[U-Boot] [PATCH v2 1/2] efi_loader: variable: support APPEND_WRITE

[AKASHI Takahiro]

On Tue, Sep 17, 2019 at 10:38:47PM +0200, Heinrich Schuchardt wrote:
> On 9/6/19 8:09 AM, AKASHI Takahiro wrote:
> >If EFI_VARIABLE_APPEND_WRITE is specified in attributes at
> >efi_set_variable(), specified data will be appended to the variable's
> >original value. Attributes other than APPEND_WRITE should not be
> >modified.
> >
> >With this patch, APPEND_WRITE test in 'variables' selftest will pass.
> >
> >Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> >---
> >  lib/efi_loader/efi_variable.c | 70 ++++++++++++++++++++++-------------
> >  1 file changed, 44 insertions(+), 26 deletions(-)
> >
> >diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
> >index 6687b69a400d..48ee255f879b 100644
> >--- a/lib/efi_loader/efi_variable.c
> >+++ b/lib/efi_loader/efi_variable.c
> >@@ -424,17 +424,17 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
> >  				     efi_uintn_t data_size, const void *data)
> >  {
> >  	char *native_name = NULL, *val = NULL, *s;
> >+	const char *old_val;
> >+	size_t old_size;
> >  	efi_status_t ret = EFI_SUCCESS;
> >  	u32 attr;
> >
> >  	EFI_ENTRY("\"%ls\" %pUl %x %zu %p", variable_name, vendor, attributes,
> >  		  data_size, data);
> >
> >-	/* TODO: implement APPEND_WRITE */
> >  	if (!variable_name || !*variable_name || !vendor ||
> >  	    ((attributes & EFI_VARIABLE_RUNTIME_ACCESS) &&
> >-	     !(attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS)) ||
> >-	    (attributes & EFI_VARIABLE_APPEND_WRITE)) {
> >+	     !(attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS))) {
> >  		ret = EFI_INVALID_PARAMETER;
> >  		goto out;
> >  	}
> >@@ -445,35 +445,51 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
> >
> >  #define ACCESS_ATTR (EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_BOOTSERVICE_ACCESS)
> >
> >-	if ((data_size == 0) || !(attributes & ACCESS_ATTR)) {
> >-		/* delete the variable: */
> >-		env_set(native_name, NULL);
> >-		ret = EFI_SUCCESS;
> >-		goto out;
> >-	}
> >+	old_val = env_get(native_name);
> >+	if (old_val) {
> >+		old_val = parse_attr(old_val, &attr);
> >
> >-	val = env_get(native_name);
> >-	if (val) {
> >-		parse_attr(val, &attr);
> >-
> >-		/* We should not free val */
> >-		val = NULL;
> >+		/* check read-only first */
> >  		if (attr & READ_ONLY) {
> >  			ret = EFI_WRITE_PROTECTED;
> >  			goto out;
> >  		}
> >
> >-		/*
> >-		 * attributes won't be changed
> >-		 * TODO: take care of APPEND_WRITE once supported
> >-		 */
> >-		if (attr != attributes) {
> >+		if ((data_size == 0) || !(attributes & ACCESS_ATTR)) {
> 
> The understanding of EDK2 is that no access attributes means 'attributes
> == 0' (Function VariableServiceSetVariable() in
> MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c).

No, it's not correct. The right place you should refer to is:
UpdateVariable (
   [snip up to l.2279 or so]
    //
    // Setting a data variable with no access, or zero DataSize attributes
    // causes it to be deleted.
    // When the EFI_VARIABLE_APPEND_WRITE attribute is set, DataSize of zero will
    // not delete the variable.
    //
    if ((((Attributes & EFI_VARIABLE_APPEND_WRITE) == 0) && (DataSize == 0))|| ((Attributes & (EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_BOOTSERVICE_ACCESS)) == 0)) {

> EFI_VARIABLE_APPEND_WRITE and data_size = 0 should not delete a variable
> according to the UEFI spec:

This is correct.

Thanks,
-Takahiro Akashi

> "Unless the EFI_VARIABLE_APPEND_WRITE,
> EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS, or
> EFI_VARIABLE_ENHANCED_AUTHENTICATED_ACCESS attribute is set (see below),
> using SetVariable() with a DataSize of zero will cause the entire
> variable to be deleted."
> 
> Best regards
> 
> Heinrich
> 
> >+			/* delete the variable: */
> >+			env_set(native_name, NULL);
> >+			ret = EFI_SUCCESS;
> >+			goto out;
> >+		}
> >+
> >+		/* attributes won't be changed */
> >+		if (attr != (attributes & ~EFI_VARIABLE_APPEND_WRITE)) {
> >  			ret = EFI_INVALID_PARAMETER;
> >  			goto out;
> >  		}
> >+
> >+		if (attributes & EFI_VARIABLE_APPEND_WRITE) {
> >+			if (!prefix(old_val, "(blob)")) {
> >+				return EFI_DEVICE_ERROR;
> >+				goto out;
> >+			}
> >+			old_size = strlen(old_val);
> >+		} else {
> >+			old_size = 0;
> >+		}
> >+	} else {
> >+		if ((data_size == 0) || !(attributes & ACCESS_ATTR) ||
> >+		    (attributes & EFI_VARIABLE_APPEND_WRITE)) {
> >+			/* delete, but nothing to do */
> >+			ret = EFI_NOT_FOUND;
> >+			goto out;
> >+		}
> >+
> >+		old_size = 0;
> >  	}
> >
> >-	val = malloc(2 * data_size + strlen("{ro,run,boot,nv}(blob)") + 1);
> >+	val = malloc(old_size + 2 * data_size
> >+		     + strlen("{ro,run,boot,nv}(blob)") + 1);
> >  	if (!val) {
> >  		ret = EFI_OUT_OF_RESOURCES;
> >  		goto out;
> >@@ -481,10 +497,7 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
> >
> >  	s = val;
> >
> >-	/*
> >-	 * store attributes
> >-	 * TODO: several attributes are not supported
> >-	 */
> >+	/* store attributes */
> >  	attributes &= (EFI_VARIABLE_NON_VOLATILE |
> >  		       EFI_VARIABLE_BOOTSERVICE_ACCESS |
> >  		       EFI_VARIABLE_RUNTIME_ACCESS);
> >@@ -505,8 +518,13 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
> >  	}
> >  	s += sprintf(s, "}");
> >
> >+	if (old_size)
> >+		/* APPEND_WRITE */
> >+		s += sprintf(s, old_val);
> >+	else
> >+		s += sprintf(s, "(blob)");
> >+
> >  	/* store payload: */
> >-	s += sprintf(s, "(blob)");
> >  	s = bin2hex(s, data, data_size);
> >  	*s = '\0';
> >
> >
>