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powerpc/pseries: Make caller pass buffer to plpks_read_var()

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Currently, plpks_read_var() allocates a buffer to pass to the
H_PKS_READ_OBJECT hcall, then allocates another buffer into which the data
is copied, and returns that buffer to the caller.

This is a bit over the top - while we probably still want to allocate a
separate buffer to pass to the hypervisor in the hcall, we can let the
caller allocate the final buffer and specify the size.

Don't allocate var->data in plpks_read_var(), instead expect the caller to
allocate it. If the caller needs to discover the size, it can set
var->data to NULL and var->datalen will be populated. Update header file
to document this.

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230210080401.345462-20-ajd@linux.ibm.com
This commit is contained in:
Andrew Donnellan 2023-02-10 19:03:54 +11:00 committed by Michael Ellerman
parent ebdcd42347
commit 0cf2cc1fe4
2 changed files with 16 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

12
arch/powerpc/include/asm/plpks.h
View file

@ -88,16 +88,28 @@ int plpks_remove_var(char *component, u8 varos,
/**
* Returns the data for the specified os variable.
*
* Caller must allocate a buffer in var->data with length in var->datalen.
* If no buffer is provided, var->datalen will be populated with the object's
* size.
*/
int plpks_read_os_var(struct plpks_var *var);
/**
* Returns the data for the specified firmware variable.
*
* Caller must allocate a buffer in var->data with length in var->datalen.
* If no buffer is provided, var->datalen will be populated with the object's
* size.
*/
int plpks_read_fw_var(struct plpks_var *var);
/**
* Returns the data for the specified bootloader variable.
*
* Caller must allocate a buffer in var->data with length in var->datalen.
* If no buffer is provided, var->datalen will be populated with the object's
* size.
*/
int plpks_read_bootloader_var(struct plpks_var *var);

11
arch/powerpc/platforms/pseries/plpks.c
View file

@ -581,17 +581,14 @@ static int plpks_read_var(u8 consumer, struct plpks_var *var)
goto out_free_output;
}
if (var->datalen == 0 || var->datalen > retbuf[0])
if (!var->data || var->datalen > retbuf[0])
var->datalen = retbuf[0];
var->data = kzalloc(var->datalen, GFP_KERNEL);
if (!var->data) {
rc = -ENOMEM;
goto out_free_output;
}
var->policy = retbuf[1];
memcpy(var->data, output, var->datalen);
if (var->data)
memcpy(var->data, output, var->datalen);
rc = 0;
out_free_output: