[cpu] Reimplement CPUID features as util::bitset

The cpu::cpu_id class no longer looks up all known features in the
constructor, but instead provides access to the map of supported
features as a bitset from the verify() method. It also exposes the
brand_name() method instead of loading the brand name string in the
constructor and storing it as part of the object.

src/boot/hardware.cpp

@@ -1,5 +1,6 @@
+#include <cpu/cpu_id.h>
+
 #include "console.h"
-#include "cpu/cpu_id.h"
 #include "error.h"
 #include "hardware.h"
 #include "status.h"
@@ -83,19 +84,21 @@ check_cpu_supported()
     status_line status {L"Checking CPU features"};
 
     cpu::cpu_id cpu;
-    uint64_t missing = cpu.missing();
-    if (missing) {
+    cpu::cpu_id::features features = cpu.validate();
+    bool supported = true;
+
 #define CPU_FEATURE_OPT(...)
 #define CPU_FEATURE_REQ(name, ...) \
-        if (!cpu.has_feature(cpu::feature::name)) { \
+    if (!features[cpu::feature::name]) { \
         status::fail(L"CPU required feature " L ## #name, uefi::status::unsupported); \
+        supported = false; \
     }
 #include "cpu/features.inc"
 #undef CPU_FEATURE_REQ
 #undef CPU_FEATURE_OPT
 
+    if (!supported)
         error::raise(uefi::status::unsupported, L"CPU not supported");
-    }
 }
 
 

src/kernel/cpu.cpp

@@ -1,6 +1,7 @@
 #include <new>
 #include <stdint.h>
 #include <string.h>
+#include <util/bitset.h>
 
 #include "assert.h"
 #include "cpu.h"
@@ -30,18 +31,23 @@ cpu_validate()
 {
     cpu::cpu_id cpu;
 
-    log::info(logs::boot, "CPU: %s", cpu.brand_name());
+    char brand_name[50];
+    cpu.brand_name(brand_name);
+
+    cpu::cpu_id::features features = cpu.validate();
+
+    log::info(logs::boot, "CPU: %s", brand_name);
     log::debug(logs::boot, "    Vendor is %s", cpu.vendor_id());
 
     log::debug(logs::boot, "    Higest basic CPUID: 0x%02x", cpu.highest_basic());
     log::debug(logs::boot, "    Higest ext CPUID:   0x%02x", cpu.highest_ext() & ~cpu::cpu_id::cpuid_extended);
 
 #define CPU_FEATURE_OPT(name, ...) \
-    log::debug(logs::boot, "    Supports %9s: %s", #name, cpu.has_feature(cpu::feature::name) ? "yes" : "no");
+    log::debug(logs::boot, "    Supports %9s: %s", #name, features[cpu::feature::name] ? "yes" : "no");
 
 #define CPU_FEATURE_REQ(name, feat_leaf, feat_sub, regname, bit) \
-    CPU_FEATURE_OPT(name, feat_leaf, feat_sub, regname, bit); \
-    kassert(cpu.has_feature(cpu::feature::name), "Missing required CPU feature " #name );
+    log::debug(logs::boot, "    Supports %9s: %s", #name, features[cpu::feature::name] ? "yes" : "no"); \
+    kassert(features[cpu::feature::name], "Missing required CPU feature " #name );
 
 #include "cpu/features.inc"
 #undef CPU_FEATURE_OPT

src/libraries/cpu/cpu.module

@@ -2,6 +2,7 @@
 
 module("cpu",
     kind = "lib",
+    deps = [ "util" ],
     sources = [
         "cpu_id.cpp",
     ],

src/libraries/cpu/cpu/cpu_id.h

@@ -2,6 +2,7 @@
 /// \file cpu_id.h Definition of required cpu features for jsix
 
 #include <stdint.h>
+#include <util/bitset.h>
 
 namespace cpu {
 
@@ -18,6 +19,7 @@ enum class feature {
 class cpu_id
 {
 public:
+    using features = util::bitset<(unsigned)feature::max>;
     static constexpr uint32_t cpuid_extended = 0x80000000;
 
     /// CPUID result register values
@@ -42,6 +44,10 @@ public:
 
     cpu_id();
 
+    /// Check which of the cpu::feature flags this CPU supports.
+    /// \returns  A util::bitset mapping to cpu::feature values
+    features validate() const;
+
     /// The the result of a given CPUID leaf/subleaf
     /// \arg leaf     The leaf selector (initial EAX)
     /// \arg subleaf  The subleaf selector (initial ECX)
@@ -54,8 +60,11 @@ public:
     /// Get the name of the cpu vendor (eg, "GenuineIntel")
     inline const char * vendor_id() const   { return m_vendor_id; }
 
-    /// Get the brand name of this processor model
-    inline const char * brand_name() const  { return m_brand_name; }
+    /// Put the brand name of this processor model into the
+    /// provided buffer.
+    /// \arg buffer  Pointer to a buffer at least 48 bytes long
+    /// \returns     True if the brand name was obtained
+    bool brand_name(char *buffer) const;
 
     /// Get the highest basic CPUID leaf supported
     inline uint32_t highest_basic() const   { return m_high_basic; }
@@ -63,22 +72,10 @@ public:
     /// Get the highest extended CPUID leaf supported
     inline uint32_t highest_ext() const     { return m_high_ext; }
 
-    /// Get which required options are missing as flags
-    inline uint64_t missing() const         { return m_missing; }
-
-    /// Validate the CPU supports the necessary options for jsix
-    inline bool supported() const           { return m_missing; }
-
-    /// Return true if the CPU claims to support the given feature
-    bool has_feature(feature feat);
-
 private:
     uint32_t m_high_basic;
     uint32_t m_high_ext;
-    uint64_t m_features;
-    uint64_t m_missing;
     char m_vendor_id[13];
-    char m_brand_name[48];
 };
 
 }

src/libraries/cpu/cpu_id.cpp

@@ -23,9 +23,7 @@ __cpuid(
     if (edx) *edx = d;
 }
 
-cpu_id::cpu_id() :
-    m_features {0},
-    m_missing {0}
+cpu_id::cpu_id()
 {
     __cpuid(0, 0,
         &m_high_basic,
@@ -34,46 +32,31 @@ cpu_id::cpu_id() :
         reinterpret_cast<uint32_t *>(&m_vendor_id[4]));
 
     __cpuid(cpuid_extended, 0, &m_high_ext);
+}
 
-    if (m_high_ext >= cpuid_extended + 4) {
-        __cpuid(cpuid_extended + 2, 0,
-            reinterpret_cast<uint32_t *>(&m_brand_name[0]),
-            reinterpret_cast<uint32_t *>(&m_brand_name[4]),
-            reinterpret_cast<uint32_t *>(&m_brand_name[8]),
-            reinterpret_cast<uint32_t *>(&m_brand_name[12]));
-        __cpuid(cpuid_extended + 3, 0,
-            reinterpret_cast<uint32_t *>(&m_brand_name[16]),
-            reinterpret_cast<uint32_t *>(&m_brand_name[20]),
-            reinterpret_cast<uint32_t *>(&m_brand_name[24]),
-            reinterpret_cast<uint32_t *>(&m_brand_name[28]));
-        __cpuid(cpuid_extended + 4, 0,
-            reinterpret_cast<uint32_t *>(&m_brand_name[32]),
-            reinterpret_cast<uint32_t *>(&m_brand_name[36]),
-            reinterpret_cast<uint32_t *>(&m_brand_name[40]),
-            reinterpret_cast<uint32_t *>(&m_brand_name[44]));
-    } else {
-        m_brand_name[0] = 0;
-    }
-
+cpu_id::features
+cpu_id::validate() const
+{
+    cpu_id::features feats;
     uint32_t leaf = -1u;
     uint32_t sub = -1u;
     regs r;
+
 #define CPU_FEATURE_OPT(name, feat_leaf, feat_sub, regname, bit) \
     if (leaf != feat_leaf || sub != feat_sub) { \
         leaf = feat_leaf; sub = feat_sub; r = get(leaf, sub); \
     } \
     if (r.regname & (1ull << bit)) \
-        m_features |= (1ull << static_cast<uint64_t>(feature::name)); \
+        feats.set(feature::name);
 
 #define CPU_FEATURE_REQ(name, feat_leaf, feat_sub, regname, bit) \
-    CPU_FEATURE_OPT(name, feat_leaf, feat_sub, regname, bit); \
-    if ((r.regname & (1ull << bit)) == 0) { \
-        m_missing |= (1ull << static_cast<uint64_t>(feature::name)); \
-    }
+    CPU_FEATURE_OPT(name, feat_leaf, feat_sub, regname, bit);
 
 #include "cpu/features.inc"
 #undef CPU_FEATURE_OPT
 #undef CPU_FEATURE_REQ
+
+    return feats;
 }
 
 cpu_id::regs
@@ -88,12 +71,6 @@ cpu_id::get(uint32_t leaf, uint32_t sub) const
     return ret;
 }
 
-bool
-cpu_id::has_feature(feature feat)
-{
-    return (m_features & (1 << static_cast<uint64_t>(feat))) != 0;
-}
-
 uint8_t
 cpu_id::local_apic_id() const
 {
@@ -103,4 +80,29 @@ cpu_id::local_apic_id() const
     return static_cast<uint8_t>(ebx >> 24);
 }
 
+bool
+cpu_id::brand_name(char *buffer) const
+{
+    if (m_high_ext < cpuid_extended + 4)
+        return false;
+
+    __cpuid(cpuid_extended + 2, 0,
+        reinterpret_cast<uint32_t *>(&buffer[0]),
+        reinterpret_cast<uint32_t *>(&buffer[4]),
+        reinterpret_cast<uint32_t *>(&buffer[8]),
+        reinterpret_cast<uint32_t *>(&buffer[12]));
+    __cpuid(cpuid_extended + 3, 0,
+        reinterpret_cast<uint32_t *>(&buffer[16]),
+        reinterpret_cast<uint32_t *>(&buffer[20]),
+        reinterpret_cast<uint32_t *>(&buffer[24]),
+        reinterpret_cast<uint32_t *>(&buffer[28]));
+    __cpuid(cpuid_extended + 4, 0,
+        reinterpret_cast<uint32_t *>(&buffer[32]),
+        reinterpret_cast<uint32_t *>(&buffer[36]),
+        reinterpret_cast<uint32_t *>(&buffer[40]),
+        reinterpret_cast<uint32_t *>(&buffer[44]));
+
+    return true;
+}
+
 }

src/libraries/util/util.module

@@ -9,6 +9,7 @@ module("util",
     public_headers = [
         "util/basic_types.h",
         "util/bip_buffer.h",
+        "util/bitset.h",
         "util/counted.h",
         "util/deque.h",
         "util/enum_bitfields.h",