linux-kernel - Re: [PATCH v2 1/3] x86/kprobes: Refactor can

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Date: Sun, 4 Feb 2024 21:10:39 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Jinghao Jia <jinghao7@...inois.edu>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, Peter Zijlstra
 <peterz@...radead.org>, Xin Li <xin@...or.com>,
 linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] x86/kprobes: Refactor can_{probe,boost} return
 type to bool

On Sat,  3 Feb 2024 21:12:58 -0600
Jinghao Jia <jinghao7@...inois.edu> wrote:

> Both can_probe and can_boost have int return type but are using int as
> boolean in their context.
> 
> Refactor both functions to make them actually return boolean.
> 

This and next one looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Let me pick those.

> Signed-off-by: Jinghao Jia <jinghao7@...inois.edu>
> ---
>  arch/x86/kernel/kprobes/common.h |  2 +-
>  arch/x86/kernel/kprobes/core.c   | 33 +++++++++++++++-----------------
>  2 files changed, 16 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/x86/kernel/kprobes/common.h b/arch/x86/kernel/kprobes/common.h
> index c993521d4933..e772276f5aa9 100644
> --- a/arch/x86/kernel/kprobes/common.h
> +++ b/arch/x86/kernel/kprobes/common.h
> @@ -78,7 +78,7 @@
>  #endif
>  
>  /* Ensure if the instruction can be boostable */
> -extern int can_boost(struct insn *insn, void *orig_addr);
> +extern bool can_boost(struct insn *insn, void *orig_addr);
>  /* Recover instruction if given address is probed */
>  extern unsigned long recover_probed_instruction(kprobe_opcode_t *buf,
>  					 unsigned long addr);
> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> index e8babebad7b8..644d416441fb 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -137,14 +137,14 @@ NOKPROBE_SYMBOL(synthesize_relcall);
>   * Returns non-zero if INSN is boostable.
>   * RIP relative instructions are adjusted at copying time in 64 bits mode
>   */
> -int can_boost(struct insn *insn, void *addr)
> +bool can_boost(struct insn *insn, void *addr)
>  {
>  	kprobe_opcode_t opcode;
>  	insn_byte_t prefix;
>  	int i;
>  
>  	if (search_exception_tables((unsigned long)addr))
> -		return 0;	/* Page fault may occur on this address. */
> +		return false;	/* Page fault may occur on this address. */
>  
>  	/* 2nd-byte opcode */
>  	if (insn->opcode.nbytes == 2)
> @@ -152,7 +152,7 @@ int can_boost(struct insn *insn, void *addr)
>  				(unsigned long *)twobyte_is_boostable);
>  
>  	if (insn->opcode.nbytes != 1)
> -		return 0;
> +		return false;
>  
>  	for_each_insn_prefix(insn, i, prefix) {
>  		insn_attr_t attr;
> @@ -160,7 +160,7 @@ int can_boost(struct insn *insn, void *addr)
>  		attr = inat_get_opcode_attribute(prefix);
>  		/* Can't boost Address-size override prefix and CS override prefix */
>  		if (prefix == 0x2e || inat_is_address_size_prefix(attr))
> -			return 0;
> +			return false;
>  	}
>  
>  	opcode = insn->opcode.bytes[0];
> @@ -181,12 +181,12 @@ int can_boost(struct insn *insn, void *addr)
>  	case 0xf6 ... 0xf7:	/* Grp3 */
>  	case 0xfe:		/* Grp4 */
>  		/* ... are not boostable */
> -		return 0;
> +		return false;
>  	case 0xff:		/* Grp5 */
>  		/* Only indirect jmp is boostable */
>  		return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;
>  	default:
> -		return 1;
> +		return true;
>  	}
>  }
>  
> @@ -253,20 +253,18 @@ unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long add
>  }
>  
>  /* Check if paddr is at an instruction boundary */
> -static int can_probe(unsigned long paddr)
> +static bool can_probe(unsigned long paddr)
>  {
>  	unsigned long addr, __addr, offset = 0;
>  	struct insn insn;
>  	kprobe_opcode_t buf[MAX_INSN_SIZE];
>  
>  	if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
> -		return 0;
> +		return false;
>  
>  	/* Decode instructions */
>  	addr = paddr - offset;
>  	while (addr < paddr) {
> -		int ret;
> -
>  		/*
>  		 * Check if the instruction has been modified by another
>  		 * kprobe, in which case we replace the breakpoint by the
> @@ -277,11 +275,10 @@ static int can_probe(unsigned long paddr)
>  		 */
>  		__addr = recover_probed_instruction(buf, addr);
>  		if (!__addr)
> -			return 0;
> +			return false;
>  
> -		ret = insn_decode_kernel(&insn, (void *)__addr);
> -		if (ret < 0)
> -			return 0;
> +		if (insn_decode_kernel(&insn, (void *)__addr) < 0)
> +			return false;
>  
>  #ifdef CONFIG_KGDB
>  		/*
> @@ -290,7 +287,7 @@ static int can_probe(unsigned long paddr)
>  		 */
>  		if (insn.opcode.bytes[0] == INT3_INSN_OPCODE &&
>  		    kgdb_has_hit_break(addr))
> -			return 0;
> +			return false;
>  #endif
>  		addr += insn.length;
>  	}
> @@ -310,10 +307,10 @@ static int can_probe(unsigned long paddr)
>  		 */
>  		__addr = recover_probed_instruction(buf, addr);
>  		if (!__addr)
> -			return 0;
> +			return false;
>  
>  		if (insn_decode_kernel(&insn, (void *)__addr) < 0)
> -			return 0;
> +			return false;
>  
>  		if (insn.opcode.value == 0xBA)
>  			offset = 12;
> @@ -324,7 +321,7 @@ static int can_probe(unsigned long paddr)
>  
>  		/* This movl/addl is used for decoding CFI. */
>  		if (is_cfi_trap(addr + offset))
> -			return 0;
> +			return false;
>  	}
>  
>  out:
> -- 
> 2.43.0
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>