[libc] Fix longstanding signal handling bug with improperly set DS re…

…gister
ghaerr · Jan 20, 2025 · 3d4300d · 3d4300d
1 parent 1fb2a47
commit 3d4300d
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Showing 3 changed files with 7 additions and 0 deletions.
diff --git a/elks/arch/i86/kernel/process.c b/elks/arch/i86/kernel/process.c
@@ -132,6 +132,7 @@ void arch_setup_user_stack (register struct task_struct * t, word_t entry)
 void arch_setup_sighandler_stack(register struct task_struct *t,
                                  __kern_sighandler_t addr,unsigned signr)
 {
+    printk("SIGCB %d: DS %x SS %x\n", t->pid, t->t_regs.ds, t->t_regs.ss);
     debug("Stack %x:%x was %x %x %x %x\n", _FP_SEG(addr), _FP_OFF(addr),
            get_ustack(t,0), get_ustack(t,2), get_ustack(t,4), get_ustack(t,6));
     put_ustack(t, -6, (int)get_ustack(t,0));

diff --git a/libc/system/signalcb.S b/libc/system/signalcb.S
@@ -20,7 +20,10 @@ _signal_cbhandler:
 	push %dx
 	push %si
 	push %di
+	push %ds
 	push %es
+	mov %ss,%ax
+	mov %ax,%ds
 
 	mov 6(%bp),%bx
 #ifndef __IA16_CALLCVT_REGPARMCALL
@@ -43,6 +46,7 @@ _signal_cbhandler:
 #endif
 
 	pop %es
+	pop %ds
 	pop %di
 	pop %si
 	pop %dx

diff --git a/libc/watcom/asm/signalcb.asm b/libc/watcom/asm/signalcb.asm
@@ -20,6 +20,8 @@ __signal_cbhandler proc far
         push di
         push ds
         push es
+        mov ax,ss                   ; ensure valid DS (=SS)
+        mov ds,ax
 
         mov ax,6[bp]                ; get signal #
         callf _signal_wchandler_    ; call user function from C