_IMM_11_0_MASK << I_IMM_11_0_OPOFF);
> +
> +               /* add the adapted IMMs */
> +               call[0] |= to_auipc_imm(imm1);
> +               call[1] |= to_jalr_imm(imm1);
> +
> +               /* patch the call place again */
> +               patch_text_nosync(alt_ptr + i, call, 8);
> +       }
> +}
> +
>  static bool errata_probe_iocp(unsigned int stage, unsigned long arch_id, unsigned long impid)
>  {
>         if (!IS_ENABLED(CONFIG_ERRATA_ANDES_CMO))
> --
> 2.25.1
>


-- 
Best Regards
 Guo Ren