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DebugFS interface
=================
The optional DebugFS interface is accessed through a Vendor specific EL3 service. Refer
to the component documentation for details.
String parameters are passed through a shared buffer using a specific union:
.. code:: c
union debugfs_parms {
struct {
char fname[MAX_PATH_LEN];
} open;
struct mount {
char srv[MAX_PATH_LEN];
char where[MAX_PATH_LEN];
char spec[MAX_PATH_LEN];
} mount;
struct {
char path[MAX_PATH_LEN];
dir_t dir;
} stat;
struct {
char oldpath[MAX_PATH_LEN];
char newpath[MAX_PATH_LEN];
} bind;
};
Format of the dir_t structure as such:
.. code:: c
typedef struct {
char name[NAMELEN];
long length;
unsigned char mode;
unsigned char index;
unsigned char dev;
qid_t qid;
} dir_t;
* Identifiers
======================== =============================================
SMC_OK 0
SMC_UNK -1
DEBUGFS_E_INVALID_PARAMS -2
======================== =============================================
======================== =============================================
MOUNT 0
CREATE 1
OPEN 2
CLOSE 3
READ 4
WRITE 5
SEEK 6
BIND 7
STAT 8
INIT 10
VERSION 11
======================== =============================================
MOUNT
~~~~~
Description
^^^^^^^^^^^
This operation mounts a blob of data pointed to by path stored in `src`, at
filesystem location pointed to by path stored in `where`, using driver pointed
to by path in `spec`.
Parameters
^^^^^^^^^^
======== ============================================================
uint32_t FunctionID (0x87000010 / 0xC7000010)
uint32_t ``MOUNT``
======== ============================================================
Return values
^^^^^^^^^^^^^
=============== ==========================================================
int32_t w0 == SMC_OK on success
w0 == DEBUGFS_E_INVALID_PARAMS if mount operation failed
=============== ==========================================================
OPEN
~~~~
Description
^^^^^^^^^^^
This operation opens the file path pointed to by `fname`.
Parameters
^^^^^^^^^^
======== ============================================================
uint32_t FunctionID (0x87000010 / 0xC7000010)
uint32_t ``OPEN``
uint32_t mode
======== ============================================================
mode can be one of:
.. code:: c
enum mode {
O_READ = 1 << 0,
O_WRITE = 1 << 1,
O_RDWR = 1 << 2,
O_BIND = 1 << 3,
O_DIR = 1 << 4,
O_STAT = 1 << 5
};
Return values
^^^^^^^^^^^^^
=============== ==========================================================
int32_t w0 == SMC_OK on success
w0 == DEBUGFS_E_INVALID_PARAMS if open operation failed
uint32_t w1: file descriptor id on success.
=============== ==========================================================
CLOSE
~~~~~
Description
^^^^^^^^^^^
This operation closes a file described by a file descriptor obtained by a
previous call to OPEN.
Parameters
^^^^^^^^^^
======== ============================================================
uint32_t FunctionID (0x87000010 / 0xC7000010)
uint32_t ``CLOSE``
uint32_t File descriptor id returned by OPEN
======== ============================================================
Return values
^^^^^^^^^^^^^
=============== ==========================================================
int32_t w0 == SMC_OK on success
w0 == DEBUGFS_E_INVALID_PARAMS if close operation failed
=============== ==========================================================
READ
~~~~
Description
^^^^^^^^^^^
This operation reads a number of bytes from a file descriptor obtained by
a previous call to OPEN.
Parameters
^^^^^^^^^^
======== ============================================================
uint32_t FunctionID (0x87000010 / 0xC7000010)
uint32_t ``READ``
uint32_t File descriptor id returned by OPEN
uint32_t Number of bytes to read
======== ============================================================
Return values
^^^^^^^^^^^^^
On success, the read data is retrieved from the shared buffer after the
operation.
=============== ==========================================================
int32_t w0 == SMC_OK on success
w0 == DEBUGFS_E_INVALID_PARAMS if read operation failed
uint32_t w1: number of bytes read on success.
=============== ==========================================================
SEEK
~~~~
Description
^^^^^^^^^^^
Move file pointer for file described by given `file descriptor` of given
`offset` related to `whence`.
Parameters
^^^^^^^^^^
======== ============================================================
uint32_t FunctionID (0x87000010 / 0xC7000010)
uint32_t ``SEEK``
uint32_t File descriptor id returned by OPEN
sint32_t offset in the file relative to whence
uint32_t whence
======== ============================================================
whence can be one of:
========= ============================================================
KSEEK_SET 0
KSEEK_CUR 1
KSEEK_END 2
========= ============================================================
Return values
^^^^^^^^^^^^^
=============== ==========================================================
int32_t w0 == SMC_OK on success
w0 == DEBUGFS_E_INVALID_PARAMS if seek operation failed
=============== ==========================================================
BIND
~~~~
Description
^^^^^^^^^^^
Create a link from `oldpath` to `newpath`.
Parameters
^^^^^^^^^^
======== ============================================================
uint32_t FunctionID (0x87000010 / 0xC7000010)
uint32_t ``BIND``
======== ============================================================
Return values
^^^^^^^^^^^^^
=============== ==========================================================
int32_t w0 == SMC_OK on success
w0 == DEBUGFS_E_INVALID_PARAMS if bind operation failed
=============== ==========================================================
STAT
~~~~
Description
^^^^^^^^^^^
Perform a stat operation on provided file `name` and returns the directory
entry statistics into `dir`.
Parameters
^^^^^^^^^^
======== ============================================================
uint32_t FunctionID (0x87000010 / 0xC7000010)
uint32_t ``STAT``
======== ============================================================
Return values
^^^^^^^^^^^^^
=============== ==========================================================
int32_t w0 == SMC_OK on success
w0 == DEBUGFS_E_INVALID_PARAMS if stat operation failed
=============== ==========================================================
INIT
~~~~
Description
^^^^^^^^^^^
Initial call to setup the shared exchange buffer. Notice if successful once,
subsequent calls fail after a first initialization. The caller maps the same
page frame in its virtual space and uses this buffer to exchange string
parameters with filesystem primitives.
Parameters
^^^^^^^^^^
======== ============================================================
uint32_t FunctionID (0x87000010 / 0xC7000010)
uint32_t ``INIT``
uint64_t Physical address of the shared buffer.
======== ============================================================
Return values
^^^^^^^^^^^^^
=============== ======================================================
int32_t w0 == SMC_OK on success
w0 == DEBUGFS_E_INVALID_PARAMS if already initialized,
or internal error occurred.
=============== ======================================================
VERSION
~~~~~~~
Description
^^^^^^^^^^^
Returns the debugfs interface version if implemented in TF-A.
Parameters
^^^^^^^^^^
======== ============================================================
uint32_t FunctionID (0x87000010 / 0xC7000010)
uint32_t ``VERSION``
======== ============================================================
Return values
^^^^^^^^^^^^^
=============== ======================================================
int32_t w0 == SMC_OK on success
w0 == SMC_UNK if interface is not implemented
uint32_t w1: On success, debugfs interface version, 32 bits
value with major version number in upper 16 bits and
minor version in lower 16 bits.
=============== ======================================================
* CREATE(1) and WRITE (5) command identifiers are unimplemented and
return `SMC_UNK`.
--------------
*Copyright (c) 2024, Arm Limited and Contributors. All rights reserved.*