On Mon, 11 Jan 2021 14:51:14 -0800 Ben Widawsky <[email protected]> wrote:
> The send command allows userspace to issue mailbox commands directly to > the hardware. The driver will verify basic properties of the command and > possible inspect the input (or output) payload to determine whether or > not the command is allowed (or might taint the kernel). > > The list of allowed commands and their properties can be determined by > using the QUERY IOCTL for CXL memory devices. > > Signed-off-by: Ben Widawsky <[email protected]> > --- > drivers/cxl/mem.c | 204 ++++++++++++++++++++++++++++++++++- > include/uapi/linux/cxl_mem.h | 39 +++++++ > 2 files changed, 239 insertions(+), 4 deletions(-) > > diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c > index d4eb3f5b9469..f979788b4d9f 100644 > --- a/drivers/cxl/mem.c > +++ b/drivers/cxl/mem.c > @@ -84,6 +84,13 @@ static DEFINE_IDR(cxl_mem_idr); > /* protect cxl_mem_idr allocations */ > static DEFINE_MUTEX(cxl_memdev_lock); > > +#undef C > +#define C(a, b) { b } I'm not following why this is here? > +static struct { > + const char *name; > +} command_names[] = { CMDS }; > +#undef C > + > #define CXL_CMD(_id, _flags, sin, sout, f) > \ > [CXL_MEM_COMMAND_ID_##_id] = { \ > { \ ... > + > +/** > + * handle_mailbox_cmd_from_user() - Dispatch a mailbox command. > + * @cxlmd: 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. > + * @u: The command submitted by userspace. Has output fields. > + * > + * Return: > + * * %0 - Mailbox transaction succeeded. > + * * %-EFAULT - Something happened with copy_to/from_user. > + * * %-EINTR - Mailbox acquisition interrupted. > + * * %-E2BIG - Output payload would overrun buffer. > + * > + * Creates the appropriate mailbox command on behalf of a userspace request. > + * Return value, size, and output payload are all copied out to @u. The > + * parameters for the command must be validated before calling this function. > + * > + * A 0 return code indicates the command executed successfully, not that it > was > + * itself successful. IOW, the retval should always be checked if wanting to cmd->retval perhaps to be more explicit? > + * determine the actual result. > + */ > +static int handle_mailbox_cmd_from_user(struct cxl_memdev *cxlmd, > + const struct cxl_mem_command *cmd, > + u64 in_payload, > + u64 out_payload, > + struct cxl_send_command __user *u) > +{ > + struct mbox_cmd mbox_cmd = { > + .opcode = cmd->opcode, > + .size_in = cmd->info.size_in, > + .payload = NULL, /* Copied by copy_to|from_user() */ > + }; > + int rc; > + > + if (cmd->info.size_in) { > + /* > + * Directly copy the userspace payload into the hardware. UAPI > + * states that the buffer must already be little endian. > + */ > + if (copy_from_user((__force void > *)cxl_payload_regs(cxlmd->cxlm), > + u64_to_user_ptr(in_payload), > + cmd->info.size_in)) { > + cxl_mem_mbox_put(cxlmd->cxlm); mbox_get is after this point though it shouldn't be given we just wrote into the mbox registers. This seems unlikely to be a high performance path, so perhaps just use a local buffer and let cxl_mem_mbox_send_cmd copy it into the registers. > + return -EFAULT; > + } > + } > + > + rc = cxl_mem_mbox_get(cxlmd->cxlm, true); > + if (rc) > + return rc; > + > + dev_dbg(&cxlmd->dev, > + "Submitting %s command for user\n" > + "\topcode: %x\n" > + "\tsize: %ub\n", > + command_names[cmd->info.id].name, mbox_cmd.opcode, > + cmd->info.size_in); > + > + rc = cxl_mem_mbox_send_cmd(cxlmd->cxlm, &mbox_cmd); > + cxl_mem_mbox_put(cxlmd->cxlm); > + if (rc) > + return rc; > + > + if (mbox_cmd.size_out > cmd->info.size_out) > + return -E2BIG; > + > + rc = put_user(mbox_cmd.return_code, &u->retval); > + if (rc) > + return rc; > + > + rc = put_user(mbox_cmd.size_out, &u->size_out); > + if (rc) > + return rc; > + > + if (mbox_cmd.size_out) > + if (copy_to_user(u64_to_user_ptr(out_payload), > + (__force void *)cxl_payload_regs(cxlmd->cxlm), > + mbox_cmd.size_out)) > + return -EFAULT; > + > + return 0; > +} > + ... > > static long cxl_mem_ioctl(struct file *file, unsigned int cmd, unsigned long > arg) > @@ -479,6 +644,37 @@ static long cxl_mem_ioctl(struct file *file, unsigned > int cmd, unsigned long arg > if (j == n_commands) > break; > } > + > + return 0; Ah. That should have been in the earlier patch. Explains why the code works :) > + } else if (cmd == CXL_MEM_SEND_COMMAND) { > + struct cxl_send_command send, __user *u = (void __user *)arg; > + struct cxl_mem_command c; > + int rc; > + > + dev_dbg(dev, "Send IOCTL\n"); > + > + if (copy_from_user(&send, u, sizeof(send))) > + return -EFAULT; > + > + rc = device_lock_interruptible(dev); > + if (rc) > + return rc; > + > + if (!get_live_device(dev)) { > + device_unlock(dev); > + return -ENXIO; > + } > + > + rc = cxl_validate_cmd_from_user(cxlmd->cxlm, &send, &c); > + if (!rc) > + rc = handle_mailbox_cmd_from_user(cxlmd, &c, > + send.in_payload, > + send.out_payload, u); > + > + put_device(dev); > + device_unlock(dev); > + > + return rc; > } > > return -ENOTTY; > @@ -837,7 +1033,7 @@ static int cxl_mem_identify(struct cxl_mem *cxlm) > int rc; > > /* Retrieve initial device memory map */ > - rc = cxl_mem_mbox_get(cxlm); > + rc = cxl_mem_mbox_get(cxlm, false); > if (rc) > return rc; > > diff --git a/include/uapi/linux/cxl_mem.h b/include/uapi/linux/cxl_mem.h > index 847f825bbe18..cb4e2bee5228 100644 > --- a/include/uapi/linux/cxl_mem.h > +++ b/include/uapi/linux/cxl_mem.h > @@ -26,6 +26,7 @@ extern "C" { > */ > > #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) > > #undef CMDS > #define CMDS > \ > @@ -69,6 +70,7 @@ struct cxl_command_info { > #define CXL_MEM_COMMAND_FLAG_NONE 0 > #define CXL_MEM_COMMAND_FLAG_KERNEL BIT(0) > #define CXL_MEM_COMMAND_FLAG_MUTEX BIT(1) > +#define CXL_MEM_COMMAND_FLAG_MASK GENMASK(31, 2) Instinctively I'd expect FLAG_MASK to be GENMASK(1, 0) and to be used as ~FLAG_MASK. As it's mask of flags, not the mask to leave only valid flags. > > __s32 size_in; > __s32 size_out; > @@ -110,6 +112,43 @@ struct cxl_mem_query_commands { > 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). > + * @size_in: Size of the payload to provide to the device (input). > + * @size_out: 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. > + * @in_payload: Pointer to memory for payload input (little endian order). > + * @out_payload: Pointer to memory for payload output (little endian order). > + * > + * Mechanism for userspace to send a command to the hardware for processing. > The > + * driver will do basic validation on the command sizes, but the payload > input > + * and output are not introspected. Userspace is required to allocate large > + * enough buffers for max(size_in, size_out). That sounds like both buffers must be the maximum between size_in and size_out. Is intent that this is the maximum size_in for in_payload and max(size_out) for out_payload? > + */ > +struct cxl_send_command { > + __u32 id; > + __u32 flags; > + __u32 rsvd; > + __u32 retval; > + > + struct { > + __s32 size_in; > + __u64 in_payload; > + }; > + > + struct { > + __s32 size_out; > + __u64 out_payload; > + }; > +}; > + > #if defined(__cplusplus) > } > #endif
