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Fri, 18 Dec 2020 13:41:48 -0800 (PST) Date: Fri, 18 Dec 2020 13:41:41 -0800 In-Reply-To: <20201218214142.3673709-1-scw@google.com> Message-Id: <20201218214142.3673709-2-scw@google.com> Mime-Version: 1.0 References: <20201218214142.3673709-1-scw@google.com> X-Mailer: git-send-email 2.29.2.684.gfbc64c5ab5-goog Subject: [PATCH 1/2] thunk: supports flexible arrays To: qemu-devel@nongnu.org Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2607:f8b0:4864:20::f4a; envelope-from=3HCLdXwMKCtkN7RBJJBG9.7JHL9HP-89Q9GIJIBIP.JMB@flex--scw.bounces.google.com; helo=mail-qv1-xf4a.google.com X-Spam_score_int: -95 X-Spam_score: -9.6 X-Spam_bar: --------- X-Spam_report: (-9.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_MED=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Riku Voipio , Shu-Chun Weng Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Reply-to: Shu-Chun Weng From: Shu-Chun Weng via Flexible arrays may appear in the last field of a struct and are heavily used in the ioctl(SIOCETHTOOL) system call on Linux. E.g. struct ethtool_regs { __u32 cmd; __u32 version; /* driver-specific, indicates different chips/revs */ __u32 len; /* bytes */ __u8 data[0]; }; where number of elements in `data` is specified in `len`. It is translated into: STRUCT(ethtool_regs, TYPE_INT, /* cmd */ TYPE_INT, /* version */ TYPE_INT, /* len */ MK_FLEXIBLE_ARRAY(TYPE_CHAR, 2)) /* data[0]: len */ where the "2" passed to `MK_FLEXIBLE_ARRAY` means the number of element is specified by field number 2 (0-index). Signed-off-by: Shu-Chun Weng --- include/exec/user/thunk.h | 24 ++++++ thunk.c | 152 +++++++++++++++++++++++++++++++++++++- 2 files changed, 174 insertions(+), 2 deletions(-) diff --git a/include/exec/user/thunk.h b/include/exec/user/thunk.h index 300a840d58..42c58db7f0 100644 --- a/include/exec/user/thunk.h +++ b/include/exec/user/thunk.h @@ -39,12 +39,21 @@ typedef enum argtype { TYPE_ARRAY, TYPE_STRUCT, TYPE_OLDDEVT, + TYPE_FLEXIBLE_ARRAY, } argtype; #define MK_PTR(type) TYPE_PTR, type #define MK_ARRAY(type, size) TYPE_ARRAY, (int)(size), type #define MK_STRUCT(id) TYPE_STRUCT, id +/* + * Should only appear as the last element of a TYPE_STRUCT. `len_field_idx` is + * the index into the fields in the enclosing struct that specify the length of + * the flexibly array. The length field MUST be a TYPE_INT field. + */ +#define MK_FLEXIBLE_ARRAY(type, len_field_idx) \ + TYPE_FLEXIBLE_ARRAY, (len_field_idx), type + #define THUNK_TARGET 0 #define THUNK_HOST 1 @@ -56,6 +65,8 @@ typedef struct { /* special handling */ void (*convert[2])(void *dst, const void *src); void (*print)(void *arg); + int (*thunk_size[2])(const void *src); + int size[2]; int align[2]; const char *name; @@ -76,6 +87,11 @@ const argtype *thunk_convert(void *dst, const void *src, const argtype *type_ptr, int to_host); const argtype *thunk_print(void *arg, const argtype *type_ptr); +bool thunk_type_has_flexible_array(const argtype *type_ptr); +/* thunk_type_size but can handle TYPE_FLEXIBLE_ARRAY */ +int thunk_type_size_with_src(const void *src, const argtype *type_ptr, + int is_host); + extern StructEntry *struct_entries; int thunk_type_size_array(const argtype *type_ptr, int is_host); @@ -138,6 +154,12 @@ static inline int thunk_type_size(const argtype *type_ptr, int is_host) case TYPE_STRUCT: se = struct_entries + type_ptr[1]; return se->size[is_host]; + case TYPE_FLEXIBLE_ARRAY: + /* + * Flexible arrays do not count toward sizeof(). Users of structures + * containing them need to calculate it themselves. + */ + return 0; default: g_assert_not_reached(); } @@ -188,6 +210,8 @@ static inline int thunk_type_align(const argtype *type_ptr, int is_host) case TYPE_STRUCT: se = struct_entries + type_ptr[1]; return se->align[is_host]; + case TYPE_FLEXIBLE_ARRAY: + return thunk_type_align_array(type_ptr + 2, is_host); default: g_assert_not_reached(); } diff --git a/thunk.c b/thunk.c index fc5be1a502..f13e96cc4f 100644 --- a/thunk.c +++ b/thunk.c @@ -50,6 +50,8 @@ static inline const argtype *thunk_type_next(const argtype *type_ptr) return thunk_type_next_ptr(type_ptr + 1); case TYPE_STRUCT: return type_ptr + 1; + case TYPE_FLEXIBLE_ARRAY: + return thunk_type_next_ptr(type_ptr + 1); default: return NULL; } @@ -122,6 +124,34 @@ void thunk_register_struct_direct(int id, const char *name, se->name = name; } +static const argtype * +thunk_convert_flexible_array(void *dst, const void *src, + const uint8_t *dst_struct, + const uint8_t *src_struct, const argtype *type_ptr, + const StructEntry *se, int to_host) { + int len_field_idx, dst_size, src_size, i; + uint32_t array_length; + uint8_t *d; + const uint8_t *s; + + assert(*type_ptr == TYPE_FLEXIBLE_ARRAY); + type_ptr++; + len_field_idx = *type_ptr++; + array_length = + *(const uint32_t *)(to_host ? + dst_struct + se->field_offsets[1][len_field_idx] : + src_struct + se->field_offsets[0][len_field_idx]); + dst_size = thunk_type_size(type_ptr, to_host); + src_size = thunk_type_size(type_ptr, to_host); + d = dst; + s = src; + for (i = 0; i < array_length; i++) { + thunk_convert(d, s, type_ptr, to_host); + d += dst_size; + s += src_size; + } + return thunk_type_next(type_ptr); +} /* now we can define the main conversion functions */ const argtype *thunk_convert(void *dst, const void *src, @@ -246,7 +276,7 @@ const argtype *thunk_convert(void *dst, const void *src, assert(*type_ptr < max_struct_entries); se = struct_entries + *type_ptr++; - if (se->convert[0] != NULL) { + if (se->convert[to_host] != NULL) { /* specific conversion is needed */ (*se->convert[to_host])(dst, src); } else { @@ -256,7 +286,18 @@ const argtype *thunk_convert(void *dst, const void *src, src_offsets = se->field_offsets[1 - to_host]; d = dst; s = src; - for(i = 0;i < se->nb_fields; i++) { + for (i = 0; i < se->nb_fields; i++) { + if (*field_types == TYPE_FLEXIBLE_ARRAY) { + field_types = thunk_convert_flexible_array( + d + dst_offsets[i], + s + src_offsets[i], + d, + s, + field_types, + se, + to_host); + continue; + } field_types = thunk_convert(d + dst_offsets[i], s + src_offsets[i], field_types, to_host); @@ -264,6 +305,11 @@ const argtype *thunk_convert(void *dst, const void *src, } } break; + case TYPE_FLEXIBLE_ARRAY: + fprintf(stderr, + "Invalid flexible array (type 0x%x) outside of a structure\n", + type); + break; default: fprintf(stderr, "Invalid type 0x%x\n", type); break; @@ -271,6 +317,45 @@ const argtype *thunk_convert(void *dst, const void *src, return type_ptr; } +static const argtype * +thunk_print_flexible_array(void *arg, const uint8_t *arg_struct, + const argtype *type_ptr, const StructEntry *se) { + int array_length, len_field_idx, arg_size, i; + uint8_t *a; + int is_string = 0; + + assert(*type_ptr == TYPE_FLEXIBLE_ARRAY); + type_ptr++; + len_field_idx = *type_ptr++; + + array_length = tswap32( + *(const uint32_t *)(arg_struct + se->field_offsets[0][len_field_idx])); + arg_size = thunk_type_size(type_ptr, 0); + a = arg; + + if (*type_ptr == TYPE_CHAR) { + qemu_log("\""); + is_string = 1; + } else { + qemu_log("["); + } + + for (i = 0; i < array_length; i++) { + if (i > 0 && !is_string) { + qemu_log(","); + } + thunk_print(a, type_ptr); + a += arg_size; + } + + if (is_string) { + qemu_log("\""); + } else { + qemu_log("]"); + } + return thunk_type_next(type_ptr); +} + const argtype *thunk_print(void *arg, const argtype *type_ptr) { int type; @@ -418,18 +503,81 @@ const argtype *thunk_print(void *arg, const argtype *type_ptr) if (i > 0) { qemu_log(","); } + if (*field_types == TYPE_FLEXIBLE_ARRAY) { + field_types = thunk_print_flexible_array( + a + arg_offsets[i], a, field_types, se); + continue; + } field_types = thunk_print(a + arg_offsets[i], field_types); } qemu_log("}"); } } break; + case TYPE_FLEXIBLE_ARRAY: + fprintf(stderr, + "Invalid flexible array (type 0x%x) outside of a structure\n", + type); + break; default: g_assert_not_reached(); } return type_ptr; } +bool thunk_type_has_flexible_array(const argtype *type_ptr) +{ + int i; + const StructEntry *se; + const argtype *field_types; + if (*type_ptr != TYPE_STRUCT) { + return false; + } + se = struct_entries + type_ptr[1]; + field_types = se->field_types; + for (i = 0; i < se->nb_fields; i++) { + if (*field_types == TYPE_FLEXIBLE_ARRAY) { + return true; + } + field_types = thunk_type_next(type_ptr); + } + return false; +} + +int thunk_type_size_with_src(const void *src, const argtype *type_ptr, + int is_host) +{ + switch (*type_ptr) { + case TYPE_STRUCT: { + int i; + const StructEntry *se = struct_entries + type_ptr[1]; + const argtype *field_types; + if (se->thunk_size[is_host] != NULL) { + return (*se->thunk_size[is_host])(src); + } + + field_types = se->field_types; + for (i = 0; i < se->nb_fields; i++) { + if (*field_types == TYPE_FLEXIBLE_ARRAY) { + uint32_t array_length = *(const uint32_t *)( + (const uint8_t *)src + + se->field_offsets[is_host][field_types[1]]); + if (!is_host) { + array_length = tswap32(array_length); + } + return se->size[is_host] + + array_length * + thunk_type_size(field_types + 2, is_host); + } + field_types = thunk_type_next(type_ptr); + } + return se->size[is_host]; + } + default: + return thunk_type_size(type_ptr, is_host); + } +} + /* from em86 */ /* Utility function: Table-driven functions to translate bitmasks -- 2.29.2.684.gfbc64c5ab5-goog