lowlevel-z80: put back the basics for the zero pointer trap

diff --git a/Kernel/lowlevel-z80.s b/Kernel/lowlevel-z80.s
index 79af2d4..f8499bf 100644 (file)
--- a/Kernel/lowlevel-z80.s
+++ b/Kernel/lowlevel-z80.s
@@ -116,6 +116,11 @@ deliver_signals_2:
 signal_return:
        pop hl          ; argument
        di
+       ;
+       ;       We must keep IRQ disabled in the kernel mapped
+       ;       element of this processing, as we don't want to
+       ;       set INSYS flags here.
+       ;
        ld (U_DATA__U_SYSCALL_SP), sp
        ld sp, #kstack_top
        call map_kernel
@@ -159,6 +164,9 @@ unix_syscall_entry:
         ld de, #U_DATA__U_ARGN
         ldir           ; copy
 
+       ld a, #1
+       ld (U_DATA__U_INSYS), a
+
         ; save process stack pointer
         ld (U_DATA__U_SYSCALL_SP), sp
         ; switch to kernel stack
@@ -178,11 +186,17 @@ unix_syscall_entry:
        ; 1. fork() will return twice from _unix_syscall
        ; 2. execve() will not return here but will hit _doexec()
        ;
+       ; The fork case returns with a different U_DATA mapped so the
+       ; U_DATA referencing code is fine, but globals are usually not
 
         di
 
+
        call map_process_always
 
+       xor a
+       ld (U_DATA__U_INSYS), a
+
        ; Back to the user stack
        ld sp, (U_DATA__U_SYSCALL_SP)
 
@@ -274,20 +288,6 @@ _doexec:
         ei
         jp (hl)
 
-;
-;      Trap handlers
-;
-;      Enter with HL being the signal to send ourself
-;
-trap_signal:
-        push hl
-       ld hl, (U_DATA__U_PTAB);
-        push hl
-        call _ssig
-        pop hl
-        pop hl
-       ret
-
 ;
 ;  Called from process context (hopefully)
 ;
@@ -354,7 +354,6 @@ interrupt_handler:
         push hl
         push ix
         push iy
-       di
 
        ; Some platforms (MSX for example) have devices we *must*
        ; service irrespective of kernel state in order to shut them
@@ -380,6 +379,8 @@ interrupt_handler:
        ld (istack_switched_sp), sp
        ld sp, #istack_top
 
+       ld a, (0)
+
        call map_save
        ;
        ;       FIXME: re-implement sanity checks and add a stack one
@@ -388,6 +389,9 @@ interrupt_handler:
        ; We need the kernel mapped for the IRQ handling
        call map_kernel
 
+       cp #0xC3
+       call nz, null_pointer_trap
+
        ; So the kernel can check rapidly for interrupt status
        ; FIXME: move to the C code
        ld a, #1
@@ -452,6 +456,23 @@ interrupt_pop:
         ei                     ; Must be instruction before ret
        ret                     ; runs in the ei interrupt shadow
 
+;
+;      Called with the kernel mapped, mid interrupt and on the IRQ stack
+;
+null_pointer_trap:
+       ld a, #0xC3
+       ld (0), a
+
+trap_signal:
+       push hl
+       ld hl, (U_DATA__U_PTAB);
+        push hl
+        call _ssig
+        pop hl
+        pop hl
+       ret
+
+
 ;
 ;      Pre-emption. We need to get off the interrupt stack, switch task
 ;      and clean up the IRQ state carefully

diff --git a/Kernel/process.c b/Kernel/process.c
index 25df8fb..b9a4670 100644 (file)
--- a/Kernel/process.c
+++ b/Kernel/process.c
@@ -387,7 +387,6 @@ void timer_interrupt(void)
 void unix_syscall(void)
 {
        // NO LOCAL VARIABLES PLEASE
-       udata.u_insys = true;
        udata.u_error = 0;
 
        /* Fuzix saves the Stack Pointer and arguments in the
@@ -422,7 +421,6 @@ void unix_syscall(void)
                switchout();
        }
        ei();
-       udata.u_insys = false;
 }
 
 void sgrpsig(uint16_t pgrp, uint16_t sig)