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bpf: print unused fields of union bpf_attr if one of them is non-zero

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When the size argument specifies more data than necessary for the given
command, kernel checks that all unused fields of union bpf_attr are
zero.  Print this extra data when it contains non-zero bytes to enhance
debugging experience.

* bpf.c (decode_attr_extra_data): New function.
(decode_BPF_MAP_CREATE, decode_BPF_MAP_UPDATE_ELEM,
decode_BPF_MAP_DELETE_ELEM, bpf_map_io, decode_BPF_PROG_LOAD,
decode_BPF_OBJ_PIN, decode_BPF_OBJ_GET, decode_BPF_PROG_ATTACH,
decode_BPF_PROG_DETACH): Use it to print extra data passed
via bpf_attr pointer.
(bpf_obj_manage, bpf_prog_attach_detach): Remove.
* tests/bpf.c (map_delete_elem): New function.
(main): Use it.
This commit is contained in:
Дмитрий Левин 2017-07-26 10:28:25 +00:00
parent 26b3867cef
commit 78de224180
2 changed files with 89 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

115
bpf.c
View File

@ -56,6 +56,34 @@ bpf_cmd_decoder(struct tcb *const tcp, \
typedef DECL_BPF_CMD_DECODER((*bpf_cmd_decoder_t));
static int
decode_attr_extra_data(struct tcb *const tcp,
const char *data,
unsigned int size,
const size_t attr_size)
{
if (size <= attr_size)
return 0;
data += attr_size;
size -= attr_size;
unsigned int i;
for (i = 0; i < size; ++i) {
if (data[i]) {
tprints(", ");
if (abbrev(tcp))
tprints("...");
else
print_quoted_string(data, size,
QUOTE_FORCE_HEX);
return RVAL_DECODED;
}
}
return 0;
}
DEF_BPF_CMD_DECODER(BPF_MAP_CREATE)
{
struct {
@ -70,6 +98,7 @@ DEF_BPF_CMD_DECODER(BPF_MAP_CREATE)
PRINT_FIELD_U(", ", attr, key_size);
PRINT_FIELD_U(", ", attr, value_size);
PRINT_FIELD_U(", ", attr, max_entries);
decode_attr_extra_data(tcp, data, size, sizeof(attr));
tprints("}");
return RVAL_DECODED | RVAL_FD;
@ -92,6 +121,7 @@ DEF_BPF_CMD_DECODER(BPF_MAP_UPDATE_ELEM)
PRINT_FIELD_X(", ", attr, value);
PRINT_FIELD_XVAL(", ", attr, flags, bpf_map_update_elem_flags,
"BPF_???");
decode_attr_extra_data(tcp, data, size, sizeof(attr));
tprints("}");
return RVAL_DECODED;
@ -109,6 +139,7 @@ DEF_BPF_CMD_DECODER(BPF_MAP_DELETE_ELEM)
PRINT_FIELD_FD("{", attr, map_fd, tcp);
PRINT_FIELD_X(", ", attr, key);
decode_attr_extra_data(tcp, data, size, sizeof(attr));
tprints("}");
return RVAL_DECODED;
@ -147,7 +178,11 @@ bpf_map_io(struct tcb *const tcp,
PRINT_FIELD_FD("{", attr, map_fd, tcp);
PRINT_FIELD_X(", ", attr, key);
return 0;
int rc = decode_attr_extra_data(tcp, data, size, sizeof(attr));
if (rc & RVAL_DECODED)
tprints("}");
return rc;
}
DEF_BPF_CMD_DECODER(BPF_MAP_LOOKUP_ELEM)
@ -162,14 +197,16 @@ DEF_BPF_CMD_DECODER(BPF_MAP_GET_NEXT_KEY)
DEF_BPF_CMD_DECODER(BPF_PROG_LOAD)
{
struct {
struct bpf_prog_load {
uint32_t prog_type, insn_cnt;
uint64_t ATTRIBUTE_ALIGNED(8) insns, license;
uint32_t log_level, log_size;
uint64_t ATTRIBUTE_ALIGNED(8) log_buf;
uint32_t kern_version;
} attr = {};
const unsigned int len = size < sizeof(attr) ? size : sizeof(attr);
const size_t attr_size =
offsetofend(struct bpf_prog_load, kern_version);
const unsigned int len = size < attr_size ? size : attr_size;
memcpy(&attr, data, len);
@ -182,23 +219,7 @@ DEF_BPF_CMD_DECODER(BPF_PROG_LOAD)
PRINT_FIELD_U(", ", attr, log_size);
PRINT_FIELD_X(", ", attr, log_buf);
PRINT_FIELD_U(", ", attr, kern_version);
tprints("}");
return RVAL_DECODED | RVAL_FD;
}
static DECL_BPF_CMD_DECODER(bpf_obj_manage)
{
struct {
uint64_t ATTRIBUTE_ALIGNED(8) pathname;
uint32_t bpf_fd;
} attr = {};
const unsigned int len = size < sizeof(attr) ? size : sizeof(attr);
memcpy(&attr, data, len);
PRINT_FIELD_PATH("{", attr, pathname, tcp);
PRINT_FIELD_FD(", ", attr, bpf_fd, tcp);
decode_attr_extra_data(tcp, data, size, attr_size);
tprints("}");
return RVAL_DECODED | RVAL_FD;
@ -206,17 +227,27 @@ static DECL_BPF_CMD_DECODER(bpf_obj_manage)
DEF_BPF_CMD_DECODER(BPF_OBJ_PIN)
{
return bpf_obj_manage(tcp, addr, size, data);
struct bpf_obj {
uint64_t ATTRIBUTE_ALIGNED(8) pathname;
uint32_t bpf_fd;
} attr = {};
const size_t attr_size =
offsetofend(struct bpf_obj, bpf_fd);
const unsigned int len = size < attr_size ? size : attr_size;
memcpy(&attr, data, len);
PRINT_FIELD_PATH("{", attr, pathname, tcp);
PRINT_FIELD_FD(", ", attr, bpf_fd, tcp);
decode_attr_extra_data(tcp, data, size, attr_size);
tprints("}");
return RVAL_DECODED | RVAL_FD;
}
DEF_BPF_CMD_DECODER(BPF_OBJ_GET)
{
return bpf_obj_manage(tcp, addr, size, data);
}
#define decode_BPF_OBJ_GET decode_BPF_OBJ_PIN
static int
bpf_prog_attach_detach(struct tcb *const tcp, void *const data,
unsigned int size, bool print_attach)
DEF_BPF_CMD_DECODER(BPF_PROG_ATTACH)
{
struct {
uint32_t target_fd, attach_bpf_fd, attach_type, attach_flags;
@ -226,25 +257,31 @@ bpf_prog_attach_detach(struct tcb *const tcp, void *const data,
memcpy(&attr, data, len);
PRINT_FIELD_FD("{", attr, target_fd, tcp);
if (print_attach)
PRINT_FIELD_FD(", ", attr, attach_bpf_fd, tcp);
PRINT_FIELD_FD(", ", attr, attach_bpf_fd, tcp);
PRINT_FIELD_XVAL(", ", attr, attach_type, bpf_attach_type, "BPF_???");
if (print_attach)
PRINT_FIELD_FLAGS(", ", attr, attach_flags, bpf_attach_flags,
"BPF_F_???");
PRINT_FIELD_FLAGS(", ", attr, attach_flags, bpf_attach_flags,
"BPF_F_???");
decode_attr_extra_data(tcp, data, size, sizeof(attr));
tprints("}");
return RVAL_DECODED;
}
DEF_BPF_CMD_DECODER(BPF_PROG_ATTACH)
{
return bpf_prog_attach_detach(tcp, data, size, true);
}
DEF_BPF_CMD_DECODER(BPF_PROG_DETACH)
{
return bpf_prog_attach_detach(tcp, data, size, false);
struct {
uint32_t target_fd, dummy, attach_type;
} attr = {};
const unsigned int len = size < sizeof(attr) ? size : sizeof(attr);
memcpy(&attr, data, len);
PRINT_FIELD_FD("{", attr, target_fd, tcp);
PRINT_FIELD_XVAL(", ", attr, attach_type, bpf_attach_type, "BPF_???");
decode_attr_extra_data(tcp, data, size, sizeof(attr));
tprints("}");
return RVAL_DECODED;
}
SYS_FUNC(bpf)

14
tests/bpf.c
View File

@ -73,6 +73,18 @@ map_any(int cmd)
return sys_bpf(cmd, (unsigned long) t_attr, sizeof(attr));
}
static int
map_delete_elem(void)
{
union bpf_attr attr = {
.map_fd = -1,
.key = 0xdeadbeef,
};
void *const t_attr = tail_memdup(&attr, sizeof(attr));
return sys_bpf(BPF_MAP_DELETE_ELEM,
(unsigned long) t_attr, sizeof(attr));
}
static int
prog_load(void)
{
@ -172,7 +184,7 @@ main(void)
(unsigned) sizeof(union bpf_attr), errstr);
BOGUS_BPF(BPF_MAP_UPDATE_ELEM);
map_any(BPF_MAP_DELETE_ELEM);
map_delete_elem();
printf("bpf(BPF_MAP_DELETE_ELEM"
", {map_fd=-1, key=0xdeadbeef}, %u) = %s\n",
(unsigned) sizeof(union bpf_attr), errstr);