[U-Boot] [RFC 6/6] efi_loader: variable: support runtime variable access via cache

AKASHI Takahiro takahiro.akashi at linaro.org
Tue Jun 18 01:19:06 UTC 2019


On Mon, Jun 17, 2019 at 09:52:34PM +0200, Heinrich Schuchardt wrote:
> On 6/17/19 3:51 AM, AKASHI Takahiro wrote:
> >On Sat, Jun 15, 2019 at 09:01:56PM +0200, Heinrich Schuchardt wrote:
> >>On 6/5/19 6:21 AM, AKASHI Takahiro wrote:
> >>>With this patch, cache buffer for UEFI variables will be created
> >>>so that we will still be able to access, at least retrieve,
> >>>UEFI variables when we exit from boottime services,
> >>>
> >>>This feature is a "should" behavior described in EBBR v1.0
> >>>section 2.5.3.
> >>>
> >>>Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> >>>---
> >>>  include/efi_loader.h          |  17 ++
> >>>  lib/efi_loader/Kconfig        |   9 +
> >>>  lib/efi_loader/efi_boottime.c |  10 +-
> >>>  lib/efi_loader/efi_runtime.c  |  13 +
> >>>  lib/efi_loader/efi_variable.c | 467 ++++++++++++++++++++++++++++++++++
> >>>  5 files changed, 515 insertions(+), 1 deletion(-)
> >>
> >>Please, put the cache into a separate file.
> >
> >Why?
> 
> It is a separate set of functions. In C++ programming you wouldn't put
> two classes into the same file.

? I don't get your point.
This is not C++, but C.

> >
> >>>
> >>>diff --git a/include/efi_loader.h b/include/efi_loader.h
> >>>index 93f7ece814a0..acab657b9d70 100644
> >>>--- a/include/efi_loader.h
> >>>+++ b/include/efi_loader.h
> >>>@@ -620,6 +620,23 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
> >>>  				     const efi_guid_t *vendor, u32 attributes,
> >>>  				     efi_uintn_t data_size, const void *data);
> >>>
> >>>+#ifdef CONFIG_EFI_RUNTIME_GET_VARIABLE_CACHING
> >>>+efi_status_t efi_freeze_variable_table(void);
> >>>+
> >>>+/* runtime version of APIs */
> >>>+efi_status_t
> >>>+__efi_runtime EFIAPI efi_get_variable_runtime(u16 *variable_name,
> >>
> >>I think one version of the functions serving at runtime and boottime is
> >>enough.
> >>
> >>The cache should be used both at runtime and at boottime.
> >
> >So do you mean that we should replace the existing "boottime" version
> >of get/set_variable with my code (algorithm)?
> >
> >This is a bit complicated work because we should be able to *udpate*
> >UEFI variables at boottime, but my version of hsearch_runtime() is
> >a stripped (and modified) version and doesn't support it.
> 
> Do we really need a multilevel hash table? I would not expect hundreds
> of variables.

Please don't change your point suddenly.
Here we are discussing whether "The cache should be used both at runtime
and at boottime" or not.

> >
> >Making the existing hsearch_r() executable at UEFI runtime is,
> >as I said before, quite painful.
> 
> You could start the cache implementation with a less complicated data
> structure like a linked list.

This is totally a different issue. I listed this issue
in my cover letter.

> >
> >>Essentially I
> >>expect three modules working together:
> >>
> >>UEFI API implementation <-> Cache <-> Persistence driver
> >>
> >>I would suggest to put each of these into a separate file.
> >>
> >>Both the API implementation and the Cache have to be available at
> >>Boottime and at Runtime. A first version of the persistence driver may
> >>only be working at boottime.
> >
> >Unfortunately, this is not practical right now because there is
> >already some sort of assumption (and consensus) that we would re-use
> >"Standalone MM services", which is already there in EDK2, as
> >secure storage for UEFI variables.
> >In the case, all the cache would be bypassed.
> >In my old prototype, I utilized the cache but dropped that feature
> >for several reasons.
> 
> What has EDK2 code to do with it?

Did you follow my comment below?
> >Unfortunately, this is not practical right now because there is
> >already some sort of assumption (and consensus) that we would re-use
> >"Standalone MM services", which is already there in EDK2, as
> >secure storage for UEFI variables.

> In case of write you could do a write-through in your cache if needed.
> 
> >
> >>The NV-cache content should be written to non-volatile memory on Reset()
> >>and on ExitBootServices() and if possible when updating variables at
> >>runtime.
> >
> >I'm not sure your intent here, but are you going to write back
> >the cache only once?
> >It won't work as every change of UEFI variable must be flushed
> >to persistent storage instantly.
> 
> The cache should support write and read. Only NV variables have to be

Why?
I don't think it make sense that we support volatile variable, but not
non-volatile variable at runtime.
Even UEFI specification doesn't describe such an irregular behavior.
See EFI_RT_SUPPORTED_XXX definitions.
Do you have a meaningful use case that you want to support?

> written to a medium. If you do not support this currently just return
> some error code vor NV variables. But you could accept still accept
> changes to non-NV variables. This way we can test the code at runtime
> even before implementing runtime persistence.
> 
> >
> >>>+					      const efi_guid_t *vendor,
> >>>+					      u32 *attributes,
> >>>+					      efi_uintn_t *data_size,
> >>>+					      void *data);
> >>>+efi_status_t
> >>>+__efi_runtime EFIAPI efi_get_next_variable_name_runtime(
> >>>+						efi_uintn_t *variable_name_size,
> >>>+						u16 *variable_name,
> >>>+						const efi_guid_t *vendor);
> >>>+#endif /* CONFIG_EFI_RUNTIME_GET_VARIABLE_CACHING */
> >>>+
> >>>  /*
> >>>   * See section 3.1.3 in the v2.7 UEFI spec for more details on
> >>>   * the layout of EFI_LOAD_OPTION.  In short it is:
> >>>diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
> >>>index e2ef43157568..3f284795648f 100644
> >>>--- a/lib/efi_loader/Kconfig
> >>>+++ b/lib/efi_loader/Kconfig
> >>>@@ -59,6 +59,15 @@ config EFI_RUNTIME_CONVERT_POINTER
> >>>  	  to be called by UEFI drivers in relocating themselves to virtual
> >>>  	  address space.
> >>>
> >>>+config EFI_RUNTIME_GET_VARIABLE_CACHING
> >>>+	bool "runtime_service: GetVariable: Enable runtime access via cache (read-only)"
> >>>+	default y
> >>>+	help
> >>>+	  Select this option if you want to access UEFI variables at
> >>>+	  runtime even though you cannot update values on the fly.
> >>>+	  With or without this option, you can access UEFI variables
> >>>+	  at boottime.
> >>
> >>Updates of volatile variables should always be possible.
> >
> >Why "should"?
> >Give me any use case.
> >UEFI spec does not describe such a variant implementation at all.
> 
> See above. I would like to be able to test setting variables at runtime
> even if persisting NV variables is not yet implemented.

Just for testing? No real use case?
Please note that if we *have* persistent storage at runtime,
we don't need cache because we can access that storage.

> >
> >>>+
> >>>  config EFI_DEVICE_PATH_TO_TEXT
> >>>  	bool "Device path to text protocol"
> >>>  	default y
> >>>diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> >>>index e4abaf3601d9..14e343abbd43 100644
> >>>--- a/lib/efi_loader/efi_boottime.c
> >>>+++ b/lib/efi_loader/efi_boottime.c
> >>>@@ -1892,6 +1892,9 @@ static efi_status_t EFIAPI efi_exit_boot_services(efi_handle_t image_handle,
> >>>  						  efi_uintn_t map_key)
> >>>  {
> >>>  	struct efi_event *evt;
> >>>+#ifdef CONFIG_EFI_RUNTIME_GET_VARIABLE_CACHING
> >>>+	efi_status_t ret;
> >>>+#endif
> >>>
> >>>  	EFI_ENTRY("%p, %zx", image_handle, map_key);
> >>>
> >>>@@ -1921,7 +1924,12 @@ static efi_status_t EFIAPI efi_exit_boot_services(efi_handle_t image_handle,
> >>>  		}
> >>>  	}
> >>>
> >>>-	/* TODO: Should persist EFI variables here */
> >>>+#ifdef CONFIG_EFI_RUNTIME_GET_VARIABLE_CACHING
> >>
> >>Can we have weak functions for initializing and persisting the cache, e.g.
> >>
> >>efi_status_t __weak
> >>efi_load_variable_cache(cache_entry *cache, size_t *size)
> >>{
> >>         cache->len = 0;
> >>         return EFI_SUCCESS;
> >>}
> >>
> >>efi_status_t __runtime __weak
> >>efi_write_variable_cache(cache_entry *cache, size_t size)
> >>{
> >>         return EFI_UNSUPPORTED;
> >>}
> >>
> >>Then we can override these in whatever driver we implement.
> >
> >What is the difference between yours and my env_efi_load/save()
> >with backing-storage driver?
> 
> I cannot see that you clearly separate the functions API, cache,
> persistence.

I don't get your point.
For instance, efi_boottime.c has a lot of different type of functions.
Do you want to separate them into different files?

> I would like to see clearly define interfaces into which we can plug
> different persistence implementations.

Your assertion doesn't clarify why you want to separate API and cache.

Regarding persistent storage, as I said, efi_[get|set]_variable()
will be completely replaced with the corresponding functions
(at least, in case of Standalone MM services).


> >
> >>
> >>>+	/* No more variable update */
> >>>+	ret = efi_freeze_variable_table();
> >>>+	if (ret != EFI_SUCCESS)
> >>>+		return EFI_EXIT(ret);
> >>>+#endif
> >>>
> >>>  	board_quiesce_devices();
> >>>
> >>>diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c
> >>>index fc5bdee80e00..b60f70f04613 100644
> >>>--- a/lib/efi_loader/efi_runtime.c
> >>>+++ b/lib/efi_loader/efi_runtime.c
> >>>@@ -111,6 +111,11 @@ efi_status_t efi_init_runtime_supported(void)
> >>>  	efi_runtime_services_supported |=
> >>>  				EFI_RT_SUPPORTED_CONVERT_POINTER;
> >>>  #endif
> >>>+#ifdef CONFIG_EFI_RUNTIME_GET_VARIABLE_CACHING
> >>>+	efi_runtime_services_supported |=
> >>>+				(EFI_RT_SUPPORTED_GET_VARIABLE |
> >>>+				 EFI_RT_SUPPORTED_GET_NEXT_VARIABLE_NAME);
> >>>+#endif
> >>>
> >>>  	return EFI_CALL(efi_set_variable(L"RuntimeServicesSupported",
> >>>  					 &efi_global_variable_guid,
> >>>@@ -469,10 +474,18 @@ static struct efi_runtime_detach_list_struct efi_runtime_detach_list[] = {
> >>>  		.patchto = NULL,
> >>>  	}, {
> >>>  		.ptr = &efi_runtime_services.get_variable,
> >>>+#ifdef CONFIG_EFI_RUNTIME_GET_VARIABLE_CACHING
> >>>+		.patchto = &efi_get_variable_runtime,
> >>>+#else
> >>>  		.patchto = &efi_device_error,
> >>>+#endif
> >>>  	}, {
> >>>  		.ptr = &efi_runtime_services.get_next_variable_name,
> >>>+#ifdef CONFIG_EFI_RUNTIME_GET_VARIABLE_CACHING
> >>>+		.patchto = &efi_get_next_variable_name,
> >>>+#else
> >>>  		.patchto = &efi_device_error,
> >>>+#endif
> >>>  	}, {
> >>>  		.ptr = &efi_runtime_services.set_variable,
> >>>  		.patchto = &efi_device_error,
> >>>diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
> >>>index d9887be938c2..ee21892dd291 100644
> >>>--- a/lib/efi_loader/efi_variable.c
> >>>+++ b/lib/efi_loader/efi_variable.c
> >>>@@ -706,3 +706,470 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
> >>>
> >>>  	return EFI_EXIT(ret);
> >>>  }
> >>>+
> >>>+#ifdef CONFIG_EFI_RUNTIME_GET_VARIABLE_CACHING
> >>>+/*
> >>>+ * runtime version of APIs
> >>>+ * We only support read-only variable access.
> >>>+ * The table is in U-Boot's hash table format, but has its own
> >>>+ * _ENTRY structure for specific use.
> >>>+ *
> >>>+ * Except for efi_freeze_variable_table(), which is to be called in
> >>>+ * exit_boot_services(), all the functions and data below must be
> >>>+ * placed in either RUNTIME_SERVICES_CODE or RUNTIME_SERVICES_DATA.
> >>>+ */
> >>>+typedef struct _ENTRY {
> >>>+	unsigned int used;	/* hash value; 0 for not used */
> >>>+	size_t name;		/* name offset from itself */
> >>>+	efi_guid_t vendor;
> >>>+	u32 attributes;
> >>>+	size_t data;		/* data offset from itself */
> >>>+	size_t data_size;
> >>>+} _ENTRY;
> >>>+
> >>>+static inline u16 *entry_name(_ENTRY *e) { return (void *)e + e->name; }
> >>>+static inline u16 *entry_data(_ENTRY *e) { return (void *)e + e->data; }
> >>>+
> >>>+static struct hsearch_data *efi_variable_table __efi_runtime_data;
> >>>+
> >>>+static size_t __efi_runtime u16_strlen_runtime(const u16 *s1)
> >>
> >>
> >>Please, do not duplicate existing functions. If they have to be runtime
> >>simply change the existing function to __runtime.
> >
> >We should do that if possible, but please note that [str|mem]xxx() functions
> >are *architecture* dependent.
> >Do you want to mark all the functions across all the architectures?

Agree or not agree?


> >>>+{
> >>>+	size_t n = 0;
> >>>+
> >>>+	while (*s1) {
> >>>+		n++;
> >>>+		s1++;
> >>>+	}
> >>>+
> >>>+	return n;
> >>>+}
> >>>+
> >>>+static int __efi_runtime memcmp_runtime(const void *m1, const void *m2,
> >>>+					size_t n)
> >>
> >>I dislike duplicate code. Can't we simply define the existing memcmp
> >>function as __runtime?
> >
> >ditto
> >
> >>>+{
> >>>+	while (n && *(u8 *)m1 == *(u8 *)m2) {
> >>>+		n--;
> >>>+		m1++;
> >>>+		m2++;
> >>>+	}
> >>>+
> >>>+	if (n)
> >>>+		return *(u8 *)m1 - *(u8 *)m2;
> >>>+
> >>>+	return 0;
> >>>+}
> >>>+
> >>>+static void __efi_runtime memcpy_runtime(void *m1, const void *m2, size_t n)
> >>>+{
> >>
> >>Can't we simply define the existing memcpy function as __runtime?
> >>
> >>>+	for (; n; n--, m1++, m2++)
> >>>+		*(u8 *)m1 = *(u8 *)m2;
> >>>+}
> >>>+
> >>>+static int __efi_runtime efi_cmpkey(_ENTRY *e, const u16 *name,
> >>>+				    const efi_guid_t *vendor)
> >>>+{
> >>>+	size_t name_len;
> >>>+
> >>>+	name_len = u16_strlen_runtime(entry_name(e));
> >>>+
> >>>+	/* return zero if matched */
> >>>+	return name_len != u16_strlen_runtime(name) ||
> >>>+	       memcmp_runtime(entry_name(e), name, name_len * 2) ||
> >>>+	       memcmp_runtime(e->vendor.b, vendor->b, sizeof(vendor));
> >>>+}
> >>>+
> >>>+/* simplified and slightly different version of hsearch_r() */
> >>
> >>These hash functions are so complicated that they really need a unit
> >>test testing them rigorously.
> >
> >Do you know that there are no any tests for hsearch_r()?
> >Moreover, this function would better be exercised well
> >if we could add *runtime* tests.
> 
> Have a look at test/env/hashtable.c

Okay, but why not re-use this test for my stripped version?

> I think efi_selftest could work after SetVirtualMemoryMap if we do not
> change the map for memory actually used by U-Boot.

Maybe.

-Takahiro Akashi

> Or we use a minimum Linux kernel and put our tests into an init binary.
> 
> >
> >>
> >>>+static int __efi_runtime hsearch_runtime(const u16 *name,
> >>>+					 const efi_guid_t *vendor,
> >>>+					 ACTION action,
> >>>+					 _ENTRY **retval,
> >>>+					 struct hsearch_data *htab)
> >>>+{
> >>>+	unsigned int hval;
> >>>+	unsigned int count;
> >>>+	unsigned int len;
> >>>+	unsigned int idx, new;
> >>>+
> >>>+	/* Compute an value for the given string. */
> >>>+	len = u16_strlen_runtime(name);
>  >>
> >>Can't the same variable name exist for different GUIDs? Why is the GUID
> >>not considered in the hash?
> >
> >efi_cmpkey() does take into consideration GUID as well as the name.
> 
> My question concerned the hash.
> 
> >
> >>>+	hval = len;
> >>>+	count = len;
> >>>+	while (count-- > 0) {
> >>>+		hval <<= 4;
> >>>+		hval += name[count];
> >>>+	}
> >>>+
> >>>+	/*
> >>>+	 * First hash function:
> >>>+	 * simply take the modulo but prevent zero.
> >>>+	 */
> >>>+	hval %= htab->size;
> >>>+	if (hval == 0)
> >>>+		++hval;
> >>>+
> >>>+	/* The first index tried. */
> >>>+	new = -1; /* not found */
> >>>+	idx = hval;
> >>>+
> >>>+	if (htab->table[idx].used) {
> >>>+		/*
> >>>+		 * Further action might be required according to the
> >>>+		 * action value.
> >>>+		 */
> >>>+		unsigned int hval2;
> >>>+
> >>>+		if (htab->table[idx].used == hval &&
> >>>+		    !efi_cmpkey(&htab->table[idx], name, vendor)) {
> >>>+			if (action == FIND) {
> >>>+				*retval = &htab->table[idx];
> >>>+				return idx;
> >>>+			}
> >>>+			/* we don't need to support overwrite */
> >>>+			return -1;
> >>>+		}
> >>>+
> >>>+		/*
> >>>+		 * Second hash function:
> >>>+		 * as suggested in [Knuth]
> >>>+		 */
> >>>+		hval2 = 1 + hval % (htab->size - 2);
> >>>+
> >>>+		do {
> >>>+			/*
> >>>+			 * Because SIZE is prime this guarantees to
> >>>+			 * step through all available indices.
> >>>+			 */
> >>>+			if (idx <= hval2)
> >>>+				idx = htab->size + idx - hval2;
> >>>+			else
> >>>+				idx -= hval2;
> >>>+
> >>>+			/*
> >>>+			 * If we visited all entries leave the loop
> >>>+			 * unsuccessfully.
> >>>+			 */
> >>>+			if (idx == hval)
> >>>+				break;
> >>>+
> >>>+			/* If entry is found use it. */
> >>>+			if (htab->table[idx].used == hval &&
> >>>+			    !efi_cmpkey(&htab->table[idx], name, vendor)) {
> >>>+				if (action == FIND) {
> >>>+					*retval = &htab->table[idx];
> >>>+					return idx;
> >>>+				}
> >>>+				/* we don't need to support overwrite */
> >>>+				return -1;
> >>>+			}
> >>>+		} while (htab->table[idx].used);
> >>>+
> >>>+		if (!htab->table[idx].used)
> >>>+			new = idx;
> >>>+	} else {
> >>>+		new = idx;
> >>>+	}
> >>>+
> >>>+	/*
> >>>+	 * An empty bucket has been found.
> >>>+	 * The following code should never be executed after
> >>>+	 * exit_boot_services()
> >>>+	 */
> >>>+	if (action == ENTER) {
> >>>+		/*
> >>>+		 * If table is full and another entry should be
> >>>+		 * entered return with error.
> >>>+		 */
> >>>+		if (htab->filled == htab->size) {
> >>>+			*retval = NULL;
> >>>+			return 0;
> >>>+		}
> >>>+
> >>>+		/* Create new entry */
> >>>+		htab->table[new].used = hval;
> >>>+		++htab->filled;
> >>>+
> >>>+		/* return new entry */
> >>>+		*retval = &htab->table[new];
> >>>+		return 1;
> >>>+	}
> >>>+
> >>>+	*retval = NULL;
> >>>+	return 0;
> >>>+}
> >>>+
> >>>+/* from lib/hashtable.c */
> >>>+static inline int isprime(unsigned int number)
> >>>+{
> >>>+	/* no even number will be passed */
> >>>+	unsigned int div = 3;
> >>>+
> >>>+	while (div * div < number && number % div != 0)
> >>>+		div += 2;
> >>>+
> >>>+	return number % div != 0;
> >>>+}
> >>>+
> >>>+efi_status_t efi_freeze_variable_table(void)
> >>
> >>Please, add comments to your functions. It is not self-evident what this
> >>function is meant to do.
> >>
> >>I cannot imagine why a variable cache should be frozen. It is a living
> >>data structure until the system is switched off.
> >
> >I don't get your point.
> 
> Please, explain what you mean by freeze.
> 
> I suggest that the cache is read/write at all times.
> 
> Best regards
> 
> Heinrich
> 
> >
> >>For a variable cache I expect that you allocate memory before handling
> >>the first variable and never again. At runtime you will not have chance
> >>to allocate memory anyway.
> >
> >I don't get your point.
> >
> >>This function is way too long. Pleae, break it down.
> >
> >Freezing is implemented in 2-phase steps, and some complexity
> >is inevitable. I suppose adding some comments would be enough.
> >
> >-Takahiro Akashi
> >
> >>Best regards
> >>
> >>Heinrich
> >>
> >>>+{
> >>>+	int var_num = 0;
> >>>+	size_t var_data_size = 0;
> >>>+	u16 *name;
> >>>+	efi_uintn_t name_buf_len, name_len;
> >>>+	efi_guid_t vendor;
> >>>+	u32 attributes;
> >>>+	u8 *mem_pool, *var_buf = NULL;
> >>>+	size_t table_size, var_size, var_buf_size;
> >>>+	_ENTRY *new = NULL;
> >>>+	efi_status_t ret;
> >>>+
> >>>+	/* phase-1 loop */
> >>>+	name_buf_len = 128;
> >>>+	name = malloc(name_buf_len);
> >>>+	if (!name)
> >>>+		return EFI_OUT_OF_RESOURCES;
> >>>+	name[0] = 0;
> >>>+	for (;;) {
> >>>+		name_len = name_buf_len;
> >>>+		ret = EFI_CALL(efi_get_next_variable_name(&name_len, name,
> >>>+							  &vendor));
> >>>+		if (ret == EFI_NOT_FOUND) {
> >>>+			break;
> >>>+		} else if (ret == EFI_BUFFER_TOO_SMALL) {
> >>>+			u16 *buf;
> >>>+
> >>>+			name_buf_len = name_len;
> >>>+			buf = realloc(name, name_buf_len);
> >>>+			if (!buf) {
> >>>+				free(name);
> >>>+				return EFI_OUT_OF_RESOURCES;
> >>>+			}
> >>>+			name = buf;
> >>>+			name_len = name_buf_len;
> >>>+			ret = EFI_CALL(efi_get_next_variable_name(&name_len,
> >>>+								  name,
> >>>+								  &vendor));
> >>>+		}
> >>>+
> >>>+		if (ret != EFI_SUCCESS)
> >>>+			return ret;
> >>>+
> >>>+		var_size = 0;
> >>>+		ret = EFI_CALL(efi_get_variable(name, &vendor, &attributes,
> >>>+						&var_size, NULL));
> >>>+		if (ret != EFI_BUFFER_TOO_SMALL)
> >>>+			return ret;
> >>>+
> >>>+		if (!(attributes & EFI_VARIABLE_RUNTIME_ACCESS))
> >>>+			continue;
> >>>+
> >>>+		var_num++;
> >>>+		var_data_size += (u16_strlen_runtime(name) + 1) * sizeof(u16);
> >>>+		var_data_size += var_size;
> >>>+		/* mem_pool must 2-byte aligned for u16 variable name */
> >>>+		if (var_data_size & 0x1)
> >>>+			var_data_size++;
> >>>+	}
> >>>+
> >>>+	/*
> >>>+	 * total of entries in hash table must be a prime number.
> >>>+	 * The logic below comes from lib/hashtable.c
> >>>+	 */
> >>>+	var_num |= 1;               /* make odd */
> >>>+	while (!isprime(var_num))
> >>>+		var_num += 2;
> >>>+
> >>>+	/* We need table[var_num] for hsearch_runtime algo */
> >>>+	table_size = sizeof(*efi_variable_table)
> >>>+			+ sizeof(_ENTRY) * (var_num + 1) + var_data_size;
> >>>+	ret = efi_allocate_pool(EFI_RUNTIME_SERVICES_DATA,
> >>>+				table_size, (void **)&efi_variable_table);
> >>>+	if (ret != EFI_SUCCESS)
> >>>+		return ret;
> >>>+
> >>>+	efi_variable_table->size = var_num;
> >>>+	efi_variable_table->table = (void *)efi_variable_table
> >>>+					+ sizeof(*efi_variable_table);
> >>>+	mem_pool = (u8 *)efi_variable_table->table
> >>>+			+ sizeof(_ENTRY) * (var_num + 1);
> >>>+
> >>>+	var_buf_size = 128;
> >>>+	var_buf = malloc(var_buf_size);
> >>>+	if (!var_buf) {
> >>>+		ret = EFI_OUT_OF_RESOURCES;
> >>>+		goto err;
> >>>+	}
> >>>+
> >>>+	/* phase-2 loop */
> >>>+	name[0] = 0;
> >>>+	name_len = name_buf_len;
> >>>+	for (;;) {
> >>>+		name_len = name_buf_len;
> >>>+		ret = EFI_CALL(efi_get_next_variable_name(&name_len, name,
> >>>+							  &vendor));
> >>>+		if (ret == EFI_NOT_FOUND)
> >>>+			break;
> >>>+		else if (ret != EFI_SUCCESS)
> >>>+			goto err;
> >>>+
> >>>+		var_size = var_buf_size;
> >>>+		ret = EFI_CALL(efi_get_variable(name, &vendor, &attributes,
> >>>+						&var_size, var_buf));
> >>>+		if (ret == EFI_BUFFER_TOO_SMALL) {
> >>>+			free(var_buf);
> >>>+			var_buf_size = var_size;
> >>>+			var_buf = malloc(var_buf_size);
> >>>+			if (!var_buf) {
> >>>+				ret = EFI_OUT_OF_RESOURCES;
> >>>+				goto err;
> >>>+			}
> >>>+			ret = EFI_CALL(efi_get_variable(name, &vendor,
> >>>+							&attributes,
> >>>+							&var_size, var_buf));
> >>>+		}
> >>>+		if (ret != EFI_SUCCESS)
> >>>+			goto err;
> >>>+
> >>>+		if (!(attributes & EFI_VARIABLE_RUNTIME_ACCESS))
> >>>+			continue;
> >>>+
> >>>+		if (hsearch_runtime(name, &vendor, ENTER, &new,
> >>>+				    efi_variable_table) <= 0) {
> >>>+			/* This should not happen */
> >>>+			ret = EFI_INVALID_PARAMETER;
> >>>+			goto err;
> >>>+		}
> >>>+
> >>>+		/* allocate space from RUNTIME DATA */
> >>>+		name_len = (u16_strlen_runtime(name) + 1) * sizeof(u16);
> >>>+		memcpy_runtime(mem_pool, name, name_len);
> >>>+		new->name = mem_pool - (u8 *)new; /* offset */
> >>>+		mem_pool += name_len;
> >>>+
> >>>+		memcpy_runtime(&new->vendor.b, &vendor.b, sizeof(vendor));
> >>>+
> >>>+		new->attributes = attributes;
> >>>+
> >>>+		memcpy_runtime(mem_pool, var_buf, var_size);
> >>>+		new->data = mem_pool - (u8 *)new; /* offset */
> >>>+		new->data_size = var_size;
> >>>+		mem_pool += var_size;
> >>>+
> >>>+		/* mem_pool must 2-byte aligned for u16 variable name */
> >>>+		if ((uintptr_t)mem_pool & 0x1)
> >>>+			mem_pool++;
> >>>+	}
> >>>+#ifdef DEBUG
> >>>+	name[0] = 0;
> >>>+	name_len = name_buf_len;
> >>>+	for (;;) {
> >>>+		name_len = name_buf_len;
> >>>+		ret = efi_get_next_variable_name_runtime(&name_len, name,
> >>>+							 &vendor);
> >>>+		if (ret == EFI_NOT_FOUND)
> >>>+			break;
> >>>+		else if (ret != EFI_SUCCESS)
> >>>+			goto err;
> >>>+
> >>>+		var_size = var_buf_size;
> >>>+		ret = efi_get_variable_runtime(name, &vendor, &attributes,
> >>>+					       &var_size, var_buf);
> >>>+		if (ret != EFI_SUCCESS)
> >>>+			goto err;
> >>>+
> >>>+		printf("%ls_%pUl:\n", name, &vendor);
> >>>+		printf("    attributes: 0x%x\n", attributes);
> >>>+		printf("    value (size: 0x%lx)\n", var_size);
> >>>+	}
> >>>+#endif
> >>>+	ret = EFI_SUCCESS;
> >>>+
> >>>+err:
> >>>+	free(name);
> >>>+	free(var_buf);
> >>>+	if (ret != EFI_SUCCESS && efi_variable_table) {
> >>>+		efi_free_pool(efi_variable_table);
> >>>+		efi_variable_table = NULL;
> >>>+	}
> >>>+
> >>>+	return ret;
> >>>+}
> >>>+
> >>>+efi_status_t
> >>>+__efi_runtime EFIAPI efi_get_variable_runtime(u16 *variable_name,
> >>>+					      const efi_guid_t *vendor,
> >>>+					      u32 *attributes,
> >>>+					      efi_uintn_t *data_size,
> >>>+					      void *data)
> >>>+{
> >>>+	_ENTRY *new;
> >>>+
> >>>+	if (!variable_name || !vendor || !data_size)
> >>>+		return EFI_EXIT(EFI_INVALID_PARAMETER);
> >>>+
> >>>+	if (hsearch_runtime(variable_name, vendor, FIND, &new,
> >>>+			    efi_variable_table) <= 0)
> >>>+		return EFI_NOT_FOUND;
> >>>+
> >>>+	if (attributes)
> >>>+		*attributes = new->attributes;
> >>>+	if (*data_size < new->data_size) {
> >>>+		*data_size = new->data_size;
> >>>+		return EFI_BUFFER_TOO_SMALL;
> >>>+	}
> >>>+
> >>>+	*data_size = new->data_size;
> >>>+	memcpy_runtime(data, entry_data(new), new->data_size);
> >>>+
> >>>+	return EFI_SUCCESS;
> >>>+}
> >>>+
> >>>+static int prev_idx __efi_runtime_data;
> >>>+
> >>>+efi_status_t
> >>>+__efi_runtime EFIAPI efi_get_next_variable_name_runtime(
> >>>+						efi_uintn_t *variable_name_size,
> >>>+						u16 *variable_name,
> >>>+						const efi_guid_t *vendor)
> >>>+{
> >>>+	_ENTRY *e;
> >>>+	u16 *name;
> >>>+	efi_uintn_t name_size;
> >>>+
> >>>+	if (!variable_name_size || !variable_name || !vendor)
> >>>+		return EFI_INVALID_PARAMETER;
> >>>+
> >>>+	if (variable_name[0]) {
> >>>+		/* sanity check for previous variable */
> >>>+		if (prev_idx < 0)
> >>>+			return EFI_INVALID_PARAMETER;
> >>>+
> >>>+		e = &efi_variable_table->table[prev_idx];
> >>>+		if (!e->used || efi_cmpkey(e, variable_name, vendor))
> >>>+			return EFI_INVALID_PARAMETER;
> >>>+	} else {
> >>>+		prev_idx = -1;
> >>>+	}
> >>>+
> >>>+	/* next variable */
> >>>+	while (++prev_idx <= efi_variable_table->size) {
> >>>+		e = &efi_variable_table->table[prev_idx];
> >>>+		if (e->used)
> >>>+			break;
> >>>+	}
> >>>+	if (prev_idx > efi_variable_table->size)
> >>>+		return EFI_NOT_FOUND;
> >>>+
> >>>+	name = entry_name(e);
> >>>+	name_size = (u16_strlen_runtime(name) + 1)
> >>>+			* sizeof(u16);
> >>>+	if (*variable_name_size < name_size) {
> >>>+		*variable_name_size = name_size;
> >>>+		return EFI_BUFFER_TOO_SMALL;
> >>>+	}
> >>>+
> >>>+	memcpy_runtime(variable_name, name, name_size);
> >>>+	memcpy_runtime((void *)&vendor->b, &e->vendor.b, sizeof(vendor));
> >>>+
> >>>+	return EFI_SUCCESS;
> >>>+}
> >>>+#endif /* CONFIG_EFI_RUNTIME_GET_VARIABLE_CACHING */
> >>>
> >>
> >
> 


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