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authorAlexander Momchilov <alexandermomchilov@gmail.com>2021-09-23 19:44:20 -0400
committerAlexander Momchilov <alexandermomchilov@gmail.com>2021-09-26 10:58:47 -0400
commite26a2cf431272ad92e66c9a55dee80df1db79ff4 (patch)
tree23ba340d31eaa89dd4496922ed8c465a04c7edee
parentd527bc9132c2adf94666dc5b9593609d357ea1e4 (diff)
Workaround for Rosetta 2 on Darwin
rdar://FB9546856 https://openradar.appspot.com/radar?id=5055988478509056
-rw-r--r--darwin/PlatformHelpers.c62
-rw-r--r--darwin/PlatformHelpers.h6
2 files changed, 64 insertions, 4 deletions
diff --git a/darwin/PlatformHelpers.c b/darwin/PlatformHelpers.c
index dc9879c5..bde90685 100644
--- a/darwin/PlatformHelpers.c
+++ b/darwin/PlatformHelpers.c
@@ -58,14 +58,68 @@ bool Platform_KernelVersionIsBetween(KernelVersion lowerBound, KernelVersion upp
&& Platform_CompareKernelVersion(upperBound) < 0;
}
+void Platform_getCPUBrandString(char *cpuBrandString, size_t cpuBrandStringSize) {
+ if (sysctlbyname("machdep.cpu.brand_string", cpuBrandString, &cpuBrandStringSize, NULL, 0) == -1) {
+ fprintf(stderr,
+ "WARN: Unable to determine the CPU brand string.\n"
+ "errno: %i, %s\n", errno, strerror(errno));
+
+ String_safeStrncpy(cpuBrandString, "UNKNOWN!", cpuBrandStringSize);
+ }
+}
+
+// Adapted from https://developer.apple.com/documentation/apple-silicon/about-the-rosetta-translation-environment
+bool Platform_isRunningTranslated() {
+ int ret = 0;
+ size_t size = sizeof(ret);
+ errno = 0;
+ if (sysctlbyname("sysctl.proc_translated", &ret, &size, NULL, 0) == -1) {
+ if (errno == ENOENT) return false;
+
+ fprintf(stderr,
+ "WARN: Could not determine if this process was running in a translation environment like Rosetta 2.\n"
+ "Assuming that we're not.\n"
+ "errno: %i, %s\n", errno, strerror(errno));
+
+ return false;
+ }
+ return ret;
+}
+
double Platform_calculateNanosecondsPerMachTick() {
// Check if we can determine the timebase used on this system.
// If the API is unavailable assume we get our timebase in nanoseconds.
-#ifdef HAVE_MACH_TIMEBASE_INFO
+#ifndef HAVE_MACH_TIMEBASE_INFO
+ return 1.0;
+#else
mach_timebase_info_data_t info;
- mach_timebase_info(&info);
+
+ /* WORKAROUND for `mach_timebase_info` giving incorrect values on M1 under Rosetta 2.
+ * rdar://FB9546856 https://openradar.appspot.com/radar?id=5055988478509056
+ *
+ * We don't know exactly what feature/attribute of the M1 chip causes this mistake under Rosetta 2.
+ * Until we have more Apple ARM chips to compare against, the best we can do is special-case
+ * the "Apple M1" chip specifically when running under Rosetta 2.
+ */
+
+ size_t cpuBrandStringSize = 1024;
+ char cpuBrandString[cpuBrandStringSize];
+ Platform_getCPUBrandString(cpuBrandString, cpuBrandStringSize);
+
+ bool isRunningUnderRosetta2 = Platform_isRunningTranslated();
+
+ // Kernel version 20.0.0 is macOS 11.0 (Big Sur)
+ bool isBuggedVersion = Platform_KernelVersionIsBetween((KernelVersion) {20, 0, 0}, (KernelVersion) {999, 999, 999});
+
+ if (isRunningUnderRosetta2 && String_eq(cpuBrandString, "Apple M1") && isBuggedVersion) {
+ // In this case `mach_timebase_info` provides the wrong value, so we hard-code the correct factor,
+ // as determined from `mach_timebase_info` when the process running natively.
+ info = (mach_timebase_info_data_t) { .numer = 125, .denom = 3 };
+ } else {
+ // No workarounds needed, use the OS-provided value.
+ mach_timebase_info(&info);
+ }
+
return (double)info.numer / (double)info.denom;
-#else
- return 1.0;
#endif
}
diff --git a/darwin/PlatformHelpers.h b/darwin/PlatformHelpers.h
index f78ca4ea..f1af1c0b 100644
--- a/darwin/PlatformHelpers.h
+++ b/darwin/PlatformHelpers.h
@@ -31,4 +31,10 @@ bool Platform_KernelVersionIsBetween(KernelVersion lowerBound, KernelVersion upp
double Platform_calculateNanosecondsPerMachTick(void);
+void Platform_getCPUBrandString(char *cpuBrandString, size_t cpuBrandStringSize);
+
+bool Platform_isRunningTranslated(void);
+
+double Platform_calculateNanosecondsPerMachTick(void);
+
#endif

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