include/linux/fs_parser.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /* Filesystem parameter description and parser
   3  *
   4  * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #ifndef _LINUX_FS_PARSER_H
   9 #define _LINUX_FS_PARSER_H
  10
  11 #include <linux/fs_context.h>
  12
  13 struct path;
  14
  15 struct constant_table {
  16         const char      *name;
  17         int             value;
  18 };
  19
  20 struct fs_parameter_spec;
  21 struct fs_parse_result;
  22 typedef int fs_param_type(struct p_log *,
  23                           const struct fs_parameter_spec *,
  24                           struct fs_parameter *,
  25                           struct fs_parse_result *);
  26 /*
  27  * The type of parameter expected.
  28  */
  29 fs_param_type fs_param_is_bool, fs_param_is_u32, fs_param_is_s32, fs_param_is_u64,
  30         fs_param_is_enum, fs_param_is_string, fs_param_is_blob, fs_param_is_blockdev,
  31         fs_param_is_path, fs_param_is_fd, fs_param_is_uid, fs_param_is_gid,
  32         fs_param_is_file_or_string;
  33
  34 /*
  35  * Specification of the type of value a parameter wants.
  36  *
  37  * Note that the fsparam_flag(), fsparam_string(), fsparam_u32(), ... macros
  38  * should be used to generate elements of this type.
  39  */
  40 struct fs_parameter_spec {
  41         const char              *name;
  42         fs_param_type           *type;  /* The desired parameter type */
  43         u8                      opt;    /* Option number (returned by fs_parse()) */
  44         unsigned short          flags;
  45 #define fs_param_neg_with_no    0x0002  /* "noxxx" is negative param */
  46 #define fs_param_can_be_empty   0x0004  /* "xxx=" is allowed */
  47 #define fs_param_deprecated     0x0008  /* The param is deprecated */
  48         const void              *data;
  49 };
  50
  51 /*
  52  * Result of parse.
  53  */
  54 struct fs_parse_result {
  55         bool                    negated;        /* T if param was "noxxx" */
  56         union {
  57                 bool            boolean;        /* For spec_bool */
  58                 int             int_32;         /* For spec_s32/spec_enum */
  59                 unsigned int    uint_32;        /* For spec_u32{,_octal,_hex}/spec_enum */
  60                 u64             uint_64;        /* For spec_u64 */
  61                 kuid_t          uid;
  62                 kgid_t          gid;
  63         };
  64 };
  65
  66 extern int __fs_parse(struct p_log *log,
  67                     const struct fs_parameter_spec *desc,
  68                     struct fs_parameter *value,
  69                     struct fs_parse_result *result);
  70
  71 static inline int fs_parse(struct fs_context *fc,
  72              const struct fs_parameter_spec *desc,
  73              struct fs_parameter *param,
  74              struct fs_parse_result *result)
  75 {
  76         return __fs_parse(&fc->log, desc, param, result);
  77 }
  78
  79 extern int fs_lookup_param(struct fs_context *fc,
  80                            struct fs_parameter *param,
  81                            bool want_bdev,
  82                            unsigned int flags,
  83                            struct path *_path);
  84
  85 extern int lookup_constant(const struct constant_table tbl[], const char *name, int not_found);
  86
  87 #ifdef CONFIG_VALIDATE_FS_PARSER
  88 extern bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
  89                                     int low, int high, int special);
  90 extern bool fs_validate_description(const char *name,
  91                                     const struct fs_parameter_spec *desc);
  92 #else
  93 static inline bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
  94                                            int low, int high, int special)
  95 { return true; }
  96 static inline bool fs_validate_description(const char *name,
  97                                            const struct fs_parameter_spec *desc)
  98 { return true; }
  99 #endif
 100
 101 /*
 102  * Parameter type, name, index and flags element constructors.  Use as:
 103  *
 104  *  fsparam_xxxx("foo", Opt_foo)
 105  *
 106  * If existing helpers are not enough, direct use of __fsparam() would
 107  * work, but any such case is probably a sign that new helper is needed.
 108  * Helpers will remain stable; low-level implementation may change.
 109  */
 110 #define __fsparam(TYPE, NAME, OPT, FLAGS, DATA) \
 111         { \
 112                 .name = NAME, \
 113                 .opt = OPT, \
 114                 .type = TYPE, \
 115                 .flags = FLAGS, \
 116                 .data = DATA \
 117         }
 118
 119 #define fsparam_flag(NAME, OPT) __fsparam(NULL, NAME, OPT, 0, NULL)
 120 #define fsparam_flag_no(NAME, OPT) \
 121                         __fsparam(NULL, NAME, OPT, fs_param_neg_with_no, NULL)
 122 #define fsparam_bool(NAME, OPT) __fsparam(fs_param_is_bool, NAME, OPT, 0, NULL)
 123 #define fsparam_u32(NAME, OPT)  __fsparam(fs_param_is_u32, NAME, OPT, 0, NULL)
 124 #define fsparam_u32oct(NAME, OPT) \
 125                         __fsparam(fs_param_is_u32, NAME, OPT, 0, (void *)8)
 126 #define fsparam_u32hex(NAME, OPT) \
 127                         __fsparam(fs_param_is_u32_hex, NAME, OPT, 0, (void *)16)
 128 #define fsparam_s32(NAME, OPT)  __fsparam(fs_param_is_s32, NAME, OPT, 0, NULL)
 129 #define fsparam_u64(NAME, OPT)  __fsparam(fs_param_is_u64, NAME, OPT, 0, NULL)
 130 #define fsparam_enum(NAME, OPT, array)  __fsparam(fs_param_is_enum, NAME, OPT, 0, array)
 131 #define fsparam_string(NAME, OPT) \
 132                                 __fsparam(fs_param_is_string, NAME, OPT, 0, NULL)
 133 #define fsparam_blob(NAME, OPT) __fsparam(fs_param_is_blob, NAME, OPT, 0, NULL)
 134 #define fsparam_bdev(NAME, OPT) __fsparam(fs_param_is_blockdev, NAME, OPT, 0, NULL)
 135 #define fsparam_path(NAME, OPT) __fsparam(fs_param_is_path, NAME, OPT, 0, NULL)
 136 #define fsparam_fd(NAME, OPT)   __fsparam(fs_param_is_fd, NAME, OPT, 0, NULL)
 137 #define fsparam_file_or_string(NAME, OPT) \
 138                                 __fsparam(fs_param_is_file_or_string, NAME, OPT, 0, NULL)
 139 #define fsparam_uid(NAME, OPT) __fsparam(fs_param_is_uid, NAME, OPT, 0, NULL)
 140 #define fsparam_gid(NAME, OPT) __fsparam(fs_param_is_gid, NAME, OPT, 0, NULL)
 141
 142 /* String parameter that allows empty argument */
 143 #define fsparam_string_empty(NAME, OPT) \
 144         __fsparam(fs_param_is_string, NAME, OPT, fs_param_can_be_empty, NULL)
 145
 146 #endif /* _LINUX_FS_PARSER_H */