tools/wmi: add a sample for dell smbios communication over WMI

This application uses the character device /dev/wmi/dell-smbios
to perform SMBIOS communications from userspace.

It offers demonstrations of a few simple tasks:
 - Running a class/select command
 - Querying a token value
 - Activating a token

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Reviewed-by: Edward O'Callaghan <quasisec@google.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

2 files changed, 228 insertions, 0 deletions

diff --git a/tools/wmi/Makefile b/tools/wmi/Makefile
new file mode 100644
index 000000000000..e664f1167388
--- /dev/null
+++ b/tools/wmi/Makefile
@@ -0,0 +1,18 @@
+PREFIX ?= /usr
+SBINDIR ?= sbin
+INSTALL ?= install
+CFLAGS += -D__EXPORTED_HEADERS__ -I../../include/uapi -I../../include
+CC = $(CROSS_COMPILE)gcc
+
+TARGET = dell-smbios-example
+
+all: $(TARGET)
+
+%: %.c
+        $(CC) $(CFLAGS) $(LDFLAGS) -o $@ $<
+
+clean:
+        $(RM) $(TARGET)
+
+install: dell-smbios-example
+        $(INSTALL) -D -m 755 $(TARGET) $(DESTDIR)$(PREFIX)/$(SBINDIR)/$(TARGET)
diff --git a/tools/wmi/dell-smbios-example.c b/tools/wmi/dell-smbios-example.c
new file mode 100644
index 000000000000..9d3bde081249
--- /dev/null
+++ b/tools/wmi/dell-smbios-example.c
@@ -0,0 +1,210 @@
+/*
+ *  Sample application for SMBIOS communication over WMI interface
+ *  Performs the following:
+ *  - Simple cmd_class/cmd_select lookup for TPM information
+ *  - Simple query of known tokens and their values
+ *  - Simple activation of a token
+ *
+ *  Copyright (C) 2017 Dell, Inc.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+/* if uapi header isn't installed, this might not yet exist */
+#ifndef __packed
+#define __packed __attribute__((packed))
+#endif
+#include <linux/wmi.h>
+
+/* It would be better to discover these using udev, but for a simple
+ * application they're hardcoded
+ */
+static const char *ioctl_devfs = "/dev/wmi/dell-smbios";
+static const char *token_sysfs =
+                        "/sys/bus/platform/devices/dell-smbios.0/tokens";
+
+static void show_buffer(struct dell_wmi_smbios_buffer *buffer)
+{
+        printf("Call: %x/%x [%x,%x,%x,%x]\nResults: [%8x,%8x,%8x,%8x]\n",
+        buffer->std.cmd_class, buffer->std.cmd_select,
+        buffer->std.input[0], buffer->std.input[1],
+        buffer->std.input[2], buffer->std.input[3],
+        buffer->std.output[0], buffer->std.output[1],
+        buffer->std.output[2], buffer->std.output[3]);
+}
+
+static int run_wmi_smbios_cmd(struct dell_wmi_smbios_buffer *buffer)
+{
+        int fd;
+        int ret;
+
+        fd = open(ioctl_devfs, O_NONBLOCK);
+        ret = ioctl(fd, DELL_WMI_SMBIOS_CMD, buffer);
+        close(fd);
+        return ret;
+}
+
+static int find_token(__u16 token, __u16 *location, __u16 *value)
+{
+        char location_sysfs[60];
+        char value_sysfs[57];
+        char buf[4096];
+        FILE *f;
+        int ret;
+
+        ret = sprintf(value_sysfs, "%s/%04x_value", token_sysfs, token);
+        if (ret < 0) {
+                printf("sprintf value failed\n");
+                return 2;
+        }
+        f = fopen(value_sysfs, "rb");
+        if (!f) {
+                printf("failed to open %s\n", value_sysfs);
+                return 2;
+        }
+        fread(buf, 1, 4096, f);
+        fclose(f);
+        *value = (__u16) strtol(buf, NULL, 16);
+
+        ret = sprintf(location_sysfs, "%s/%04x_location", token_sysfs, token);
+        if (ret < 0) {
+                printf("sprintf location failed\n");
+                return 1;
+        }
+        f = fopen(location_sysfs, "rb");
+        if (!f) {
+                printf("failed to open %s\n", location_sysfs);
+                return 2;
+        }
+        fread(buf, 1, 4096, f);
+        fclose(f);
+        *location = (__u16) strtol(buf, NULL, 16);
+
+        if (*location)
+                return 0;
+        return 2;
+}
+
+static int token_is_active(__u16 *location, __u16 *cmpvalue,
+                           struct dell_wmi_smbios_buffer *buffer)
+{
+        int ret;
+
+        buffer->std.cmd_class = CLASS_TOKEN_READ;
+        buffer->std.cmd_select = SELECT_TOKEN_STD;
+        buffer->std.input[0] = *location;
+        ret = run_wmi_smbios_cmd(buffer);
+        if (ret != 0 || buffer->std.output[0] != 0)
+                return ret;
+        ret = (buffer->std.output[1] == *cmpvalue);
+        return ret;
+}
+
+static int query_token(__u16 token, struct dell_wmi_smbios_buffer *buffer)
+{
+        __u16 location;
+        __u16 value;
+        int ret;
+
+        ret = find_token(token, &location, &value);
+        if (ret != 0) {
+                printf("unable to find token %04x\n", token);
+                return 1;
+        }
+        return token_is_active(&location, &value, buffer);
+}
+
+static int activate_token(struct dell_wmi_smbios_buffer *buffer,
+                   __u16 token)
+{
+        __u16 location;
+        __u16 value;
+        int ret;
+
+        ret = find_token(token, &location, &value);
+        if (ret != 0) {
+                printf("unable to find token %04x\n", token);
+                return 1;
+        }
+        buffer->std.cmd_class = CLASS_TOKEN_WRITE;
+        buffer->std.cmd_select = SELECT_TOKEN_STD;
+        buffer->std.input[0] = location;
+        buffer->std.input[1] = 1;
+        ret = run_wmi_smbios_cmd(buffer);
+        return ret;
+}
+
+static int query_buffer_size(__u64 *buffer_size)
+{
+        FILE *f;
+
+        f = fopen(ioctl_devfs, "rb");
+        if (!f)
+                return -EINVAL;
+        fread(buffer_size, sizeof(__u64), 1, f);
+        fclose(f);
+        return EXIT_SUCCESS;
+}
+
+int main(void)
+{
+        struct dell_wmi_smbios_buffer *buffer;
+        int ret;
+        __u64 value = 0;
+
+        ret = query_buffer_size(&value);
+        if (ret == EXIT_FAILURE || !value) {
+                printf("Unable to read buffer size\n");
+                goto out;
+        }
+        printf("Detected required buffer size %lld\n", value);
+
+        buffer = malloc(value);
+        if (buffer == NULL) {
+                printf("failed to alloc memory for ioctl\n");
+                ret = -ENOMEM;
+                goto out;
+        }
+        buffer->length = value;
+
+        /* simple SMBIOS call for looking up TPM info */
+        buffer->std.cmd_class = CLASS_FLASH_INTERFACE;
+        buffer->std.cmd_select = SELECT_FLASH_INTERFACE;
+        buffer->std.input[0] = 2;
+        ret = run_wmi_smbios_cmd(buffer);
+        if (ret) {
+                printf("smbios ioctl failed: %d\n", ret);
+                ret = EXIT_FAILURE;
+                goto out;
+        }
+        show_buffer(buffer);
+
+        /* query some tokens */
+        ret = query_token(CAPSULE_EN_TOKEN, buffer);
+        printf("UEFI Capsule enabled token is: %d\n", ret);
+        ret = query_token(CAPSULE_DIS_TOKEN, buffer);
+        printf("UEFI Capsule disabled token is: %d\n", ret);
+
+        /* activate UEFI capsule token if disabled */
+        if (ret) {
+                printf("Enabling UEFI capsule token");
+                if (activate_token(buffer, CAPSULE_EN_TOKEN)) {
+                        printf("activate failed\n");
+                        ret = -1;
+                        goto out;
+                }
+        }
+        ret = EXIT_SUCCESS;
+out:
+        free(buffer);
+        return ret;
+}