Port Mono to Raspberry Pi, ship as new linux-armv6 RID (#62594)

* Initial ARMv6 arch addition. Builds mono runtime, not CoreCLR (Mono already supports the CPU arch subset used by Raspberry Pi, whilst porting CoreCLR to e.g. VFPv2 would be major work)
* Build small clr subset on ARMv6, it's needed for SDK and we want to check it works

7 files changed, 51 insertions, 7 deletions

diff --git a/eng/native/build-commons.sh b/eng/native/build-commons.sh
index 373091b13a0..294e9832ad3 100755
--- a/eng/native/build-commons.sh
+++ b/eng/native/build-commons.sh
@@ -197,7 +197,7 @@ usage()
     echo ""
     echo "Common Options:"
     echo ""
-    echo "BuildArch can be: -arm, -armel, -arm64, -loongarch64, -s390x, x64, x86, -wasm"
+    echo "BuildArch can be: -arm, -armv6, -armel, -arm64, -loongarch64, -s390x, x64, x86, -wasm"
     echo "BuildType can be: -debug, -checked, -release"
     echo "-os: target OS (defaults to running OS)"
     echo "-bindir: output directory (defaults to $__ProjectRoot/artifacts)"
@@ -270,6 +270,10 @@ while :; do
             __BuildArch=arm
             ;;
 
+        armv6|-armv6)
+            __BuildArch=armv6
+            ;;
+
         arm64|-arm64)
             __BuildArch=arm64
             ;;
diff --git a/eng/native/configurecompiler.cmake b/eng/native/configurecompiler.cmake
index fad1ac58d39..b67594cb60f 100644
--- a/eng/native/configurecompiler.cmake
+++ b/eng/native/configurecompiler.cmake
@@ -213,6 +213,9 @@ elseif (CLR_CMAKE_HOST_ARCH_I386)
 elseif (CLR_CMAKE_HOST_ARCH_ARM)
   set(ARCH_HOST_NAME arm)
   add_definitions(-DHOST_ARM)
+elseif (CLR_CMAKE_HOST_ARCH_ARMV6)
+  set(ARCH_HOST_NAME armv6)
+  add_definitions(-DHOST_ARMV6)
 elseif (CLR_CMAKE_HOST_ARCH_ARM64)
   set(ARCH_HOST_NAME arm64)
   add_definitions(-DHOST_ARM64 -DHOST_64BIT)
@@ -238,6 +241,8 @@ if (CLR_CMAKE_HOST_UNIX)
       message("Detected Linux x86_64")
     elseif(CLR_CMAKE_HOST_UNIX_ARM)
       message("Detected Linux ARM")
+    elseif(CLR_CMAKE_HOST_UNIX_ARMV6)
+      message("Detected Linux ARMv6")
     elseif(CLR_CMAKE_HOST_UNIX_ARM64)
       message("Detected Linux ARM64")
     elseif(CLR_CMAKE_HOST_UNIX_LOONGARCH64)
@@ -301,6 +306,12 @@ elseif (CLR_CMAKE_TARGET_ARCH_ARM)
     set(ARCH_TARGET_NAME arm)
     add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_ARCH>>>:TARGET_ARM>)
     add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_ARCH>>>:TARGET_32BIT>)
+elseif (CLR_CMAKE_TARGET_ARCH_ARMV6)
+    set(ARCH_SOURCES_DIR arm)
+    set(ARCH_TARGET_NAME armv6)
+    add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_ARCH>>>:TARGET_ARM>)
+    add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_ARCH>>>:TARGET_ARMV6>)
+    add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_ARCH>>>:TARGET_32BIT>)
 elseif (CLR_CMAKE_TARGET_ARCH_I386)
     set(ARCH_TARGET_NAME x86)
     set(ARCH_SOURCES_DIR i386)
@@ -507,6 +518,14 @@ if(CLR_CMAKE_HOST_UNIX_ARM)
    endif(ARM_SOFTFP)
 endif(CLR_CMAKE_HOST_UNIX_ARM)
 
+if(CLR_CMAKE_HOST_UNIX_ARMV6)
+   add_compile_options(-mfpu=vfp)
+   add_definitions(-DCLR_ARM_FPU_CAPABILITY=0x0)
+   add_compile_options(-march=armv6zk)
+   add_compile_options(-mcpu=arm1176jzf-s)
+   add_compile_options(-mfloat-abi=hard)
+endif(CLR_CMAKE_HOST_UNIX_ARMV6)
+
 if(CLR_CMAKE_HOST_UNIX_X86)
   add_compile_options(-msse2)
 endif()
diff --git a/eng/native/configureplatform.cmake b/eng/native/configureplatform.cmake
index cdf33430b49..ecf10a8d4c3 100644
--- a/eng/native/configureplatform.cmake
+++ b/eng/native/configureplatform.cmake
@@ -41,6 +41,8 @@ if(CLR_CMAKE_HOST_OS STREQUAL Linux)
             set(CLR_CMAKE_HOST_UNIX_ARMV7L 1)
         elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL arm OR CMAKE_SYSTEM_PROCESSOR STREQUAL armv7-a)
             set(CLR_CMAKE_HOST_UNIX_ARM 1)
+        elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL armv6 OR CMAKE_SYSTEM_PROCESSOR STREQUAL armv6l)
+            set(CLR_CMAKE_HOST_UNIX_ARMV6 1)
         elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL aarch64 OR CMAKE_SYSTEM_PROCESSOR STREQUAL arm64)
             set(CLR_CMAKE_HOST_UNIX_ARM64 1)
         elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL loongarch64 OR CMAKE_SYSTEM_PROCESSOR STREQUAL loongarch64)
@@ -217,6 +219,13 @@ if(CLR_CMAKE_HOST_UNIX_ARM)
     if(CLR_CMAKE_HOST_UNIX_ARMV7L)
         set(CLR_CMAKE_HOST_ARCH_ARMV7L 1)
     endif()
+elseif(CLR_CMAKE_HOST_UNIX_ARMV6)
+    set(CLR_CMAKE_HOST_ARCH_ARMV6 1)
+    set(CLR_CMAKE_HOST_ARCH "armv6")
+
+    if(CLR_CMAKE_HOST_UNIX_ARMV6L)
+        set(CLR_CMAKE_HOST_ARCH_ARMV6L 1)
+    endif()
 elseif(CLR_CMAKE_HOST_UNIX_ARM64)
     set(CLR_CMAKE_HOST_ARCH_ARM64 1)
     set(CLR_CMAKE_HOST_ARCH "arm64")
@@ -277,6 +286,8 @@ if (CLR_CMAKE_TARGET_ARCH STREQUAL x64)
     set(CLR_CMAKE_TARGET_ARCH_LOONGARCH64 1)
   elseif(CLR_CMAKE_TARGET_ARCH STREQUAL arm)
     set(CLR_CMAKE_TARGET_ARCH_ARM 1)
+  elseif(CLR_CMAKE_TARGET_ARCH STREQUAL armv6)
+    set(CLR_CMAKE_TARGET_ARCH_ARMV6 1)
   elseif(CLR_CMAKE_TARGET_ARCH STREQUAL armel)
     set(CLR_CMAKE_TARGET_ARCH_ARM 1)
     set(CLR_CMAKE_TARGET_ARCH_ARMV7L 1)
@@ -379,6 +390,8 @@ if(CLR_CMAKE_TARGET_UNIX)
         set(CLR_CMAKE_TARGET_UNIX_ARM 1)
     elseif(CLR_CMAKE_TARGET_ARCH STREQUAL arm)
         set(CLR_CMAKE_TARGET_UNIX_ARM 1)
+    elseif(CLR_CMAKE_TARGET_ARCH STREQUAL armv6)
+        set(CLR_CMAKE_TARGET_UNIX_ARMV6 1)
     elseif(CLR_CMAKE_TARGET_ARCH STREQUAL arm64)
         set(CLR_CMAKE_TARGET_UNIX_ARM64 1)
     elseif(CLR_CMAKE_TARGET_ARCH STREQUAL loongarch64)
diff --git a/eng/native/configuretools.cmake b/eng/native/configuretools.cmake
index 136cd67925d..ad5dc38107c 100644
--- a/eng/native/configuretools.cmake
+++ b/eng/native/configuretools.cmake
@@ -52,8 +52,8 @@ if(NOT WIN32 AND NOT CLR_CMAKE_TARGET_BROWSER)
 
     if(CLR_CMAKE_TARGET_ANDROID)
       set(TOOLSET_PREFIX ${ANDROID_TOOLCHAIN_PREFIX})
-    elseif(CMAKE_CROSSCOMPILING AND NOT DEFINED CLR_CROSS_COMPONENTS_BUILD AND (CMAKE_SYSTEM_PROCESSOR STREQUAL armv7l OR
-       CMAKE_SYSTEM_PROCESSOR STREQUAL aarch64 OR CMAKE_SYSTEM_PROCESSOR STREQUAL arm OR CMAKE_SYSTEM_PROCESSOR STREQUAL s390x))
+    elseif(CMAKE_CROSSCOMPILING AND NOT DEFINED CLR_CROSS_COMPONENTS_BUILD AND
+        CMAKE_SYSTEM_PROCESSOR MATCHES "^(armv7l|armv6l|aarch64|arm|s390x)$")
       set(TOOLSET_PREFIX "${TOOLCHAIN}-")
     else()
       set(TOOLSET_PREFIX "")
diff --git a/eng/native/functions.cmake b/eng/native/functions.cmake
index c4af68ba7dc..0c28f75706d 100644
--- a/eng/native/functions.cmake
+++ b/eng/native/functions.cmake
@@ -4,7 +4,7 @@ function(clr_unknown_arch)
     elseif(CLR_CROSS_COMPONENTS_BUILD)
         message(FATAL_ERROR "Only AMD64, I386 host are supported for linux cross-architecture component. Found: ${CMAKE_SYSTEM_PROCESSOR}")
     else()
-        message(FATAL_ERROR "Only AMD64, ARM64, LOONGARCH64 and ARM are supported. Found: ${CMAKE_SYSTEM_PROCESSOR}")
+        message(FATAL_ERROR "Only AMD64, ARMV6, ARM64, LOONGARCH64 and ARM are supported. Found: ${CMAKE_SYSTEM_PROCESSOR}")
     endif()
 endfunction()
 
@@ -155,6 +155,10 @@ function(find_unwind_libs UnwindLibs)
       find_library(UNWIND_ARCH NAMES unwind-arm)
     endif()
 
+    if(CLR_CMAKE_HOST_ARCH_ARMV6)
+      find_library(UNWIND_ARCH NAMES unwind-arm)
+    endif()
+
     if(CLR_CMAKE_HOST_ARCH_ARM64)
       find_library(UNWIND_ARCH NAMES unwind-aarch64)
     endif()
diff --git a/eng/native/init-os-and-arch.sh b/eng/native/init-os-and-arch.sh
index 586534be1c8..eda07a5feeb 100644
--- a/eng/native/init-os-and-arch.sh
+++ b/eng/native/init-os-and-arch.sh
@@ -53,6 +53,10 @@ case "$CPUName" in
         fi
         ;;
 
+    armv6l)
+        arch=armv6
+        ;;
+
     i[3-6]86)
         echo "Unsupported CPU $CPUName detected, build might not succeed!"
         arch=x86
diff --git a/eng/native/tryrun.cmake b/eng/native/tryrun.cmake
index e8a04c5698a..fca410fcb4b 100644
--- a/eng/native/tryrun.cmake
+++ b/eng/native/tryrun.cmake
@@ -68,7 +68,7 @@ if(DARWIN)
   else()
     message(FATAL_ERROR "Arch is ${TARGET_ARCH_NAME}. Only arm64 or x64 is supported for OSX cross build!")
   endif()
-elseif(TARGET_ARCH_NAME MATCHES "^(armel|arm|arm64|loongarch64|s390x|x86)$" OR FREEBSD OR ILLUMOS)
+elseif(TARGET_ARCH_NAME MATCHES "^(armel|arm|armv6|arm64|loongarch64|s390x|x86)$" OR FREEBSD OR ILLUMOS)
   set_cache_value(FILE_OPS_CHECK_FERROR_OF_PREVIOUS_CALL_EXITCODE 1)
   set_cache_value(GETPWUID_R_SETS_ERRNO_EXITCODE 0)
   set_cache_value(HAS_POSIX_SEMAPHORES_EXITCODE 0)
@@ -146,9 +146,9 @@ elseif(TARGET_ARCH_NAME MATCHES "^(armel|arm|arm64|loongarch64|s390x|x86)$" OR F
     set_cache_value(HAVE_FUNCTIONAL_PTHREAD_ROBUST_MUTEXES_EXITCODE 0)
   endif()
 else()
-  message(FATAL_ERROR "Arch is ${TARGET_ARCH_NAME}. Only armel, arm, arm64, loongarch64, s390x and x86 are supported!")
+  message(FATAL_ERROR "Arch is ${TARGET_ARCH_NAME}. Only armel, arm, armv6, arm64, loongarch64, s390x and x86 are supported!")
 endif()
 
-if(TARGET_ARCH_NAME STREQUAL "x86" OR TARGET_ARCH_NAME STREQUAL "s390x" OR TARGET_ARCH_NAME STREQUAL "loongarch64")
+if(TARGET_ARCH_NAME STREQUAL "x86" OR TARGET_ARCH_NAME STREQUAL "s390x" OR TARGET_ARCH_NAME STREQUAL "armv6" OR TARGET_ARCH_NAME STREQUAL "loongarch64")
   set_cache_value(HAVE_FUNCTIONAL_PTHREAD_ROBUST_MUTEXES_EXITCODE 0)
 endif()