dmi_scan: refactor dmi_scan_machine(), {smbios,dmi}_present()

Move the calls to memcpy_fromio() up into the loop in
dmi_scan_machine(), and move the signature checks back down into
dmi_decode().  We need to check at 16-byte intervals but keep a 32-byte
buffer for an SMBIOS entry, so shift the buffer after each iteration.

Merge smbios_present() into dmi_present(), so we look for an SMBIOS
signature at the beginning of the given buffer and then for a DMI
signature at an offset of 16 bytes.

[artem.savkov@gmail.com: use proper buf type in dmi_present()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Reported-by: Tim McGrath <tmhikaru@gmail.com>
Tested-by: Tim Mcgrath <tmhikaru@gmail.com>
Cc: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Signed-off-by: Artem Savkov <artem.savkov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 37 insertions, 43 deletions

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 98c62081c034..b95159b33c39 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -419,22 +419,45 @@ static void __init dmi_format_ids(char *buf, size_t len)
                             dmi_get_system_info(DMI_BIOS_DATE));
 }
 
-static int __init dmi_present(const char __iomem *p)
+static int __init dmi_present(const u8 *buf)
 {
-        u8 buf[15];
+        int smbios_ver;
 
-        memcpy_fromio(buf, p, 15);
-        if (dmi_checksum(buf, 15)) {
+        if (memcmp(buf, "_SM_", 4) == 0 &&
+            buf[5] < 32 && dmi_checksum(buf, buf[5])) {
+                smbios_ver = (buf[6] << 8) + buf[7];
+
+                /* Some BIOS report weird SMBIOS version, fix that up */
+                switch (smbios_ver) {
+                case 0x021F:
+                case 0x0221:
+                        pr_debug("SMBIOS version fixup(2.%d->2.%d)\n",
+                                 smbios_ver & 0xFF, 3);
+                        smbios_ver = 0x0203;
+                        break;
+                case 0x0233:
+                        pr_debug("SMBIOS version fixup(2.%d->2.%d)\n", 51, 6);
+                        smbios_ver = 0x0206;
+                        break;
+                }
+        } else {
+                smbios_ver = 0;
+        }
+
+        buf += 16;
+
+        if (memcmp(buf, "_DMI_", 5) == 0 && dmi_checksum(buf, 15)) {
                 dmi_num = (buf[13] << 8) | buf[12];
                 dmi_len = (buf[7] << 8) | buf[6];
                 dmi_base = (buf[11] << 24) | (buf[10] << 16) |
                         (buf[9] << 8) | buf[8];
 
                 if (dmi_walk_early(dmi_decode) == 0) {
-                        if (dmi_ver)
+                        if (smbios_ver) {
+                                dmi_ver = smbios_ver;
                                 pr_info("SMBIOS %d.%d present.\n",
                                        dmi_ver >> 8, dmi_ver & 0xFF);
-                        else {
+                        } else {
                                 dmi_ver = (buf[14] & 0xF0) << 4 |
                                            (buf[14] & 0x0F);
                                 pr_info("Legacy DMI %d.%d present.\n",
@@ -445,40 +468,14 @@ static int __init dmi_present(const char __iomem *p)
                         return 0;
                 }
         }
-        dmi_ver = 0;
-        return 1;
-}
 
-static int __init smbios_present(const char __iomem *p)
-{
-        u8 buf[32];
-
-        memcpy_fromio(buf, p, 32);
-        if ((buf[5] < 32) && dmi_checksum(buf, buf[5])) {
-                dmi_ver = (buf[6] << 8) + buf[7];
-
-                /* Some BIOS report weird SMBIOS version, fix that up */
-                switch (dmi_ver) {
-                case 0x021F:
-                case 0x0221:
-                        pr_debug("SMBIOS version fixup(2.%d->2.%d)\n",
-                               dmi_ver & 0xFF, 3);
-                        dmi_ver = 0x0203;
-                        break;
-                case 0x0233:
-                        pr_debug("SMBIOS version fixup(2.%d->2.%d)\n", 51, 6);
-                        dmi_ver = 0x0206;
-                        break;
-                }
-                return memcmp(p + 16, "_DMI_", 5) || dmi_present(p + 16);
-        }
         return 1;
 }
 
 void __init dmi_scan_machine(void)
 {
         char __iomem *p, *q;
-        int rc;
+        char buf[32];
 
         if (efi_enabled(EFI_CONFIG_TABLES)) {
                 if (efi.smbios == EFI_INVALID_TABLE_ADDR)
@@ -491,10 +488,10 @@ void __init dmi_scan_machine(void)
                 p = dmi_ioremap(efi.smbios, 32);
                 if (p == NULL)
                         goto error;
-
-                rc = smbios_present(p);
+                memcpy_fromio(buf, p, 32);
                 dmi_iounmap(p, 32);
-                if (!rc) {
+
+                if (!dmi_present(buf)) {
                         dmi_available = 1;
                         goto out;
                 }
@@ -509,18 +506,15 @@ void __init dmi_scan_machine(void)
                 if (p == NULL)
                         goto error;
 
+                memset(buf, 0, 16);
                 for (q = p; q < p + 0x10000; q += 16) {
-                        if (memcmp(q, "_SM_", 4) == 0 && q - p <= 0xFFE0)
-                                rc = smbios_present(q);
-                        else if (memcmp(q, "_DMI_", 5) == 0)
-                                rc = dmi_present(q);
-                        else
-                                continue;
-                        if (!rc) {
+                        memcpy_fromio(buf + 16, q, 16);
+                        if (!dmi_present(buf)) {
                                 dmi_available = 1;
                                 dmi_iounmap(p, 0x10000);
                                 goto out;
                         }
+                        memcpy(buf, buf + 16, 16);
                 }
                 dmi_iounmap(p, 0x10000);
         }