[vm] Enable Dart VM to run in QEMU user-mode emulation for ARM.

sjindel-google · commit-bot@chromium.org · commit 6a8aae0095b3 · 2019-11-18T16:58:53.000Z
Normally we consult /proc to determine the host architecture. However, this reports the actual host architecture, not the QEMU-simulated one. Also, GDB cannot debug position-independent executables in QEMU, so we disable PIE when compiling for execution in QEMU. Pass '--use-qemu' to 'gn.py' to build for QEMU. Change-Id: Ib125127ceb0582b66754cfc0da22e09d224ee1e9 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/125267 Commit-Queue: Samir Jindel <sjindel@google.com> Reviewed-by: Martin Kustermann <kustermann@google.com>
diff --git a/build/config/BUILDCONFIG.gn b/build/config/BUILDCONFIG.gn
@@ -133,6 +133,9 @@ declare_args() {
 
   # Compile for Undefined Behavior Sanitizer to find reliance on undefined behavior.
   is_ubsan = false
+
+  # Compile for execution in user-mode QEMU.
+  is_qemu = false
 }
 
 # =============================================================================
diff --git a/build/config/linux/BUILD.gn b/build/config/linux/BUILD.gn
@@ -6,6 +6,7 @@ import("//build/config/sysroot.gni")
 
 config("sdk") {
   ldflags = []
+  cflags = []
 
   if (is_asan || is_lsan || is_msan || is_tsan || is_ubsan) {
     ldflags += [ "-lrt" ]
@@ -23,7 +24,7 @@ config("sdk") {
   }
 
   if (sysroot != "") {
-    cflags = [ "--sysroot=" + sysroot ]
+    cflags += [ "--sysroot=" + sysroot ]
     ldflags += [ "--sysroot=" + sysroot ]
 
     # Need to get some linker flags out of the sysroot.
@@ -44,10 +45,18 @@ config("sdk") {
       ]
     }
   }
+
+  if (is_qemu) {
+    cflags += ["-DDART_RUN_IN_QEMU_ARMv7"]
+  }
 }
 
 config("executable_config") {
-  if (current_cpu != "x86") {
+  # GDB cannot find the executable's mapping in QEMU when PIE is enabled.
+  if (is_qemu) {
+    cflags = [ "-fno-pie" ]
+    ldflags = [ "-no-pie" ]
+  } else if (current_cpu != "x86") {
     cflags = [ "-fPIE" ]
     ldflags = [ "-pie" ]
   }
diff --git a/runtime/vm/cpu_arm.cc b/runtime/vm/cpu_arm.cc
@@ -175,7 +175,11 @@ void HostCPUFeatures::Init() {
              CpuInfo::FieldContains(kCpuInfoModel, "ARMv7")) {
     arm_version_ = ARMv7;
   } else {
-    FATAL("Unsupported ARM CPU architecture.");
+#if defined(DART_RUN_IN_QEMU_ARMv7)
+    arm_version_ = ARMv7;
+#else
+    FATAL("Unrecognized ARM CPU architecture.");
+#endif
   }
 
   // Has floating point unit.
diff --git a/tools/gn.py b/tools/gn.py
@@ -247,6 +247,7 @@ def ToGnArgs(args, mode, arch, target_os, use_nnbd):
     gn_args['is_tsan'] = args.tsan
     gn_args['is_ubsan'] = args.ubsan
     gn_args['include_dart2native'] = True
+    gn_args['is_qemu'] = args.use_qemu
 
     if not args.platform_sdk and not gn_args['target_cpu'].startswith('arm'):
         gn_args['dart_platform_sdk'] = args.platform_sdk
@@ -522,6 +523,11 @@ def parse_args(args):
         default=False,
         dest='use_crashpad',
         action='store_true')
+    other_group.add_argument(
+        '--use-qemu',
+        default=False,
+        dest='use_qemu',
+        action='store_true')
 
     options = parser.parse_args(args)
     if not ProcessOptions(options):

Original file line number	Diff line number	Diff line change
`@@ -133,6 +133,9 @@ declare_args() {`
`133`	`133`
`134`	`134`	`# Compile for Undefined Behavior Sanitizer to find reliance on undefined behavior.`
`135`	`135`	`is_ubsan = false`
	`136`	`+`
	`137`	`+ # Compile for execution in user-mode QEMU.`
	`138`	`+ is_qemu = false`
`136`	`139`	`}`
`137`	`140`
`138`	`141`	`# =============================================================================`
Original file line number	Diff line number	Diff line change
`@@ -6,6 +6,7 @@ import("//build/config/sysroot.gni")`
`6`	`6`
`7`	`7`	`config("sdk") {`
`8`	`8`	`ldflags = []`
	`9`	`+ cflags = []`
`9`	`10`
`10`	`11`	`if (is_asan \|\| is_lsan \|\| is_msan \|\| is_tsan \|\| is_ubsan) {`
`11`	`12`	`ldflags += [ "-lrt" ]`
`@@ -23,7 +24,7 @@ config("sdk") {`
`23`	`24`	`}`
`24`	`25`
`25`	`26`	`if (sysroot != "") {`
`26`		`- cflags = [ "--sysroot=" + sysroot ]`
	`27`	`+ cflags += [ "--sysroot=" + sysroot ]`
`27`	`28`	`ldflags += [ "--sysroot=" + sysroot ]`
`28`	`29`
`29`	`30`	`# Need to get some linker flags out of the sysroot.`
`@@ -44,10 +45,18 @@ config("sdk") {`
`44`	`45`	`]`
`45`	`46`	`}`
`46`	`47`	`}`
	`48`	`+`
	`49`	`+ if (is_qemu) {`
	`50`	`+ cflags += ["-DDART_RUN_IN_QEMU_ARMv7"]`
	`51`	`+ }`
`47`	`52`	`}`
`48`	`53`
`49`	`54`	`config("executable_config") {`
`50`		`- if (current_cpu != "x86") {`
	`55`	`+ # GDB cannot find the executable's mapping in QEMU when PIE is enabled.`
	`56`	`+ if (is_qemu) {`
	`57`	`+ cflags = [ "-fno-pie" ]`
	`58`	`+ ldflags = [ "-no-pie" ]`
	`59`	`+ } else if (current_cpu != "x86") {`
`51`	`60`	`cflags = [ "-fPIE" ]`
`52`	`61`	`ldflags = [ "-pie" ]`
`53`	`62`	`}`