nfit, libnvdimm: limited/whitelisted dimm command marshaling mechanism

There are currently 4 known similar but incompatible definitions of the
command sets that can be sent to an NVDIMM through ACPI.  It is also
clear that future platform generations (ACPI or not) will continue to
revise and extend the DIMM command set as new devices and use cases
arrive.

It is obviously untenable to continue to proliferate divergence
of these command definitions, and to that end a standardization process
has begun to provide for a unified specification.  However, that leaves a
problem about what to do with this first generation where vendors are
already shipping divergence.

The Linux kernel can support these initial diverged platforms without
giving platform-firmware free reign to continue to diverge and compound
kernel maintenance overhead.  The kernel implementation can encourage
standardization in two ways:

1/ Require that any function code that userspace wants to send be
   explicitly white-listed in the implementation.  For ACPI this means
   function codes marked as supported by acpi_check_dsm() may
   only be invoked if they appear in the white-list.  A function must be
   publicly documented before it is added to the white-list.

2/ The above restrictions can be trivially bypassed by using the
   "vendor-specific" payload command.  However, since vendor-specific
   commands are by definition not publicly documented and have the
   potential to corrupt the kernel's view of the dimm state, we provide a
   toggle to disable vendor-specific operations.  Enabling undefined
   behavior is a policy decision that can be made by the platform owner
   and encourages firmware implementations to choose public over
   private command implementations.

Based on an initial patch from Jerry Hoemann
Cc: Jerry Hoemann <jerry.hoemann@hpe.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
index cb2042a..395a9fb 100644
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -439,6 +439,12 @@ static const struct nd_cmd_desc __nd_cmd_dimm_descs[] = {
 		.out_num = 3,
 		.out_sizes = { 4, 4, UINT_MAX, },
 	},
+	[ND_CMD_CALL] = {
+		.in_num = 2,
+		.in_sizes = { sizeof(struct nd_cmd_pkg), UINT_MAX, },
+		.out_num = 1,
+		.out_sizes = { UINT_MAX, },
+	},
 };
 
 const struct nd_cmd_desc *nd_cmd_dimm_desc(int cmd)
@@ -473,6 +479,12 @@ static const struct nd_cmd_desc __nd_cmd_bus_descs[] = {
 		.out_num = 3,
 		.out_sizes = { 4, 4, 8, },
 	},
+	[ND_CMD_CALL] = {
+		.in_num = 2,
+		.in_sizes = { sizeof(struct nd_cmd_pkg), UINT_MAX, },
+		.out_num = 1,
+		.out_sizes = { UINT_MAX, },
+	},
 };
 
 const struct nd_cmd_desc *nd_cmd_bus_desc(int cmd)
@@ -500,6 +512,10 @@ u32 nd_cmd_in_size(struct nvdimm *nvdimm, int cmd,
 		struct nd_cmd_vendor_hdr *hdr = buf;
 
 		return hdr->in_length;
+	} else if (cmd == ND_CMD_CALL) {
+		struct nd_cmd_pkg *pkg = buf;
+
+		return pkg->nd_size_in;
 	}
 
 	return UINT_MAX;
@@ -522,6 +538,12 @@ u32 nd_cmd_out_size(struct nvdimm *nvdimm, int cmd,
 		return out_field[1];
 	else if (!nvdimm && cmd == ND_CMD_ARS_STATUS && idx == 2)
 		return out_field[1] - 8;
+	else if (cmd == ND_CMD_CALL) {
+		struct nd_cmd_pkg *pkg = (struct nd_cmd_pkg *) in_field;
+
+		return pkg->nd_size_out;
+	}
+
 
 	return UINT_MAX;
 }
@@ -588,6 +610,7 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
 	unsigned int cmd = _IOC_NR(ioctl_cmd);
 	void __user *p = (void __user *) arg;
 	struct device *dev = &nvdimm_bus->dev;
+	struct nd_cmd_pkg pkg;
 	const char *cmd_name, *dimm_name;
 	unsigned long cmd_mask;
 	void *buf;
@@ -605,6 +628,11 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
 		dimm_name = "bus";
 	}
 
+	if (cmd == ND_CMD_CALL) {
+		if (copy_from_user(&pkg, p, sizeof(pkg)))
+			return -EFAULT;
+	}
+
 	if (!desc || (desc->out_num + desc->in_num == 0) ||
 			!test_bit(cmd, &cmd_mask))
 		return -ENOTTY;
@@ -616,6 +644,7 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
 		case ND_CMD_SET_CONFIG_DATA:
 		case ND_CMD_ARS_START:
 		case ND_CMD_CLEAR_ERROR:
+		case ND_CMD_CALL:
 			dev_dbg(&nvdimm_bus->dev, "'%s' command while read-only.\n",
 					nvdimm ? nvdimm_cmd_name(cmd)
 					: nvdimm_bus_cmd_name(cmd));
@@ -643,6 +672,16 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
 		in_len += in_size;
 	}
 
+	if (cmd == ND_CMD_CALL) {
+		dev_dbg(dev, "%s:%s, idx: %llu, in: %zu, out: %zu, len %zu\n",
+				__func__, dimm_name, pkg.nd_command,
+				in_len, out_len, buf_len);
+
+		for (i = 0; i < ARRAY_SIZE(pkg.nd_reserved2); i++)
+			if (pkg.nd_reserved2[i])
+				return -EINVAL;
+	}
+
 	/* process an output envelope */
 	for (i = 0; i < desc->out_num; i++) {
 		u32 out_size = nd_cmd_out_size(nvdimm, cmd, desc, i,