On Mon, 15 Feb 2021 17:45:33 -0800 Ben Widawsky <ben.widaw...@intel.com> wrote:
> Add a straightforward IOCTL that provides a mechanism for userspace to > query the supported memory device commands. CXL commands as they appear > to userspace are described as part of the UAPI kerneldoc. The command > list returned via this IOCTL will contain the full set of commands that > the driver supports, however, some of those commands may not be > available for use by userspace. > > Memory device commands first appear in the CXL 2.0 specification. They > are submitted through a mailbox mechanism specified in the CXL 2.0 > specification. > > The send command allows userspace to issue mailbox commands directly to > the hardware. The list of available commands to send are the output of > the query command. The driver verifies basic properties of the command > and possibly inspect the input (or output) payload to determine whether > or not the command is allowed (or might taint the kernel). > > Reported-by: kernel test robot <l...@intel.com> # bug in earlier revision > Signed-off-by: Ben Widawsky <ben.widaw...@intel.com> > Reviewed-by: Dan Williams <dan.j.willi...@intel.com> (v2) I may be missreading this but I think the logic to ensure commands using a variable sized buffer have enough space is broken. Jonathan > --- > .clang-format | 1 + > .../userspace-api/ioctl/ioctl-number.rst | 1 + > drivers/cxl/mem.c | 288 +++++++++++++++++- > include/uapi/linux/cxl_mem.h | 154 ++++++++++ > 4 files changed, 443 insertions(+), 1 deletion(-) > create mode 100644 include/uapi/linux/cxl_mem.h > > diff --git a/.clang-format b/.clang-format > index 10dc5a9a61b3..3f11c8901b43 100644 > --- a/.clang-format > +++ b/.clang-format > @@ -109,6 +109,7 @@ ForEachMacros: > - 'css_for_each_child' > - 'css_for_each_descendant_post' > - 'css_for_each_descendant_pre' > + - 'cxl_for_each_cmd' > - 'device_for_each_child_node' > - 'dma_fence_chain_for_each' > - 'do_for_each_ftrace_op' > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst > b/Documentation/userspace-api/ioctl/ioctl-number.rst > index a4c75a28c839..6eb8e634664d 100644 > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst > @@ -352,6 +352,7 @@ Code Seq# Include File > Comments > > <mailto:michael.kl...@puffin.lb.shuttle.de> > 0xCC 00-0F drivers/misc/ibmvmc.h pseries > VMC driver > 0xCD 01 linux/reiserfs_fs.h > +0xCE 01-02 uapi/linux/cxl_mem.h Compute > Express Link Memory Devices > 0xCF 02 fs/cifs/ioctl.c > 0xDB 00-0F drivers/char/mwave/mwavepub.h > 0xDD 00-3F ZFCP > device driver see drivers/s390/scsi/ > diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c > index 410adb1bdffc..a4298cb1182d 100644 > --- a/drivers/cxl/mem.c > +++ b/drivers/cxl/mem.c > @@ -1,5 +1,6 @@ > // SPDX-License-Identifier: GPL-2.0-only > /* Copyright(c) 2020 Intel Corporation. All rights reserved. */ > +#include <uapi/linux/cxl_mem.h> > #include <linux/module.h> > #include <linux/mutex.h> > #include <linux/cdev.h> > @@ -40,6 +41,7 @@ > #define CXL_MAILBOX_TIMEOUT_MS (2 * HZ) > > enum opcode { > + CXL_MBOX_OP_INVALID = 0x0000, > CXL_MBOX_OP_IDENTIFY = 0x4000, > CXL_MBOX_OP_MAX = 0x10000 > }; > @@ -91,6 +93,49 @@ struct cxl_memdev { > static int cxl_mem_major; > static DEFINE_IDA(cxl_memdev_ida); > > +/** > + * struct cxl_mem_command - Driver representation of a memory device command > + * @info: Command information as it exists for the UAPI > + * @opcode: The actual bits used for the mailbox protocol > + * > + * The cxl_mem_command is the driver's internal representation of commands > that > + * are supported by the driver. Some of these commands may not be supported > by > + * the hardware. The driver will use @info to validate the fields passed in > by > + * the user then submit the @opcode to the hardware. > + * > + * See struct cxl_command_info. > + */ > +struct cxl_mem_command { > + struct cxl_command_info info; > + enum opcode opcode; > +}; > + > +#define CXL_CMD(_id, sin, sout) > \ > + [CXL_MEM_COMMAND_ID_##_id] = { \ > + .info = { \ > + .id = CXL_MEM_COMMAND_ID_##_id, \ > + .size_in = sin, \ > + .size_out = sout, \ > + }, \ > + .opcode = CXL_MBOX_OP_##_id, \ > + } > + > +/* > + * This table defines the supported mailbox commands for the driver. This > table > + * is made up of a UAPI structure. Non-negative values as parameters in the > + * table will be validated against the user's input. For example, if size_in > is > + * 0, and the user passed in 1, it is an error. > + */ > +static struct cxl_mem_command mem_commands[] = { > + CXL_CMD(IDENTIFY, 0, 0x43), > +}; > + > +#define cxl_for_each_cmd(cmd) > \ > + for ((cmd) = &mem_commands[0]; \ > + ((cmd) - mem_commands) < ARRAY_SIZE(mem_commands); (cmd)++) > + > +#define cxl_cmd_count ARRAY_SIZE(mem_commands) > + > static int cxl_mem_wait_for_doorbell(struct cxl_mem *cxlm) > { > const unsigned long start = jiffies; > @@ -312,6 +357,247 @@ static void cxl_mem_mbox_put(struct cxl_mem *cxlm) > mutex_unlock(&cxlm->mbox_mutex); > } > > +/** > + * handle_mailbox_cmd_from_user() - Dispatch a mailbox command for userspace. > + * @cxlm: The CXL memory device to communicate with. > + * @cmd: The validated command. > + * @in_payload: Pointer to userspace's input payload. > + * @out_payload: Pointer to userspace's output payload. > + * @size_out: (Input) Max payload size to copy out. > + * (Output) Payload size hardware generated. > + * @retval: Hardware generated return code from the operation. > + * > + * Return: > + * * %0 - Mailbox transaction succeeded. This implies the mailbox > + * protocol completed successfully not that the operation itself > + * was successful. > + * * %-ENOMEM - Couldn't allocate a bounce buffer. > + * * %-EFAULT - Something happened with copy_to/from_user. > + * * %-EINTR - Mailbox acquisition interrupted. > + * * %-* - Transaction level failures. > + * > + * Creates the appropriate mailbox command and dispatches it on behalf of a > + * userspace request. The input and output payloads are copied between > + * userspace. > + * > + * See cxl_send_cmd(). > + */ > +static int handle_mailbox_cmd_from_user(struct cxl_mem *cxlm, > + const struct cxl_mem_command *cmd, > + u64 in_payload, u64 out_payload, > + s32 *size_out, u32 *retval) > +{ > + struct device *dev = &cxlm->pdev->dev; > + struct mbox_cmd mbox_cmd = { > + .opcode = cmd->opcode, > + .size_in = cmd->info.size_in, > + }; > + int rc; > + > + if (cmd->info.size_out) { > + mbox_cmd.payload_out = kvzalloc(cmd->info.size_out, GFP_KERNEL); > + if (!mbox_cmd.payload_out) > + return -ENOMEM; > + } > + > + if (cmd->info.size_in) { > + mbox_cmd.payload_in = kvzalloc(cmd->info.size_in, GFP_KERNEL); > + if (!mbox_cmd.payload_in) { > + rc = -ENOMEM; > + goto out; > + } > + > + if (copy_from_user(mbox_cmd.payload_in, > + u64_to_user_ptr(in_payload), > + cmd->info.size_in)) { > + rc = -EFAULT; > + goto out; > + } > + } > + > + rc = cxl_mem_mbox_get(cxlm); > + if (rc) > + goto out; > + > + dev_dbg(dev, > + "Submitting %s command for user\n" > + "\topcode: %x\n" > + "\tsize: %ub\n", > + cxl_command_names[cmd->info.id].name, mbox_cmd.opcode, > + cmd->info.size_in); > + > + rc = __cxl_mem_mbox_send_cmd(cxlm, &mbox_cmd); > + cxl_mem_mbox_put(cxlm); > + if (rc) > + goto out; > + > + /* > + * @size_out contains the max size that's allowed to be written back out > + * to userspace. While the payload may have written more output than > + * this it will have to be ignored. > + */ See below for why I don't think this works. The size of mbox_cmd.payload_out seems to always be the size userspace specified, never the 1MB this code is assuming. So if the hardware returns more than userspace asks for you have a buffer overrun. > + if (mbox_cmd.size_out) { > + if (copy_to_user(u64_to_user_ptr(out_payload), > + mbox_cmd.payload_out, *size_out)) { > + rc = -EFAULT; > + goto out; > + } > + } > + > + /* > + * Reporting the actual size, even if it was greater than @size_out > + * allows userspace to try the command again with a bigger buffer. > + */ > + *size_out = mbox_cmd.size_out; > + *retval = mbox_cmd.return_code; > + > +out: > + kvfree(mbox_cmd.payload_in); > + kvfree(mbox_cmd.payload_out); > + return rc; > +} > + > +/** > + * cxl_validate_cmd_from_user() - Check fields for CXL_MEM_SEND_COMMAND. > + * @cxlm: &struct cxl_mem device whose mailbox will be used. > + * @send_cmd: &struct cxl_send_command copied in from userspace. > + * @out_cmd: Sanitized and populated &struct cxl_mem_command. > + * > + * Return: > + * * %0 - @out_cmd is ready to send. > + * * %-ENOTTY - Invalid command specified. > + * * %-EINVAL - Reserved fields or invalid values were used. > + * * %-ENOMEM - Input or output buffer wasn't sized properly. > + * > + * The result of this command is a fully validated command in @out_cmd that > is > + * safe to send to the hardware. > + * > + * See handle_mailbox_cmd_from_user() > + */ > +static int cxl_validate_cmd_from_user(struct cxl_mem *cxlm, > + const struct cxl_send_command *send_cmd, > + struct cxl_mem_command *out_cmd) > +{ > + const struct cxl_command_info *info; > + struct cxl_mem_command *c; > + > + if (send_cmd->id == 0 || send_cmd->id >= CXL_MEM_COMMAND_ID_MAX) > + return -ENOTTY; > + > + /* > + * The user can never specify an input payload larger than what hardware > + * supports, but output can be arbitrarily large (simply write out as > + * much data as the hardware provides). > + */ > + if (send_cmd->in.size > cxlm->payload_size) > + return -EINVAL; > + > + if (send_cmd->flags & ~CXL_MEM_COMMAND_FLAG_MASK) > + return -EINVAL; > + > + if (send_cmd->rsvd) > + return -EINVAL; > + > + if (send_cmd->in.rsvd || send_cmd->out.rsvd) > + return -EINVAL; > + > + /* Convert user's command into the internal representation */ > + c = &mem_commands[send_cmd->id]; > + info = &c->info; > + > + /* Check the input buffer is the expected size */ > + if (info->size_in >= 0 && info->size_in != send_cmd->in.size) > + return -ENOMEM; > + > + /* Check the output buffer is at least large enough */ > + if (info->size_out >= 0 && send_cmd->out.size < info->size_out) > + return -ENOMEM; > + > + memcpy(out_cmd, c, sizeof(*c)); > + out_cmd->info.size_in = send_cmd->in.size; > + out_cmd->info.size_out = send_cmd->out.size; > + > + return 0; > +} > + > +static int cxl_query_cmd(struct cxl_memdev *cxlmd, > + struct cxl_mem_query_commands __user *q) > +{ > + struct device *dev = &cxlmd->dev; > + struct cxl_mem_command *cmd; > + u32 n_commands; > + int j = 0; > + > + dev_dbg(dev, "Query IOCTL\n"); > + > + if (get_user(n_commands, &q->n_commands)) > + return -EFAULT; > + > + /* returns the total number if 0 elements are requested. */ > + if (n_commands == 0) > + return put_user(cxl_cmd_count, &q->n_commands); > + > + /* > + * otherwise, return max(n_commands, total commands) cxl_command_info > + * structures. > + */ > + cxl_for_each_cmd(cmd) { > + const struct cxl_command_info *info = &cmd->info; > + > + if (copy_to_user(&q->commands[j++], info, sizeof(*info))) > + return -EFAULT; > + > + if (j == n_commands) > + break; > + } > + > + return 0; > +} > + > +static int cxl_send_cmd(struct cxl_memdev *cxlmd, > + struct cxl_send_command __user *s) > +{ > + struct cxl_mem *cxlm = cxlmd->cxlm; > + struct device *dev = &cxlmd->dev; > + struct cxl_send_command send; > + struct cxl_mem_command c; > + int rc; > + > + dev_dbg(dev, "Send IOCTL\n"); > + > + if (copy_from_user(&send, s, sizeof(send))) > + return -EFAULT; > + > + rc = cxl_validate_cmd_from_user(cxlmd->cxlm, &send, &c); > + if (rc) > + return rc; Userspace will pass in send.out set to the size of it's available buffer. Then cxl_validate_cmd_from_user() will fill c.info.size_out with send.out.size > + > + /* Prepare to handle a full payload for variable sized output */ > + if (c.info.size_out < 0) So this check only works if userspace set the command to have variable size. That's not what the docs below suggest should happen. > + c.info.size_out = cxlm->payload_size; > + > + rc = handle_mailbox_cmd_from_user(cxlm, &c, send.in.payload, > + send.out.payload, &send.out.size, > + &send.retval); > + if (rc) > + return rc; > + > + return copy_to_user(s, &send, sizeof(send)); > +} > + > +static long __cxl_memdev_ioctl(struct cxl_memdev *cxlmd, unsigned int cmd, > + unsigned long arg) > +{ > + switch (cmd) { > + case CXL_MEM_QUERY_COMMANDS: > + return cxl_query_cmd(cxlmd, (void __user *)arg); > + case CXL_MEM_SEND_COMMAND: > + return cxl_send_cmd(cxlmd, (void __user *)arg); > + default: > + return -ENOTTY; > + } > +} > + > static long cxl_memdev_ioctl(struct file *file, unsigned int cmd, > unsigned long arg) > { > @@ -325,7 +611,7 @@ static long cxl_memdev_ioctl(struct file *file, unsigned > int cmd, > if (!percpu_ref_tryget_live(&cxlmd->ops_active)) > return -ENXIO; > > - /* TODO: ioctl body */ > + rc = __cxl_memdev_ioctl(cxlmd, cmd, arg); > > percpu_ref_put(&cxlmd->ops_active); > > diff --git a/include/uapi/linux/cxl_mem.h b/include/uapi/linux/cxl_mem.h > new file mode 100644 > index 000000000000..18cea908ad0b > --- /dev/null > +++ b/include/uapi/linux/cxl_mem.h > @@ -0,0 +1,154 @@ > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ > +/* > + * CXL IOCTLs for Memory Devices > + */ > + > +#ifndef _UAPI_CXL_MEM_H_ > +#define _UAPI_CXL_MEM_H_ > + > +#include <linux/types.h> > + > +/** > + * DOC: UAPI > + * > + * Not all of all commands that the driver supports are always available for > use > + * by userspace. Userspace must check the results from the QUERY command in > + * order to determine the live set of commands. > + */ > + > +#define CXL_MEM_QUERY_COMMANDS _IOR(0xCE, 1, struct cxl_mem_query_commands) > +#define CXL_MEM_SEND_COMMAND _IOWR(0xCE, 2, struct cxl_send_command) > + > +#define CXL_CMDS \ > + ___C(INVALID, "Invalid Command"), \ > + ___C(IDENTIFY, "Identify Command"), \ > + ___C(MAX, "invalid / last command") > + > +#define ___C(a, b) CXL_MEM_COMMAND_ID_##a > +enum { CXL_CMDS }; > + > +#undef ___C > +#define ___C(a, b) { b } > +static const struct { > + const char *name; > +} cxl_command_names[] = { CXL_CMDS }; > + > +/* > + * Here's how this actually breaks out: > + * cxl_command_names[] = { > + * [CXL_MEM_COMMAND_ID_INVALID] = { "Invalid Command" }, > + * [CXL_MEM_COMMAND_ID_IDENTIFY] = { "Identify Command" }, > + * ... > + * [CXL_MEM_COMMAND_ID_MAX] = { "invalid / last command" }, > + * }; > + */ Thanks, this is great. > + > +#undef ___C > + > +/** > + * struct cxl_command_info - Command information returned from a query. > + * @id: ID number for the command. > + * @flags: Flags that specify command behavior. > + * @size_in: Expected input size, or -1 if variable length. > + * @size_out: Expected output size, or -1 if variable length. > + * > + * Represents a single command that is supported by both the driver and the > + * hardware. This is returned as part of an array from the query ioctl. The > + * following would be a command that takes a variable length input and > returns 0 > + * bytes of output. > + * > + * - @id = 10 > + * - @flags = 0 > + * - @size_in = -1 > + * - @size_out = 0 > + * > + * See struct cxl_mem_query_commands. > + */ > +struct cxl_command_info { > + __u32 id; > + > + __u32 flags; > +#define CXL_MEM_COMMAND_FLAG_MASK GENMASK(0, 0) > + > + __s32 size_in; > + __s32 size_out; > +}; > + > +/** > + * struct cxl_mem_query_commands - Query supported commands. > + * @n_commands: In/out parameter. When @n_commands is > 0, the driver will > + * return min(num_support_commands, n_commands). When @n_commands > + * is 0, driver will return the number of total supported commands. > + * @rsvd: Reserved for future use. > + * @commands: Output array of supported commands. This array must be > allocated > + * by userspace to be at least min(num_support_commands, > @n_commands) > + * > + * Allow userspace to query the available commands supported by both the > driver, > + * and the hardware. Commands that aren't supported by either the driver, or > the > + * hardware are not returned in the query. > + * > + * Examples: > + * > + * - { .n_commands = 0 } // Get number of supported commands > + * - { .n_commands = 15, .commands = buf } // Return first 15 (or less) > + * supported commands > + * > + * See struct cxl_command_info. > + */ > +struct cxl_mem_query_commands { > + /* > + * Input: Number of commands to return (space allocated by user) > + * Output: Number of commands supported by the driver/hardware > + * > + * If n_commands is 0, kernel will only return number of commands and > + * not try to populate commands[], thus allowing userspace to know how > + * much space to allocate > + */ This is fairly well described in the docs above the structure. Perhaps combine the two. > + __u32 n_commands; > + __u32 rsvd; > + > + struct cxl_command_info __user commands[]; /* out: supported commands */ > +}; > + > +/** > + * struct cxl_send_command - Send a command to a memory device. > + * @id: The command to send to the memory device. This must be one of the > + * commands returned by the query command. > + * @flags: Flags for the command (input). > + * @rsvd: Must be zero. > + * @retval: Return value from the memory device (output). > + * @in.size: Size of the payload to provide to the device (input). > + * @in.rsvd: Must be zero. > + * @in.payload: Pointer to memory for payload input, payload is little > endian. > + * @out.size: Size of the payload received from the device (input/output). > This > + * field is filled in by userspace to let the driver know how much > + * space was allocated for output. It is populated by the driver to > + * let userspace know how large the output payload actually was. > + * @out.rsvd: Must be zero. > + * @out.payload: Pointer to memory for payload output, payload is little > endian. > + * > + * Mechanism for userspace to send a command to the hardware for processing. > The > + * driver will do basic validation on the command sizes. In some cases even > the > + * payload may be introspected. Userspace is required to allocate large > enough > + * buffers for size_out which can be variable length in certain situations. > + */ > +struct cxl_send_command { > + __u32 id; > + __u32 flags; > + __u32 rsvd; > + __u32 retval; > + > + struct { > + __s32 size; > + __u32 rsvd; > + __u64 payload; > + } in; > + > + struct { > + __s32 size; > + __u32 rsvd; > + __u64 payload; > + } out; > +}; > + > +#endif
