Workaround for Rosetta 2 on Darwin

rdar://FB9546856

https://openradar.appspot.com/radar?id=5055988478509056
This commit is contained in:
Alexander Momchilov 2021-09-23 19:44:20 -04:00
parent d527bc9132
commit e26a2cf431
2 changed files with 65 additions and 5 deletions

View File

@ -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
mach_timebase_info_data_t info;
mach_timebase_info(&info);
return (double)info.numer / (double)info.denom;
#else
#ifndef HAVE_MACH_TIMEBASE_INFO
return 1.0;
#else
mach_timebase_info_data_t 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;
#endif
}

View File

@ -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