Re: [PATCH bpf] tools: bpftool: JIT limited misreported as negative value on aarch64

[Jiri Olsa <olsajiri@gmail.com>]

On Fri, May 12, 2023 at 12:31:34PM +0100, Alan Maguire wrote:
> On aarch64, "bpftool feature" reports an incorrect BPF JIT limit:
> 
> $ sudo /sbin/bpftool feature
> Scanning system configuration...
> bpf() syscall restricted to privileged users
> JIT compiler is enabled
> JIT compiler hardening is disabled
> JIT compiler kallsyms exports are enabled for root
> skipping kernel config, can't open file: No such file or directory
> Global memory limit for JIT compiler for unprivileged users is -201326592 bytes
> 
> This is because /proc/sys/net/core/bpf_jit_limit reports
> 
> $ sudo cat /proc/sys/net/core/bpf_jit_limit
> 68169519595520
> 
> ...and an int is assumed in read_procfs().  Change read_procfs()
> to return a long to avoid negative value reporting.
> 
> Fixes: 7a4522bbef0c ("tools: bpftool: add probes for /proc/ eBPF parameters")
> Reported-by: Nicky Veitch <nicky.veitch@oracle.com>
> Signed-off-by: Alan Maguire <alan.maguire@oracle.com>

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> ---
>  tools/bpf/bpftool/feature.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
> index da16e6a27ccc..0675d6a46413 100644
> --- a/tools/bpf/bpftool/feature.c
> +++ b/tools/bpf/bpftool/feature.c
> @@ -167,12 +167,12 @@ static int get_vendor_id(int ifindex)
>  	return strtol(buf, NULL, 0);
>  }
>  
> -static int read_procfs(const char *path)
> +static long read_procfs(const char *path)
>  {
>  	char *endptr, *line = NULL;
>  	size_t len = 0;
>  	FILE *fd;
> -	int res;
> +	long res;
>  
>  	fd = fopen(path, "r");
>  	if (!fd)
> @@ -194,7 +194,7 @@ static int read_procfs(const char *path)
>  
>  static void probe_unprivileged_disabled(void)
>  {
> -	int res;
> +	long res;
>  
>  	/* No support for C-style ouptut */
>  
> @@ -216,14 +216,14 @@ static void probe_unprivileged_disabled(void)
>  			printf("Unable to retrieve required privileges for bpf() syscall\n");
>  			break;
>  		default:
> -			printf("bpf() syscall restriction has unknown value %d\n", res);
> +			printf("bpf() syscall restriction has unknown value %ld\n", res);
>  		}
>  	}
>  }
>  
>  static void probe_jit_enable(void)
>  {
> -	int res;
> +	long res;
>  
>  	/* No support for C-style ouptut */
>  
> @@ -245,7 +245,7 @@ static void probe_jit_enable(void)
>  			printf("Unable to retrieve JIT-compiler status\n");
>  			break;
>  		default:
> -			printf("JIT-compiler status has unknown value %d\n",
> +			printf("JIT-compiler status has unknown value %ld\n",
>  			       res);
>  		}
>  	}
> @@ -253,7 +253,7 @@ static void probe_jit_enable(void)
>  
>  static void probe_jit_harden(void)
>  {
> -	int res;
> +	long res;
>  
>  	/* No support for C-style ouptut */
>  
> @@ -275,7 +275,7 @@ static void probe_jit_harden(void)
>  			printf("Unable to retrieve JIT hardening status\n");
>  			break;
>  		default:
> -			printf("JIT hardening status has unknown value %d\n",
> +			printf("JIT hardening status has unknown value %ld\n",
>  			       res);
>  		}
>  	}
> @@ -283,7 +283,7 @@ static void probe_jit_harden(void)
>  
>  static void probe_jit_kallsyms(void)
>  {
> -	int res;
> +	long res;
>  
>  	/* No support for C-style ouptut */
>  
> @@ -302,14 +302,14 @@ static void probe_jit_kallsyms(void)
>  			printf("Unable to retrieve JIT kallsyms export status\n");
>  			break;
>  		default:
> -			printf("JIT kallsyms exports status has unknown value %d\n", res);
> +			printf("JIT kallsyms exports status has unknown value %ld\n", res);
>  		}
>  	}
>  }
>  
>  static void probe_jit_limit(void)
>  {
> -	int res;
> +	long res;
>  
>  	/* No support for C-style ouptut */
>  
> @@ -322,7 +322,7 @@ static void probe_jit_limit(void)
>  			printf("Unable to retrieve global memory limit for JIT compiler for unprivileged users\n");
>  			break;
>  		default:
> -			printf("Global memory limit for JIT compiler for unprivileged users is %d bytes\n", res);
> +			printf("Global memory limit for JIT compiler for unprivileged users is %ld bytes\n", res);
>  		}
>  	}
>  }
> -- 
> 2.31.1
>