pc kernel: make syscall() return thru forkret() to handle exceptions

forkret() labels the instructions that can raise exceptions
so they can be handled in trap(). this can happen when
segment descriptors get invalidated.

3 files changed, 44 insertions, 109 deletions

diff --git a/sys/src/9/pc/l.s b/sys/src/9/pc/l.s
index e86b22449..3a6eab1d0 100644
--- a/sys/src/9/pc/l.s
+++ b/sys/src/9/pc/l.s
@@ -17,6 +17,8 @@
 #define INVLPG	BYTE $0x0F; BYTE $0x01; BYTE $0x39	/* INVLPG (%ecx) */
 #define WBINVD	BYTE $0x0F; BYTE $0x09
 
+#define VectorSYSCALL	0x40
+
 /*
  * Macros for calculating offsets within the page directory base
  * and page tables. Note that these are assembler-specific hence
@@ -280,61 +282,6 @@ TEXT load_gs(SB), $0
 	RET
 
 /*
- * Save registers.
- */
-TEXT saveregs(SB), $0
-	/* appease 8l */
-	SUBL $32, SP
-	POPL AX
-	POPL AX
-	POPL AX
-	POPL AX
-	POPL AX
-	POPL AX
-	POPL AX
-	POPL AX
-	
-	PUSHL	AX
-	PUSHL	BX
-	PUSHL	CX
-	PUSHL	DX
-	PUSHL	BP
-	PUSHL	DI
-	PUSHL	SI
-	PUSHFL
-
-	XCHGL	32(SP), AX	/* swap return PC and saved flags */
-	XCHGL	0(SP), AX
-	XCHGL	32(SP), AX
-	RET
-
-TEXT restoreregs(SB), $0
-	/* appease 8l */
-	PUSHL	AX
-	PUSHL	AX
-	PUSHL	AX
-	PUSHL	AX
-	PUSHL	AX
-	PUSHL	AX
-	PUSHL	AX
-	PUSHL	AX
-	ADDL	$32, SP
-	
-	XCHGL	32(SP), AX	/* swap return PC and saved flags */
-	XCHGL	0(SP), AX
-	XCHGL	32(SP), AX
-
-	POPFL
-	POPL	SI
-	POPL	DI
-	POPL	BP
-	POPL	DX
-	POPL	CX
-	POPL	BX
-	POPL	AX
-	RET
-
-/*
  * BIOS32.
  */
 TEXT bios32call(SB), $0
@@ -925,7 +872,26 @@ _rndbytes:
 	LOOP _rndbytes
 _rnddone:
 	RET
-	
+
+/*
+ *  Used to get to the first process:
+ * 	set up an interrupt return frame and IRET to user level.
+ */
+TEXT touser(SB), $0
+	PUSHL	$(UDSEL)			/* old ss */
+	MOVL	sp+0(FP), AX			/* old sp */
+	PUSHL	AX
+	MOVL	$0x200, AX			/* interrupt enable flag */
+	PUSHL	AX				/* old flags */
+	PUSHL	$(UESEL)			/* old cs */
+	PUSHL	$(UTZERO+32)			/* old pc */
+	MOVL	$(UDSEL), AX
+	MOVW	AX, DS
+	MOVW	AX, ES
+	MOVW	AX, GS
+	MOVW	AX, FS
+	IRETL
+
 /*
  * Interrupt/exception handling.
  * Each entry in the vector table calls either _strayintr or _strayintrx depending
@@ -975,6 +941,28 @@ TEXT _forkretpopds(SB), $0
 TEXT _forkretiret(SB), $0
 	IRETL
 
+/*
+ * This is merely _strayintr optimised to vector
+ * to syscall() without going through trap().
+ */
+TEXT _syscallintr(SB), $0
+	PUSHL	$VectorSYSCALL		/* trap type */
+
+	PUSHL	DS
+	PUSHL	ES
+	PUSHL	FS
+	PUSHL	GS
+	PUSHAL
+	MOVL	$(KDSEL), AX
+	MOVW	AX, DS
+	MOVW	AX, ES
+
+	MOVL	$syscall(SB), AX
+
+	PUSHL	SP			/* Ureg* argument to syscall */
+	PUSHL	$forkret(SB)		/* return pc */
+	JMP	*AX
+
 TEXT vectortable(SB), $0
 	CALL _strayintr(SB); BYTE $0x00		/* divide error */
 	CALL _strayintr(SB); BYTE $0x01		/* debug exception */
diff --git a/sys/src/9/pc/mkfile b/sys/src/9/pc/mkfile
index 7a409c7ae..ded288fed 100644
--- a/sys/src/9/pc/mkfile
+++ b/sys/src/9/pc/mkfile
@@ -45,7 +45,6 @@ PORT=\
 
 OBJ=\
 	l.$O\
-	plan9l.$O\
 	cga.$O\
 	i8253.$O\
 	i8259.$O\
diff --git a/sys/src/9/pc/plan9l.s b/sys/src/9/pc/plan9l.s
deleted file mode 100644
index e44671ac7..000000000
--- a/sys/src/9/pc/plan9l.s
+++ /dev/null
@@ -1,52 +0,0 @@
-#include "mem.h"
-
-/*
- * This must match io.h.
- */
-#define VectorSYSCALL	0x40
-
-/*
- *  Used to get to the first process:
- * 	set up an interrupt return frame and IRET to user level.
- */
-TEXT touser(SB), $0
-	PUSHL	$(UDSEL)			/* old ss */
-	MOVL	sp+0(FP), AX			/* old sp */
-	PUSHL	AX
-	MOVL	$0x200, AX			/* interrupt enable flag */
-	PUSHL	AX				/* old flags */
-	PUSHL	$(UESEL)			/* old cs */
-	PUSHL	$(UTZERO+32)			/* old pc */
-	MOVL	$(UDSEL), AX
-	MOVW	AX, DS
-	MOVW	AX, ES
-	MOVW	AX, GS
-	MOVW	AX, FS
-	IRETL
-
-/*
- * This is merely _strayintr from l.s optimised to vector
- * to syscall() without going through trap().
- */
-TEXT _syscallintr(SB), $0
-	PUSHL	$VectorSYSCALL			/* trap type */
-
-	PUSHL	DS
-	PUSHL	ES
-	PUSHL	FS
-	PUSHL	GS
-	PUSHAL
-	MOVL	$(KDSEL), AX
-	MOVW	AX, DS
-	MOVW	AX, ES
-	PUSHL	SP
-	CALL	syscall(SB)
-
-	POPL	AX
-	POPAL
-	POPL	GS
-	POPL	FS
-	POPL	ES
-	POPL	DS
-	ADDL	$8, SP				/* pop error code and trap type */
-	IRETL