From ec5fa92761dd605ac9d695894782afea59b4664e Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Mon, 26 Mar 2012 22:22:59 +0200
Subject: [PATCH] Programmers can now redirect what the errno macro refers to.

---
 libmaxsi/decl/errno_decl.h        | 11 +++++++++--
 libmaxsi/error.cpp                | 18 +++++++++++++++---
 libmaxsi/include/libmaxsi/error.h | 10 ++++++++++
 sortix/process.cpp                |  4 ++--
 sortix/process.h                  |  2 +-
 sortix/syscall.cpp                |  4 ++--
 sortix/x64/syscall.s              |  2 +-
 sortix/x86/syscall.s              |  2 +-
 8 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/libmaxsi/decl/errno_decl.h b/libmaxsi/decl/errno_decl.h
index 777a00a0..11a603cc 100644
--- a/libmaxsi/decl/errno_decl.h
+++ b/libmaxsi/decl/errno_decl.h
@@ -1,7 +1,14 @@
 #ifndef _ERRNO_DECL
 #define _ERRNO_DECL
 
-extern volatile int errno;
-#define errno errno
+/* Returns the address of the errno variable for this thread. */
+extern int* get_errno_location(void);
+
+/* get_errno_location will forward the request to a user-specified function if
+   specified, or if NULL, will return the global thread-shared errno value. */
+typedef int* (*errno_location_func_t)(void);
+extern void set_errno_location_func(errno_location_func_t func);
+
+#define errno (*get_errno_location())
 
 #endif
diff --git a/libmaxsi/error.cpp b/libmaxsi/error.cpp
index 188e4860..39e8dd31 100644
--- a/libmaxsi/error.cpp
+++ b/libmaxsi/error.cpp
@@ -33,18 +33,30 @@
 namespace Maxsi {
 namespace Error {
 
-extern "C" { int errno = 0; }
+extern "C" { int global_errno = 0; }
+extern "C" { errno_location_func_t errno_location_func = NULL; }
 
 #ifndef SORTIX_KERNEL
 DEFN_SYSCALL1(int, SysRegisterErrno, SYSCALL_REGISTER_ERRNO, int*);
 
 extern "C" void init_error_functions()
 {
-	errno = 0;
-	SysRegisterErrno(&errno);
+	global_errno = 0;
+	SysRegisterErrno(&global_errno);
 }
 #endif
 
+extern "C" int* get_errno_location(void)
+{
+	if ( errno_location_func ) { return errno_location_func(); }
+	return &global_errno;
+}
+
+extern "C" void set_errno_location_func(errno_location_func_t func)
+{
+	errno_location_func = func;
+}
+
 extern "C" const char* sortix_strerror(int errnum)
 {
 	switch ( errnum )
diff --git a/libmaxsi/include/libmaxsi/error.h b/libmaxsi/include/libmaxsi/error.h
index f2f9dbe8..5e0c3363 100644
--- a/libmaxsi/include/libmaxsi/error.h
+++ b/libmaxsi/include/libmaxsi/error.h
@@ -37,6 +37,16 @@ namespace Maxsi
 	{
 		inline int Last() { return errno; }
 		inline void Set(int error) { errno = error; }
+
+		inline int* GetErrnoLocation()
+		{
+			return get_errno_location();
+		}
+
+		inline void SetErrnoLocationFunc(errno_location_func_t func)
+		{
+			set_errno_location_func(func);
+		}
 	}
 }
 
diff --git a/sortix/process.cpp b/sortix/process.cpp
index 280ac0dc..cc285e33 100644
--- a/sortix/process.cpp
+++ b/sortix/process.cpp
@@ -204,7 +204,7 @@ namespace Sortix
 
 		// Copy variables.
 		clone->mmapfrom = mmapfrom;
-		clone->errno = errno;
+		clone->errnop = errnop;
 		if ( workingdir ) { clone->workingdir = String::Clone(workingdir); }
 		else { clone->workingdir = NULL; }
 
@@ -783,7 +783,7 @@ namespace Sortix
 
 	int SysRegisterErrno(int* errnop)
 	{
-		CurrentProcess()->errno = errnop;
+		CurrentProcess()->errnop = errnop;
 		return 0;
 	}
 
diff --git a/sortix/process.h b/sortix/process.h
index 1aab20e0..f5518706 100644
--- a/sortix/process.h
+++ b/sortix/process.h
@@ -76,7 +76,7 @@ namespace Sortix
 		int exitstatus;
 		char* workingdir;
 		pid_t pid;
-		int* errno;
+		int* errnop;
 
 	public:
 		Process* parent;
diff --git a/sortix/syscall.cpp b/sortix/syscall.cpp
index a47b04ea..a98f6564 100644
--- a/sortix/syscall.cpp
+++ b/sortix/syscall.cpp
@@ -104,9 +104,9 @@ namespace Sortix
 			int error = Error::Last();
 			if ( !error ) { return; }
 			Process* process = CurrentProcess();
-			if ( !process->errno ) { return; }
+			if ( !process->errnop ) { return; }
 			// TODO: Validate that process->errno is in userspace memory!
-			*process->errno = error;
+			*process->errnop = error;
 		}
 
 		extern "C" size_t resume_syscall(void* scfunc, size_t scsize, size_t* scstate);
diff --git a/sortix/x64/syscall.s b/sortix/x64/syscall.s
index e97a9730..2fe79704 100644
--- a/sortix/x64/syscall.s
+++ b/sortix/x64/syscall.s
@@ -73,7 +73,7 @@ syscall_handler:
 	movl $0, system_was_incomplete
 
 	# Reset the kernel errno.
-	movl $0, errno
+	movl $0, global_errno
 
 	# Make sure the requested system call is valid.
 	cmp SYSCALL_MAX, %rax
diff --git a/sortix/x86/syscall.s b/sortix/x86/syscall.s
index f482a84a..439ffe9e 100644
--- a/sortix/x86/syscall.s
+++ b/sortix/x86/syscall.s
@@ -59,7 +59,7 @@ syscall_handler:
 	movl $0, system_was_incomplete
 
 	# Reset the kernel errno.
-	movl $0, errno
+	movl $0, global_errno
 
 	# Make sure the requested system call is valid.
 	cmp SYSCALL_MAX, %eax