linux-kernel - RE: [PATCH v8 02/31] kallsyms: avoid hardcoding buffer size

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Date:   Tue, 2 Aug 2022 08:29:58 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Miguel Ojeda' <ojeda@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     "rust-for-linux@...r.kernel.org" <rust-for-linux@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Jarkko Sakkinen" <jarkko@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>
Subject: RE: [PATCH v8 02/31] kallsyms: avoid hardcoding buffer size

From: Miguel Ojeda
> Sent: 02 August 2022 02:50
> 
> From: Boqun Feng <boqun.feng@...il.com>
> 
> This introduces `KSYM_NAME_LEN_BUFFER` in place of the previously
> hardcoded size of the input buffer.
> 
> It will also make it easier to update the size in a single place
> in a later patch.
> 
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> Co-developed-by: Miguel Ojeda <ojeda@...nel.org>
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
> ---
>  scripts/kallsyms.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index 52f5488c61bc..f3c5a2623f71 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -27,8 +27,14 @@
> 
>  #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
> 
> +#define _stringify_1(x)	#x
> +#define _stringify(x)	_stringify_1(x)
> +
>  #define KSYM_NAME_LEN		128
> 
> +/* A substantially bigger size than the current maximum. */
> +#define KSYM_NAME_LEN_BUFFER	499
> +
>  struct sym_entry {
>  	unsigned long long addr;
>  	unsigned int len;
> @@ -198,13 +204,13 @@ static void check_symbol_range(const char *sym, unsigned long long addr,
> 
>  static struct sym_entry *read_symbol(FILE *in)
>  {
> -	char name[500], type;
> +	char name[KSYM_NAME_LEN_BUFFER+1], type;
>  	unsigned long long addr;
>  	unsigned int len;
>  	struct sym_entry *sym;
>  	int rc;
> 
> -	rc = fscanf(in, "%llx %c %499s\n", &addr, &type, name);
> +	rc = fscanf(in, "%llx %c %" _stringify(KSYM_NAME_LEN_BUFFER) "s\n", &addr, &type, name);

Think I'd use "%*s" - simpler.
Although I normally completely avoid scanf() - too easy to get wrong.

	David

>  	if (rc != 3) {
>  		if (rc != EOF && fgets(name, sizeof(name), in) == NULL)
>  			fprintf(stderr, "Read error or end of file.\n");
> --
> 2.37.1

-
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