x86/microcode/intel: Reuse find_matching_signature()

IFS uses test images provided by Intel that can be regarded as firmware.
An IFS test image carries microcode header with an extended signature
table.

Reuse find_matching_signature() for verifying if the test image header
or the extended signature table indicate whether that image is fit to
run on a system.

No functional changes.
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20221117035935.4136738-6-jithu.joseph@intel.com

arch/x86/include/asm/cpu.h

@@ -95,5 +95,6 @@ static inline bool intel_cpu_signatures_match(unsigned int s1, unsigned int p1,
 }
 
 extern u64 x86_read_arch_cap_msr(void);
+int intel_find_matching_signature(void *mc, unsigned int csig, int cpf);
 
 #endif /* _ASM_X86_CPU_H */

arch/x86/kernel/cpu/intel.c

@@ -215,6 +215,35 @@ int intel_cpu_collect_info(struct ucode_cpu_info *uci)
 }
 EXPORT_SYMBOL_GPL(intel_cpu_collect_info);
 
+/*
+ * Returns 1 if update has been found, 0 otherwise.
+ */
+int intel_find_matching_signature(void *mc, unsigned int csig, int cpf)
+{
+	struct microcode_header_intel *mc_hdr = mc;
+	struct extended_sigtable *ext_hdr;
+	struct extended_signature *ext_sig;
+	int i;
+
+	if (intel_cpu_signatures_match(csig, cpf, mc_hdr->sig, mc_hdr->pf))
+		return 1;
+
+	/* Look for ext. headers: */
+	if (get_totalsize(mc_hdr) <= get_datasize(mc_hdr) + MC_HEADER_SIZE)
+		return 0;
+
+	ext_hdr = mc + get_datasize(mc_hdr) + MC_HEADER_SIZE;
+	ext_sig = (void *)ext_hdr + EXT_HEADER_SIZE;
+
+	for (i = 0; i < ext_hdr->count; i++) {
+		if (intel_cpu_signatures_match(csig, cpf, ext_sig->sig, ext_sig->pf))
+			return 1;
+		ext_sig++;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(intel_find_matching_signature);
+
 static void early_init_intel(struct cpuinfo_x86 *c)
 {
 	u64 misc_enable;

arch/x86/kernel/cpu/microcode/intel.c

@@ -45,34 +45,6 @@ static struct microcode_intel *intel_ucode_patch;
 /* last level cache size per core */
 static int llc_size_per_core;
 
-/*
- * Returns 1 if update has been found, 0 otherwise.
- */
-static int find_matching_signature(void *mc, unsigned int csig, int cpf)
-{
-	struct microcode_header_intel *mc_hdr = mc;
-	struct extended_sigtable *ext_hdr;
-	struct extended_signature *ext_sig;
-	int i;
-
-	if (intel_cpu_signatures_match(csig, cpf, mc_hdr->sig, mc_hdr->pf))
-		return 1;
-
-	/* Look for ext. headers: */
-	if (get_totalsize(mc_hdr) <= get_datasize(mc_hdr) + MC_HEADER_SIZE)
-		return 0;
-
-	ext_hdr = mc + get_datasize(mc_hdr) + MC_HEADER_SIZE;
-	ext_sig = (void *)ext_hdr + EXT_HEADER_SIZE;
-
-	for (i = 0; i < ext_hdr->count; i++) {
-		if (intel_cpu_signatures_match(csig, cpf, ext_sig->sig, ext_sig->pf))
-			return 1;
-		ext_sig++;
-	}
-	return 0;
-}
-
 /*
  * Returns 1 if update has been found, 0 otherwise.
  */
@@ -83,7 +55,7 @@ static int has_newer_microcode(void *mc, unsigned int csig, int cpf, int new_rev
 	if (mc_hdr->rev <= new_rev)
 		return 0;
 
-	return find_matching_signature(mc, csig, cpf);
+	return intel_find_matching_signature(mc, csig, cpf);
 }
 
 static struct ucode_patch *memdup_patch(void *data, unsigned int size)
@@ -117,7 +89,7 @@ static void save_microcode_patch(struct ucode_cpu_info *uci, void *data, unsigne
 		sig	     = mc_saved_hdr->sig;
 		pf	     = mc_saved_hdr->pf;
 
-		if (find_matching_signature(data, sig, pf)) {
+		if (intel_find_matching_signature(data, sig, pf)) {
 			prev_found = true;
 
 			if (mc_hdr->rev <= mc_saved_hdr->rev)
@@ -149,7 +121,7 @@ static void save_microcode_patch(struct ucode_cpu_info *uci, void *data, unsigne
 	if (!p)
 		return;
 
-	if (!find_matching_signature(p->data, uci->cpu_sig.sig, uci->cpu_sig.pf))
+	if (!intel_find_matching_signature(p->data, uci->cpu_sig.sig, uci->cpu_sig.pf))
 		return;
 
 	/*
@@ -286,8 +258,8 @@ scan_microcode(void *data, size_t size, struct ucode_cpu_info *uci, bool save)
 
 		size -= mc_size;
 
-		if (!find_matching_signature(data, uci->cpu_sig.sig,
-					     uci->cpu_sig.pf)) {
+		if (!intel_find_matching_signature(data, uci->cpu_sig.sig,
+						   uci->cpu_sig.pf)) {
 			data += mc_size;
 			continue;
 		}
@@ -652,9 +624,9 @@ static struct microcode_intel *find_patch(struct ucode_cpu_info *uci)
 		if (phdr->rev <= uci->cpu_sig.rev)
 			continue;
 
-		if (!find_matching_signature(phdr,
-					     uci->cpu_sig.sig,
-					     uci->cpu_sig.pf))
+		if (!intel_find_matching_signature(phdr,
+						   uci->cpu_sig.sig,
+						   uci->cpu_sig.pf))
 			continue;
 
 		return iter->data;