Re: [PATCH 09/12] riscv: extable: add `type` and `data` fields
From: Jisheng Zhang
Date: Thu Nov 18 2021 - 06:51:31 EST
On Thu, 18 Nov 2021 19:26:05 +0800 Jisheng Zhang wrote:
> From: Jisheng Zhang <jszhang@xxxxxxxxxx>
>
> This is a riscv port of commit d6e2cc564775("arm64: extable: add `type`
> and `data` fields").
>
> We will add specialized handlers for fixups, the `type` field is for
> fixup handler type, the `data` field is used to pass specific data to
> each handler, for example register numbers.
>
> Signed-off-by: Jisheng Zhang <jszhang@xxxxxxxxxx>
> ---
> arch/riscv/include/asm/asm-extable.h | 25 +++++++++++++++++--------
> arch/riscv/include/asm/extable.h | 17 ++++++++++++++---
> arch/riscv/kernel/vmlinux.lds.S | 2 +-
> arch/riscv/mm/extable.c | 25 +++++++++++++++++++++----
> arch/riscv/net/bpf_jit_comp64.c | 5 +++--
> scripts/sorttable.c | 4 +++-
> 6 files changed, 59 insertions(+), 19 deletions(-)
>
> diff --git a/arch/riscv/include/asm/asm-extable.h b/arch/riscv/include/asm/asm-extable.h
> index b790c02dbdda..1b1f4ffd8d37 100644
> --- a/arch/riscv/include/asm/asm-extable.h
> +++ b/arch/riscv/include/asm/asm-extable.h
> @@ -2,31 +2,40 @@
> #ifndef __ASM_ASM_EXTABLE_H
> #define __ASM_ASM_EXTABLE_H
>
> +#define EX_TYPE_NONE 0
> +#define EX_TYPE_FIXUP 1
> +#define EX_TYPE_BPF 2
> +
> #ifdef __ASSEMBLY__
>
> -#define __ASM_EXTABLE_RAW(insn, fixup) \
> - .pushsection __ex_table, "a"; \
> - .balign 4; \
> - .long ((insn) - .); \
> - .long ((fixup) - .); \
> +#define __ASM_EXTABLE_RAW(insn, fixup, type, data) \
> + .pushsection __ex_table, "a"; \
> + .balign 4; \
> + .long ((insn) - .); \
> + .long ((fixup) - .); \
> + .short (type); \
> + .short (data); \
> .popsection;
>
> .macro _asm_extable, insn, fixup
> - __ASM_EXTABLE_RAW(\insn, \fixup)
> + __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0)
> .endm
>
> #else /* __ASSEMBLY__ */
>
> #include <linux/stringify.h>
>
> -#define __ASM_EXTABLE_RAW(insn, fixup) \
> +#define __ASM_EXTABLE_RAW(insn, fixup, type, data) \
> ".pushsection __ex_table, \"a\"\n" \
> ".balign 4\n" \
> ".long ((" insn ") - .)\n" \
> ".long ((" fixup ") - .)\n" \
> + ".short (" type ")\n" \
> + ".short (" data ")\n" \
> ".popsection\n"
>
> -#define _ASM_EXTABLE(insn, fixup) __ASM_EXTABLE_RAW(#insn, #fixup)
> +#define _ASM_EXTABLE(insn, fixup) \
> + __ASM_EXTABLE_RAW(#insn, #fixup, __stringify(EX_TYPE_FIXUP), "0")
>
> #endif /* __ASSEMBLY__ */
>
> diff --git a/arch/riscv/include/asm/extable.h b/arch/riscv/include/asm/extable.h
> index e4374dde02b4..512012d193dc 100644
> --- a/arch/riscv/include/asm/extable.h
> +++ b/arch/riscv/include/asm/extable.h
> @@ -17,18 +17,29 @@
>
> struct exception_table_entry {
> int insn, fixup;
> + short type, data;
> };
>
> #define ARCH_HAS_RELATIVE_EXTABLE
>
> +#define swap_ex_entry_fixup(a, b, tmp, delta) \
> +do { \
> + (a)->fixup = (b)->fixup + (delta); \
> + (b)->fixup = (tmp).fixup - (delta); \
> + (a)->type = (b)->type; \
> + (b)->type = (tmp).type; \
> + (a)->data = (b)->data; \
> + (b)->data = (tmp).data; \
> +} while (0)
> +
> bool fixup_exception(struct pt_regs *regs);
>
> #if defined(CONFIG_BPF_JIT) && defined(CONFIG_ARCH_RV64I)
> -bool rv_bpf_fixup_exception(const struct exception_table_entry *ex, struct pt_regs *regs);
> +bool ex_handler_bpf(const struct exception_table_entry *ex, struct pt_regs *regs);
> #else
> static inline bool
> -rv_bpf_fixup_exception(const struct exception_table_entry *ex,
> - struct pt_regs *regs)
> +ex_handler_bpf(const struct exception_table_entry *ex,
> + struct pt_regs *regs)
> {
> return false;
> }
> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
> index 5104f3a871e3..0e5ae851929e 100644
> --- a/arch/riscv/kernel/vmlinux.lds.S
> +++ b/arch/riscv/kernel/vmlinux.lds.S
> @@ -4,7 +4,7 @@
> * Copyright (C) 2017 SiFive
> */
>
> -#define RO_EXCEPTION_TABLE_ALIGN 16
> +#define RO_EXCEPTION_TABLE_ALIGN 4
>
> #ifdef CONFIG_XIP_KERNEL
> #include "vmlinux-xip.lds.S"
> diff --git a/arch/riscv/mm/extable.c b/arch/riscv/mm/extable.c
> index 3c561f1d0115..91e52c4bb33a 100644
> --- a/arch/riscv/mm/extable.c
> +++ b/arch/riscv/mm/extable.c
> @@ -10,6 +10,20 @@
> #include <linux/extable.h>
> #include <linux/module.h>
> #include <linux/uaccess.h>
> +#include <asm/asm-extable.h>
> +
> +static inline unsigned long
> +get_ex_fixup(const struct exception_table_entry *ex)
> +{
> + return ((unsigned long)&ex->fixup + ex->fixup);
> +}
> +
> +static bool ex_handler_fixup(const struct exception_table_entry *ex,
> + struct pt_regs *regs)
> +{
> + regs->epc = get_ex_fixup(ex);
> + return true;
> +}
>
> bool fixup_exception(struct pt_regs *regs)
> {
> @@ -19,9 +33,12 @@ bool fixup_exception(struct pt_regs *regs)
> if (!ex)
> return false;
>
> - if (regs->epc >= BPF_JIT_REGION_START && regs->epc < BPF_JIT_REGION_END)
> - return rv_bpf_fixup_exception(ex, regs);
> + switch (ex->type) {
> + case EX_TYPE_FIXUP:
> + return ex_handler_fixup(ex, regs);
> + case EX_TYPE_BPF:
> + return ex_handler_bpf(ex, regs);
> + }
>
> - regs->epc = (unsigned long)&ex->fixup + ex->fixup;
> - return true;
> + BUG();
> }
> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> index 7714081cbb64..69bab7e28f91 100644
> --- a/arch/riscv/net/bpf_jit_comp64.c
> +++ b/arch/riscv/net/bpf_jit_comp64.c
> @@ -459,8 +459,8 @@ static int emit_call(bool fixed, u64 addr, struct rv_jit_context *ctx)
> #define BPF_FIXUP_OFFSET_MASK GENMASK(26, 0)
> #define BPF_FIXUP_REG_MASK GENMASK(31, 27)
>
> -bool rv_bpf_fixup_exception(const struct exception_table_entry *ex,
> - struct pt_regs *regs)
> +bool ex_handler_bpf(const struct exception_table_entry *ex,
> + struct pt_regs *regs)
> {
> off_t offset = FIELD_GET(BPF_FIXUP_OFFSET_MASK, ex->fixup);
> int regs_offset = FIELD_GET(BPF_FIXUP_REG_MASK, ex->fixup);
> @@ -514,6 +514,7 @@ static int add_exception_handler(const struct bpf_insn *insn,
>
> ex->fixup = FIELD_PREP(BPF_FIXUP_OFFSET_MASK, offset) |
> FIELD_PREP(BPF_FIXUP_REG_MASK, dst_reg);
> + ex->type = EX_TYPE_BPF;
>
> ctx->nexentries++;
> return 0;
> diff --git a/scripts/sorttable.c b/scripts/sorttable.c
> index 0c031e47a419..5b5472b543f5 100644
> --- a/scripts/sorttable.c
> +++ b/scripts/sorttable.c
> @@ -376,9 +376,11 @@ static int do_file(char const *const fname, void *addr)
> case EM_PARISC:
> case EM_PPC:
> case EM_PPC64:
> - case EM_RISCV:
> custom_sort = sort_relative_table;
> break;
> + case EM_RISCV:
> + custom_sort = arm64_sort_relative_table;
Hi Mark, Thomas,
x86 and arm64 version of sort_relative_table routine are the same, I want to
unify them, and then use the common function for riscv, but I'm not sure
which name is better. Could you please suggest?
Thanks
> + break;
> case EM_ARCOMPACT:
> case EM_ARCV2:
> case EM_ARM: