[PATCH 2/2] ntdll: Populate the ARM64 processor ID register registry keys.

[Billy Laws]

From: Billy Laws

Takes advantage of linux's ID register emulation. The msr instruction is
manually assembled to support older compilers and those that disallow
reading e.g. SVE ID registers if unsupported by the target, even though
they RAZ if unsupported.
---
 dlls/ntdll/unix/system.c | 95 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/dlls/ntdll/unix/system.c b/dlls/ntdll/unix/system.c
index f87c9b09124..eadf5a61e31 100644
--- a/dlls/ntdll/unix/system.c
+++ b/dlls/ntdll/unix/system.c
@@ -1309,6 +1309,96 @@ static void init_tsc_frequency(void)

#endif

+#ifdef __aarch64__
+#ifdef linux
+
+static NTSTATUS fill_arm64_id_reg_keys(void)
+{
+    static const char processor_key[] = "\Registry\Machine\Hardware\Description\System\CentralProcessor\%u";
+    static const char midr_el1_path[] = "/sys/devices/system/cpu/cpu%u/regs/identification/midr_el1";
+    static const char reg_value_name[] = "CP %04X";
+    NTSTATUS status = STATUS_SUCCESS;
+    OBJECT_ATTRIBUTES attr;
+    UNICODE_STRING name;
+    WCHAR bufferW[256];
+    char buffer[256];
+    unsigned int i;
+
+    InitializeObjectAttributes( &attr, &name, OBJ_CASE_INSENSITIVE, 0, NULL );
+    for (i = 0; i < peb->NumberOfProcessors; i++)
+    {
+        unsigned long long value;
+        HANDLE key;
+        FILE *fp;
+
+        snprintf( buffer, sizeof(buffer), processor_key, i );
+        ascii_to_unicode( bufferW, buffer, strlen(buffer) + 1 );
+        init_unicode_string( &name, bufferW );
+        if ((status = create_key_recursive( &key, KEY_ALL_ACCESS, &attr, 0, NULL, REG_OPTION_VOLATILE, NULL )))
+            return status;
+
+        /* MIDR_EL1 can vary across cores, so read it from sysfs. */
+        snprintf( buffer, sizeof(buffer), midr_el1_path, i );
+        if ((fp = fopen( buffer, "r" )))
+        {
+            fscanf( fp, "%llx", &value );
+            fclose( fp );
+            snprintf( buffer, sizeof(buffer), reg_value_name, 0x4000 );
+            ascii_to_unicode( bufferW, buffer, strlen(buffer) + 1 );
+            init_unicode_string( &name, bufferW );
+            NtSetValueKey( key, &name, 0, REG_QWORD, &value, sizeof(value) );
+        }
+
+#define STR(a) #a
+#define READ_ID_REG(reg_id) \
+    snprintf( buffer, sizeof(buffer), reg_value_name, reg_id ); \
+    ascii_to_unicode( bufferW, buffer, strlen(buffer) + 1 ); \
+    init_unicode_string( &name, bufferW ); \
+    /* mrs x0, #reg_id */ \
+    __asm__ __volatile__( ".inst " STR(0xd5300000 | reg_id << 5) "\n\t" \
+                          "mov %0, x0" : "=r"(value) :: "x0" ); \
+    NtSetValueKey( key, &name, 0, REG_QWORD, &value, sizeof(UINT64) )
+
+        /* Linux traps reads to these ID registers and emulates them. They do not vary across cores,
+         * if the kernel doesn't support a specific ID register it will read as zero. */
+        READ_ID_REG( 0x4020 ); /* ID_AA64PFR0_EL1 */
+        READ_ID_REG( 0x4021 ); /* ID_AA64PFR1_EL1 */
+        READ_ID_REG( 0x4024 ); /* ID_AA64ZFR0_EL1 */
+        READ_ID_REG( 0x4025 ); /* ID_AA64SMFR0_EL1 */
+        READ_ID_REG( 0x4028 ); /* ID_AA64DFR0_EL1 */
+        READ_ID_REG( 0x4029 ); /* ID_AA64DFR1_EL1 */
+        READ_ID_REG( 0x402C ); /* ID_AA64AFR0_EL1 */
+        READ_ID_REG( 0x402D ); /* ID_AA64AFR1_EL1 */
+        READ_ID_REG( 0x4030 ); /* ID_AA64ISAR0_EL1 */
+        READ_ID_REG( 0x4031 ); /* ID_AA64ISAR1_EL1 */
+        READ_ID_REG( 0x4032 ); /* ID_AA64ISAR2_EL1 */
+        READ_ID_REG( 0x4038 ); /* ID_AA64MMFR0_EL1 */
+        READ_ID_REG( 0x4039 ); /* ID_AA64MMFR1_EL1 */
+        READ_ID_REG( 0x403A ); /* ID_AA64MMFR2_EL1 */
+        READ_ID_REG( 0x5801 ); /* CTR_EL0 */
+        /* Windows also creates keys for SCTLR_EL1, ACTLR_EL1, TTBR0_EL1 and MAIR_EL1, but these are
+         * inaccessible under linux so leave them unpopulated. */
+
+#undef READ_ID_REG
+#undef STR
+        NtClose( key );
+    }
+
+    return status;
+}
+
+#else
+
+static void fill_arm64_id_reg_keys(void)
+{
+    FIXME("stub\n");
+    return STATUS_NOT_IMPLEMENTED;
+}
+
+#endif
+#endif
+
+
 /******************************************************************
  *		init_cpu_info
  *
@@ -1368,6 +1458,11 @@ void init_cpu_info(void)
         logical_proc_info_ex_alloc_size = logical_proc_info_ex_size;
     }
     init_tsc_frequency();
+
+#ifdef __aarch64__
+    if ((status = fill_arm64_id_reg_keys()))
+        ERR( "Failed to populate ARM64 ID register registry keys, status %#x.\n", status );
+#endif
 }

static NTSTATUS create_cpuset_info(SYSTEM_CPU_SET_INFORMATION *info)