Re: [PATCH bpf-next v4 2/3] bpf: btf: add btf print functionality

On Wed, Jul 11, 2018 at 10:08:35PM +0200, Daniel Borkmann wrote:

On 07/11/2018 09:10 PM, Jakub Kicinski wrote:

quoted

Thank you for all the changes made so far.

On Tue, 10 Jul 2018 20:21:10 -0700, Okash Khawaja wrote:

quoted

--- /dev/null
+++ b/tools/bpf/bpftool/btf_dumper.c

@@ -0,0 +1,248 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2018 Facebook */
+
+#include <linux/btf.h>
+#include <linux/err.h>
+#include <stdio.h> /* for (FILE *) used by json_writer */
+#include <linux/bitops.h>
+#include <string.h>
+#include <ctype.h>

Again, please sort the headers the way I suggested.  Otherwise as the
list of includes grows it's hard to know what's already there.

quoted

+#include "btf.h"
+#include "json_writer.h"
+#include "main.h"
+
+#define BITS_PER_BYTE_MASK (BITS_PER_BYTE - 1)
+#define BITS_PER_BYTE_MASKED(bits) ((bits) & BITS_PER_BYTE_MASK)
+#define BITS_ROUNDDOWN_BYTES(bits) ((bits) >> 3)
+#define BITS_ROUNDUP_BYTES(bits) \
+	(BITS_ROUNDDOWN_BYTES(bits) + !!BITS_PER_BYTE_MASKED(bits))
+
+static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id,
+			      __u8 bit_offset, const void *data);
+
+static void btf_dumper_ptr(const void *data, json_writer_t *jw,
+			   bool is_plain_text)
+{
+	if (is_plain_text)
+		jsonw_printf(jw, "%p", *((unsigned long *)data));
+	else
+		jsonw_printf(jw, "%u", *((unsigned long *)data));

Again, please drop the extraneous parens. 

quoted

+}
+

quoted

+static void btf_dumper_int_bits(__u32 int_type, __u8 bit_offset,
+				const void *data, json_writer_t *jw,
+				bool is_plain_text)
+{
+	int left_shift_bits, right_shift_bits;
+	int nr_bits = BTF_INT_BITS(int_type);
+	int total_bits_offset;
+	int bytes_to_copy;
+	int bits_to_copy;
+	__u64 print_num;
+
+	total_bits_offset = bit_offset + BTF_INT_OFFSET(int_type);
+	data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
+	bit_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
+	bits_to_copy = bit_offset + nr_bits;
+	bytes_to_copy = BITS_ROUNDUP_BYTES(bits_to_copy);
+
+	print_num = 0;
+	memcpy(&print_num, data, bytes_to_copy);
+#ifdef __BIG_ENDIAN_BITFIELD
+	left_shift_bits = bit_offset;
+#else
+	left_shift_bits = 64 - bits_to_copy;
+#endif
+	right_shift_bits = 64 - nr_bits;

Please include <asm/byteorder.h> as I suggested to you previously.
This is dead code right now, look:

$ git diff

diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
index c64465094b92..045add07b721 100644
--- a/tools/bpf/bpftool/btf_dumper.c
+++ b/tools/bpf/bpftool/btf_dumper.c

@@ -91,7 +91,8 @@ static void btf_dumper_int_bits(__u32 int_type, __u8 bit_offset,
 
        print_num = 0;
        memcpy(&print_num, data, bytes_to_copy);
-#ifdef __BIG_ENDIAN_BITFIELD
+#ifndef __LITTLE_ENDIAN_BITFIELD
+#error "abc"
        left_shift_bits = bit_offset;
 #else
        left_shift_bits = 64 - bits_to_copy;

$ make -C tools/bpf/bpftool/ CC=gcc-8
make: Entering directory '/home/jkicinski/devel/linux/tools/bpf/bpftool'
  CC       btf_dumper.o
btf_dumper.c: In function ‘btf_dumper_int_bits’:
btf_dumper.c:95:2: error: #error "abc"
 #error "abc"
  ^~~~~
Makefile:96: recipe for target 'btf_dumper.o' failed
make: *** [btf_dumper.o] Error 1
make: Leaving directory '/home/jkicinski/devel/linux/tools/bpf/bpftool'

You could also easily test this on s390x (big endian) through a LinuxONE
test instance, this is how I usually test changes related to their JIT.

Thanks. I've been using MIPS qemu set up. This will definitely help.

Thanks,
Daniel