S390X Support (#274)

* support for s390x

* added z15 T01, T02 model checking

* removed z15 checking

* removed empty strings

* added s390x unit tests

* added reference url for hwcaps

* moved documentation to S390XFeatures struct, updated copyright date, removed unused include statement

* changed num_processors to int

* removed newlines from test inputs

* scripts: Add bootlin s390x support

* cmake(ci): Add s390x support

* ci: Add s390x workflow

Co-authored-by: Marcos <marcos.araque.fiallos@ibm.com>
Co-authored-by: Corentin Le Molgat <corentinl@google.com>

11 files changed, 457 insertions, 1 deletions

diff --git a/.github/workflows/s390x_linux_cmake.yml b/.github/workflows/s390x_linux_cmake.yml
new file mode 100644
index 0000000..5be96a1
--- /dev/null
+++ b/.github/workflows/s390x_linux_cmake.yml
@@ -0,0 +1,27 @@
+name: s390x Linux CMake
+
+on:
+  push:
+  pull_request:
+  schedule:
+    # min hours day(month) month day(week)
+    - cron: '0 0 7,22 * *'
+
+jobs:
+  # Building using the github runner environement directly.
+  make:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        targets: [
+          [s390x],
+        ]
+      fail-fast: false
+    env:
+      TARGET: ${{ matrix.targets[0] }}
+    steps:
+    - uses: actions/checkout@v2
+    - name: Build
+      run: make --directory=cmake/ci ${TARGET}_build
+    - name: Test
+      run: make --directory=cmake/ci ${TARGET}_test
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 15d7aad..e2ffbe2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -49,6 +49,7 @@ set(PROCESSOR_IS_ARM FALSE)
 set(PROCESSOR_IS_AARCH64 FALSE)
 set(PROCESSOR_IS_X86 FALSE)
 set(PROCESSOR_IS_POWER FALSE)
+set(PROCESSOR_IS_S390X FALSE)
 
 if(CMAKE_SYSTEM_PROCESSOR MATCHES "^mips")
   set(PROCESSOR_IS_MIPS TRUE)
@@ -60,6 +61,8 @@ elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "(x86_64)|(AMD64|amd64)|(^i.86$)")
   set(PROCESSOR_IS_X86 TRUE)
 elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(powerpc|ppc)")
   set(PROCESSOR_IS_POWER TRUE)
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(s390x)")
+  set(PROCESSOR_IS_S390X TRUE)
 endif()
 
 macro(add_cpu_features_headers_and_sources HDRS_LIST_NAME SRCS_LIST_NAME)
@@ -79,6 +82,8 @@ macro(add_cpu_features_headers_and_sources HDRS_LIST_NAME SRCS_LIST_NAME)
       list(APPEND ${SRCS_LIST_NAME} ${PROJECT_SOURCE_DIR}/include/internal/windows_utils.h)
   elseif(PROCESSOR_IS_POWER)
       list(APPEND ${HDRS_LIST_NAME} ${PROJECT_SOURCE_DIR}/include/cpuinfo_ppc.h)
+  elseif(PROCESSOR_IS_S390X)
+      list(APPEND ${HDRS_LIST_NAME} ${PROJECT_SOURCE_DIR}/include/cpuinfo_s390x.h)
   else()
     message(FATAL_ERROR "Unsupported architectures ${CMAKE_SYSTEM_PROCESSOR}")
   endif()
diff --git a/cmake/ci/Makefile b/cmake/ci/Makefile
index dc19af8..b4ac3f1 100644
--- a/cmake/ci/Makefile
+++ b/cmake/ci/Makefile
@@ -50,6 +50,7 @@ help:
 	@echo -e "\t\t${BOLD}mips64${RESET} (codespace toolchain)"
 	@echo -e "\t\t${BOLD}mips32el${RESET} (codespace toolchain)"
 	@echo -e "\t\t${BOLD}mips64el${RESET} (codespace toolchain)"
+	@echo -e "\t\t${BOLD}s390x${RESET} (bootlin toolchain)"
 	@echo
 	@echo -e "\tWith ${BOLD}<toolchain_stage>${RESET}:"
 	@echo -e "\t\t${BOLD}env${RESET}"
@@ -145,7 +146,8 @@ $(clean_targets_amd64): clean_amd64_%:
 TOOLCHAIN_TARGETS = \
  arm-linux-gnueabihf armv8l-linux-gnueabihf arm-linux-gnueabi armeb-linux-gnueabihf armeb-linux-gnueabi \
  aarch64-linux-gnu aarch64_be-linux-gnu \
- mips32 mips32el mips64 mips64el
+ mips32 mips32el mips64 mips64el \
+ s390x
 TOOLCHAIN_STAGES = env devel build test
 define toolchain-stage-target =
 #$$(info STAGE: $1)
diff --git a/include/cpu_features_macros.h b/include/cpu_features_macros.h
index 09f8297..b759220 100644
--- a/include/cpu_features_macros.h
+++ b/include/cpu_features_macros.h
@@ -63,6 +63,10 @@
 #define CPU_FEATURES_ARCH_PPC
 #endif
 
+#if defined(__s390x__)
+#define CPU_FEATURES_ARCH_S390X
+#endif
+
 #if defined(__riscv)
 #define CPU_FEATURES_ARCH_RISCV
 #endif
diff --git a/include/cpuinfo_s390x.h b/include/cpuinfo_s390x.h
new file mode 100644
index 0000000..48864de
--- /dev/null
+++ b/include/cpuinfo_s390x.h
@@ -0,0 +1,108 @@
+// Copyright 2022 IBM
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CPU_FEATURES_INCLUDE_CPUINFO_S390X_H_
+#define CPU_FEATURES_INCLUDE_CPUINFO_S390X_H_
+
+#include "cpu_features_cache_info.h"
+#include "cpu_features_macros.h"
+
+CPU_FEATURES_START_CPP_NAMESPACE
+
+typedef struct {
+  int esan3: 1;     // instructions named N3, "backported" to esa-mode
+  int zarch: 1;     // z/Architecture mode active
+  int stfle: 1;     // store-facility-list-extended
+  int msa: 1;       // message-security assist
+  int ldisp: 1;     // long-displacement
+  int eimm: 1;      // extended-immediate
+  int dfp: 1;       // decimal floating point & perform floating point operation
+  int edat: 1;      // huge page support
+  int etf3eh: 1;    // extended-translation facility 3 enhancement
+  int highgprs: 1;  // 64-bit register support for 31-bit processes
+  int te: 1;        // transactional execution
+  int vx: 1;        // vector extension facility
+  int vxd: 1;       // vector-packed-decimal facility
+  int vxe: 1;       // vector-enhancement facility 1
+  int gs: 1;        // guarded-storage facility
+  int vxe2: 1;      // vector-enhancements facility 2
+  int vxp: 1;       // vector-packed-decimal-enhancement facility
+  int sort: 1;      // enhanced-sort facility
+  int dflt: 1;      // deflate-conversion facility
+  int vxp2: 1;      // vector-packed-decimal-enhancement facility 2
+  int nnpa: 1;      // neural network processing assist facility
+  int pcimio: 1;    // PCI mio facility
+  int sie: 1;       // virtualization support
+
+  // Make sure to update S390XFeaturesEnum below if you add a field here.
+} S390XFeatures;
+
+typedef struct {
+  S390XFeatures features;
+} S390XInfo;
+
+S390XInfo GetS390XInfo(void);
+
+typedef struct {
+  char platform[64];       // 0 terminated string
+} S390XPlatformTypeStrings;
+
+typedef struct {
+  int num_processors;      // -1 if N/A
+  S390XPlatformTypeStrings type;
+} S390XPlatformStrings;
+
+S390XPlatformStrings GetS390XPlatformStrings(void);
+
+////////////////////////////////////////////////////////////////////////////////
+// Introspection functions
+
+typedef enum {
+  S390_ESAN3,
+  S390_ZARCH,
+  S390_STFLE,
+  S390_MSA,
+  S390_LDISP,
+  S390_EIMM,
+  S390_DFP,
+  S390_EDAT,
+  S390_ETF3EH,
+  S390_HIGHGPRS,
+  S390_TE,
+  S390_VX,
+  S390_VXD,
+  S390_VXE,
+  S390_GS,
+  S390_VXE2,
+  S390_VXP,
+  S390_SORT,
+  S390_DFLT,
+  S390_VXP2,
+  S390_NNPA,
+  S390_PCIMIO,
+  S390_SIE,
+  S390X_LAST_,
+} S390XFeaturesEnum;
+
+int GetS390XFeaturesEnumValue(const S390XFeatures* features, S390XFeaturesEnum value);
+
+const char* GetS390XFeaturesEnumName(S390XFeaturesEnum);
+
+CPU_FEATURES_END_CPP_NAMESPACE
+
+#if !defined(CPU_FEATURES_ARCH_S390X)
+#error "Including cpuinfo_s390x.h from a non-s390x target."
+#endif
+
+#endif  // CPU_FEATURES_INCLUDE_CPUINFO_S390X_H_
diff --git a/include/internal/hwcaps.h b/include/internal/hwcaps.h
index f916b81..5030582 100644
--- a/include/internal/hwcaps.h
+++ b/include/internal/hwcaps.h
@@ -176,6 +176,34 @@ CPU_FEATURES_START_CPP_NAMESPACE
 #define PPC_FEATURE2_HTM_NO_SUSPEND 0x00080000
 #endif
 
+// https://elixir.bootlin.com/linux/v6.0-rc6/source/arch/s390/include/asm/elf.h
+#define HWCAP_S390_ESAN3        1
+#define HWCAP_S390_ZARCH        2
+#define HWCAP_S390_STFLE        4
+#define HWCAP_S390_MSA          8
+#define HWCAP_S390_LDISP        16
+#define HWCAP_S390_EIMM         32
+#define HWCAP_S390_DFP          64
+#define HWCAP_S390_HPAGE        128
+#define HWCAP_S390_ETF3EH       256
+#define HWCAP_S390_HIGH_GPRS    512
+#define HWCAP_S390_TE           1024
+#define HWCAP_S390_VX           2048
+#define HWCAP_S390_VXRS         HWCAP_S390_VX
+#define HWCAP_S390_VXD          4096
+#define HWCAP_S390_VXRS_BCD     HWCAP_S390_VXD
+#define HWCAP_S390_VXE          8192
+#define HWCAP_S390_VXRS_EXT     HWCAP_S390_VXE
+#define HWCAP_S390_GS           16384
+#define HWCAP_S390_VXRS_EXT2    32768
+#define HWCAP_S390_VXRS_PDE     65536
+#define HWCAP_S390_SORT         131072
+#define HWCAP_S390_DFLT         262144
+#define HWCAP_S390_VXRS_PDE2    524288
+#define HWCAP_S390_NNPA         1048576
+#define HWCAP_S390_PCI_MIO      2097152
+#define HWCAP_S390_SIE          4194304
+
 // https://elixir.bootlin.com/linux/latest/source/arch/riscv/include/uapi/asm/hwcap.h
 #define RISCV_HWCAP_A (1UL << ('A' - 'A'))
 #define RISCV_HWCAP_C (1UL << ('C' - 'A'))
diff --git a/scripts/run_integration.sh b/scripts/run_integration.sh
index 645cb6a..10a0968 100755
--- a/scripts/run_integration.sh
+++ b/scripts/run_integration.sh
@@ -140,6 +140,62 @@ QEMU_ARGS+=( -L "${SYSROOT_DIR}" )
 QEMU_ARGS+=( -E LD_LIBRARY_PATH=/lib )
 }
 
+function expand_bootlin_config() {
+  # ref: https://toolchains.bootlin.com/
+  local -r GCC_DIR=${ARCHIVE_DIR}/${GCC_RELATIVE_DIR}
+
+  case "${TARGET}" in
+    "s390x")
+      local -r POWER_URL="https://toolchains.bootlin.com/downloads/releases/toolchains/s390x-z13/tarballs/s390x-z13--glibc--stable-2022.08-1.tar.bz2"
+      local -r GCC_PREFIX="s390x"
+      ;;
+    *)
+      >&2 echo 'unknown power platform'
+      exit 1 ;;
+  esac
+
+  local -r POWER_RELATIVE_DIR="${TARGET}"
+  unpack "${POWER_URL}" "${POWER_RELATIVE_DIR}"
+  local -r EXTRACT_DIR="${ARCHIVE_DIR}/$(basename ${POWER_URL%.tar.bz2})"
+
+  local -r POWER_DIR=${ARCHIVE_DIR}/${POWER_RELATIVE_DIR}
+  if [[ -d "${EXTRACT_DIR}" ]]; then
+    mv "${EXTRACT_DIR}" "${POWER_DIR}"
+  fi
+
+  local -r SYSROOT_DIR="${POWER_DIR}/${GCC_PREFIX}-buildroot-linux-gnu/sysroot"
+  #local -r STAGING_DIR=${SYSROOT_DIR}-stage
+
+  # Write a Toolchain file
+  # note: This is manadatory to use a file in order to have the CMake variable
+  # 'CMAKE_CROSSCOMPILING' set to TRUE.
+  # ref: https://cmake.org/cmake/help/latest/manual/cmake-toolchains.7.html#cross-compiling-for-linux
+  cat >"${TOOLCHAIN_FILE}" <<EOL
+set(CMAKE_SYSTEM_NAME Linux)
+set(CMAKE_SYSTEM_PROCESSOR ${GCC_PREFIX})
+
+set(CMAKE_SYSROOT ${SYSROOT_DIR})
+#set(CMAKE_STAGING_PREFIX ${STAGING_DIR})
+
+set(tools ${POWER_DIR})
+
+set(CMAKE_C_COMPILER \${tools}/bin/${GCC_PREFIX}-linux-gcc)
+set(CMAKE_C_FLAGS "${POWER_FLAGS}")
+set(CMAKE_CXX_COMPILER \${tools}/bin/${GCC_PREFIX}-linux-g++)
+set(CMAKE_CXX_FLAGS "${POWER_FLAGS} -L${SYSROOT_DIR}/lib")
+
+set(CMAKE_FIND_ROOT_PATH ${POWER_DIR})
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
+EOL
+
+CMAKE_ADDITIONAL_ARGS+=( -DCMAKE_TOOLCHAIN_FILE="${TOOLCHAIN_FILE}" )
+QEMU_ARGS+=( -L "${SYSROOT_DIR}" )
+QEMU_ARGS+=( -E LD_PRELOAD="${SYSROOT_DIR}/usr/lib/libstdc++.so.6:${SYSROOT_DIR}/lib/libgcc_s.so.1" )
+}
+
 function expand_codescape_config() {
   # ref: https://codescape.mips.com/components/toolchain/2020.06-01/downloads.html
   # ref: https://codescape.mips.com/components/toolchain/2019.02-04/downloads.html
@@ -269,6 +325,7 @@ DESCRIPTION
 \t\tarmeb-linux-gnueabihf armeb-linux-gnueabi
 \t\tmips32 mips32el
 \t\tmips64 mips64el
+\t\ts390x (bootlin)
 
 OPTIONS
 \t-h --help: show this help text
@@ -339,6 +396,9 @@ function main() {
     mips64el)
       expand_codescape_config
       declare -r QEMU_ARCH=mips64el ;;
+    s390x)
+      expand_bootlin_config
+      declare -r QEMU_ARCH=s390x ;;
     *)
       >&2 echo "Unknown TARGET '${TARGET}'..."
       exit 1 ;;
diff --git a/src/impl_s390x_linux.c b/src/impl_s390x_linux.c
new file mode 100644
index 0000000..2b8b865
--- /dev/null
+++ b/src/impl_s390x_linux.c
@@ -0,0 +1,120 @@
+// Copyright 2022 IBM.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "cpu_features_macros.h"
+
+#ifdef CPU_FEATURES_ARCH_S390X
+#ifdef CPU_FEATURES_OS_LINUX
+
+#include "cpuinfo_s390x.h"
+
+////////////////////////////////////////////////////////////////////////////////
+// Definitions for introspection.
+////////////////////////////////////////////////////////////////////////////////
+#define INTROSPECTION_TABLE                                                    \
+  LINE(S390_ESAN3, esan3, "esan3", HWCAP_S390_ESAN3, 0)                              \
+  LINE(S390_ZARCH, zarch, "zarch", HWCAP_S390_ZARCH, 0)                              \
+  LINE(S390_STFLE, stfle, "stfle", HWCAP_S390_STFLE, 0)                              \
+  LINE(S390_MSA, msa, "msa", HWCAP_S390_MSA, 0)                                      \
+  LINE(S390_LDISP, ldisp, "ldisp", HWCAP_S390_LDISP, 0)                              \
+  LINE(S390_EIMM, eimm, "eimm", HWCAP_S390_EIMM, 0)                                  \
+  LINE(S390_DFP, dfp, "dfp", HWCAP_S390_DFP, 0)                                      \
+  LINE(S390_EDAT, edat, "edat", HWCAP_S390_HPAGE, 0)                                 \
+  LINE(S390_ETF3EH, etf3eh, "etf3eh", HWCAP_S390_ETF3EH, 0)                          \
+  LINE(S390_HIGHGPRS, highgprs, "highgprs", HWCAP_S390_HIGH_GPRS, 0)                 \
+  LINE(S390_TE, te, "te", HWCAP_S390_TE, 0)                                          \
+  LINE(S390_VX, vx, "vx", HWCAP_S390_VXRS, 0)                                        \
+  LINE(S390_VXD, vxd, "vxd", HWCAP_S390_VXRS_BCD, 0)                                 \
+  LINE(S390_VXE, vxe, "vxe", HWCAP_S390_VXRS_EXT, 0)                                 \
+  LINE(S390_GS, gs, "gs", HWCAP_S390_GS, 0)                                          \
+  LINE(S390_VXE2, vxe2, "vxe2", HWCAP_S390_VXRS_EXT2, 0)                             \
+  LINE(S390_VXP, vxp, "vxp", HWCAP_S390_VXRS_PDE, 0)                                 \
+  LINE(S390_SORT, sort, "sort", HWCAP_S390_SORT, 0)                                  \
+  LINE(S390_DFLT, dflt, "dflt", HWCAP_S390_DFLT, 0)                                  \
+  LINE(S390_VXP2, vxp2, "vxp2", HWCAP_S390_VXRS_PDE2, 0)                             \
+  LINE(S390_NNPA, nnpa, "nnpa", HWCAP_S390_NNPA, 0)                                  \
+  LINE(S390_PCIMIO, pcimio, "pcimio", HWCAP_S390_PCI_MIO, 0)                         \
+  LINE(S390_SIE, sie, "sie", HWCAP_S390_SIE, 0)
+#define INTROSPECTION_PREFIX S390X
+#define INTROSPECTION_ENUM_PREFIX S390X
+#include "define_introspection_and_hwcaps.inl"
+
+////////////////////////////////////////////////////////////////////////////////
+// Implementation.
+////////////////////////////////////////////////////////////////////////////////
+
+#include <stdbool.h>
+
+#include "internal/bit_utils.h"
+#include "internal/filesystem.h"
+#include "internal/hwcaps.h"
+#include "internal/stack_line_reader.h"
+#include "internal/string_view.h"
+
+static bool HandleS390XLine(const LineResult result,
+                          S390XPlatformStrings* const strings) {
+  StringView line = result.line;
+  StringView key, value;
+  if (CpuFeatures_StringView_GetAttributeKeyValue(line, &key, &value)) {
+    if (CpuFeatures_StringView_IsEquals(key, str("# processors"))) {
+        strings->num_processors = CpuFeatures_StringView_ParsePositiveNumber(value);
+    }
+  }
+  return !result.eof;
+}
+
+static void FillProcCpuInfoData(S390XPlatformStrings* const strings) {
+  const int fd = CpuFeatures_OpenFile("/proc/cpuinfo");
+  if (fd >= 0) {
+    StackLineReader reader;
+    StackLineReader_Initialize(&reader, fd);
+    for (;;) {
+      if (!HandleS390XLine(StackLineReader_NextLine(&reader), strings)) {
+        break;
+      }
+    }
+    CpuFeatures_CloseFile(fd);
+  }
+}
+
+static const S390XInfo kEmptyS390XInfo;
+
+S390XInfo GetS390XInfo(void) {
+  S390XInfo info = kEmptyS390XInfo;
+  const HardwareCapabilities hwcaps = CpuFeatures_GetHardwareCapabilities();
+  for (size_t i = 0; i < S390X_LAST_; ++i) {
+    if (CpuFeatures_IsHwCapsSet(kHardwareCapabilities[i], hwcaps)) {
+      kSetters[i](&info.features, true);
+    }
+  }
+  return info;
+}
+
+static const S390XPlatformStrings kEmptyS390XPlatformStrings;
+
+S390XPlatformStrings GetS390XPlatformStrings(void) {
+  S390XPlatformStrings strings = kEmptyS390XPlatformStrings;
+  const char* platform = CpuFeatures_GetPlatformPointer();
+
+  FillProcCpuInfoData(&strings);
+
+  if (platform != NULL)
+    CpuFeatures_StringView_CopyString(str(platform), strings.type.platform,
+                                      sizeof(strings.type.platform));
+
+  return strings;
+}
+
+#endif  // CPU_FEATURES_OS_LINUX
+#endif  // CPU_FEATURES_ARCH_S390X
diff --git a/src/utils/list_cpu_features.c b/src/utils/list_cpu_features.c
index 4d7fe14..b280f69 100644
--- a/src/utils/list_cpu_features.c
+++ b/src/utils/list_cpu_features.c
@@ -35,6 +35,8 @@
 #include "cpuinfo_mips.h"
 #elif defined(CPU_FEATURES_ARCH_PPC)
 #include "cpuinfo_ppc.h"
+#elif defined(CPU_FEATURES_ARCH_S390X)
+#include "cpuinfo_s390x.h"
 #endif
 
 // Design principles
@@ -205,6 +207,9 @@ DEFINE_ADD_FLAGS(GetMipsFeaturesEnumValue, GetMipsFeaturesEnumName,
 #elif defined(CPU_FEATURES_ARCH_PPC)
 DEFINE_ADD_FLAGS(GetPPCFeaturesEnumValue, GetPPCFeaturesEnumName, PPCFeatures,
                  PPC_LAST_)
+#elif defined(CPU_FEATURES_ARCH_S390X)
+DEFINE_ADD_FLAGS(GetS390XFeaturesEnumValue, GetS390XFeaturesEnumName, S390XFeatures,
+                 S390X_LAST_)
 #endif
 
 // Prints a json string with characters escaping.
@@ -408,6 +413,14 @@ static Node* CreateTree(void) {
   AddMapEntry(root, "microarchitecture",
               CreateString(strings.type.base_platform));
   AddFlags(root, &info.features);
+#elif defined(CPU_FEATURES_ARCH_S390X)
+  const S390XInfo info = GetS390XInfo();
+  const S390XPlatformStrings strings = GetS390XPlatformStrings();
+  AddMapEntry(root, "arch", CreateString("s390x"));
+  AddMapEntry(root, "platform", CreateString("zSeries"));
+  AddMapEntry(root, "model", CreateString(strings.type.platform));
+  AddMapEntry(root, "# processors", CreateInt(strings.num_processors));
+  AddFlags(root, &info.features);
 #endif
   return root;
 }
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 8e8f72a..a87d18a 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -89,3 +89,10 @@ if(PROCESSOR_IS_POWER)
   target_link_libraries(cpuinfo_ppc_test all_libraries)
   add_test(NAME cpuinfo_ppc_test COMMAND cpuinfo_ppc_test)
 endif()
+##------------------------------------------------------------------------------
+## cpuinfo_s390x_test
+if(PROCESSOR_IS_S390X)
+  add_executable(cpuinfo_s390x_test cpuinfo_s390x_test.cc  ../src/impl_s390x_linux.c)
+  target_link_libraries(cpuinfo_s390x_test all_libraries)
+  add_test(NAME cpuinfo_s390x_test COMMAND cpuinfo_s390x_test)
+endif()
diff --git a/test/cpuinfo_s390x_test.cc b/test/cpuinfo_s390x_test.cc
new file mode 100644
index 0000000..800d3e9
--- /dev/null
+++ b/test/cpuinfo_s390x_test.cc
@@ -0,0 +1,82 @@
+// Copyright 2022 IBM.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "cpuinfo_s390x.h"
+#include "filesystem_for_testing.h"
+#include "gtest/gtest.h"
+#include "hwcaps_for_testing.h"
+
+namespace cpu_features {
+namespace {
+
+TEST(CpustringsS390XTest, S390XFeaturesEnum) {
+   const char *last_name = GetS390XFeaturesEnumName(S390X_LAST_);
+   EXPECT_STREQ(last_name, "unknown_feature");
+   for (int i = static_cast<int>(S390_ZARCH); i != static_cast<int>(S390X_LAST_); ++i) {
+      const auto feature = static_cast<S390XFeaturesEnum>(i);
+      const char *name = GetS390XFeaturesEnumName(feature);
+      ASSERT_FALSE(name == nullptr);
+      EXPECT_STRNE(name, "");
+      EXPECT_STRNE(name, last_name);
+   }
+}
+
+TEST(CpustringsS390XTest, FromHardwareCap) {
+  ResetHwcaps();
+  SetHardwareCapabilities(HWCAP_S390_ESAN3 | HWCAP_S390_HPAGE |
+          HWCAP_S390_NNPA | HWCAP_S390_SIE, 0);
+  GetEmptyFilesystem();  // disabling /proc/cpuinfo
+  const auto info = GetS390XInfo();
+  EXPECT_TRUE(info.features.esan3);
+  EXPECT_TRUE(info.features.edat);
+  EXPECT_TRUE(info.features.nnpa);
+  EXPECT_TRUE(info.features.sie);
+  EXPECT_FALSE(info.features.msa);
+  EXPECT_FALSE(info.features.stfle);
+  EXPECT_FALSE(info.features.vxp2);
+  EXPECT_FALSE(info.features.pcimio);
+}
+
+TEST(CpustringsS390XTest, z16) {
+  ResetHwcaps();
+  auto& fs = GetEmptyFilesystem();
+  fs.CreateFile("/proc/cpuinfo",
+                R"(vendor_id       : IBM/S390
+# processors    : 24
+bogomips per cpu: 26315.00
+max thread id   : 1
+features	: esan3 zarch stfle msa ldisp eimm dfp edat etf3eh highgprs te vx vxd vxe gs vxe2 vxp sort dflt vxp2 nnpa pcimio sie )");
+  SetPlatformPointer("z16");
+  const auto strings = GetS390XPlatformStrings();
+  EXPECT_EQ(strings.num_processors, 24);
+  ASSERT_STREQ(strings.type.platform, "z16");
+}
+
+TEST(CpustringsS390XTest, z15) {
+  ResetHwcaps();
+  auto& fs = GetEmptyFilesystem();
+  fs.CreateFile("/proc/cpuinfo",
+                R"(vendor_id       : IBM/S390
+# processors    : 2
+bogomips per cpu: 24038.00
+max thread id   : 1
+features    : esan3 zarch stfle msa ldisp eimm dfp edat etf3eh highgprs te vx vxd vxe gs vxe2 vxp sort dflt sie)");
+  SetPlatformPointer("z15");
+  const auto strings = GetS390XPlatformStrings();
+  EXPECT_EQ(strings.num_processors, 2);
+  ASSERT_STREQ(strings.type.platform, "z15");
+}
+
+}  // namespace
+}  // namespace cpu_features