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Use managed APIs for Unix startup metadata #28337

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41 changes: 4 additions & 37 deletions src/powershell/Program.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,9 +48,6 @@ public StartupException(string callName, int exitCode)
private const string LOGIN_ENV_VAR_NAME = "__PWSH_LOGIN_CHECKED";
private const string LOGIN_ENV_VAR_VALUE = "1";

// Linux p/Invoke constants
private const int LINUX_PATH_MAX = 4096;

// MacOS p/Invoke constants
private const int MACOS_CTL_KERN = 1;
private const int MACOS_KERN_ARGMAX = 8;
Expand Down Expand Up @@ -113,11 +110,7 @@ private static void AttemptExecPwshLogin(string[] args)
return;
}

// Read the symlink to the startup executable
IntPtr linkPathPtr = Marshal.AllocHGlobal(LINUX_PATH_MAX);
IntPtr bufSize = ReadLink("/proc/self/exe", linkPathPtr, (UIntPtr)LINUX_PATH_MAX);
pwshPath = Marshal.PtrToStringAnsi(linkPathPtr, (int)bufSize);
Marshal.FreeHGlobal(linkPathPtr);
pwshPath = Environment.ProcessPath;

ArgumentNullException.ThrowIfNull(pwshPath);

Expand All @@ -143,7 +136,7 @@ private static void AttemptExecPwshLogin(string[] args)
}

// Get the PID so we can query this process' args
int pid = GetPid();
int pid = Environment.ProcessId;

// The following logic is based on https://gist.github.com/nonowarn/770696

Expand Down Expand Up @@ -317,8 +310,8 @@ private static int ExecPwshLogin(string[] args, string pwshPath, bool isMacOS)
// A null is required by exec.
execArgs[execArgs.Length - 1] = null;

// We can't use Environment.SetEnvironmentVariable() here.
// See https://github.com/dotnet/corefx/issues/40130#issuecomment-519420648.
// Environment.SetEnvironmentVariable() updates the managed environment cache on Unix,
// but execv inherits the native libc environment, so setenv is required here.
ThrowOnFailure("setenv", SetEnv(LOGIN_ENV_VAR_NAME, LOGIN_ENV_VAR_VALUE, overwrite: true));

// On macOS, sh doesn't support login, so we run /bin/zsh in sh emulation mode.
Expand Down Expand Up @@ -439,32 +432,6 @@ private static void ThrowOnFailure(string call, int code)
SetLastError = true)]
private static extern int Exec(string path, string?[] args);

/// <summary>
/// The `readlink` POSIX syscall we use to read the symlink from /proc/self/exe
/// to get the executable path of pwsh on Linux.
/// </summary>
/// <param name="pathname">The path to the symlink to read.</param>
/// <param name="buf">Pointer to a buffer to fill with the result.</param>
/// <param name="size">The size of the buffer we have supplied.</param>
/// <returns>The number of bytes placed in the buffer.</returns>
[DllImport("libc",
EntryPoint = "readlink",
CallingConvention = CallingConvention.Cdecl,
CharSet = CharSet.Ansi,
SetLastError = true)]
private static extern IntPtr ReadLink(string pathname, IntPtr buf, UIntPtr size);

/// <summary>
/// The `getpid` POSIX syscall we use to quickly get the current process PID on macOS.
/// </summary>
/// <returns>The pid of the current process.</returns>
[DllImport("libc",
EntryPoint = "getpid",
CallingConvention = CallingConvention.Cdecl,
CharSet = CharSet.Ansi,
SetLastError = true)]
private static extern int GetPid();

/// <summary>
/// The `setenv` POSIX syscall used to set an environment variable in the process.
/// </summary>
Expand Down