[PATCH v6 00/13] powerpc/pseries: New character devices for system parameters and VPD

[PATCH v6 00/13] powerpc/pseries: New character devices for system parameters and VPD

[Nathan Lynch via B4 Relay]

Add character devices that expose PAPR-specific system parameters and
VPD to user space.

The problem: important platform features are enabled on Linux VMs
through the powerpc-specific rtas() syscall in combination with
writeable mappings of /dev/mem. In typical usage, this is encapsulated
behind APIs provided by the librtas library. This paradigm is
incompatible with lockdown, which prohibits /dev/mem access. It also
is too low-level in many cases: a single logical operation may require
multiple sys_rtas() calls in succession to complete. This carries the
risk that a process may exit while leaving an operation unfinished. It
also means that callers must coordinate their use of the syscall for
functions that cannot tolerate multiple concurrent clients, such as
ibm,get-vpd.

These are the general problems, but it's difficult to formulate a
similarly general solution in the form of a single replacement ABI for
sys_rtas(). Instead, each platform facility we expose to user space
needs a specific interface that forms the kernel-user interactions at
a higher level than individual RTAS calls.

I've identified system parameter support as a high priority for this
effort, since the software that communicates with the management
console relies on it and therefore does not work at all with lockdown
enabled on current kernels. VPD retrieval is also important (for
licensing/entitlement things I think?), and serves as a good initial
example of encapsulating sequence-based RTAS calls. So this series
proposes a model for incrementally solving these issues by introducing
a small pseries-specific "driver" for each of these platform
functions. The new drivers expose these facilities to user space in
ways that are compatible with lockdown, and they require no
coordination between their clients.

In preparation, per-function mutexes are added to the core RTAS code
to serialize access to sequence-based RTAS functions. These prevent
kernel-based sequences from interfering with each other, and they
prevent sys_rtas() users from disrupting kernel-based users. The RTAS
core enforces correct lock usage when lockdep is enabled.

Both drivers could potentially support poll() methods to notify
clients of changes to parameters or VPD that happen due to partition
migration and other events. But that should be safe to leave for
later, assuming there's any interest.

I have made changes to librtas to prefer the new interfaces and
verified that existing clients work correctly with the new code. A
draft PR for that work is here:

https://github.com/ibm-power-utilities/librtas/pull/36

The user-space ABI has not changed since v1 of this series.

I expect to propose at least one more small driver in this style for
platform dump retrieval in a separate submission in the future. Other
facilities may follow as needs are identified.

---
Changes in v6:
- Require FMODE_WRITE for setting system parameters in papr-sysparm
  and add a corresponding testcase.
- Update existing sysparm testcases to open the device writable when
  attempting to set parameters.
- Link to v5: https://lore.kernel.org/r/20231207-papr-sys_rtas-vs-lockdown-v5-0-2ce965636a58@linux.ibm.com

Changes in v5:
- Add to the front of the queue another fix for a latent bug where
  sys_rtas() users can trigger a spurious warning backtrace.
- Merge "powerpc/uapi: Export papr-miscdev.h header" into "Add
  papr-vpd character driver for VPD retrieval" so we don't temporarily
  expose the PAPR_MISCDEV_IOC_ID constant via UAPI without also
  updating the ioctl-number documentation. (Michael Ellerman)
- Drop rtas_function_{un}lock() in favor of more explicit use of the new
  per-function mutexes; make rtas_ibm_get_vpd_lock extern for use by
  papr-vpd.
- Assert that rtas_ibm_get_vpd_lock is held in rtas_ibm_get_vpd().
- Add example usage to "powerpc/rtas: Facilitate high-level call
  sequences". (Aneesh Kumar K.V)
- Drop the now-unnecessary 04/13 "powerpc/rtas: Factor out function
  descriptor lookup".
- Include document version when citing the PAPR+ specification
  throughout. (Michael Ellerman)
- Add missing include directives to papr-vpd and papr-sysparm. (Michal
  Suchánek)
- Fix spurious testcase failure in environments without a working
  ibm,set-system-parameter RTAS function. (Michael Ellerman)
- Link to v4: https://lore.kernel.org/r/20231117-papr-sys_rtas-vs-lockdown-v4-0-b794d8cb8502@linux.ibm.com

Changes in v4:
- Fix latent issue in rtas_token_to_function() which causes boot-time
  crashes.
- More small preparatory changes: a function table iterator and
  additional symbolic constants for RTAS function return values.
- Use symbolic constants for ibm,get-vpd statuses in papr-vpd.c.
- Add commentary to papr_vpd_ioc_create_handle() explaining choice to
  retrieve all VPD at file handle creation time instead of deferring
  it to the read handler.
- Rebase on current powerpc/next.
- Link to v3: https://lore.kernel.org/r/20231025-papr-sys_rtas-vs-lockdown-v3-0-5eb04559e7d8@linux.ibm.com

Changes in v3:
- Add new rtas_function_lock()/unlock() APIs and convert existing code
  to use them.
- Convert papr-vpd to use rtas_function_lock()/unlock() instead of
  having sys_rtas() obtain a driver-private mutex.
- Rebase on current powerpc/next.
- Link to v2: https://lore.kernel.org/r/20231013-papr-sys_rtas-vs-lockdown-v2-0-ead01ce01722@linux.ibm.com

Changes in v2:
- Fix unused-but-set variable warning in papr-sysparm code.
- Rebase on powerpc/next branch.
- Link to v1: https://lore.kernel.org/r/20231006-papr-sys_rtas-vs-lockdown-v1-0-3a36bfb66e2e@linux.ibm.com

Changes in v1 vs initial RFC:
- Add papr-sysparm driver and tests.
- Add a papr-miscdev.h uapi header.
- Prevent sys_rtas() from interfering with papr-vpd call sequences.
- Handle -4 ("VPD changed") status in papr-vpd.
- Include string_helpers.h in papr-vpd.c, per Michal Suchánek
- Link to RFC: https://lore.kernel.org/r/20230822-papr-sys_rtas-vs-lockdown-v1-0-932623cf3c7b@linux.ibm.com

---
Nathan Lynch (13):
      powerpc/rtas: Avoid warning on invalid token argument to sys_rtas()
      powerpc/rtas: Add for_each_rtas_function() iterator
      powerpc/rtas: Fall back to linear search on failed token->function lookup
      powerpc/rtas: Add function return status constants
      powerpc/rtas: Move token validation from block_rtas_call() to sys_rtas()
      powerpc/rtas: Facilitate high-level call sequences
      powerpc/rtas: Serialize firmware activation sequences
      powerpc/rtas: Warn if per-function lock isn't held
      powerpc/pseries: Add papr-vpd character driver for VPD retrieval
      powerpc/pseries/papr-sysparm: Validate buffer object lengths
      powerpc/pseries/papr-sysparm: Expose character device to user space
      powerpc/selftests: Add test for papr-vpd
      powerpc/selftests: Add test for papr-sysparm

 Documentation/userspace-api/ioctl/ioctl-number.rst |   4 +
 arch/powerpc/include/asm/papr-sysparm.h            |  17 +-
 arch/powerpc/include/asm/rtas.h                    |  28 +-
 arch/powerpc/include/uapi/asm/papr-miscdev.h       |   9 +
 arch/powerpc/include/uapi/asm/papr-sysparm.h       |  58 +++
 arch/powerpc/include/uapi/asm/papr-vpd.h           |  22 +
 arch/powerpc/kernel/rtas.c                         | 184 +++++--
 arch/powerpc/platforms/pseries/Makefile            |   1 +
 arch/powerpc/platforms/pseries/papr-sysparm.c      | 205 +++++++-
 arch/powerpc/platforms/pseries/papr-vpd.c          | 541 +++++++++++++++++++++
 tools/testing/selftests/powerpc/Makefile           |   2 +
 .../selftests/powerpc/papr_sysparm/.gitignore      |   1 +
 .../selftests/powerpc/papr_sysparm/Makefile        |  12 +
 .../selftests/powerpc/papr_sysparm/papr_sysparm.c  | 196 ++++++++
 .../testing/selftests/powerpc/papr_vpd/.gitignore  |   1 +
 tools/testing/selftests/powerpc/papr_vpd/Makefile  |  12 +
 .../testing/selftests/powerpc/papr_vpd/papr_vpd.c  | 352 ++++++++++++++
 17 files changed, 1596 insertions(+), 49 deletions(-)
---
base-commit: 27951e1d8274e9f9a2925b069e4492939a3f2099
change-id: 20230817-papr-sys_rtas-vs-lockdown-5c54505db792

Best regards,
-- 
Nathan Lynch <nathanl@linux.ibm.com>

[PATCH v6 01/13] powerpc/rtas: Avoid warning on invalid token argument to sys_rtas()

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

rtas_token_to_function() WARNs when passed an invalid token; it's
meant to catch bugs in kernel-based users of RTAS functions. However,
user space controls the token value passed to rtas_token_to_function()
by block_rtas_call(), so user space with sufficient privilege to use
sys_rtas() can trigger the warnings at will:

  unexpected failed lookup for token 2048
  WARNING: CPU: 20 PID: 2247 at arch/powerpc/kernel/rtas.c:556
    rtas_token_to_function+0xfc/0x110
  ...
  NIP rtas_token_to_function+0xfc/0x110
  LR  rtas_token_to_function+0xf8/0x110
  Call Trace:
    rtas_token_to_function+0xf8/0x110 (unreliable)
    sys_rtas+0x188/0x880
    system_call_exception+0x268/0x530
    system_call_common+0x160/0x2c4

It's desirable to continue warning on bogus tokens in
rtas_token_to_function(). Currently it is used to look up RTAS
function descriptors when tracing, where we know there has to have
been a successful descriptor lookup by different means already, and it
would be a serious inconsistency for the reverse lookup to fail.

So instead of weakening rtas_token_to_function()'s contract by
removing the warnings, introduce rtas_token_to_function_untrusted(),
which has no opinion on failed lookups. Convert block_rtas_call() and
rtas_token_to_function() to use it.

Fixes: 8252b88294d2 ("powerpc/rtas: improve function information lookups")
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/kernel/rtas.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index c49f078382a9..ce37dc9860ef 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -544,6 +544,21 @@ static int __init rtas_token_to_function_xarray_init(void)
 }
 arch_initcall(rtas_token_to_function_xarray_init);
 
+/*
+ * For use by sys_rtas(), where the token value is provided by user
+ * space and we don't want to warn on failed lookups.
+ */
+static const struct rtas_function *rtas_token_to_function_untrusted(s32 token)
+{
+	return xa_load(&rtas_token_to_function_xarray, token);
+}
+
+/*
+ * Reverse lookup for deriving the function descriptor from a
+ * known-good token value in contexts where the former is not already
+ * available. @token must be valid, e.g. derived from the result of a
+ * prior lookup against the function table.
+ */
 static const struct rtas_function *rtas_token_to_function(s32 token)
 {
 	const struct rtas_function *func;
@@ -551,7 +566,7 @@ static const struct rtas_function *rtas_token_to_function(s32 token)
 	if (WARN_ONCE(token < 0, "invalid token %d", token))
 		return NULL;
 
-	func = xa_load(&rtas_token_to_function_xarray, token);
+	func = rtas_token_to_function_untrusted(token);
 
 	if (WARN_ONCE(!func, "unexpected failed lookup for token %d", token))
 		return NULL;
@@ -1721,7 +1736,7 @@ static bool block_rtas_call(int token, int nargs,
 	 * If this token doesn't correspond to a function the kernel
 	 * understands, you're not allowed to call it.
 	 */
-	func = rtas_token_to_function(token);
+	func = rtas_token_to_function_untrusted(token);
 	if (!func)
 		goto err;
 	/*

-- 
2.41.0

[PATCH v6 02/13] powerpc/rtas: Add for_each_rtas_function() iterator

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

Add a convenience macro for iterating over every element of the
internal function table and convert the one site that can use it. An
additional user of the macro is anticipated in changes to follow.

Reviewed-by: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/kernel/rtas.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index ce37dc9860ef..ae9b10c954a1 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -454,6 +454,11 @@ static struct rtas_function rtas_function_table[] __ro_after_init = {
 	},
 };
 
+#define for_each_rtas_function(funcp)                                       \
+	for (funcp = &rtas_function_table[0];                               \
+	     funcp < &rtas_function_table[ARRAY_SIZE(rtas_function_table)]; \
+	     ++funcp)
+
 /*
  * Nearly all RTAS calls need to be serialized. All uses of the
  * default rtas_args block must hold rtas_lock.
@@ -525,10 +530,10 @@ static DEFINE_XARRAY(rtas_token_to_function_xarray);
 
 static int __init rtas_token_to_function_xarray_init(void)
 {
+	const struct rtas_function *func;
 	int err = 0;
 
-	for (size_t i = 0; i < ARRAY_SIZE(rtas_function_table); ++i) {
-		const struct rtas_function *func = &rtas_function_table[i];
+	for_each_rtas_function(func) {
 		const s32 token = func->token;
 
 		if (token == RTAS_UNKNOWN_SERVICE)

-- 
2.41.0

[PATCH v6 03/13] powerpc/rtas: Fall back to linear search on failed token->function lookup

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

Enabling any of the powerpc:rtas_* tracepoints at boot is likely to
result in an oops on RTAS platforms. For example, booting a QEMU
pseries model with 'trace_event=powerpc:rtas_input' in the command
line leads to:

  BUG: Kernel NULL pointer dereference on read at 0x00000008
  Oops: Kernel access of bad area, sig: 7 [#1]
  NIP [c00000000004231c] do_enter_rtas+0x1bc/0x460
  LR [c00000000004231c] do_enter_rtas+0x1bc/0x460
  Call Trace:
    do_enter_rtas+0x1bc/0x460 (unreliable)
    rtas_call+0x22c/0x4a0
    rtas_get_boot_time+0x80/0x14c
    read_persistent_clock64+0x124/0x150
    read_persistent_wall_and_boot_offset+0x28/0x58
    timekeeping_init+0x70/0x348
    start_kernel+0xa0c/0xc1c
    start_here_common+0x1c/0x20

(This is preceded by a warning for the failed lookup in
rtas_token_to_function().)

This happens when __do_enter_rtas_trace() attempts a token to function
descriptor lookup before the xarray containing the mappings has been
set up.

Fall back to linear scan of the table if rtas_token_to_function_xarray
is empty.

Fixes: 24098f580e2b ("powerpc/rtas: add tracepoints around RTAS entry")
Reviewed-by: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/kernel/rtas.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index ae9b10c954a1..f60a8e7bd5ed 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -572,11 +572,21 @@ static const struct rtas_function *rtas_token_to_function(s32 token)
 		return NULL;
 
 	func = rtas_token_to_function_untrusted(token);
+	if (func)
+		return func;
+	/*
+	 * Fall back to linear scan in case the reverse mapping hasn't
+	 * been initialized yet.
+	 */
+	if (xa_empty(&rtas_token_to_function_xarray)) {
+		for_each_rtas_function(func) {
+			if (func->token == token)
+				return func;
+		}
+	}
 
-	if (WARN_ONCE(!func, "unexpected failed lookup for token %d", token))
-		return NULL;
-
-	return func;
+	WARN_ONCE(true, "unexpected failed lookup for token %d", token);
+	return NULL;
 }
 
 /* This is here deliberately so it's only used in this file */

-- 
2.41.0

[PATCH v6 04/13] powerpc/rtas: Add function return status constants

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

Not all of the generic RTAS function statuses specified in PAPR have
symbolic constants and descriptions in rtas.h. Fix this, providing a
little more background, slightly updating the existing wording, and
improving the formatting.

Reviewed-by: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/include/asm/rtas.h | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
index a7110ed52e25..08d19e6904f7 100644
--- a/arch/powerpc/include/asm/rtas.h
+++ b/arch/powerpc/include/asm/rtas.h
@@ -201,12 +201,25 @@ typedef struct {
 /* Memory set aside for sys_rtas to use with calls that need a work area. */
 #define RTAS_USER_REGION_SIZE (64 * 1024)
 
-/* RTAS return status codes */
-#define RTAS_HARDWARE_ERROR	-1    /* Hardware Error */
-#define RTAS_BUSY		-2    /* RTAS Busy */
-#define RTAS_INVALID_PARAMETER	-3    /* Invalid indicator/domain/sensor etc. */
-#define RTAS_EXTENDED_DELAY_MIN	9900
-#define RTAS_EXTENDED_DELAY_MAX	9905
+/*
+ * Common RTAS function return values, derived from the table "RTAS
+ * Status Word Values" in PAPR+ v2.13 7.2.8: "Return Codes". If a
+ * function can return a value in this table then generally it has the
+ * meaning listed here. More extended commentary in the documentation
+ * for rtas_call().
+ *
+ * RTAS functions may use negative and positive numbers not in this
+ * set for function-specific error and success conditions,
+ * respectively.
+ */
+#define RTAS_SUCCESS                     0 /* Success. */
+#define RTAS_HARDWARE_ERROR             -1 /* Hardware or other unspecified error. */
+#define RTAS_BUSY                       -2 /* Retry immediately. */
+#define RTAS_INVALID_PARAMETER          -3 /* Invalid indicator/domain/sensor etc. */
+#define RTAS_UNEXPECTED_STATE_CHANGE    -7 /* Seems limited to EEH and slot reset. */
+#define RTAS_EXTENDED_DELAY_MIN       9900 /* Retry after delaying for ~1ms. */
+#define RTAS_EXTENDED_DELAY_MAX       9905 /* Retry after delaying for ~100s. */
+#define RTAS_ML_ISOLATION_ERROR      -9000 /* Multi-level isolation error. */
 
 /* statuses specific to ibm,suspend-me */
 #define RTAS_SUSPEND_ABORTED     9000 /* Suspension aborted */

-- 
2.41.0

[PATCH v6 05/13] powerpc/rtas: Move token validation from block_rtas_call() to sys_rtas()

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

The rtas system call handler sys_rtas() delegates certain input
validation steps to a helper function: block_rtas_call(). One of these
steps ensures that the user-supplied token value maps to a known RTAS
function. This is done by performing a "reverse" token-to-function
lookup via rtas_token_to_function_untrusted() to obtain an
rtas_function object.

In changes to come, sys_rtas() itself will need the function
descriptor for the token. To prepare:

* Move the lookup and validation up into sys_rtas() and pass the
  resulting rtas_function pointer to block_rtas_call(), which is
  otherwise unconcerned with the token value.

* Change block_rtas_call() to report the RTAS function name instead of
  the token value on validation failures, since it can now rely on
  having a valid function descriptor.

One behavior change is that sys_rtas() now silently errors out when
passed a bad token, before calling block_rtas_call(). So we will no
longer log "RTAS call blocked - exploit attempt?" on invalid
tokens. This is consistent with how sys_rtas() currently handles other
"metadata" (nargs and nret), while block_rtas_call() is primarily
concerned with validating the arguments to be passed to specific RTAS
functions.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/kernel/rtas.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index f60a8e7bd5ed..ca5bb0b994ac 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -1738,24 +1738,18 @@ static bool in_rmo_buf(u32 base, u32 end)
 		end < (rtas_rmo_buf + RTAS_USER_REGION_SIZE);
 }
 
-static bool block_rtas_call(int token, int nargs,
+static bool block_rtas_call(const struct rtas_function *func, int nargs,
 			    struct rtas_args *args)
 {
-	const struct rtas_function *func;
 	const struct rtas_filter *f;
-	const bool is_platform_dump = token == rtas_function_token(RTAS_FN_IBM_PLATFORM_DUMP);
-	const bool is_config_conn = token == rtas_function_token(RTAS_FN_IBM_CONFIGURE_CONNECTOR);
+	const bool is_platform_dump =
+		func == &rtas_function_table[RTAS_FNIDX__IBM_PLATFORM_DUMP];
+	const bool is_config_conn =
+		func == &rtas_function_table[RTAS_FNIDX__IBM_CONFIGURE_CONNECTOR];
 	u32 base, size, end;
 
 	/*
-	 * If this token doesn't correspond to a function the kernel
-	 * understands, you're not allowed to call it.
-	 */
-	func = rtas_token_to_function_untrusted(token);
-	if (!func)
-		goto err;
-	/*
-	 * And only functions with filters attached are allowed.
+	 * Only functions with filters attached are allowed.
 	 */
 	f = func->filter;
 	if (!f)
@@ -1812,14 +1806,15 @@ static bool block_rtas_call(int token, int nargs,
 	return false;
 err:
 	pr_err_ratelimited("sys_rtas: RTAS call blocked - exploit attempt?\n");
-	pr_err_ratelimited("sys_rtas: token=0x%x, nargs=%d (called by %s)\n",
-			   token, nargs, current->comm);
+	pr_err_ratelimited("sys_rtas: %s nargs=%d (called by %s)\n",
+			   func->name, nargs, current->comm);
 	return true;
 }
 
 /* We assume to be passed big endian arguments */
 SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
 {
+	const struct rtas_function *func;
 	struct pin_cookie cookie;
 	struct rtas_args args;
 	unsigned long flags;
@@ -1849,13 +1844,18 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
 			   nargs * sizeof(rtas_arg_t)) != 0)
 		return -EFAULT;
 
-	if (token == RTAS_UNKNOWN_SERVICE)
+	/*
+	 * If this token doesn't correspond to a function the kernel
+	 * understands, you're not allowed to call it.
+	 */
+	func = rtas_token_to_function_untrusted(token);
+	if (!func)
 		return -EINVAL;
 
 	args.rets = &args.args[nargs];
 	memset(args.rets, 0, nret * sizeof(rtas_arg_t));
 
-	if (block_rtas_call(token, nargs, &args))
+	if (block_rtas_call(func, nargs, &args))
 		return -EINVAL;
 
 	if (token_is_restricted_errinjct(token)) {

-- 
2.41.0

[PATCH v6 06/13] powerpc/rtas: Facilitate high-level call sequences

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

On RTAS platforms there is a general restriction that the OS must not
enter RTAS on more than one CPU at a time. This low-level
serialization requirement is satisfied by holding a spin
lock (rtas_lock) across most RTAS function invocations.

However, some pseries RTAS functions require multiple successive calls
to complete a logical operation. Beginning a new call sequence for such a
function may disrupt any other sequences of that function already in
progress. Safe and reliable use of these functions effectively
requires higher-level serialization beyond what is already done at the
level of RTAS entry and exit.

Where a sequence-based RTAS function is invoked only through
sys_rtas(), with no in-kernel users, there is no issue as far as the
kernel is concerned. User space is responsible for appropriately
serializing its call sequences. (Whether user space code actually
takes measures to prevent sequence interleaving is another matter.)
Examples of such functions currently include ibm,platform-dump and
ibm,get-vpd.

But where a sequence-based RTAS function has both user space and
in-kernel uesrs, there is a hazard. Even if the in-kernel call sites
of such a function serialize their sequences correctly, a user of
sys_rtas() can invoke the same function at any time, potentially
disrupting a sequence in progress.

So in order to prevent disruption of kernel-based RTAS call sequences,
they must serialize not only with themselves but also with sys_rtas()
users, somehow. Preferably without adding more function-specific hacks
to sys_rtas(). This is a prerequisite for adding an in-kernel call
sequence of ibm,get-vpd, which is in a change to follow.

Note that it has never been feasible for the kernel to prevent
sys_rtas()-based sequences from being disrupted because control
returns to user space on every call. sys_rtas()-based users of these
functions have always been, and continue to be, responsible for
coordinating their call sequences with other users, even those which
may invoke the RTAS functions through less direct means than
sys_rtas(). This is an unavoidable consequence of exposing
sequence-based RTAS functions through sys_rtas().

* Add an optional mutex member to struct rtas_function.

* Statically define a mutex for each RTAS function with known call
  sequence serialization requirements, and assign its address to the
  .lock member of the corresponding function table entry, along with
  justifying commentary.

* In sys_rtas(), if the table entry for the RTAS function being
  called has a populated lock member, acquire it before taking
  rtas_lock and entering RTAS.

* Kernel-based RTAS call sequences are expected to access the
  appropriate mutex explicitly by name. For example, a user of the
  ibm,activate-firmware RTAS function would do:

        int token = rtas_function_token(RTAS_FN_IBM_ACTIVATE_FIRMWARE);
        int fwrc;

        mutex_lock(&rtas_ibm_activate_firmware_lock);

        do {
                fwrc = rtas_call(token, 0, 1, NULL);
        } while (rtas_busy_delay(fwrc));

        mutex_unlock(&rtas_ibm_activate_firmware_lock);

There should be no perceivable change introduced here except that
concurrent callers of the same RTAS function via sys_rtas() may block
on a mutex instead of spinning on rtas_lock.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/include/asm/rtas.h |  3 ++
 arch/powerpc/kernel/rtas.c      | 83 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+)

diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
index 08d19e6904f7..9bb2210c8d44 100644
--- a/arch/powerpc/include/asm/rtas.h
+++ b/arch/powerpc/include/asm/rtas.h
@@ -3,6 +3,7 @@
 #define _POWERPC_RTAS_H
 #ifdef __KERNEL__
 
+#include <linux/mutex.h>
 #include <linux/spinlock.h>
 #include <asm/page.h>
 #include <asm/rtas-types.h>
@@ -512,6 +513,8 @@ extern char rtas_data_buf[RTAS_DATA_BUF_SIZE];
 /* RMO buffer reserved for user-space RTAS use */
 extern unsigned long rtas_rmo_buf;
 
+extern struct mutex rtas_ibm_get_vpd_lock;
+
 #define GLOBAL_INTERRUPT_QUEUE 9005
 
 /**
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index ca5bb0b994ac..4d28983e8b1d 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -18,6 +18,7 @@
 #include <linux/kernel.h>
 #include <linux/lockdep.h>
 #include <linux/memblock.h>
+#include <linux/mutex.h>
 #include <linux/of.h>
 #include <linux/of_fdt.h>
 #include <linux/reboot.h>
@@ -70,14 +71,33 @@ struct rtas_filter {
  *                            ppc64le, and we want to keep it that way. It does
  *                            not make sense for this to be set when @filter
  *                            is NULL.
+ * @lock: Pointer to an optional dedicated per-function mutex. This
+ *        should be set for functions that require multiple calls in
+ *        sequence to complete a single operation, and such sequences
+ *        will disrupt each other if allowed to interleave. Users of
+ *        this function are required to hold the associated lock for
+ *        the duration of the call sequence. Add an explanatory
+ *        comment to the function table entry if setting this member.
  */
 struct rtas_function {
 	s32 token;
 	const bool banned_for_syscall_on_le:1;
 	const char * const name;
 	const struct rtas_filter *filter;
+	struct mutex *lock;
 };
 
+/*
+ * Per-function locks for sequence-based RTAS functions.
+ */
+static DEFINE_MUTEX(rtas_ibm_activate_firmware_lock);
+static DEFINE_MUTEX(rtas_ibm_get_dynamic_sensor_state_lock);
+static DEFINE_MUTEX(rtas_ibm_get_indices_lock);
+static DEFINE_MUTEX(rtas_ibm_lpar_perftools_lock);
+static DEFINE_MUTEX(rtas_ibm_physical_attestation_lock);
+static DEFINE_MUTEX(rtas_ibm_set_dynamic_indicator_lock);
+DEFINE_MUTEX(rtas_ibm_get_vpd_lock);
+
 static struct rtas_function rtas_function_table[] __ro_after_init = {
 	[RTAS_FNIDX__CHECK_EXCEPTION] = {
 		.name = "check-exception",
@@ -125,6 +145,13 @@ static struct rtas_function rtas_function_table[] __ro_after_init = {
 			.buf_idx1 = -1, .size_idx1 = -1,
 			.buf_idx2 = -1, .size_idx2 = -1,
 		},
+		/*
+		 * PAPR+ as of v2.13 doesn't explicitly impose any
+		 * restriction, but this typically requires multiple
+		 * calls before success, and there's no reason to
+		 * allow sequences to interleave.
+		 */
+		.lock = &rtas_ibm_activate_firmware_lock,
 	},
 	[RTAS_FNIDX__IBM_CBE_START_PTCAL] = {
 		.name = "ibm,cbe-start-ptcal",
@@ -196,6 +223,13 @@ static struct rtas_function rtas_function_table[] __ro_after_init = {
 			.buf_idx1 = 1, .size_idx1 = -1,
 			.buf_idx2 = -1, .size_idx2 = -1,
 		},
+		/*
+		 * PAPR+ v2.13 R1–7.3.19–3 is explicit that the OS
+		 * must not call ibm,get-dynamic-sensor-state with
+		 * different inputs until a non-retry status has been
+		 * returned.
+		 */
+		.lock = &rtas_ibm_get_dynamic_sensor_state_lock,
 	},
 	[RTAS_FNIDX__IBM_GET_INDICES] = {
 		.name = "ibm,get-indices",
@@ -203,6 +237,12 @@ static struct rtas_function rtas_function_table[] __ro_after_init = {
 			.buf_idx1 = 2, .size_idx1 = 3,
 			.buf_idx2 = -1, .size_idx2 = -1,
 		},
+		/*
+		 * PAPR+ v2.13 R1–7.3.17–2 says that the OS must not
+		 * interleave ibm,get-indices call sequences with
+		 * different inputs.
+		 */
+		.lock = &rtas_ibm_get_indices_lock,
 	},
 	[RTAS_FNIDX__IBM_GET_RIO_TOPOLOGY] = {
 		.name = "ibm,get-rio-topology",
@@ -220,6 +260,11 @@ static struct rtas_function rtas_function_table[] __ro_after_init = {
 			.buf_idx1 = 0, .size_idx1 = -1,
 			.buf_idx2 = 1, .size_idx2 = 2,
 		},
+		/*
+		 * PAPR+ v2.13 R1–7.3.20–4 indicates that sequences
+		 * should not be allowed to interleave.
+		 */
+		.lock = &rtas_ibm_get_vpd_lock,
 	},
 	[RTAS_FNIDX__IBM_GET_XIVE] = {
 		.name = "ibm,get-xive",
@@ -239,6 +284,11 @@ static struct rtas_function rtas_function_table[] __ro_after_init = {
 			.buf_idx1 = 2, .size_idx1 = 3,
 			.buf_idx2 = -1, .size_idx2 = -1,
 		},
+		/*
+		 * PAPR+ v2.13 R1–7.3.26–6 says the OS should allow
+		 * only one call sequence in progress at a time.
+		 */
+		.lock = &rtas_ibm_lpar_perftools_lock,
 	},
 	[RTAS_FNIDX__IBM_MANAGE_FLASH_IMAGE] = {
 		.name = "ibm,manage-flash-image",
@@ -277,6 +327,14 @@ static struct rtas_function rtas_function_table[] __ro_after_init = {
 			.buf_idx1 = 0, .size_idx1 = 1,
 			.buf_idx2 = -1, .size_idx2 = -1,
 		},
+		/*
+		 * This follows a sequence-based pattern similar to
+		 * ibm,get-vpd et al. Since PAPR+ restricts
+		 * interleaving call sequences for other functions of
+		 * this style, assume the restriction applies here,
+		 * even though it's not explicit in the spec.
+		 */
+		.lock = &rtas_ibm_physical_attestation_lock,
 	},
 	[RTAS_FNIDX__IBM_PLATFORM_DUMP] = {
 		.name = "ibm,platform-dump",
@@ -284,6 +342,13 @@ static struct rtas_function rtas_function_table[] __ro_after_init = {
 			.buf_idx1 = 4, .size_idx1 = 5,
 			.buf_idx2 = -1, .size_idx2 = -1,
 		},
+		/*
+		 * PAPR+ v2.13 7.3.3.4.1 indicates that concurrent
+		 * sequences of ibm,platform-dump are allowed if they
+		 * are operating on different dump tags. So leave the
+		 * lock pointer unset for now. This may need
+		 * reconsideration if kernel-internal users appear.
+		 */
 	},
 	[RTAS_FNIDX__IBM_POWER_OFF_UPS] = {
 		.name = "ibm,power-off-ups",
@@ -326,6 +391,12 @@ static struct rtas_function rtas_function_table[] __ro_after_init = {
 			.buf_idx1 = 2, .size_idx1 = -1,
 			.buf_idx2 = -1, .size_idx2 = -1,
 		},
+		/*
+		 * PAPR+ v2.13 R1–7.3.18–3 says the OS must not call
+		 * this function with different inputs until a
+		 * non-retry status has been returned.
+		 */
+		.lock = &rtas_ibm_set_dynamic_indicator_lock,
 	},
 	[RTAS_FNIDX__IBM_SET_EEH_OPTION] = {
 		.name = "ibm,set-eeh-option",
@@ -1888,6 +1959,15 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
 
 	buff_copy = get_errorlog_buffer();
 
+	/*
+	 * If this function has a mutex assigned to it, we must
+	 * acquire it to avoid interleaving with any kernel-based uses
+	 * of the same function. Kernel-based sequences acquire the
+	 * appropriate mutex explicitly.
+	 */
+	if (func->lock)
+		mutex_lock(func->lock);
+
 	raw_spin_lock_irqsave(&rtas_lock, flags);
 	cookie = lockdep_pin_lock(&rtas_lock);
 
@@ -1903,6 +1983,9 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
 	lockdep_unpin_lock(&rtas_lock, cookie);
 	raw_spin_unlock_irqrestore(&rtas_lock, flags);
 
+	if (func->lock)
+		mutex_unlock(func->lock);
+
 	if (buff_copy) {
 		if (errbuf)
 			log_error(errbuf, ERR_TYPE_RTAS_LOG, 0);

-- 
2.41.0

[PATCH v6 07/13] powerpc/rtas: Serialize firmware activation sequences

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

Use rtas_ibm_activate_firmware_lock to prevent interleaving call
sequences of the ibm,activate-firmware RTAS function, which typically
requires multiple calls to complete the update. While the spec does
not specifically prohibit interleaved sequences, there's almost
certainly no advantage to allowing them.

Reviewed-by: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/kernel/rtas.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 4d28983e8b1d..72f6b5a402dd 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -1734,10 +1734,14 @@ void rtas_activate_firmware(void)
 		return;
 	}
 
+	mutex_lock(&rtas_ibm_activate_firmware_lock);
+
 	do {
 		fwrc = rtas_call(token, 0, 1, NULL);
 	} while (rtas_busy_delay(fwrc));
 
+	mutex_unlock(&rtas_ibm_activate_firmware_lock);
+
 	if (fwrc)
 		pr_err("ibm,activate-firmware failed (%i)\n", fwrc);
 }

-- 
2.41.0

[PATCH v6 08/13] powerpc/rtas: Warn if per-function lock isn't held

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

If the function descriptor has a populated lock member, then callers
are required to hold it across calls. Now that the firmware activation
sequence is appropriately guarded, we can warn when the requirement
isn't satisfied.

__do_enter_rtas_trace() gets reorganized a bit as a result of
performing the function descriptor lookup unconditionally now.

Reviewed-by: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/kernel/rtas.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 72f6b5a402dd..7e793b503e29 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -671,28 +671,25 @@ static void __do_enter_rtas(struct rtas_args *args)
 
 static void __do_enter_rtas_trace(struct rtas_args *args)
 {
-	const char *name = NULL;
+	const struct rtas_function *func = rtas_token_to_function(be32_to_cpu(args->token));
 
-	if (args == &rtas_args)
-		lockdep_assert_held(&rtas_lock);
 	/*
-	 * If the tracepoints that consume the function name aren't
-	 * active, avoid the lookup.
+	 * If there is a per-function lock, it must be held by the
+	 * caller.
 	 */
-	if ((trace_rtas_input_enabled() || trace_rtas_output_enabled())) {
-		const s32 token = be32_to_cpu(args->token);
-		const struct rtas_function *func = rtas_token_to_function(token);
+	if (func->lock)
+		lockdep_assert_held(func->lock);
 
-		name = func->name;
-	}
+	if (args == &rtas_args)
+		lockdep_assert_held(&rtas_lock);
 
-	trace_rtas_input(args, name);
+	trace_rtas_input(args, func->name);
 	trace_rtas_ll_entry(args);
 
 	__do_enter_rtas(args);
 
 	trace_rtas_ll_exit(args);
-	trace_rtas_output(args, name);
+	trace_rtas_output(args, func->name);
 }
 
 static void do_enter_rtas(struct rtas_args *args)

-- 
2.41.0

[PATCH v6 09/13] powerpc/pseries: Add papr-vpd character driver for VPD retrieval

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

PowerVM LPARs may retrieve Vital Product Data (VPD) for system
components using the ibm,get-vpd RTAS function.

We can expose this to user space with a /dev/papr-vpd character
device, where the programming model is:

  struct papr_location_code plc = { .str = "", }; /* obtain all VPD */
  int devfd = open("/dev/papr-vpd", O_RDONLY);
  int vpdfd = ioctl(devfd, PAPR_VPD_CREATE_HANDLE, &plc);
  size_t size = lseek(vpdfd, 0, SEEK_END);
  char *buf = malloc(size);
  pread(devfd, buf, size, 0);

When a file descriptor is obtained from ioctl(PAPR_VPD_CREATE_HANDLE),
the file contains the result of a complete ibm,get-vpd sequence. The
file contents are immutable from the POV of user space. To get a new
view of the VPD, the client must create a new handle.

This design choice insulates user space from most of the complexities
that ibm,get-vpd brings:

* ibm,get-vpd must be called more than once to obtain complete
  results.

* Only one ibm,get-vpd call sequence should be in progress at a time;
  interleaved sequences will disrupt each other. Callers must have a
  protocol for serializing their use of the function.

* A call sequence in progress may receive a "VPD changed, try again"
  status, requiring the client to abandon the sequence and start
  over.

The memory required for the VPD buffers seems acceptable, around 20KB
for all VPD on one of my systems. And the value of the
/rtas/ibm,vpd-size DT property (the estimated maximum size of VPD) is
consistently 300KB across various systems I've checked.

I've implemented support for this new ABI in the rtas_get_vpd()
function in librtas, which the vpdupdate command currently uses to
populate its VPD database. I've verified that an unmodified vpdupdate
binary generates an identical database when using a librtas.so that
prefers the new ABI.

Along with the papr-vpd.h header exposed to user space, this
introduces a common papr-miscdev.h uapi header to share a base ioctl
ID with similar drivers to come.

Tested-by: Michal Suchánek <msuchanek@suse.de>
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 Documentation/userspace-api/ioctl/ioctl-number.rst |   2 +
 arch/powerpc/include/uapi/asm/papr-miscdev.h       |   9 +
 arch/powerpc/include/uapi/asm/papr-vpd.h           |  22 +
 arch/powerpc/platforms/pseries/Makefile            |   1 +
 arch/powerpc/platforms/pseries/papr-vpd.c          | 541 +++++++++++++++++++++
 5 files changed, 575 insertions(+)

diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index 4ea5b837399a..a950545bf7cd 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -349,6 +349,8 @@ Code  Seq#    Include File                                           Comments
                                                                      <mailto:vgo@ratio.de>
 0xB1  00-1F                                                          PPPoX
                                                                      <mailto:mostrows@styx.uwaterloo.ca>
+0xB2  00     arch/powerpc/include/uapi/asm/papr-vpd.h                powerpc/pseries VPD API
+                                                                     <mailto:linuxppc-dev>
 0xB3  00     linux/mmc/ioctl.h
 0xB4  00-0F  linux/gpio.h                                            <mailto:linux-gpio@vger.kernel.org>
 0xB5  00-0F  uapi/linux/rpmsg.h                                      <mailto:linux-remoteproc@vger.kernel.org>
diff --git a/arch/powerpc/include/uapi/asm/papr-miscdev.h b/arch/powerpc/include/uapi/asm/papr-miscdev.h
new file mode 100644
index 000000000000..49a2a270b7f3
--- /dev/null
+++ b/arch/powerpc/include/uapi/asm/papr-miscdev.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_PAPR_MISCDEV_H_
+#define _UAPI_PAPR_MISCDEV_H_
+
+enum {
+	PAPR_MISCDEV_IOC_ID = 0xb2,
+};
+
+#endif /* _UAPI_PAPR_MISCDEV_H_ */
diff --git a/arch/powerpc/include/uapi/asm/papr-vpd.h b/arch/powerpc/include/uapi/asm/papr-vpd.h
new file mode 100644
index 000000000000..1c88e87cb420
--- /dev/null
+++ b/arch/powerpc/include/uapi/asm/papr-vpd.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_PAPR_VPD_H_
+#define _UAPI_PAPR_VPD_H_
+
+#include <asm/ioctl.h>
+#include <asm/papr-miscdev.h>
+
+struct papr_location_code {
+	/*
+	 * PAPR+ v2.13 12.3.2.4 Converged Location Code Rules - Length
+	 * Restrictions. 79 characters plus nul.
+	 */
+	char str[80];
+};
+
+/*
+ * ioctl for /dev/papr-vpd. Returns a VPD handle fd corresponding to
+ * the location code.
+ */
+#define PAPR_VPD_IOC_CREATE_HANDLE _IOW(PAPR_MISCDEV_IOC_ID, 0, struct papr_location_code)
+
+#endif /* _UAPI_PAPR_VPD_H_ */
diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index 1476c5e4433c..f936962a2946 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile
@@ -4,6 +4,7 @@ ccflags-$(CONFIG_PPC_PSERIES_DEBUG)	+= -DDEBUG
 
 obj-y			:= lpar.o hvCall.o nvram.o reconfig.o \
 			   of_helpers.o rtas-work-area.o papr-sysparm.o \
+			   papr-vpd.o \
 			   setup.o iommu.o event_sources.o ras.o \
 			   firmware.o power.o dlpar.o mobility.o rng.o \
 			   pci.o pci_dlpar.o eeh_pseries.o msi.o \
diff --git a/arch/powerpc/platforms/pseries/papr-vpd.c b/arch/powerpc/platforms/pseries/papr-vpd.c
new file mode 100644
index 000000000000..c29e85db5f35
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/papr-vpd.c
@@ -0,0 +1,541 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define pr_fmt(fmt) "papr-vpd: " fmt
+
+#include <linux/anon_inodes.h>
+#include <linux/build_bug.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/lockdep.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/signal.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/string_helpers.h>
+#include <linux/uaccess.h>
+#include <asm/machdep.h>
+#include <asm/papr-vpd.h>
+#include <asm/rtas-work-area.h>
+#include <asm/rtas.h>
+#include <uapi/asm/papr-vpd.h>
+
+/*
+ * Function-specific return values for ibm,get-vpd, derived from PAPR+
+ * v2.13 7.3.20 "ibm,get-vpd RTAS Call".
+ */
+#define RTAS_IBM_GET_VPD_COMPLETE    0 /* All VPD has been retrieved. */
+#define RTAS_IBM_GET_VPD_MORE_DATA   1 /* More VPD is available. */
+#define RTAS_IBM_GET_VPD_START_OVER -4 /* VPD changed, restart call sequence. */
+
+/**
+ * struct rtas_ibm_get_vpd_params - Parameters (in and out) for ibm,get-vpd.
+ * @loc_code:  In: Caller-provided location code buffer. Must be RTAS-addressable.
+ * @work_area: In: Caller-provided work area buffer for results.
+ * @sequence:  In: Sequence number. Out: Next sequence number.
+ * @written:   Out: Bytes written by ibm,get-vpd to @work_area.
+ * @status:    Out: RTAS call status.
+ */
+struct rtas_ibm_get_vpd_params {
+	const struct papr_location_code *loc_code;
+	struct rtas_work_area *work_area;
+	u32 sequence;
+	u32 written;
+	s32 status;
+};
+
+/**
+ * rtas_ibm_get_vpd() - Call ibm,get-vpd to fill a work area buffer.
+ * @params: See &struct rtas_ibm_get_vpd_params.
+ *
+ * Calls ibm,get-vpd until it errors or successfully deposits data
+ * into the supplied work area. Handles RTAS retry statuses. Maps RTAS
+ * error statuses to reasonable errno values.
+ *
+ * The caller is expected to invoke rtas_ibm_get_vpd() multiple times
+ * to retrieve all the VPD for the provided location code. Only one
+ * sequence should be in progress at any time; starting a new sequence
+ * will disrupt any sequence already in progress. Serialization of VPD
+ * retrieval sequences is the responsibility of the caller.
+ *
+ * The caller should inspect @params.status to determine whether more
+ * calls are needed to complete the sequence.
+ *
+ * Context: May sleep.
+ * Return: -ve on error, 0 otherwise.
+ */
+static int rtas_ibm_get_vpd(struct rtas_ibm_get_vpd_params *params)
+{
+	const struct papr_location_code *loc_code = params->loc_code;
+	struct rtas_work_area *work_area = params->work_area;
+	u32 rets[2];
+	s32 fwrc;
+	int ret;
+
+	lockdep_assert_held(&rtas_ibm_get_vpd_lock);
+
+	do {
+		fwrc = rtas_call(rtas_function_token(RTAS_FN_IBM_GET_VPD), 4, 3,
+				 rets,
+				 __pa(loc_code),
+				 rtas_work_area_phys(work_area),
+				 rtas_work_area_size(work_area),
+				 params->sequence);
+	} while (rtas_busy_delay(fwrc));
+
+	switch (fwrc) {
+	case RTAS_HARDWARE_ERROR:
+		ret = -EIO;
+		break;
+	case RTAS_INVALID_PARAMETER:
+		ret = -EINVAL;
+		break;
+	case RTAS_IBM_GET_VPD_START_OVER:
+		ret = -EAGAIN;
+		break;
+	case RTAS_IBM_GET_VPD_MORE_DATA:
+		params->sequence = rets[0];
+		fallthrough;
+	case RTAS_IBM_GET_VPD_COMPLETE:
+		params->written = rets[1];
+		/*
+		 * Kernel or firmware bug, do not continue.
+		 */
+		if (WARN(params->written > rtas_work_area_size(work_area),
+			 "possible write beyond end of work area"))
+			ret = -EFAULT;
+		else
+			ret = 0;
+		break;
+	default:
+		ret = -EIO;
+		pr_err_ratelimited("unexpected ibm,get-vpd status %d\n", fwrc);
+		break;
+	}
+
+	params->status = fwrc;
+	return ret;
+}
+
+/*
+ * Internal VPD "blob" APIs for accumulating ibm,get-vpd results into
+ * an immutable buffer to be attached to a file descriptor.
+ */
+struct vpd_blob {
+	const char *data;
+	size_t len;
+};
+
+static bool vpd_blob_has_data(const struct vpd_blob *blob)
+{
+	return blob->data && blob->len;
+}
+
+static void vpd_blob_free(const struct vpd_blob *blob)
+{
+	if (blob) {
+		kvfree(blob->data);
+		kfree(blob);
+	}
+}
+
+/**
+ * vpd_blob_extend() - Append data to a &struct vpd_blob.
+ * @blob: The blob to extend.
+ * @data: The new data to append to @blob.
+ * @len:  The length of @data.
+ *
+ * Context: May sleep.
+ * Return: -ENOMEM on allocation failure, 0 otherwise.
+ */
+static int vpd_blob_extend(struct vpd_blob *blob, const char *data, size_t len)
+{
+	const size_t new_len = blob->len + len;
+	const size_t old_len = blob->len;
+	const char *old_ptr = blob->data;
+	char *new_ptr;
+
+	new_ptr = old_ptr ?
+		kvrealloc(old_ptr, old_len, new_len, GFP_KERNEL_ACCOUNT) :
+		kvmalloc(len, GFP_KERNEL_ACCOUNT);
+
+	if (!new_ptr)
+		return -ENOMEM;
+
+	memcpy(&new_ptr[old_len], data, len);
+	blob->data = new_ptr;
+	blob->len = new_len;
+	return 0;
+}
+
+/**
+ * vpd_blob_generate() - Construct a new &struct vpd_blob.
+ * @generator: Function that supplies the blob data.
+ * @arg:       Context pointer supplied by caller, passed to @generator.
+ *
+ * The @generator callback is invoked until it returns NULL. @arg is
+ * passed to @generator in its first argument on each call. When
+ * @generator returns data, it should store the data length in its
+ * second argument.
+ *
+ * Context: May sleep.
+ * Return: A completely populated &struct vpd_blob, or NULL on error.
+ */
+static const struct vpd_blob *
+vpd_blob_generate(const char * (*generator)(void *, size_t *), void *arg)
+{
+	struct vpd_blob *blob;
+	const char *buf;
+	size_t len;
+	int err = 0;
+
+	blob  = kzalloc(sizeof(*blob), GFP_KERNEL_ACCOUNT);
+	if (!blob)
+		return NULL;
+
+	while (err == 0 && (buf = generator(arg, &len)))
+		err = vpd_blob_extend(blob, buf, len);
+
+	if (err != 0 || !vpd_blob_has_data(blob))
+		goto free_blob;
+
+	return blob;
+free_blob:
+	vpd_blob_free(blob);
+	return NULL;
+}
+
+/*
+ * Internal VPD sequence APIs. A VPD sequence is a series of calls to
+ * ibm,get-vpd for a given location code. The sequence ends when an
+ * error is encountered or all VPD for the location code has been
+ * returned.
+ */
+
+/**
+ * struct vpd_sequence - State for managing a VPD sequence.
+ * @error:  Shall be zero as long as the sequence has not encountered an error,
+ *          -ve errno otherwise. Use vpd_sequence_set_err() to update this.
+ * @params: Parameter block to pass to rtas_ibm_get_vpd().
+ */
+struct vpd_sequence {
+	int error;
+	struct rtas_ibm_get_vpd_params params;
+};
+
+/**
+ * vpd_sequence_begin() - Begin a VPD retrieval sequence.
+ * @seq:      Uninitialized sequence state.
+ * @loc_code: Location code that defines the scope of the VPD to return.
+ *
+ * Initializes @seq with the resources necessary to carry out a VPD
+ * sequence. Callers must pass @seq to vpd_sequence_end() regardless
+ * of whether the sequence succeeds.
+ *
+ * Context: May sleep.
+ */
+static void vpd_sequence_begin(struct vpd_sequence *seq,
+			       const struct papr_location_code *loc_code)
+{
+	/*
+	 * Use a static data structure for the location code passed to
+	 * RTAS to ensure it's in the RMA and avoid a separate work
+	 * area allocation. Guarded by the function lock.
+	 */
+	static struct papr_location_code static_loc_code;
+
+	/*
+	 * We could allocate the work area before acquiring the
+	 * function lock, but that would allow concurrent requests to
+	 * exhaust the limited work area pool for no benefit. So
+	 * allocate the work area under the lock.
+	 */
+	mutex_lock(&rtas_ibm_get_vpd_lock);
+	static_loc_code = *loc_code;
+	*seq = (struct vpd_sequence) {
+		.params = {
+			.work_area = rtas_work_area_alloc(SZ_4K),
+			.loc_code = &static_loc_code,
+			.sequence = 1,
+		},
+	};
+}
+
+/**
+ * vpd_sequence_end() - Finalize a VPD retrieval sequence.
+ * @seq: Sequence state.
+ *
+ * Releases resources obtained by vpd_sequence_begin().
+ */
+static void vpd_sequence_end(struct vpd_sequence *seq)
+{
+	rtas_work_area_free(seq->params.work_area);
+	mutex_unlock(&rtas_ibm_get_vpd_lock);
+}
+
+/**
+ * vpd_sequence_should_stop() - Determine whether a VPD retrieval sequence
+ *                              should continue.
+ * @seq: VPD sequence state.
+ *
+ * Examines the sequence error state and outputs of the last call to
+ * ibm,get-vpd to determine whether the sequence in progress should
+ * continue or stop.
+ *
+ * Return: True if the sequence has encountered an error or if all VPD for
+ *         this sequence has been retrieved. False otherwise.
+ */
+static bool vpd_sequence_should_stop(const struct vpd_sequence *seq)
+{
+	bool done;
+
+	if (seq->error)
+		return true;
+
+	switch (seq->params.status) {
+	case 0:
+		if (seq->params.written == 0)
+			done = false; /* Initial state. */
+		else
+			done = true; /* All data consumed. */
+		break;
+	case 1:
+		done = false; /* More data available. */
+		break;
+	default:
+		done = true; /* Error encountered. */
+		break;
+	}
+
+	return done;
+}
+
+static int vpd_sequence_set_err(struct vpd_sequence *seq, int err)
+{
+	/* Preserve the first error recorded. */
+	if (seq->error == 0)
+		seq->error = err;
+
+	return seq->error;
+}
+
+/*
+ * Generator function to be passed to vpd_blob_generate().
+ */
+static const char *vpd_sequence_fill_work_area(void *arg, size_t *len)
+{
+	struct vpd_sequence *seq = arg;
+	struct rtas_ibm_get_vpd_params *p = &seq->params;
+
+	if (vpd_sequence_should_stop(seq))
+		return NULL;
+	if (vpd_sequence_set_err(seq, rtas_ibm_get_vpd(p)))
+		return NULL;
+	*len = p->written;
+	return rtas_work_area_raw_buf(p->work_area);
+}
+
+/*
+ * Higher-level VPD retrieval code below. These functions use the
+ * vpd_blob_* and vpd_sequence_* APIs defined above to create fd-based
+ * VPD handles for consumption by user space.
+ */
+
+/**
+ * papr_vpd_run_sequence() - Run a single VPD retrieval sequence.
+ * @loc_code: Location code that defines the scope of VPD to return.
+ *
+ * Context: May sleep. Holds a mutex and an RTAS work area for its
+ *          duration. Typically performs multiple sleepable slab
+ *          allocations.
+ *
+ * Return: A populated &struct vpd_blob on success. Encoded error
+ * pointer otherwise.
+ */
+static const struct vpd_blob *papr_vpd_run_sequence(const struct papr_location_code *loc_code)
+{
+	const struct vpd_blob *blob;
+	struct vpd_sequence seq;
+
+	vpd_sequence_begin(&seq, loc_code);
+	blob = vpd_blob_generate(vpd_sequence_fill_work_area, &seq);
+	if (!blob)
+		vpd_sequence_set_err(&seq, -ENOMEM);
+	vpd_sequence_end(&seq);
+
+	if (seq.error) {
+		vpd_blob_free(blob);
+		return ERR_PTR(seq.error);
+	}
+
+	return blob;
+}
+
+/**
+ * papr_vpd_retrieve() - Return the VPD for a location code.
+ * @loc_code: Location code that defines the scope of VPD to return.
+ *
+ * Run VPD sequences against @loc_code until a blob is successfully
+ * instantiated, or a hard error is encountered, or a fatal signal is
+ * pending.
+ *
+ * Context: May sleep.
+ * Return: A fully populated VPD blob when successful. Encoded error
+ * pointer otherwise.
+ */
+static const struct vpd_blob *papr_vpd_retrieve(const struct papr_location_code *loc_code)
+{
+	const struct vpd_blob *blob;
+
+	/*
+	 * EAGAIN means the sequence errored with a -4 (VPD changed)
+	 * status from ibm,get-vpd, and we should attempt a new
+	 * sequence. PAPR+ v2.13 R1–7.3.20–5 indicates that this
+	 * should be a transient condition, not something that happens
+	 * continuously. But we'll stop trying on a fatal signal.
+	 */
+	do {
+		blob = papr_vpd_run_sequence(loc_code);
+		if (!IS_ERR(blob)) /* Success. */
+			break;
+		if (PTR_ERR(blob) != -EAGAIN) /* Hard error. */
+			break;
+		pr_info_ratelimited("VPD changed during retrieval, retrying\n");
+		cond_resched();
+	} while (!fatal_signal_pending(current));
+
+	return blob;
+}
+
+static ssize_t papr_vpd_handle_read(struct file *file, char __user *buf, size_t size, loff_t *off)
+{
+	const struct vpd_blob *blob = file->private_data;
+
+	/* bug: we should not instantiate a handle without any data attached. */
+	if (!vpd_blob_has_data(blob)) {
+		pr_err_once("handle without data\n");
+		return -EIO;
+	}
+
+	return simple_read_from_buffer(buf, size, off, blob->data, blob->len);
+}
+
+static int papr_vpd_handle_release(struct inode *inode, struct file *file)
+{
+	const struct vpd_blob *blob = file->private_data;
+
+	vpd_blob_free(blob);
+
+	return 0;
+}
+
+static loff_t papr_vpd_handle_seek(struct file *file, loff_t off, int whence)
+{
+	const struct vpd_blob *blob = file->private_data;
+
+	return fixed_size_llseek(file, off, whence, blob->len);
+}
+
+
+static const struct file_operations papr_vpd_handle_ops = {
+	.read = papr_vpd_handle_read,
+	.llseek = papr_vpd_handle_seek,
+	.release = papr_vpd_handle_release,
+};
+
+/**
+ * papr_vpd_create_handle() - Create a fd-based handle for reading VPD.
+ * @ulc: Location code in user memory; defines the scope of the VPD to
+ *       retrieve.
+ *
+ * Handler for PAPR_VPD_IOC_CREATE_HANDLE ioctl command. Validates
+ * @ulc and instantiates an immutable VPD "blob" for it. The blob is
+ * attached to a file descriptor for reading by user space. The memory
+ * backing the blob is freed when the file is released.
+ *
+ * The entire requested VPD is retrieved by this call and all
+ * necessary RTAS interactions are performed before returning the fd
+ * to user space. This keeps the read handler simple and ensures that
+ * the kernel can prevent interleaving of ibm,get-vpd call sequences.
+ *
+ * Return: The installed fd number if successful, -ve errno otherwise.
+ */
+static long papr_vpd_create_handle(struct papr_location_code __user *ulc)
+{
+	struct papr_location_code klc;
+	const struct vpd_blob *blob;
+	struct file *file;
+	long err;
+	int fd;
+
+	if (copy_from_user(&klc, ulc, sizeof(klc)))
+		return -EFAULT;
+
+	if (!string_is_terminated(klc.str, ARRAY_SIZE(klc.str)))
+		return -EINVAL;
+
+	blob = papr_vpd_retrieve(&klc);
+	if (IS_ERR(blob))
+		return PTR_ERR(blob);
+
+	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
+	if (fd < 0) {
+		err = fd;
+		goto free_blob;
+	}
+
+	file = anon_inode_getfile("[papr-vpd]", &papr_vpd_handle_ops,
+				  (void *)blob, O_RDONLY);
+	if (IS_ERR(file)) {
+		err = PTR_ERR(file);
+		goto put_fd;
+	}
+
+	file->f_mode |= FMODE_LSEEK | FMODE_PREAD;
+	fd_install(fd, file);
+	return fd;
+put_fd:
+	put_unused_fd(fd);
+free_blob:
+	vpd_blob_free(blob);
+	return err;
+}
+
+/*
+ * Top-level ioctl handler for /dev/papr-vpd.
+ */
+static long papr_vpd_dev_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
+{
+	void __user *argp = (__force void __user *)arg;
+	long ret;
+
+	switch (ioctl) {
+	case PAPR_VPD_IOC_CREATE_HANDLE:
+		ret = papr_vpd_create_handle(argp);
+		break;
+	default:
+		ret = -ENOIOCTLCMD;
+		break;
+	}
+	return ret;
+}
+
+static const struct file_operations papr_vpd_ops = {
+	.unlocked_ioctl = papr_vpd_dev_ioctl,
+};
+
+static struct miscdevice papr_vpd_dev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "papr-vpd",
+	.fops = &papr_vpd_ops,
+};
+
+static __init int papr_vpd_init(void)
+{
+	if (!rtas_function_implemented(RTAS_FN_IBM_GET_VPD))
+		return -ENODEV;
+
+	return misc_register(&papr_vpd_dev);
+}
+machine_device_initcall(pseries, papr_vpd_init);

-- 
2.41.0

[PATCH v6 10/13] powerpc/pseries/papr-sysparm: Validate buffer object lengths

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

The ability to get and set system parameters will be exposed to user
space, so let's get a little more strict about malformed
papr_sysparm_buf objects.

* Create accessors for the length field of struct papr_sysparm_buf.
  The length is always stored in MSB order and this is better than
  spreading the necessary conversions all over.

* Reject attempts to submit invalid buffers to RTAS.

* Warn if RTAS returns a buffer with an invalid length, clamping the
  returned length to a safe value that won't overrun the buffer.

These are meant as precautionary measures to mitigate both firmware
and kernel bugs in this area, should they arise, but I am not aware of
any.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/platforms/pseries/papr-sysparm.c | 47 +++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/papr-sysparm.c b/arch/powerpc/platforms/pseries/papr-sysparm.c
index fedc61599e6c..a1e7aeac7416 100644
--- a/arch/powerpc/platforms/pseries/papr-sysparm.c
+++ b/arch/powerpc/platforms/pseries/papr-sysparm.c
@@ -23,6 +23,46 @@ void papr_sysparm_buf_free(struct papr_sysparm_buf *buf)
 	kfree(buf);
 }
 
+static size_t papr_sysparm_buf_get_length(const struct papr_sysparm_buf *buf)
+{
+	return be16_to_cpu(buf->len);
+}
+
+static void papr_sysparm_buf_set_length(struct papr_sysparm_buf *buf, size_t length)
+{
+	WARN_ONCE(length > sizeof(buf->val),
+		  "bogus length %zu, clamping to safe value", length);
+	length = min(sizeof(buf->val), length);
+	buf->len = cpu_to_be16(length);
+}
+
+/*
+ * For use on buffers returned from ibm,get-system-parameter before
+ * returning them to callers. Ensures the encoded length of valid data
+ * cannot overrun buf->val[].
+ */
+static void papr_sysparm_buf_clamp_length(struct papr_sysparm_buf *buf)
+{
+	papr_sysparm_buf_set_length(buf, papr_sysparm_buf_get_length(buf));
+}
+
+/*
+ * Perform some basic diligence on the system parameter buffer before
+ * submitting it to RTAS.
+ */
+static bool papr_sysparm_buf_can_submit(const struct papr_sysparm_buf *buf)
+{
+	/*
+	 * Firmware ought to reject buffer lengths that exceed the
+	 * maximum specified in PAPR, but there's no reason for the
+	 * kernel to allow them either.
+	 */
+	if (papr_sysparm_buf_get_length(buf) > sizeof(buf->val))
+		return false;
+
+	return true;
+}
+
 /**
  * papr_sysparm_get() - Retrieve the value of a PAPR system parameter.
  * @param: PAPR system parameter token as described in
@@ -63,6 +103,9 @@ int papr_sysparm_get(papr_sysparm_t param, struct papr_sysparm_buf *buf)
 	if (token == RTAS_UNKNOWN_SERVICE)
 		return -ENOENT;
 
+	if (!papr_sysparm_buf_can_submit(buf))
+		return -EINVAL;
+
 	work_area = rtas_work_area_alloc(sizeof(*buf));
 
 	memcpy(rtas_work_area_raw_buf(work_area), buf, sizeof(*buf));
@@ -77,6 +120,7 @@ int papr_sysparm_get(papr_sysparm_t param, struct papr_sysparm_buf *buf)
 	case 0:
 		ret = 0;
 		memcpy(buf, rtas_work_area_raw_buf(work_area), sizeof(*buf));
+		papr_sysparm_buf_clamp_length(buf);
 		break;
 	case -3: /* parameter not implemented */
 		ret = -EOPNOTSUPP;
@@ -115,6 +159,9 @@ int papr_sysparm_set(papr_sysparm_t param, const struct papr_sysparm_buf *buf)
 	if (token == RTAS_UNKNOWN_SERVICE)
 		return -ENOENT;
 
+	if (!papr_sysparm_buf_can_submit(buf))
+		return -EINVAL;
+
 	work_area = rtas_work_area_alloc(sizeof(*buf));
 
 	memcpy(rtas_work_area_raw_buf(work_area), buf, sizeof(*buf));

-- 
2.41.0

[PATCH v6 11/13] powerpc/pseries/papr-sysparm: Expose character device to user space

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

Until now the papr_sysparm APIs have been kernel-internal. But user
space needs access to PAPR system parameters too. The only method
available to user space today to get or set system parameters is using
sys_rtas() and /dev/mem to pass RTAS-addressable buffers between user
space and firmware. This is incompatible with lockdown and should be
deprecated.

So provide an alternative ABI to user space in the form of a
/dev/papr-sysparm character device with just two ioctl commands (get
and set). The data payloads involved are small enough to fit in the
ioctl argument buffer, making the code relatively simple.

Exposing the system parameters through sysfs has been considered but
it would be too awkward:

* The kernel currently does not have to contain an exhaustive list of
  defined system parameters. This is a convenient property to maintain
  because we don't have to update the kernel whenever a new parameter
  is added to PAPR. Exporting a named attribute in sysfs for each
  parameter would negate this.

* Some system parameters are text-based and some are not.

* Retrieval of at least one system parameter requires input data,
  which a simple read-oriented interface can't support.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 Documentation/userspace-api/ioctl/ioctl-number.rst |   2 +
 arch/powerpc/include/asm/papr-sysparm.h            |  17 ++-
 arch/powerpc/include/uapi/asm/papr-sysparm.h       |  58 ++++++++
 arch/powerpc/platforms/pseries/papr-sysparm.c      | 158 ++++++++++++++++++++-
 4 files changed, 227 insertions(+), 8 deletions(-)

diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index a950545bf7cd..d8b6cb1a3636 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -351,6 +351,8 @@ Code  Seq#    Include File                                           Comments
                                                                      <mailto:mostrows@styx.uwaterloo.ca>
 0xB2  00     arch/powerpc/include/uapi/asm/papr-vpd.h                powerpc/pseries VPD API
                                                                      <mailto:linuxppc-dev>
+0xB2  01-02  arch/powerpc/include/uapi/asm/papr-sysparm.h            powerpc/pseries system parameter API
+                                                                     <mailto:linuxppc-dev>
 0xB3  00     linux/mmc/ioctl.h
 0xB4  00-0F  linux/gpio.h                                            <mailto:linux-gpio@vger.kernel.org>
 0xB5  00-0F  uapi/linux/rpmsg.h                                      <mailto:linux-remoteproc@vger.kernel.org>
diff --git a/arch/powerpc/include/asm/papr-sysparm.h b/arch/powerpc/include/asm/papr-sysparm.h
index f5fdbd8ae9db..0dbbff59101d 100644
--- a/arch/powerpc/include/asm/papr-sysparm.h
+++ b/arch/powerpc/include/asm/papr-sysparm.h
@@ -2,8 +2,10 @@
 #ifndef _ASM_POWERPC_PAPR_SYSPARM_H
 #define _ASM_POWERPC_PAPR_SYSPARM_H
 
+#include <uapi/asm/papr-sysparm.h>
+
 typedef struct {
-	const u32 token;
+	u32 token;
 } papr_sysparm_t;
 
 #define mk_papr_sysparm(x_) ((papr_sysparm_t){ .token = x_, })
@@ -20,11 +22,14 @@ typedef struct {
 #define PAPR_SYSPARM_TLB_BLOCK_INVALIDATE_ATTRS    mk_papr_sysparm(50)
 #define PAPR_SYSPARM_LPAR_NAME                     mk_papr_sysparm(55)
 
-enum {
-	PAPR_SYSPARM_MAX_INPUT  = 1024,
-	PAPR_SYSPARM_MAX_OUTPUT = 4000,
-};
-
+/**
+ * struct papr_sysparm_buf - RTAS work area layout for system parameter functions.
+ *
+ * This is the memory layout of the buffers passed to/from
+ * ibm,get-system-parameter and ibm,set-system-parameter. It is
+ * distinct from the papr_sysparm_io_block structure that is passed
+ * between user space and the kernel.
+ */
 struct papr_sysparm_buf {
 	__be16 len;
 	char val[PAPR_SYSPARM_MAX_OUTPUT];
diff --git a/arch/powerpc/include/uapi/asm/papr-sysparm.h b/arch/powerpc/include/uapi/asm/papr-sysparm.h
new file mode 100644
index 000000000000..9f9a0f267ea5
--- /dev/null
+++ b/arch/powerpc/include/uapi/asm/papr-sysparm.h
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_PAPR_SYSPARM_H_
+#define _UAPI_PAPR_SYSPARM_H_
+
+#include <linux/types.h>
+#include <asm/ioctl.h>
+#include <asm/papr-miscdev.h>
+
+enum {
+	PAPR_SYSPARM_MAX_INPUT  = 1024,
+	PAPR_SYSPARM_MAX_OUTPUT = 4000,
+};
+
+struct papr_sysparm_io_block {
+	__u32 parameter;
+	__u16 length;
+	char data[PAPR_SYSPARM_MAX_OUTPUT];
+};
+
+/**
+ * PAPR_SYSPARM_IOC_GET - Retrieve the value of a PAPR system parameter.
+ *
+ * Uses _IOWR because of one corner case: Retrieving the value of the
+ * "OS Service Entitlement Status" parameter (60) requires the caller
+ * to supply input data (a date string) in the buffer passed to
+ * firmware. So the @length and @data of the incoming
+ * papr_sysparm_io_block are always used to initialize the work area
+ * supplied to ibm,get-system-parameter. No other parameters are known
+ * to parameterize the result this way, and callers are encouraged
+ * (but not required) to zero-initialize @length and @data in the
+ * common case.
+ *
+ * On error the contents of the ioblock are indeterminate.
+ *
+ * Return:
+ * 0: Success; @length is the length of valid data in @data, not to exceed @PAPR_SYSPARM_MAX_OUTPUT.
+ * -EIO: Platform error. (-1)
+ * -EINVAL: Incorrect data length or format. (-9999)
+ * -EPERM: The calling partition is not allowed to access this parameter. (-9002)
+ * -EOPNOTSUPP: Parameter not supported on this platform (-3)
+ */
+#define PAPR_SYSPARM_IOC_GET _IOWR(PAPR_MISCDEV_IOC_ID, 1, struct papr_sysparm_io_block)
+
+/**
+ * PAPR_SYSPARM_IOC_SET - Update the value of a PAPR system parameter.
+ *
+ * The contents of the ioblock are unchanged regardless of success.
+ *
+ * Return:
+ * 0: Success; the parameter has been updated.
+ * -EIO: Platform error. (-1)
+ * -EINVAL: Incorrect data length or format. (-9999)
+ * -EPERM: The calling partition is not allowed to access this parameter. (-9002)
+ * -EOPNOTSUPP: Parameter not supported on this platform (-3)
+ */
+#define PAPR_SYSPARM_IOC_SET _IOW(PAPR_MISCDEV_IOC_ID, 2, struct papr_sysparm_io_block)
+
+#endif /* _UAPI_PAPR_SYSPARM_H_ */
diff --git a/arch/powerpc/platforms/pseries/papr-sysparm.c b/arch/powerpc/platforms/pseries/papr-sysparm.c
index a1e7aeac7416..7063ce8884e4 100644
--- a/arch/powerpc/platforms/pseries/papr-sysparm.c
+++ b/arch/powerpc/platforms/pseries/papr-sysparm.c
@@ -2,14 +2,20 @@
 
 #define pr_fmt(fmt)	"papr-sysparm: " fmt
 
+#include <linux/anon_inodes.h>
 #include <linux/bug.h>
+#include <linux/file.h>
+#include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/miscdevice.h>
 #include <linux/printk.h>
 #include <linux/slab.h>
-#include <asm/rtas.h>
+#include <linux/uaccess.h>
+#include <asm/machdep.h>
 #include <asm/papr-sysparm.h>
 #include <asm/rtas-work-area.h>
+#include <asm/rtas.h>
 
 struct papr_sysparm_buf *papr_sysparm_buf_alloc(void)
 {
@@ -87,7 +93,6 @@ static bool papr_sysparm_buf_can_submit(const struct papr_sysparm_buf *buf)
  *
  * Return: 0 on success, -errno otherwise. @buf is unmodified on error.
  */
-
 int papr_sysparm_get(papr_sysparm_t param, struct papr_sysparm_buf *buf)
 {
 	const s32 token = rtas_function_token(RTAS_FN_IBM_GET_SYSTEM_PARAMETER);
@@ -196,3 +201,152 @@ int papr_sysparm_set(papr_sysparm_t param, const struct papr_sysparm_buf *buf)
 
 	return ret;
 }
+
+static struct papr_sysparm_buf *
+papr_sysparm_buf_from_user(const struct papr_sysparm_io_block __user *user_iob)
+{
+	struct papr_sysparm_buf *kern_spbuf;
+	long err;
+	u16 len;
+
+	/*
+	 * The length of valid data that userspace claims to be in
+	 * user_iob->data[].
+	 */
+	if (get_user(len, &user_iob->length))
+		return ERR_PTR(-EFAULT);
+
+	static_assert(sizeof(user_iob->data) >= PAPR_SYSPARM_MAX_INPUT);
+	static_assert(sizeof(kern_spbuf->val) >= PAPR_SYSPARM_MAX_INPUT);
+
+	if (len > PAPR_SYSPARM_MAX_INPUT)
+		return ERR_PTR(-EINVAL);
+
+	kern_spbuf = papr_sysparm_buf_alloc();
+	if (!kern_spbuf)
+		return ERR_PTR(-ENOMEM);
+
+	papr_sysparm_buf_set_length(kern_spbuf, len);
+
+	if (len > 0 && copy_from_user(kern_spbuf->val, user_iob->data, len)) {
+		err = -EFAULT;
+		goto free_sysparm_buf;
+	}
+
+	return kern_spbuf;
+
+free_sysparm_buf:
+	papr_sysparm_buf_free(kern_spbuf);
+	return ERR_PTR(err);
+}
+
+static int papr_sysparm_buf_to_user(const struct papr_sysparm_buf *kern_spbuf,
+				    struct papr_sysparm_io_block __user *user_iob)
+{
+	u16 len_out = papr_sysparm_buf_get_length(kern_spbuf);
+
+	if (put_user(len_out, &user_iob->length))
+		return -EFAULT;
+
+	static_assert(sizeof(user_iob->data) >= PAPR_SYSPARM_MAX_OUTPUT);
+	static_assert(sizeof(kern_spbuf->val) >= PAPR_SYSPARM_MAX_OUTPUT);
+
+	if (copy_to_user(user_iob->data, kern_spbuf->val, PAPR_SYSPARM_MAX_OUTPUT))
+		return -EFAULT;
+
+	return 0;
+}
+
+static long papr_sysparm_ioctl_get(struct papr_sysparm_io_block __user *user_iob)
+{
+	struct papr_sysparm_buf *kern_spbuf;
+	papr_sysparm_t param;
+	long ret;
+
+	if (get_user(param.token, &user_iob->parameter))
+		return -EFAULT;
+
+	kern_spbuf = papr_sysparm_buf_from_user(user_iob);
+	if (IS_ERR(kern_spbuf))
+		return PTR_ERR(kern_spbuf);
+
+	ret = papr_sysparm_get(param, kern_spbuf);
+	if (ret)
+		goto free_sysparm_buf;
+
+	ret = papr_sysparm_buf_to_user(kern_spbuf, user_iob);
+	if (ret)
+		goto free_sysparm_buf;
+
+	ret = 0;
+
+free_sysparm_buf:
+	papr_sysparm_buf_free(kern_spbuf);
+	return ret;
+}
+
+
+static long papr_sysparm_ioctl_set(struct papr_sysparm_io_block __user *user_iob)
+{
+	struct papr_sysparm_buf *kern_spbuf;
+	papr_sysparm_t param;
+	long ret;
+
+	if (get_user(param.token, &user_iob->parameter))
+		return -EFAULT;
+
+	kern_spbuf = papr_sysparm_buf_from_user(user_iob);
+	if (IS_ERR(kern_spbuf))
+		return PTR_ERR(kern_spbuf);
+
+	ret = papr_sysparm_set(param, kern_spbuf);
+	if (ret)
+		goto free_sysparm_buf;
+
+	ret = 0;
+
+free_sysparm_buf:
+	papr_sysparm_buf_free(kern_spbuf);
+	return ret;
+}
+
+static long papr_sysparm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
+{
+	void __user *argp = (__force void __user *)arg;
+	long ret;
+
+	switch (ioctl) {
+	case PAPR_SYSPARM_IOC_GET:
+		ret = papr_sysparm_ioctl_get(argp);
+		break;
+	case PAPR_SYSPARM_IOC_SET:
+		if (filp->f_mode & FMODE_WRITE)
+			ret = papr_sysparm_ioctl_set(argp);
+		else
+			ret = -EBADF;
+		break;
+	default:
+		ret = -ENOIOCTLCMD;
+		break;
+	}
+	return ret;
+}
+
+static const struct file_operations papr_sysparm_ops = {
+	.unlocked_ioctl = papr_sysparm_ioctl,
+};
+
+static struct miscdevice papr_sysparm_dev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "papr-sysparm",
+	.fops = &papr_sysparm_ops,
+};
+
+static __init int papr_sysparm_init(void)
+{
+	if (!rtas_function_implemented(RTAS_FN_IBM_GET_SYSTEM_PARAMETER))
+		return -ENODEV;
+
+	return misc_register(&papr_sysparm_dev);
+}
+machine_device_initcall(pseries, papr_sysparm_init);

-- 
2.41.0

[PATCH v6 12/13] powerpc/selftests: Add test for papr-vpd

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

Add selftests for /dev/papr-vpd, exercising the common expected use
cases:

* Retrieve all VPD by passing an empty location code.
* Retrieve the "system VPD" by passing a location code derived from DT
  root node properties, as done by the vpdupdate command.

The tests also verify that certain intended properties of the driver
hold:

* Passing an unterminated location code to PAPR_VPD_CREATE_HANDLE gets
  EINVAL.
* Passing a NULL location code pointer to PAPR_VPD_CREATE_HANDLE gets
  EFAULT.
* Closing the device node without first issuing a
  PAPR_VPD_CREATE_HANDLE command to it succeeds.
* Releasing a handle without first consuming any data from it
  succeeds.
* Re-reading the contents of a handle returns the same data as the
  first time.

Some minimal validation of the returned data is performed.

The tests are skipped on systems where the papr-vpd driver does not
initialize, making this useful only on PowerVM LPARs at this point.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 tools/testing/selftests/powerpc/Makefile           |   1 +
 .../testing/selftests/powerpc/papr_vpd/.gitignore  |   1 +
 tools/testing/selftests/powerpc/papr_vpd/Makefile  |  12 +
 .../testing/selftests/powerpc/papr_vpd/papr_vpd.c  | 352 +++++++++++++++++++++
 4 files changed, 366 insertions(+)

diff --git a/tools/testing/selftests/powerpc/Makefile b/tools/testing/selftests/powerpc/Makefile
index 7ea42fa02eab..05fc68d446c2 100644
--- a/tools/testing/selftests/powerpc/Makefile
+++ b/tools/testing/selftests/powerpc/Makefile
@@ -32,6 +32,7 @@ SUB_DIRS = alignment		\
 	   vphn         \
 	   math		\
 	   papr_attributes	\
+	   papr_vpd		\
 	   ptrace	\
 	   security	\
 	   mce
diff --git a/tools/testing/selftests/powerpc/papr_vpd/.gitignore b/tools/testing/selftests/powerpc/papr_vpd/.gitignore
new file mode 100644
index 000000000000..49285031a656
--- /dev/null
+++ b/tools/testing/selftests/powerpc/papr_vpd/.gitignore
@@ -0,0 +1 @@
+/papr_vpd
diff --git a/tools/testing/selftests/powerpc/papr_vpd/Makefile b/tools/testing/selftests/powerpc/papr_vpd/Makefile
new file mode 100644
index 000000000000..06b719703bfd
--- /dev/null
+++ b/tools/testing/selftests/powerpc/papr_vpd/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+noarg:
+	$(MAKE) -C ../
+
+TEST_GEN_PROGS := papr_vpd
+
+top_srcdir = ../../../../..
+include ../../lib.mk
+
+$(TEST_GEN_PROGS): ../harness.c ../utils.c
+
+$(OUTPUT)/papr_vpd: CFLAGS += $(KHDR_INCLUDES)
diff --git a/tools/testing/selftests/powerpc/papr_vpd/papr_vpd.c b/tools/testing/selftests/powerpc/papr_vpd/papr_vpd.c
new file mode 100644
index 000000000000..98cbb9109ee6
--- /dev/null
+++ b/tools/testing/selftests/powerpc/papr_vpd/papr_vpd.c
@@ -0,0 +1,352 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+#include <asm/papr-vpd.h>
+
+#include "utils.h"
+
+#define DEVPATH "/dev/papr-vpd"
+
+static int dev_papr_vpd_open_close(void)
+{
+	const int devfd = open(DEVPATH, O_RDONLY);
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+	FAIL_IF(close(devfd) != 0);
+
+	return 0;
+}
+
+static int dev_papr_vpd_get_handle_all(void)
+{
+	const int devfd = open(DEVPATH, O_RDONLY);
+	struct papr_location_code lc = { .str = "", };
+	off_t size;
+	int fd;
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	errno = 0;
+	fd = ioctl(devfd, PAPR_VPD_IOC_CREATE_HANDLE, &lc);
+	FAIL_IF(errno != 0);
+	FAIL_IF(fd < 0);
+
+	FAIL_IF(close(devfd) != 0);
+
+	size = lseek(fd, 0, SEEK_END);
+	FAIL_IF(size <= 0);
+
+	void *buf = malloc((size_t)size);
+	FAIL_IF(!buf);
+
+	ssize_t consumed = pread(fd, buf, size, 0);
+	FAIL_IF(consumed != size);
+
+	/* Ensure EOF */
+	FAIL_IF(read(fd, buf, size) != 0);
+	FAIL_IF(close(fd));
+
+	/* Verify that the buffer looks like VPD */
+	static const char needle[] = "System VPD";
+	FAIL_IF(!memmem(buf, size, needle, strlen(needle)));
+
+	return 0;
+}
+
+static int dev_papr_vpd_get_handle_byte_at_a_time(void)
+{
+	const int devfd = open(DEVPATH, O_RDONLY);
+	struct papr_location_code lc = { .str = "", };
+	int fd;
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	errno = 0;
+	fd = ioctl(devfd, PAPR_VPD_IOC_CREATE_HANDLE, &lc);
+	FAIL_IF(errno != 0);
+	FAIL_IF(fd < 0);
+
+	FAIL_IF(close(devfd) != 0);
+
+	size_t consumed = 0;
+	while (1) {
+		ssize_t res;
+		char c;
+
+		errno = 0;
+		res = read(fd, &c, sizeof(c));
+		FAIL_IF(res > sizeof(c));
+		FAIL_IF(res < 0);
+		FAIL_IF(errno != 0);
+		consumed += res;
+		if (res == 0)
+			break;
+	}
+
+	FAIL_IF(consumed != lseek(fd, 0, SEEK_END));
+
+	FAIL_IF(close(fd));
+
+	return 0;
+}
+
+
+static int dev_papr_vpd_unterm_loc_code(void)
+{
+	const int devfd = open(DEVPATH, O_RDONLY);
+	struct papr_location_code lc = {};
+	int fd;
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	/*
+	 * Place a non-null byte in every element of loc_code; the
+	 * driver should reject this input.
+	 */
+	memset(lc.str, 'x', ARRAY_SIZE(lc.str));
+
+	errno = 0;
+	fd = ioctl(devfd, PAPR_VPD_IOC_CREATE_HANDLE, &lc);
+	FAIL_IF(fd != -1);
+	FAIL_IF(errno != EINVAL);
+
+	FAIL_IF(close(devfd) != 0);
+	return 0;
+}
+
+static int dev_papr_vpd_null_handle(void)
+{
+	const int devfd = open(DEVPATH, O_RDONLY);
+	int rc;
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	errno = 0;
+	rc = ioctl(devfd, PAPR_VPD_IOC_CREATE_HANDLE, NULL);
+	FAIL_IF(rc != -1);
+	FAIL_IF(errno != EFAULT);
+
+	FAIL_IF(close(devfd) != 0);
+	return 0;
+}
+
+static int papr_vpd_close_handle_without_reading(void)
+{
+	const int devfd = open(DEVPATH, O_RDONLY);
+	struct papr_location_code lc;
+	int fd;
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	errno = 0;
+	fd = ioctl(devfd, PAPR_VPD_IOC_CREATE_HANDLE, &lc);
+	FAIL_IF(errno != 0);
+	FAIL_IF(fd < 0);
+
+	/* close the handle without reading it */
+	FAIL_IF(close(fd) != 0);
+
+	FAIL_IF(close(devfd) != 0);
+	return 0;
+}
+
+static int papr_vpd_reread(void)
+{
+	const int devfd = open(DEVPATH, O_RDONLY);
+	struct papr_location_code lc = { .str = "", };
+	int fd;
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	errno = 0;
+	fd = ioctl(devfd, PAPR_VPD_IOC_CREATE_HANDLE, &lc);
+	FAIL_IF(errno != 0);
+	FAIL_IF(fd < 0);
+
+	FAIL_IF(close(devfd) != 0);
+
+	const off_t size = lseek(fd, 0, SEEK_END);
+	FAIL_IF(size <= 0);
+
+	char *bufs[2];
+
+	for (size_t i = 0; i < ARRAY_SIZE(bufs); ++i) {
+		bufs[i] = malloc(size);
+		FAIL_IF(!bufs[i]);
+		ssize_t consumed = pread(fd, bufs[i], size, 0);
+		FAIL_IF(consumed != size);
+	}
+
+	FAIL_IF(memcmp(bufs[0], bufs[1], size));
+
+	FAIL_IF(close(fd) != 0);
+
+	return 0;
+}
+
+static int get_system_loc_code(struct papr_location_code *lc)
+{
+	static const char system_id_path[] = "/sys/firmware/devicetree/base/system-id";
+	static const char model_path[] = "/sys/firmware/devicetree/base/model";
+	char *system_id;
+	char *model;
+	int err = -1;
+
+	if (read_file_alloc(model_path, &model, NULL))
+		return err;
+
+	if (read_file_alloc(system_id_path, &system_id, NULL))
+		goto free_model;
+
+	char *mtm;
+	int sscanf_ret = sscanf(model, "IBM,%ms", &mtm);
+	if (sscanf_ret != 1)
+		goto free_system_id;
+
+	char *plant_and_seq;
+	if (sscanf(system_id, "IBM,%*c%*c%ms", &plant_and_seq) != 1)
+		goto free_mtm;
+	/*
+	 * Replace - with . to build location code.
+	 */
+	char *sep = strchr(mtm, '-');
+	if (!sep)
+		goto free_mtm;
+	else
+		*sep = '.';
+
+	snprintf(lc->str, sizeof(lc->str),
+		 "U%s.%s", mtm, plant_and_seq);
+	err = 0;
+
+	free(plant_and_seq);
+free_mtm:
+	free(mtm);
+free_system_id:
+	free(system_id);
+free_model:
+	free(model);
+	return err;
+}
+
+static int papr_vpd_system_loc_code(void)
+{
+	struct papr_location_code lc;
+	const int devfd = open(DEVPATH, O_RDONLY);
+	off_t size;
+	int fd;
+
+	SKIP_IF_MSG(get_system_loc_code(&lc),
+		    "Cannot determine system location code");
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	errno = 0;
+	fd = ioctl(devfd, PAPR_VPD_IOC_CREATE_HANDLE, &lc);
+	FAIL_IF(errno != 0);
+	FAIL_IF(fd < 0);
+
+	FAIL_IF(close(devfd) != 0);
+
+	size = lseek(fd, 0, SEEK_END);
+	FAIL_IF(size <= 0);
+
+	void *buf = malloc((size_t)size);
+	FAIL_IF(!buf);
+
+	ssize_t consumed = pread(fd, buf, size, 0);
+	FAIL_IF(consumed != size);
+
+	/* Ensure EOF */
+	FAIL_IF(read(fd, buf, size) != 0);
+	FAIL_IF(close(fd));
+
+	/* Verify that the buffer looks like VPD */
+	static const char needle[] = "System VPD";
+	FAIL_IF(!memmem(buf, size, needle, strlen(needle)));
+
+	return 0;
+}
+
+struct vpd_test {
+	int (*function)(void);
+	const char *description;
+};
+
+static const struct vpd_test vpd_tests[] = {
+	{
+		.function = dev_papr_vpd_open_close,
+		.description = "open/close " DEVPATH,
+	},
+	{
+		.function = dev_papr_vpd_unterm_loc_code,
+		.description = "ensure EINVAL on unterminated location code",
+	},
+	{
+		.function = dev_papr_vpd_null_handle,
+		.description = "ensure EFAULT on bad handle addr",
+	},
+	{
+		.function = dev_papr_vpd_get_handle_all,
+		.description = "get handle for all VPD"
+	},
+	{
+		.function = papr_vpd_close_handle_without_reading,
+		.description = "close handle without consuming VPD"
+	},
+	{
+		.function = dev_papr_vpd_get_handle_byte_at_a_time,
+		.description = "read all VPD one byte at a time"
+	},
+	{
+		.function = papr_vpd_reread,
+		.description = "ensure re-read yields same results"
+	},
+	{
+		.function = papr_vpd_system_loc_code,
+		.description = "get handle for system VPD"
+	},
+};
+
+int main(void)
+{
+	size_t fails = 0;
+
+	for (size_t i = 0; i < ARRAY_SIZE(vpd_tests); ++i) {
+		const struct vpd_test *t = &vpd_tests[i];
+
+		if (test_harness(t->function, t->description))
+			++fails;
+	}
+
+	return fails == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
+}

-- 
2.41.0

[PATCH v6 13/13] powerpc/selftests: Add test for papr-sysparm

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

Consistently testing system parameter access is a bit difficult by
nature -- the set of parameters available depends on the model and
system configuration, and updating a parameter should be considered a
destructive operation reserved for the admin.

So we validate some of the error paths and retrieve the SPLPAR
characteristics string, but not much else.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 tools/testing/selftests/powerpc/Makefile           |   1 +
 .../selftests/powerpc/papr_sysparm/.gitignore      |   1 +
 .../selftests/powerpc/papr_sysparm/Makefile        |  12 ++
 .../selftests/powerpc/papr_sysparm/papr_sysparm.c  | 196 +++++++++++++++++++++
 4 files changed, 210 insertions(+)

diff --git a/tools/testing/selftests/powerpc/Makefile b/tools/testing/selftests/powerpc/Makefile
index 05fc68d446c2..c376151982c4 100644
--- a/tools/testing/selftests/powerpc/Makefile
+++ b/tools/testing/selftests/powerpc/Makefile
@@ -33,6 +33,7 @@ SUB_DIRS = alignment		\
 	   math		\
 	   papr_attributes	\
 	   papr_vpd		\
+	   papr_sysparm		\
 	   ptrace	\
 	   security	\
 	   mce
diff --git a/tools/testing/selftests/powerpc/papr_sysparm/.gitignore b/tools/testing/selftests/powerpc/papr_sysparm/.gitignore
new file mode 100644
index 000000000000..f2a69bf59d40
--- /dev/null
+++ b/tools/testing/selftests/powerpc/papr_sysparm/.gitignore
@@ -0,0 +1 @@
+/papr_sysparm
diff --git a/tools/testing/selftests/powerpc/papr_sysparm/Makefile b/tools/testing/selftests/powerpc/papr_sysparm/Makefile
new file mode 100644
index 000000000000..7f79e437634a
--- /dev/null
+++ b/tools/testing/selftests/powerpc/papr_sysparm/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+noarg:
+	$(MAKE) -C ../
+
+TEST_GEN_PROGS := papr_sysparm
+
+top_srcdir = ../../../../..
+include ../../lib.mk
+
+$(TEST_GEN_PROGS): ../harness.c ../utils.c
+
+$(OUTPUT)/papr_sysparm: CFLAGS += $(KHDR_INCLUDES)
diff --git a/tools/testing/selftests/powerpc/papr_sysparm/papr_sysparm.c b/tools/testing/selftests/powerpc/papr_sysparm/papr_sysparm.c
new file mode 100644
index 000000000000..d5436de5b8ed
--- /dev/null
+++ b/tools/testing/selftests/powerpc/papr_sysparm/papr_sysparm.c
@@ -0,0 +1,196 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+#include <asm/papr-sysparm.h>
+
+#include "utils.h"
+
+#define DEVPATH "/dev/papr-sysparm"
+
+static int open_close(void)
+{
+	const int devfd = open(DEVPATH, O_RDONLY);
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+	FAIL_IF(close(devfd) != 0);
+
+	return 0;
+}
+
+static int get_splpar(void)
+{
+	struct papr_sysparm_io_block sp = {
+		.parameter = 20, // SPLPAR characteristics
+	};
+	const int devfd = open(DEVPATH, O_RDONLY);
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+	FAIL_IF(ioctl(devfd, PAPR_SYSPARM_IOC_GET, &sp) != 0);
+	FAIL_IF(sp.length == 0);
+	FAIL_IF(sp.length > sizeof(sp.data));
+	FAIL_IF(close(devfd) != 0);
+
+	return 0;
+}
+
+static int get_bad_parameter(void)
+{
+	struct papr_sysparm_io_block sp = {
+		.parameter = UINT32_MAX, // there are only ~60 specified parameters
+	};
+	const int devfd = open(DEVPATH, O_RDONLY);
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	// Ensure expected error
+	FAIL_IF(ioctl(devfd, PAPR_SYSPARM_IOC_GET, &sp) != -1);
+	FAIL_IF(errno != EOPNOTSUPP);
+
+	// Ensure the buffer is unchanged
+	FAIL_IF(sp.length != 0);
+	for (size_t i = 0; i < ARRAY_SIZE(sp.data); ++i)
+		FAIL_IF(sp.data[i] != 0);
+
+	FAIL_IF(close(devfd) != 0);
+
+	return 0;
+}
+
+static int check_efault_common(unsigned long cmd)
+{
+	const int devfd = open(DEVPATH, O_RDWR);
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	// Ensure expected error
+	FAIL_IF(ioctl(devfd, cmd, NULL) != -1);
+	FAIL_IF(errno != EFAULT);
+
+	FAIL_IF(close(devfd) != 0);
+
+	return 0;
+}
+
+static int check_efault_get(void)
+{
+	return check_efault_common(PAPR_SYSPARM_IOC_GET);
+}
+
+static int check_efault_set(void)
+{
+	return check_efault_common(PAPR_SYSPARM_IOC_SET);
+}
+
+static int set_hmc0(void)
+{
+	struct papr_sysparm_io_block sp = {
+		.parameter = 0, // HMC0, not a settable parameter
+	};
+	const int devfd = open(DEVPATH, O_RDWR);
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	// Ensure expected error
+	FAIL_IF(ioctl(devfd, PAPR_SYSPARM_IOC_SET, &sp) != -1);
+	SKIP_IF_MSG(errno == EOPNOTSUPP, "operation not supported");
+	FAIL_IF(errno != EPERM);
+
+	FAIL_IF(close(devfd) != 0);
+
+	return 0;
+}
+
+static int set_with_ro_fd(void)
+{
+	struct papr_sysparm_io_block sp = {
+		.parameter = 0, // HMC0, not a settable parameter.
+	};
+	const int devfd = open(DEVPATH, O_RDONLY);
+
+	SKIP_IF_MSG(devfd < 0 && errno == ENOENT,
+		    DEVPATH " not present");
+
+	FAIL_IF(devfd < 0);
+
+	// Ensure expected error
+	FAIL_IF(ioctl(devfd, PAPR_SYSPARM_IOC_SET, &sp) != -1);
+	SKIP_IF_MSG(errno == EOPNOTSUPP, "operation not supported");
+
+	// HMC0 isn't a settable parameter and we would normally
+	// expect to get EPERM on attempts to modify it. However, when
+	// the file is open read-only, we expect the driver to prevent
+	// the attempt with a distinct error.
+	FAIL_IF(errno != EBADF);
+
+	FAIL_IF(close(devfd) != 0);
+
+	return 0;
+}
+
+struct sysparm_test {
+	int (*function)(void);
+	const char *description;
+};
+
+static const struct sysparm_test sysparm_tests[] = {
+	{
+		.function = open_close,
+		.description = "open and close " DEVPATH " without issuing commands",
+	},
+	{
+		.function = get_splpar,
+		.description = "retrieve SPLPAR characteristics",
+	},
+	{
+		.function = get_bad_parameter,
+		.description = "verify EOPNOTSUPP for known-bad parameter",
+	},
+	{
+		.function = check_efault_get,
+		.description = "PAPR_SYSPARM_IOC_GET returns EFAULT on bad address",
+	},
+	{
+		.function = check_efault_set,
+		.description = "PAPR_SYSPARM_IOC_SET returns EFAULT on bad address",
+	},
+	{
+		.function = set_hmc0,
+		.description = "ensure EPERM on attempt to update HMC0",
+	},
+	{
+		.function = set_with_ro_fd,
+		.description = "PAPR_IOC_SYSPARM_SET returns EACCESS on read-only fd",
+	},
+};
+
+int main(void)
+{
+	size_t fails = 0;
+
+	for (size_t i = 0; i < ARRAY_SIZE(sysparm_tests); ++i) {
+		const struct sysparm_test *t = &sysparm_tests[i];
+
+		if (test_harness(t->function, t->description))
+			++fails;
+	}
+
+	return fails == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
+}

-- 
2.41.0

Re: [PATCH v6 00/13] powerpc/pseries: New character devices for system parameters and VPD

[Michael Ellerman]

On Tue, 12 Dec 2023 11:01:47 -0600, Nathan Lynch wrote:
> Add character devices that expose PAPR-specific system parameters and
> VPD to user space.
> 
> The problem: important platform features are enabled on Linux VMs
> through the powerpc-specific rtas() syscall in combination with
> writeable mappings of /dev/mem. In typical usage, this is encapsulated
> behind APIs provided by the librtas library. This paradigm is
> incompatible with lockdown, which prohibits /dev/mem access. It also
> is too low-level in many cases: a single logical operation may require
> multiple sys_rtas() calls in succession to complete. This carries the
> risk that a process may exit while leaving an operation unfinished. It
> also means that callers must coordinate their use of the syscall for
> functions that cannot tolerate multiple concurrent clients, such as
> ibm,get-vpd.
> 
> [...]

Applied to powerpc/next.

[01/13] powerpc/rtas: Avoid warning on invalid token argument to sys_rtas()
        https://git.kernel.org/powerpc/c/01e346ffefda3a7088afebf02b940614179688e7
[02/13] powerpc/rtas: Add for_each_rtas_function() iterator
        https://git.kernel.org/powerpc/c/c500c6e736df030f8956080738f59701c0b43dd8
[03/13] powerpc/rtas: Fall back to linear search on failed token->function lookup
        https://git.kernel.org/powerpc/c/669acc7eec223a81ea5e2420de85b61979ab7dad
[04/13] powerpc/rtas: Add function return status constants
        https://git.kernel.org/powerpc/c/9592aa5ad59e736727fe7894e6e820e2d851abcf
[05/13] powerpc/rtas: Move token validation from block_rtas_call() to sys_rtas()
        https://git.kernel.org/powerpc/c/e7582edb78619abb4ebf0a6e1fed125dcd7243b6
[06/13] powerpc/rtas: Facilitate high-level call sequences
        https://git.kernel.org/powerpc/c/adf7a019e5f82607fc0f0079926d0178afe8f4ef
[07/13] powerpc/rtas: Serialize firmware activation sequences
        https://git.kernel.org/powerpc/c/dc7637c402b90a197d3f21a3d78f2b00b67ea22a
[08/13] powerpc/rtas: Warn if per-function lock isn't held
        https://git.kernel.org/powerpc/c/e3681107bc9f97c5948a1c8a3a97ac64907210ce
[09/13] powerpc/pseries: Add papr-vpd character driver for VPD retrieval
        https://git.kernel.org/powerpc/c/514f6ff4369a30bf0da71a1a09fd47b2fca5d76f
[10/13] powerpc/pseries/papr-sysparm: Validate buffer object lengths
        https://git.kernel.org/powerpc/c/35aae182bd7b422be3cefc08c12207bf2b973364
[11/13] powerpc/pseries/papr-sysparm: Expose character device to user space
        https://git.kernel.org/powerpc/c/905b9e48786ec55b2c469db77fb46e20bf3e4901
[12/13] powerpc/selftests: Add test for papr-vpd
        https://git.kernel.org/powerpc/c/9118c5d32bddb5f75bc4f9f31218e70317702502
[13/13] powerpc/selftests: Add test for papr-sysparm
        https://git.kernel.org/powerpc/c/76b2ec3faeaa0c8d84705acd64ac0e5a307ce9c2

cheers