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authorAndrey Ignatov <rdna@fb.com>2019-03-18 17:55:26 -0700
committerAlexei Starovoitov <ast@kernel.org>2019-04-12 13:54:59 -0700
commitd7a4cb9b6705a89937d12c8158a35a3145dc967a (patch)
tree1a412b1d491dcc6aca5032dc2792a2a530e26af3 /kernel/bpf
parent57c3bb725a3dd97d960d7e1cd0845d88de53217f (diff)
downloadlinux-d7a4cb9b6705a89937d12c8158a35a3145dc967a.tar.bz2
bpf: Introduce bpf_strtol and bpf_strtoul helpers
Add bpf_strtol and bpf_strtoul to convert a string to long and unsigned long correspondingly. It's similar to user space strtol(3) and strtoul(3) with a few changes to the API: * instead of NUL-terminated C string the helpers expect buffer and buffer length; * resulting long or unsigned long is returned in a separate result-argument; * return value is used to indicate success or failure, on success number of consumed bytes is returned that can be used to identify position to read next if the buffer is expected to contain multiple integers; * instead of *base* argument, *flags* is used that provides base in 5 LSB, other bits are reserved for future use; * number of supported bases is limited. Documentation for the new helpers is provided in bpf.h UAPI. The helpers are made available to BPF_PROG_TYPE_CGROUP_SYSCTL programs to be able to convert string input to e.g. "ulongvec" output. E.g. "net/ipv4/tcp_mem" consists of three ulong integers. They can be parsed by calling to bpf_strtoul three times. Implementation notes: Implementation includes "../../lib/kstrtox.h" to reuse integer parsing functions. It's done exactly same way as fs/proc/base.c already does. Unfortunately existing kstrtoX function can't be used directly since they fail if any invalid character is present right after integer in the string. Existing simple_strtoX functions can't be used either since they're obsolete and don't handle overflow properly. Signed-off-by: Andrey Ignatov <rdna@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/cgroup.c4
-rw-r--r--kernel/bpf/helpers.c131
2 files changed, 135 insertions, 0 deletions
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index b2adf22139b3..789d4ab2336e 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1016,6 +1016,10 @@ static const struct bpf_func_proto *
sysctl_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
switch (func_id) {
+ case BPF_FUNC_strtol:
+ return &bpf_strtol_proto;
+ case BPF_FUNC_strtoul:
+ return &bpf_strtoul_proto;
case BPF_FUNC_sysctl_get_name:
return &bpf_sysctl_get_name_proto;
case BPF_FUNC_sysctl_get_current_value:
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index a411fc17d265..4266ffde07ca 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -18,6 +18,9 @@
#include <linux/sched.h>
#include <linux/uidgid.h>
#include <linux/filter.h>
+#include <linux/ctype.h>
+
+#include "../../lib/kstrtox.h"
/* If kernel subsystem is allowing eBPF programs to call this function,
* inside its own verifier_ops->get_func_proto() callback it should return
@@ -363,4 +366,132 @@ const struct bpf_func_proto bpf_get_local_storage_proto = {
.arg2_type = ARG_ANYTHING,
};
#endif
+
+#define BPF_STRTOX_BASE_MASK 0x1F
+
+static int __bpf_strtoull(const char *buf, size_t buf_len, u64 flags,
+ unsigned long long *res, bool *is_negative)
+{
+ unsigned int base = flags & BPF_STRTOX_BASE_MASK;
+ const char *cur_buf = buf;
+ size_t cur_len = buf_len;
+ unsigned int consumed;
+ size_t val_len;
+ char str[64];
+
+ if (!buf || !buf_len || !res || !is_negative)
+ return -EINVAL;
+
+ if (base != 0 && base != 8 && base != 10 && base != 16)
+ return -EINVAL;
+
+ if (flags & ~BPF_STRTOX_BASE_MASK)
+ return -EINVAL;
+
+ while (cur_buf < buf + buf_len && isspace(*cur_buf))
+ ++cur_buf;
+
+ *is_negative = (cur_buf < buf + buf_len && *cur_buf == '-');
+ if (*is_negative)
+ ++cur_buf;
+
+ consumed = cur_buf - buf;
+ cur_len -= consumed;
+ if (!cur_len)
+ return -EINVAL;
+
+ cur_len = min(cur_len, sizeof(str) - 1);
+ memcpy(str, cur_buf, cur_len);
+ str[cur_len] = '\0';
+ cur_buf = str;
+
+ cur_buf = _parse_integer_fixup_radix(cur_buf, &base);
+ val_len = _parse_integer(cur_buf, base, res);
+
+ if (val_len & KSTRTOX_OVERFLOW)
+ return -ERANGE;
+
+ if (val_len == 0)
+ return -EINVAL;
+
+ cur_buf += val_len;
+ consumed += cur_buf - str;
+
+ return consumed;
+}
+
+static int __bpf_strtoll(const char *buf, size_t buf_len, u64 flags,
+ long long *res)
+{
+ unsigned long long _res;
+ bool is_negative;
+ int err;
+
+ err = __bpf_strtoull(buf, buf_len, flags, &_res, &is_negative);
+ if (err < 0)
+ return err;
+ if (is_negative) {
+ if ((long long)-_res > 0)
+ return -ERANGE;
+ *res = -_res;
+ } else {
+ if ((long long)_res < 0)
+ return -ERANGE;
+ *res = _res;
+ }
+ return err;
+}
+
+BPF_CALL_4(bpf_strtol, const char *, buf, size_t, buf_len, u64, flags,
+ long *, res)
+{
+ long long _res;
+ int err;
+
+ err = __bpf_strtoll(buf, buf_len, flags, &_res);
+ if (err < 0)
+ return err;
+ if (_res != (long)_res)
+ return -ERANGE;
+ *res = _res;
+ return err;
+}
+
+const struct bpf_func_proto bpf_strtol_proto = {
+ .func = bpf_strtol,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_CONST_SIZE,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_PTR_TO_LONG,
+};
+
+BPF_CALL_4(bpf_strtoul, const char *, buf, size_t, buf_len, u64, flags,
+ unsigned long *, res)
+{
+ unsigned long long _res;
+ bool is_negative;
+ int err;
+
+ err = __bpf_strtoull(buf, buf_len, flags, &_res, &is_negative);
+ if (err < 0)
+ return err;
+ if (is_negative)
+ return -EINVAL;
+ if (_res != (unsigned long)_res)
+ return -ERANGE;
+ *res = _res;
+ return err;
+}
+
+const struct bpf_func_proto bpf_strtoul_proto = {
+ .func = bpf_strtoul,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_CONST_SIZE,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_PTR_TO_LONG,
+};
#endif