From: Matthias Kruk <m@m10k.eu>
Date: Sun, 5 Jan 2020 07:52:36 +0000 (+0900)
Subject: Implement _task_sig_stub assembly function for tasks executing signal handlers on... 
X-Git-Url: https://git.corax.cc/?a=commitdiff_plain;h=c468f8aa4e8968c467cbe3bc66cbf142cfcd5596;p=corax

Implement _task_sig_stub assembly function for tasks executing signal handlers on the way out from the kernel
---

diff --git a/kernel/arch/task.S b/kernel/arch/task.S
index fb55a27..f05f64b 100644
--- a/kernel/arch/task.S
+++ b/kernel/arch/task.S
@@ -32,6 +32,7 @@
 .global task_move_stack
 .global task_lock
 .global task_unlock
+.global _task_sig_stub
 
 task_prepare:
 	/*
@@ -498,3 +499,30 @@ task_unlock:
 	call	spinlock_unlock
 	subl	$OFFSET_TASK_LOCK, 4(%esp)
 	ret
+
+	/*
+	 * task_sig_stub is used to execute a signal handler while returning
+	 * from kernel to user space. The stack frame has to look like this:
+	 *
+	 * |      ...       |
+	 * +----------------+
+	 * | struct siginfo | the address of this is the `si' argument
+	 * |      data      | this is the `data' argument
+	 * |     signal     | this is the `sig' argument
+	 * |     handler    | (*sa_sigaction)(int sig, siginfo_t *si, void *data)
+	 * |      EIP       | the original return address of the interrupt
+	 * +----------------+
+	*/
+_task_sig_stub:
+	pusha
+	movl	36(%esp), %edx
+	movl	40(%esp), %eax
+	movl	44(%esp), %ecx
+	leal	48(%esp), %ebx
+	pushl	%ecx
+	pushl	%ebx
+	pushl	%eax
+	call	*%edx
+	addl	$12, %esp
+	popa
+	ret