Hi,

On Mon, Jul 21, 2025 at 8:44 PM Xu Kuohai [off-list ref] wrote:

On 7/22/2025 4:20 AM, Sami Tolvanen wrote:

quoted

+static inline void emit_kcfi(u32 hash, struct jit_ctx *ctx)
+{
+     if (IS_ENABLED(CONFIG_CFI_CLANG))
+             emit(hash, ctx);

I guess this won't work on big-endian cpus, since arm64 instructions
are always stored in little-endian, but data not.

Nice catch! I'll send a new version with your suggested fix.

quoted

+}
+
  /*
   * Kernel addresses in the vmalloc space use at most 48 bits, and the
   * remaining bits are guaranteed to be 0x1. So we can compose the address

@@ -476,7 +483,6 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf)
      const bool is_main_prog = !bpf_is_subprog(prog);
      const u8 fp = bpf2a64[BPF_REG_FP];
      const u8 arena_vm_base = bpf2a64[ARENA_VM_START];
-     const int idx0 = ctx->idx;
      int cur_offset;

      /*

@@ -502,6 +508,9 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf)
       *
       */

+     emit_kcfi(is_main_prog ? cfi_bpf_hash : cfi_bpf_subprog_hash, ctx);
+     const int idx0 = ctx->idx;

move the idx0 definition back to its original position to match the
coding style of the rest of the file?

The const definition needs to happen after emit_kcfi, because we
increment ctx->idx when CFI is enabled.

Sami