Added errno cmdlet

Author: Your Name

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "frida-cshell",
-  "version": "1.7.4",
+  "version": "1.7.5",
   "description": "Frida's CShell",
   "scripts": {
     "prepare": "npm run build && npm run version && npm run package && npm run copy",

package.json

@@ -82,6 +82,7 @@ import { MacroCmdLet } from '../misc/macro.js';
 import { ReplaceCmdLet } from '../breakpoints/replace.js';
 import { EchoCmdLet } from '../misc/echo.js';
 import { CorpseCmdLet } from '../misc/corpse/corpse.js';
+import { ErrnoCmdLet } from '../misc/errno.js';
 
 export class JsCmdLet extends CmdLetBase {
   name = 'js';
@@ -126,6 +127,7 @@ js path - load commandlet JS script
       DumpCmdLet: DumpCmdLet,
       EchoCmdLet: EchoCmdLet,
       EqCmdLet: EqCmdLet,
+      ErrnoCmdLet: ErrnoCmdLet,
       ExitCmdLet: ExitCmdLet,
       FalseCmdLet: FalseCmdLet,
       FdCmdLet: FdCmdLet,

src/cmdlets/development/js.ts

@@ -9,7 +9,9 @@ export class CorePattern {
   public static get(): string {
     const value = File.readAllText(CorePattern.CORE_PATTERN).trimEnd();
     if (value.startsWith('|'))
-      throw new Error(`core pattern must not start with '|' - value: '${value}'`);
+      throw new Error(
+        `core pattern must not start with '|' - value: '${value}'`,
+      );
 
     if (value.indexOf('%') !== -1)
       throw new Error(`core pattern must not contain '%' - value: '${value}'`);

src/cmdlets/misc/corpse/core_pattern.ts

@@ -0,0 +1,88 @@
+import { CmdLetBase } from '../../commands/cmdlet.js';
+import { Output } from '../../io/output.js';
+import { Token } from '../../io/token.js';
+import { Var } from '../../vars/var.js';
+
+export class ErrnoCmdLet extends CmdLetBase {
+  name = 'errno';
+  category = 'misc';
+  help = 'displays the errno value';
+  private static readonly USAGE: string = `Usage: errno
+
+errno - display the errno value`;
+
+  private fnErrnoLocation: SystemFunction<NativePointer, []> | null = null;
+
+  public runSync(tokens: Token[]): Var {
+    const retGetErrno = this.getErrno(tokens);
+    if (retGetErrno !== null) return retGetErrno;
+
+    const retSetErrno = this.setErrno(tokens);
+    if (retSetErrno !== null) return retSetErrno;
+
+    return this.usage();
+  }
+
+  private setErrno(tokens: Token[]): Var | null {
+    const vars = this.transform(tokens, [this.parseVar]);
+    if (vars === null) return null;
+    const [value] = vars as [Var];
+
+    const errno = value.toU64().toNumber();
+    const location = this.getErrnoLocation();
+    location.writeInt(errno);
+    return value;
+  }
+
+  private getErrno(tokens: Token[]): Var | null {
+    if (tokens.length !== 0) return null;
+    const location = this.getErrnoLocation();
+
+    const errno = location.readInt();
+    Output.writeln(`errno: ${errno}`);
+
+    return new Var(uint64(errno), 'errno');
+  }
+
+  private getErrnoLocation(): NativePointer {
+    const fnErrnoLocation = this.fnErrnoLocation as SystemFunction<
+      NativePointer,
+      []
+    >;
+    const location =
+      fnErrnoLocation() as UnixSystemFunctionResult<NativePointer>;
+    if (location.value.equals(ptr(0)))
+      throw new Error('failed to get __errno_location()');
+    return location.value;
+  }
+
+  public usage(): Var {
+    Output.writeln(ErrnoCmdLet.USAGE);
+    return Var.ZERO;
+  }
+
+  public override isSupported(): boolean {
+    switch (Process.platform) {
+      case 'linux': {
+        const pErrnoLocation = Module.findExportByName(
+          null,
+          '__errno_location',
+        );
+        if (pErrnoLocation === null) return false;
+        this.fnErrnoLocation = new SystemFunction(
+          pErrnoLocation,
+          'pointer',
+          [],
+        );
+        return true;
+      }
+      case 'darwin':
+      case 'freebsd':
+      case 'qnx':
+      case 'windows':
+      case 'barebone':
+      default:
+        return false;
+    }
+  }
+}

src/cmdlets/misc/errno.ts

@@ -69,6 +69,7 @@ import { MacroCmdLet } from '../cmdlets/misc/macro.js';
 import { ReplaceCmdLet } from '../cmdlets/breakpoints/replace.js';
 import { EchoCmdLet } from '../cmdlets/misc/echo.js';
 import { CorpseCmdLet } from '../cmdlets/misc/corpse/corpse.js';
+import { ErrnoCmdLet } from '../cmdlets/misc/errno.js';
 
 export class CmdLets {
   private static byName: Map<string, CmdLet> = new Map<string, CmdLet>();
@@ -91,6 +92,7 @@ export class CmdLets {
     this.registerCmdletType(EchoCmdLet);
     this.registerCmdletType(EndianCmdLet);
     this.registerCmdletType(EqCmdLet);
+    this.registerCmdletType(ErrnoCmdLet);
     this.registerCmdletType(ExitCmdLet);
     this.registerCmdletType(FalseCmdLet);
     this.registerCmdletType(FdCmdLet);