diff options
| author | Matthew Bauer <mjbauer95@gmail.com> | 2021-01-11 22:05:32 -0600 |
|---|---|---|
| committer | Matthew Bauer <mjbauer95@gmail.com> | 2021-01-11 22:40:21 -0600 |
| commit | f69820417fa65dbfea88a5f4dd0ccb5376015a6b (patch) | |
| tree | e8c2db610fc87b094cc9eabda72566824c235b18 /src | |
| parent | 6254b1f5d298ff73127d7b0f0da48f142bdc753c (diff) | |
Set kern.curproc_arch_affinity=0 to escape Rosetta
By default, once you enter x86_64 Rosetta 2, macOS will try to run
everything in x86_64. So an x86_64 Nix will still try to use x86_64
even when system = aarch64-darwin. To avoid this we can set
kern.curproc_arch_affinity sysctl. With kern.curproc_arch_affinity=0,
we ignore this preference.
This is based on how
https://opensource.apple.com/source/system_cmds/system_cmds-880.40.5/arch.tproj/arch.c.auto.html
works. Completely undocumented, but seems to work!
Note, you can verify this works with this impure Nix expression:
```
{
a = derivation {
name = "a";
system = "aarch64-darwin";
builder = "/bin/sh";
args = [ "-e" (builtins.toFile "builder" ''
[ "$(/usr/bin/arch)" = arm64 ]
[ "$(/usr/bin/arch -arch x86_64 /bin/sh -c /usr/bin/arch)" = i386 ]
[ "$(/usr/bin/arch -arch arm64 /bin/sh -c /usr/bin/arch)" = arm64 ]
/usr/bin/touch $out
'') ];
};
b = derivation {
name = "b";
system = "x86_64-darwin";
builder = "/bin/sh";
args = [ "-e" (builtins.toFile "builder" ''
[ "$(/usr/bin/arch)" = i386 ]
[ "$(/usr/bin/arch -arch x86_64 /bin/sh -c /usr/bin/arch)" = i386 ]
[ "$(/usr/bin/arch -arch arm64 /bin/sh -c /usr/bin/arch)" = arm64 ]
/usr/bin/touch $out
'') ];
};
}
```
Diffstat (limited to 'src')
| -rw-r--r-- | src/libstore/build/derivation-goal.cc | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc index 35f365795..a02ddb950 100644 --- a/src/libstore/build/derivation-goal.cc +++ b/src/libstore/build/derivation-goal.cc @@ -52,6 +52,7 @@ #if __APPLE__ #include <spawn.h> +#include <sys/sysctl.h> #endif #include <pwd.h> @@ -2869,6 +2870,10 @@ void DerivationGoal::runChild() throw SysError("failed to initialize builder"); if (drv->platform == "aarch64-darwin") { + // Unset kern.curproc_arch_affinity so we can escape Rosetta + int affinity = 0; + sysctlbyname("kern.curproc_arch_affinity", NULL, NULL, &affinity, sizeof(affinity)); + cpu_type_t cpu = CPU_TYPE_ARM64; posix_spawnattr_setbinpref_np(&attrp, 1, &cpu, NULL); } else if (drv->platform == "x86_64-darwin") { |