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bpf: improve handling of various sizes of bpf_prog_attr structure

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As program attributes have been added gradually over kernel versions,
attribute size less than expected should be printed accordingly.

* bpf.c (DEF_BPF_CMD_DECODER(BPF_PROG_LOAD)): Do not print structure
fields if their size is less than the initially introduced (in Linux
commit v3.18-rc1~52^2~1^2~7) version.  Print fields of union bpf_attr
introduced in various kernel versions when the length is big enough
(new fields were introduced in Linux commits v3.18-rc1~52^2~1^2~4,
v4.1-rc1~84^2~50, and v4.12-rc2~34^2~29^2~2).
* tests/bpf.c (print_BPF_PROG_LOAD_first): Update expected output.

Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
This commit is contained in:
Eugene Syromyatnikov 2018-02-22 03:17:04 +01:00 committed by Dmitry V. Levin
parent 8fa209cf0a
commit 2bcf86777b
2 changed files with 17 additions and 3 deletions
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17
bpf.c
View File

@ -201,7 +201,7 @@ DEF_BPF_CMD_DECODER(BPF_PROG_LOAD)
uint64_t ATTRIBUTE_ALIGNED(8) log_buf;
uint32_t kern_version, prog_flags;
} attr = {};
const unsigned int len = size < sizeof(attr) ? size : sizeof(attr);
const unsigned int len = MIN(size, sizeof(attr));
memcpy(&attr, data, len);
@ -210,15 +210,30 @@ DEF_BPF_CMD_DECODER(BPF_PROG_LOAD)
PRINT_FIELD_U(", ", attr, insn_cnt);
PRINT_FIELD_X(", ", attr, insns);
PRINT_FIELD_STR(", ", attr, license, tcp);
/* log_* fields were added in Linux commit v3.18-rc1~52^2~1^2~4. */
if (len <= offsetof(struct bpf_prog_load, log_level))
goto bpf_prog_load_end;
PRINT_FIELD_U(", ", attr, log_level);
PRINT_FIELD_U(", ", attr, log_size);
PRINT_FIELD_X(", ", attr, log_buf);
/* kern_version field was added in Linux commit v4.1-rc1~84^2~50. */
if (len <= offsetof(struct bpf_prog_load, kern_version))
goto bpf_prog_load_end;
tprintf(", kern_version=KERNEL_VERSION(%u, %u, %u)",
attr.kern_version >> 16,
(attr.kern_version >> 8) & 0xFF,
attr.kern_version & 0xFF);
/* prog_flags field was added in Linux commit v4.12-rc2~34^2~29^2~2. */
if (len <= offsetof(struct bpf_prog_load, prog_flags))
goto bpf_prog_load_end;
PRINT_FIELD_FLAGS(", ", attr, prog_flags, bpf_prog_flags, "BPF_F_???");
decode_attr_extra_data(tcp, data, size, sizeof(attr));
bpf_prog_load_end:
tprints("}");
return RVAL_DECODED | RVAL_FD;

3
tests/bpf.c
View File

@ -375,8 +375,7 @@ print_BPF_PROG_LOAD_first(const unsigned long addr)
{
printf("prog_type=BPF_PROG_TYPE_SOCKET_FILTER, insn_cnt=0, insns=0"
", license=NULL, log_level=0, log_size=0, log_buf=0"
", kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0");
", license=NULL");
}
static const struct bpf_insn insns[] = {