x86/microcode/intel: Improve microcode sanity-checking error messages

Turn them into proper sentences. Add comments to microcode_sanity_check() to
explain what it does.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1457345404-28884-5-git-send-email-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/cpu/microcode/intel_lib.c b/arch/x86/kernel/cpu/microcode/intel_lib.c
index ffb1bbf..23b1d92 100644 (file)
--- a/arch/x86/kernel/cpu/microcode/intel_lib.c
+++ b/arch/x86/kernel/cpu/microcode/intel_lib.c
@@ -57,15 +57,16 @@ int microcode_sanity_check(void *mc, int print_err)
 
        if (data_size + MC_HEADER_SIZE > total_size) {
                if (print_err)
-                       pr_err("error! Bad data size in microcode data file\n");
+                       pr_err("Error: bad microcode data file size.\n");
                return -EINVAL;
        }
 
        if (mc_header->ldrver != 1 || mc_header->hdrver != 1) {
                if (print_err)
-                       pr_err("error! Unknown microcode update format\n");
+                       pr_err("Error: invalid/unknown microcode update format.\n");
                return -EINVAL;
        }
+
        ext_table_size = total_size - (MC_HEADER_SIZE + data_size);
        if (ext_table_size) {
                u32 ext_table_sum = 0;
@@ -74,43 +75,58 @@ int microcode_sanity_check(void *mc, int print_err)
                if ((ext_table_size < EXT_HEADER_SIZE)
                 || ((ext_table_size - EXT_HEADER_SIZE) % EXT_SIGNATURE_SIZE)) {
                        if (print_err)
-                               pr_err("error! Small exttable size in microcode data file\n");
+                               pr_err("Error: truncated extended signature table.\n");
                        return -EINVAL;
                }
+
                ext_header = mc + MC_HEADER_SIZE + data_size;
                if (ext_table_size != exttable_size(ext_header)) {
                        if (print_err)
-                               pr_err("error! Bad exttable size in microcode data file\n");
+                               pr_err("Error: extended signature table size mismatch.\n");
                        return -EFAULT;
                }
+
                ext_sigcount = ext_header->count;
 
-               /* check extended table checksum */
+               /*
+                * Check extended table checksum: the sum of all dwords that
+                * comprise a valid table must be 0.
+                */
                ext_tablep = (u32 *)ext_header;
 
                i = ext_table_size / sizeof(u32);
                while (i--)
                        ext_table_sum += ext_tablep[i];
+
                if (ext_table_sum) {
                        if (print_err)
-                               pr_warn("aborting, bad extended signature table checksum\n");
+                               pr_warn("Bad extended signature table checksum, aborting.\n");
                        return -EINVAL;
                }
        }
 
-       /* calculate the checksum */
+       /*
+        * Calculate the checksum of update data and header. The checksum of
+        * valid update data and header including the extended signature table
+        * must be 0.
+        */
        orig_sum = 0;
        i = (MC_HEADER_SIZE + data_size) / sizeof(u32);
        while (i--)
                orig_sum += ((u32 *)mc)[i];
+
        if (orig_sum) {
                if (print_err)
-                       pr_err("aborting, bad checksum\n");
+                       pr_err("Bad microcode data checksum, aborting.\n");
                return -EINVAL;
        }
+
        if (!ext_table_size)
                return 0;
-       /* check extended signature checksum */
+
+       /*
+        * Check extended signature checksum: 0 => valid.
+        */
        for (i = 0; i < ext_sigcount; i++) {
                ext_sig = (void *)ext_header + EXT_HEADER_SIZE +
                          EXT_SIGNATURE_SIZE * i;
@@ -119,7 +135,7 @@ int microcode_sanity_check(void *mc, int print_err)
                        + (ext_sig->sig + ext_sig->pf + ext_sig->cksum);
                if (sum) {
                        if (print_err)
-                               pr_err("aborting, bad checksum\n");
+                               pr_err("Bad extended signature checksum, aborting.\n");
                        return -EINVAL;
                }
        }