arm64: Provide "model name" in /proc/cpuinfo for PER_LINUX32 tasks

commit e47b020a upstream.

This patch brings the PER_LINUX32 /proc/cpuinfo format more in line with
the 32-bit ARM one by providing an additional line:

model name      : ARMv8 Processor rev X (v8l)
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
[bwh: Backported to 3.16:
 - Adjust filename, context
 - Open-code MIDR_REVISION()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

arch/arm64/include/asm/elf.h

@@ -161,14 +161,14 @@ struct mm_struct;
 extern unsigned long arch_randomize_brk(struct mm_struct *mm);
 #define arch_randomize_brk arch_randomize_brk
 
-#ifdef CONFIG_COMPAT
-
 #ifdef __AARCH64EB__
 #define COMPAT_ELF_PLATFORM		("v8b")
 #else
 #define COMPAT_ELF_PLATFORM		("v8l")
 #endif
 
+#ifdef CONFIG_COMPAT
+
 #define COMPAT_ELF_ET_DYN_BASE		(randomize_et_dyn(2 * TASK_SIZE_32 / 3))
 
 /* AArch32 registers. */

arch/arm64/kernel/setup.c

@@ -44,6 +44,8 @@
 #include <linux/of_platform.h>
 #include <linux/efi.h>
 #include <linux/personality.h>
+#include <linux/compat.h>
+#include <linux/elf.h>
 
 #include <asm/fixmap.h>
 #include <asm/cputype.h>
@@ -489,6 +491,7 @@ static const char *compat_hwcap_str[] = {
 static int c_show(struct seq_file *m, void *v)
 {
 	int i, j;
+	bool compat = personality(current->personality) == PER_LINUX32;
 
 	for_each_online_cpu(i) {
 		struct cpuinfo_arm64 *cpuinfo = &per_cpu(cpu_data, i);
@@ -500,6 +503,9 @@ static int c_show(struct seq_file *m, void *v)
 		 * "processor".  Give glibc what it expects.
 		 */
 #ifdef CONFIG_SMP
+		if (compat)
+			seq_printf(m, "model name\t: ARMv8 Processor rev %d (%s)\n",
+				   midr & 0xf, COMPAT_ELF_PLATFORM);
 		seq_printf(m, "processor\t: %d\n", i);
 #endif
 
@@ -514,7 +520,7 @@ static int c_show(struct seq_file *m, void *v)
 		 * software which does already (at least for 32-bit).
 		 */
 		seq_puts(m, "Features\t:");
-		if (personality(current->personality) == PER_LINUX32) {
+		if (compat) {
 #ifdef CONFIG_COMPAT
 			for (j = 0; compat_hwcap_str[j]; j++)
 				if (compat_elf_hwcap & (1 << j))