On Fri, Jul 11, 2025 at 10:29:18AM +0200, Jiri Olsa wrote:
> +enum {
> + OPT_PART,
> + OPT_INSN,
> + UNOPT_INT3,
> + UNOPT_PART,
> +};
> +
> +struct write_opcode_ctx {
> + unsigned long base;
> + int update;
> +};
> +
> +static int is_call_insn(uprobe_opcode_t *insn)
> +{
> + return *insn == CALL_INSN_OPCODE;
> +}
> +
> +static int verify_insn(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode,
> + int nbytes, void *data)
> +{
> + struct write_opcode_ctx *ctx = data;
> + uprobe_opcode_t old_opcode[5];
> +
> + uprobe_copy_from_page(page, ctx->base, (uprobe_opcode_t *) &old_opcode, 5);
> +
> + switch (ctx->update) {
> + case OPT_PART:
> + case OPT_INSN:
> + if (is_swbp_insn(&old_opcode[0]))
> + return 1;
> + break;
> + case UNOPT_INT3:
> + if (is_call_insn(&old_opcode[0]))
> + return 1;
> + break;
> + case UNOPT_PART:
> + if (is_swbp_insn(&old_opcode[0]))
> + return 1;
> + break;
> + }
> +
> + return -1;
> +}
> +
> +static int write_insn(struct arch_uprobe *auprobe, struct vm_area_struct *vma, unsigned long vaddr,
> + uprobe_opcode_t *insn, int nbytes, void *ctx)
> +{
> + return uprobe_write(auprobe, vma, vaddr, insn, nbytes, verify_insn,
> + true /* is_register */, false /* do_update_ref_ctr */, ctx);
> +}
> +
> +static void relative_call(void *dest, long from, long to)
> +{
> + struct __packed __arch_relative_insn {
> + u8 op;
> + s32 raddr;
> + } *insn;
> +
> + insn = (struct __arch_relative_insn *)dest;
> + insn->raddr = (s32)(to - (from + 5));
> + insn->op = CALL_INSN_OPCODE;
> +}
We already have this in asm/text-patching.h, its called
__text_gen_insn().
> +
> +static int swbp_optimize(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
> + unsigned long vaddr, unsigned long tramp)
> +{
> + struct write_opcode_ctx ctx = {
> + .base = vaddr,
> + };
> + char call[5];
> + int err;
> +
> + relative_call(call, vaddr, tramp);
__text_gen_insn(call, CALL_INSN_OPCODE, vaddr, tramp, CALL_INSN_SIZE);
> +
> + /*
> + * We are in state where breakpoint (int3) is installed on top of first
> + * byte of the nop5 instruction. We will do following steps to overwrite
> + * this to call instruction:
> + *
> + * - sync cores
> + * - write last 4 bytes of the call instruction
> + * - sync cores
> + * - update the call instruction opcode
The sanctioned text poke sequence has another sync-core at the end.
Please also do this.
> + */
> +
> + smp_text_poke_sync_each_cpu();
> +
> + ctx.update = OPT_PART;
> + err = write_insn(auprobe, vma, vaddr + 1, call + 1, 4, &ctx);
> + if (err)
> + return err;
> +
> + smp_text_poke_sync_each_cpu();
> +
> + ctx.update = OPT_INSN;
> + return write_insn(auprobe, vma, vaddr, call, 1, &ctx);
> +}
> +
> +static int swbp_unoptimize(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
> + unsigned long vaddr)
> +{
> + uprobe_opcode_t int3 = UPROBE_SWBP_INSN;
> + struct write_opcode_ctx ctx = {
> + .base = vaddr,
> + };
> + int err;
> +
> + /*
> + * We need to overwrite call instruction into nop5 instruction with
> + * breakpoint (int3) installed on top of its first byte. We will:
> + *
> + * - overwrite call opcode with breakpoint (int3)
> + * - sync cores
> + * - write last 4 bytes of the nop5 instruction
> + * - sync cores
> + */
> +
> + ctx.update = UNOPT_INT3;
> + err = write_insn(auprobe, vma, vaddr, &int3, 1, &ctx);
> + if (err)
> + return err;
> +
> + smp_text_poke_sync_each_cpu();
> +
> + ctx.update = UNOPT_PART;
> + err = write_insn(auprobe, vma, vaddr + 1, (uprobe_opcode_t *) auprobe->insn + 1, 4, &ctx);
> +
> + smp_text_poke_sync_each_cpu();
> + return err;
> +}
Please unify these two functions; it makes absolutely no sense to have
two copies of this logic around.
