Previous patches enabled SetVariableRT using a RAM backend. Although EBBR [0] defines a variable format we can teach userspace tools and write the altered variables, it's better if we skip the ABI requirements completely.
So let's add a new variable, in its own namespace called "VarToFile" which contains a binary dump of the updated RT, BS and, NV variables and will be updated when GetVariable is called. Some adjustments are needed to do that. Currently we discard BS-only variables in EBS(). We need to preserve those on the RAM backend that exposes the variables. Since BS-only variables can't appear at runtime we need to move the memory masking checks from efi_var_collect() to efi_get_next_variable_name_mem()/ efi_get_variable_mem() and do the filtering at runtime. We also need an efi_var_collect() variant available at runtime, in order to construct the "VarToFile" buffer on the fly. All users and applications (for linux) have to do when updating a variable is dd that variable in the file described by "RTStorageVolatile". Linux efivarfs uses a first 4 bytes of the output to represent attributes in little-endian format. So, storing variables works like this: $~ efibootmgr -n 0001 $~ dd if=/sys/firmware/efi/efivars/VarToFile-b2ac5fc9-92b7-4acd-aeac-11e818c3130c of=/boot/efi/ubootefi.var skip=4 bs=1 [0] https://arm-software.github.io/ebbr/index.html#document-chapter5-variable-storage Suggested-by: Ard Biesheuvel <a...@kernel.org> # dumping all variables to a variable Co-developed-by: Heinrich Schuchardt <heinrich.schucha...@canonical.com> # contributed on efi_var_collect_mem() Signed-off-by: Heinrich Schuchardt <heinrich.schucha...@canonical.com> Signed-off-by: Ilias Apalodimas <ilias.apalodi...@linaro.org> --- include/efi_variable.h | 16 +++- lib/charset.c | 2 +- lib/efi_loader/efi_runtime.c | 25 +++++ lib/efi_loader/efi_var_common.c | 6 +- lib/efi_loader/efi_var_mem.c | 151 +++++++++++++++++++----------- lib/efi_loader/efi_variable.c | 6 +- lib/efi_loader/efi_variable_tee.c | 5 - 7 files changed, 146 insertions(+), 65 deletions(-) diff --git a/include/efi_variable.h b/include/efi_variable.h index 42a2b7c52bef..223bb9a4a5bd 100644 --- a/include/efi_variable.h +++ b/include/efi_variable.h @@ -271,13 +271,16 @@ const efi_guid_t *efi_auth_var_get_guid(const u16 *name); * * @variable_name_size: size of variable_name buffer in bytes * @variable_name: name of uefi variable's name in u16 + * @mask: bitmask with required attributes of variables to be collected. + * variables are only collected if all of the required + * attributes match. Use 0 to skip matching * @vendor: vendor's guid * * Return: status code */ efi_status_t __efi_runtime efi_get_next_variable_name_mem(efi_uintn_t *variable_name_size, u16 *variable_name, - efi_guid_t *vendor); + efi_guid_t *vendor, u32 mask); /** * efi_get_variable_mem() - Runtime common code across efi variable * implementations for GetVariable() from @@ -289,12 +292,15 @@ efi_get_next_variable_name_mem(efi_uintn_t *variable_name_size, u16 *variable_na * @data_size: size of the buffer to which the variable value is copied * @data: buffer to which the variable value is copied * @timep: authentication time (seconds since start of epoch) + * @mask: bitmask with required attributes of variables to be collected. + * variables are only collected if all of the required + * attributes match. Use 0 to skip matching * Return: status code */ efi_status_t __efi_runtime efi_get_variable_mem(const u16 *variable_name, const efi_guid_t *vendor, u32 *attributes, efi_uintn_t *data_size, void *data, - u64 *timep); + u64 *timep, u32 mask); /** * efi_get_variable_runtime() - runtime implementation of GetVariable() @@ -334,4 +340,10 @@ efi_get_next_variable_name_runtime(efi_uintn_t *variable_name_size, */ void efi_var_buf_update(struct efi_var_file *var_buf); +efi_status_t __efi_runtime efi_var_collect_mem(struct efi_var_file *buf, + efi_uintn_t *lenp, + u32 check_attr_mask); + +u32 efi_var_entry_len(struct efi_var_entry *var); + #endif diff --git a/lib/charset.c b/lib/charset.c index df4f04074852..182c92a50c48 100644 --- a/lib/charset.c +++ b/lib/charset.c @@ -387,7 +387,7 @@ int u16_strcasecmp(const u16 *s1, const u16 *s2) * > 0 if the first different u16 in s1 is greater than the * corresponding u16 in s2 */ -int u16_strncmp(const u16 *s1, const u16 *s2, size_t n) +int __efi_runtime u16_strncmp(const u16 *s1, const u16 *s2, size_t n) { int ret = 0; diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c index c8f7a88ba8db..73831c527e00 100644 --- a/lib/efi_loader/efi_runtime.c +++ b/lib/efi_loader/efi_runtime.c @@ -130,6 +130,8 @@ efi_status_t efi_init_runtime_supported(void) EFI_RT_SUPPORTED_CONVERT_POINTER; if (IS_ENABLED(CONFIG_EFI_RT_VOLATILE_STORE)) { + u8 s = 0; + ret = efi_set_variable_int(u"RTStorageVolatile", &efi_guid_efi_rt_var_file, EFI_VARIABLE_BOOTSERVICE_ACCESS | @@ -141,6 +143,29 @@ efi_status_t efi_init_runtime_supported(void) log_err("Failed to set RTStorageVolatile\n"); return ret; } + /* + * This variable needs to be visible so users can read it, + * but the real contents are going to be filled during + * GetVariable + */ + ret = efi_set_variable_int(u"VarToFile", + &efi_guid_efi_rt_var_file, + EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS | + EFI_VARIABLE_READ_ONLY, + sizeof(s), + &s, false); + if (ret != EFI_SUCCESS) { + log_err("Failed to set VarToFile\n"); + efi_set_variable_int(u"RTStorageVolatile", + &efi_guid_efi_rt_var_file, + EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS | + EFI_VARIABLE_READ_ONLY, + 0, NULL, false); + + return ret; + } rt_table->runtime_services_supported |= EFI_RT_SUPPORTED_SET_VARIABLE; } diff --git a/lib/efi_loader/efi_var_common.c b/lib/efi_loader/efi_var_common.c index aa8feffd3ec1..7862f2d6ce8a 100644 --- a/lib/efi_loader/efi_var_common.c +++ b/lib/efi_loader/efi_var_common.c @@ -182,7 +182,8 @@ efi_get_variable_runtime(u16 *variable_name, const efi_guid_t *guid, { efi_status_t ret; - ret = efi_get_variable_mem(variable_name, guid, attributes, data_size, data, NULL); + ret = efi_get_variable_mem(variable_name, guid, attributes, data_size, + data, NULL, EFI_VARIABLE_RUNTIME_ACCESS); /* Remove EFI_VARIABLE_READ_ONLY flag */ if (attributes) @@ -195,7 +196,8 @@ efi_status_t __efi_runtime EFIAPI efi_get_next_variable_name_runtime(efi_uintn_t *variable_name_size, u16 *variable_name, efi_guid_t *guid) { - return efi_get_next_variable_name_mem(variable_name_size, variable_name, guid); + return efi_get_next_variable_name_mem(variable_name_size, variable_name, + guid, EFI_VARIABLE_RUNTIME_ACCESS); } /** diff --git a/lib/efi_loader/efi_var_mem.c b/lib/efi_loader/efi_var_mem.c index 6c21cec5d457..940ab6638823 100644 --- a/lib/efi_loader/efi_var_mem.c +++ b/lib/efi_loader/efi_var_mem.c @@ -61,6 +61,23 @@ efi_var_mem_compare(struct efi_var_entry *var, const efi_guid_t *guid, return match; } +/** + * efi_var_entry_len() - Get the entry len including headers & name + * + * @var: pointer to variable start + * + * Return: 8-byte aligned variable entry length + */ + +u32 __efi_runtime efi_var_entry_len(struct efi_var_entry *var) +{ + if (!var) + return 0; + + return ALIGN((sizeof(u16) * (u16_strlen(var->name) + 1)) + + var->length + sizeof(*var), 8); +} + struct efi_var_entry __efi_runtime *efi_var_mem_find(const efi_guid_t *guid, const u16 *name, struct efi_var_entry **next) @@ -184,53 +201,6 @@ u64 __efi_runtime efi_var_mem_free(void) sizeof(struct efi_var_entry); } -/** - * efi_var_mem_bs_del() - delete boot service only variables - */ -static void efi_var_mem_bs_del(void) -{ - struct efi_var_entry *var = efi_var_buf->var; - - for (;;) { - struct efi_var_entry *last; - - last = (struct efi_var_entry *) - ((uintptr_t)efi_var_buf + efi_var_buf->length); - if (var >= last) - break; - if (var->attr & EFI_VARIABLE_RUNTIME_ACCESS) { - u16 *data; - - /* skip variable */ - for (data = var->name; *data; ++data) - ; - ++data; - var = (struct efi_var_entry *) - ALIGN((uintptr_t)data + var->length, 8); - } else { - /* delete variable */ - efi_var_mem_del(var); - } - } -} - -/** - * efi_var_mem_notify_exit_boot_services() - ExitBootService callback - * - * @event: callback event - * @context: callback context - */ -static void EFIAPI -efi_var_mem_notify_exit_boot_services(struct efi_event *event, void *context) -{ - EFI_ENTRY("%p, %p", event, context); - - /* Delete boot service only variables */ - efi_var_mem_bs_del(); - - EFI_EXIT(EFI_SUCCESS); -} - /** * efi_var_mem_notify_exit_boot_services() - SetVirtualMemoryMap callback * @@ -261,11 +231,7 @@ efi_status_t efi_var_mem_init(void) efi_var_buf->magic = EFI_VAR_FILE_MAGIC; efi_var_buf->length = (uintptr_t)efi_var_buf->var - (uintptr_t)efi_var_buf; - /* crc32 for 0 bytes = 0 */ - ret = efi_create_event(EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK, - efi_var_mem_notify_exit_boot_services, NULL, - NULL, &event); if (ret != EFI_SUCCESS) return ret; ret = efi_create_event(EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE, TPL_CALLBACK, @@ -276,10 +242,71 @@ efi_status_t efi_var_mem_init(void) return ret; } +/** + * efi_var_collect_mem() - Copy EFI variables matching attributes mask from + * efi_var_buf + * + * @buf: buffer containing variable collection + * @lenp: buffer length + * @mask: mask of matched attributes + * + * Return: Status code + */ +efi_status_t __efi_runtime +efi_var_collect_mem(struct efi_var_file *buf, efi_uintn_t *lenp, u32 mask) +{ + static struct efi_var_file __efi_runtime_data hdr = { + .magic = EFI_VAR_FILE_MAGIC, + }; + struct efi_var_entry *last, *var, *var_to; + + hdr.length = sizeof(struct efi_var_file); + + var = efi_var_buf->var; + last = (struct efi_var_entry *) + ((uintptr_t)efi_var_buf + efi_var_buf->length); + if (buf) + var_to = buf->var; + + while (var < last) { + u32 len = efi_var_entry_len(var); + + if ((var->attr & mask) != mask) { + var = (void *)((uintptr_t)var + len); + continue; + } + + hdr.length += len; + + if (buf && hdr.length <= *lenp) { + efi_memcpy_runtime(var_to, var, len); + var_to = (void *)var_to + len; + } + var = (void *)var + len; + } + + if (!buf && hdr.length <= *lenp) { + *lenp = hdr.length; + return EFI_INVALID_PARAMETER; + } + + if (!buf || hdr.length > *lenp) { + *lenp = hdr.length; + return EFI_BUFFER_TOO_SMALL; + } + hdr.crc32 = crc32(0, (u8 *)buf->var, + hdr.length - sizeof(struct efi_var_file)); + + efi_memcpy_runtime(buf, &hdr, sizeof(hdr)); + *lenp = hdr.length; + + return EFI_SUCCESS; +} + efi_status_t __efi_runtime efi_get_variable_mem(const u16 *variable_name, const efi_guid_t *vendor, u32 *attributes, efi_uintn_t *data_size, void *data, - u64 *timep) + u64 *timep, u32 mask) { efi_uintn_t old_size; struct efi_var_entry *var; @@ -291,11 +318,22 @@ efi_get_variable_mem(const u16 *variable_name, const efi_guid_t *vendor, if (!var) return EFI_NOT_FOUND; + /* + * This function is used at runtime to dump EFI variables. + * The memory backend we keep around has BS-only variables as + * well. At runtime we filter them here + */ + if (mask && !((var->attr & mask) == mask)) + return EFI_NOT_FOUND; + if (attributes) *attributes = var->attr; if (timep) *timep = var->time; + if (!u16_strcmp(variable_name, u"VarToFile")) + return efi_var_collect_mem(data, data_size, EFI_VARIABLE_NON_VOLATILE); + old_size = *data_size; *data_size = var->length; if (old_size < var->length) @@ -315,7 +353,8 @@ efi_get_variable_mem(const u16 *variable_name, const efi_guid_t *vendor, efi_status_t __efi_runtime efi_get_next_variable_name_mem(efi_uintn_t *variable_name_size, - u16 *variable_name, efi_guid_t *vendor) + u16 *variable_name, efi_guid_t *vendor, + u32 mask) { struct efi_var_entry *var; efi_uintn_t len, old_size; @@ -324,6 +363,7 @@ efi_get_next_variable_name_mem(efi_uintn_t *variable_name_size, if (!variable_name_size || !variable_name || !vendor) return EFI_INVALID_PARAMETER; +skip: len = *variable_name_size >> 1; if (u16_strnlen(variable_name, len) == len) return EFI_INVALID_PARAMETER; @@ -347,6 +387,11 @@ efi_get_next_variable_name_mem(efi_uintn_t *variable_name_size, efi_memcpy_runtime(variable_name, var->name, *variable_name_size); efi_memcpy_runtime(vendor, &var->guid, sizeof(efi_guid_t)); + if (mask && !((var->attr & mask) == mask)) { + *variable_name_size = old_size; + goto skip; + } + return EFI_SUCCESS; } diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c index 47bb79920575..0cbed53d1dbf 100644 --- a/lib/efi_loader/efi_variable.c +++ b/lib/efi_loader/efi_variable.c @@ -209,14 +209,16 @@ efi_get_variable_int(const u16 *variable_name, const efi_guid_t *vendor, u32 *attributes, efi_uintn_t *data_size, void *data, u64 *timep) { - return efi_get_variable_mem(variable_name, vendor, attributes, data_size, data, timep); + return efi_get_variable_mem(variable_name, vendor, attributes, data_size, + data, timep, 0); } efi_status_t __efi_runtime efi_get_next_variable_name_int(efi_uintn_t *variable_name_size, u16 *variable_name, efi_guid_t *vendor) { - return efi_get_next_variable_name_mem(variable_name_size, variable_name, vendor); + return efi_get_next_variable_name_mem(variable_name_size, variable_name, + vendor, 0); } /** diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c index dde135fd9f81..4f1aa298da13 100644 --- a/lib/efi_loader/efi_variable_tee.c +++ b/lib/efi_loader/efi_variable_tee.c @@ -959,11 +959,6 @@ void efi_variables_boot_exit_notify(void) log_err("Unable to notify the MM partition for ExitBootServices\n"); free(comm_buf); - /* - * Populate the list for runtime variables. - * asking EFI_VARIABLE_RUNTIME_ACCESS is redundant, since - * efi_var_mem_notify_exit_boot_services will clean those, but that's fine - */ ret = efi_var_collect(&var_buf, &len, EFI_VARIABLE_RUNTIME_ACCESS); if (ret != EFI_SUCCESS) log_err("Can't populate EFI variables. No runtime variables will be available\n"); -- 2.40.1
