Re: [PATCH v6 08/13] riscv/kprobe: Patch AUIPC/JALR pair to optimize kprobe

[Björn Töpel]

Chen Guokai <chenguokai17@xxxxxxxxxxxxxxxx> writes:

> diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h
> index 9a7d7346001e..ee31539de65f 100644
> --- a/arch/riscv/include/asm/patch.h
> +++ b/arch/riscv/include/asm/patch.h
> @@ -8,5 +8,6 @@
>  
>  int patch_text_nosync(void *addr, const void *insns, size_t len);
>  int patch_text(void *addr, u32 insn);
> +int patch_text_batch(void *addr, const void *insn, size_t size);
>  
>  #endif /* _ASM_RISCV_PATCH_H */
> diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
> index 765004b60513..ce324b6a6998 100644
> --- a/arch/riscv/kernel/patch.c
> +++ b/arch/riscv/kernel/patch.c
> @@ -15,7 +15,8 @@
>  
>  struct patch_insn {
>  	void *addr;
> -	u32 insn;
> +	const void *insn;
> +	size_t size;
>  	atomic_t cpu_count;
>  };
>  
> @@ -106,8 +107,7 @@ static int patch_text_cb(void *data)
>  
>  	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
>  		ret =

Nit: Please use the full width. No need for a NL here.

> -		    patch_text_nosync(patch->addr, &patch->insn,
> -					    GET_INSN_LENGTH(patch->insn));
> +		    patch_text_nosync(patch->addr, patch->insn, patch->size);
>  		atomic_inc(&patch->cpu_count);
>  	} else {
>  		while (atomic_read(&patch->cpu_count) <= num_online_cpus())
> @@ -123,7 +123,8 @@ int patch_text(void *addr, u32 insn)
>  {
>  	struct patch_insn patch = {
>  		.addr = addr,
> -		.insn = insn,
> +		.insn = &insn,
> +		.size = GET_INSN_LENGTH(insn),
>  		.cpu_count = ATOMIC_INIT(0),
>  	};
>  
> @@ -131,3 +132,17 @@ int patch_text(void *addr, u32 insn)
>  				       &patch, cpu_online_mask);
>  }
>  NOKPROBE_SYMBOL(patch_text);
> +
> +int patch_text_batch(void *addr, const void *insn, size_t size)
> +{
> +	struct patch_insn patch = {
> +		.addr = addr,
> +		.insn = insn,
> +		.size = size,
> +		.cpu_count = ATOMIC_INIT(0),
> +	};
> +
> +	return stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
> +}
> +
> +NOKPROBE_SYMBOL(patch_text_batch);
> diff --git a/arch/riscv/kernel/probes/opt.c b/arch/riscv/kernel/probes/opt.c
> index a47f7d2bf3a6..c52d5bdc748c 100644
> --- a/arch/riscv/kernel/probes/opt.c
> +++ b/arch/riscv/kernel/probes/opt.c
> @@ -8,6 +8,7 @@
>  
>  #define pr_fmt(fmt)	"optprobe: " fmt
>  
> +#include <linux/types.h>
>  #include <linux/kprobes.h>
>  #include <asm/kprobes.h>
>  #include <asm/patch.h>
> @@ -444,11 +445,19 @@ static bool can_optimize(unsigned long paddr, struct optimized_kprobe *op)
>  
>  int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
>  {
> -	return 0;
> +	return optinsn->length;
>  }
>  
>  int arch_check_optimized_kprobe(struct optimized_kprobe *op)
>  {
> +	unsigned long i;
> +	struct kprobe *p;
> +
> +	for (i = RVC_INSN_LEN; i < op->optinsn.length; i += RVC_INSN_LEN) {
> +		p = get_kprobe(op->kp.addr + i);
> +		if (p && !kprobe_disabled(p))
> +			return -EEXIST;
> +	}
>  	return 0;
>  }
>  
> @@ -509,23 +518,75 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
>  
>  void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
>  {
> +	if (op->optinsn.insn) {
> +		free_optinsn_slot(op->optinsn.insn, 1);
> +		op->optinsn.insn = NULL;
> +		op->optinsn.length = 0;
> +	}
>  }
>  
>  void arch_optimize_kprobes(struct list_head *oplist)
>  {
> +	long offs;
> +	kprobe_opcode_t insn[3];
> +	struct optimized_kprobe *op, *tmp;
> +
> +	list_for_each_entry_safe(op, tmp, oplist, list) {
> +		WARN_ON(kprobe_disabled(&op->kp));
> +
> +		/* Backup instructions which will be replaced by jump address */
> +		memcpy(op->optinsn.copied_insn,
> +		       DETOUR_ADDR(op->optinsn.insn, DETOUR_INSN_OFFSET),
> +		       op->optinsn.length);
> +
> +		/*
> +		 * After patching, it should be:
> +		 * auipc free_register, %hi(detour_buffer)
> +		 * jalr free_register, free_register, %lo(detour_buffer)
> +		 * where free_register will eventually save the return address
> +		 */
> +		offs = (unsigned long)op->optinsn.insn -
> +		       (unsigned long)op->kp.addr;
> +		insn[0] = rv_auipc(op->optinsn.rd, (offs + (1 << 11)) >> 12);
> +		insn[1] = rv_jalr(op->optinsn.rd, op->optinsn.rd, offs & 0xFFF);
> +		/* For 3 RVC + 1 RVI scenario, fill C.NOP for padding */
> +		if (op->optinsn.length > 2 * RVI_INSN_LEN)
> +			insn[2] = rvc_addi(0, 0);
> +
> +		patch_text_batch(op->kp.addr, insn, op->optinsn.length);
> +		if (memcmp(op->kp.addr, insn, op->optinsn.length))
> +			continue;
> +
> +		list_del_init(&op->list);
> +	}
>  }
>  
>  void arch_unoptimize_kprobes(struct list_head *oplist,
>  			     struct list_head *done_list)
>  {
> +	struct optimized_kprobe *op, *tmp;
> +
> +	list_for_each_entry_safe(op, tmp, oplist, list) {
> +		arch_unoptimize_kprobe(op);
> +		list_move(&op->list, done_list);
> +	}
>  }
>  
>  void arch_unoptimize_kprobe(struct optimized_kprobe *op)
>  {
> +	kprobe_opcode_t buf[MAX_COPIED_INSN];
> +
> +	memcpy(buf, op->optinsn.copied_insn, op->optinsn.length);
> +	if (GET_INSN_LENGTH(op->kp.opcode) == RVI_INSN_LEN)
> +		*(u32 *)buf = __BUG_INSN_32;
> +	else
> +		*(u16 *)buf = __BUG_INSN_16;
> +	patch_text_batch(op->kp.addr, buf, op->optinsn.length);
>  }
>  
>  int arch_within_optimized_kprobe(struct optimized_kprobe *op,
>  				 kprobe_opcode_t *addr)
>  {
> -	return 0;
> +	return (op->kp.addr <= addr &&
> +		op->kp.addr + op->optinsn.length > addr);

Nit: Use the whole 100 char line width, please.

With or w/o the nits fixed:

Reviewed-by: Björn Töpel <bjorn@xxxxxxxxxx>


Björn