From: Matthias Kruk <m@m10k.eu>
Date: Wed, 25 Sep 2019 13:46:09 +0000 (+0900)
Subject: Add privilege level information to processes and tasks
X-Git-Url: https://git.corax.cc/?a=commitdiff_plain;h=79cd88869e61f72179aa2e24512fc919abab56cd;p=corax

Add privilege level information to processes and tasks
---

diff --git a/kernel/arch/process.c b/kernel/arch/process.c
index 552abbc..f3716a1 100644
--- a/kernel/arch/process.c
+++ b/kernel/arch/process.c
@@ -8,7 +8,8 @@
 
 struct process {
 	struct pagedir *p_pgdir;
-	struct task *p_tasks;
+	struct task    *p_tasks;
+	u32_t          p_privl;
 };
 
 void foo(void)
@@ -20,7 +21,7 @@ void foo(void)
 
 extern int _pg_dir_vpxlate(pg_dir_t*, u32_t, u32_t*);
 
-int process_create(process_t **dst)
+int process_create(process_t **dst, u32_t ppl)
 {
 	int ret_val;
 	process_t *proc;
@@ -50,8 +51,10 @@ int process_create(process_t **dst)
 			goto cleanup;
 		}
 
+		proc->p_privl = ppl;
+
 		task_prepare(proc->p_tasks, (u32_t)pdbr, (u32_t)foo,
-					 (u32_t)kstack, (u32_t)ustack + PAGE_SIZE, 3);
+					 (u32_t)kstack, (u32_t)ustack + PAGE_SIZE, ppl);
 
 		proc->p_tasks->t_sp = (u32_t)(CONFIG_KERNEL_STACK_BASE +
 									  ((u32_t)proc->p_tasks->t_sp - (u32_t)kstack));
diff --git a/kernel/arch/task.S b/kernel/arch/task.S
index b78b2af..f69c1bf 100644
--- a/kernel/arch/task.S
+++ b/kernel/arch/task.S
@@ -27,6 +27,7 @@
 #define OFFSET_ESP0   0
 #define OFFSET_CR3    4
 #define OFFSET_KSTACK 8
+#define OFFSET_PRIVL  12
 
 .extern _cpu
 
@@ -52,6 +53,10 @@ task_prepare:
 	movl	8(%esp), %eax
 	movl	%eax, OFFSET_CR3(%edi)
 
+	/* store privilege level in task structure */
+	movl	24(%esp), %eax
+	movl	%eax, OFFSET_PRIVL(%edi)
+
 	/* calculate stack start (since it grows down) */
 	movl	16(%esp), %eax
 	addl	$CONFIG_KERNEL_STACK_SIZE, %eax
@@ -168,18 +173,24 @@ task_switch:
 	movl	%ecx, CPU_ESP0(%eax)
 	movl	$KERNEL_DATA, CPU_SS0(%eax)
 
+	/* set CS according to the task's privilege level */
+	movl	OFFSET_PRIVL(%edi), %ecx
+	shll	$4, %ecx
+	addl	$8, %ecx
+	orl		OFFSET_PRIVL(%edi), %ecx
+	movl	%ecx, CPU_CS(%eax)
+
 	/*
-	 * We need to figure out the task's privilege level and
-	 * set the segment registers accordingly
+	 * Set the data segment selectors (this assumes a privilege
+	 * level's DS descriptor follows the CS descriptor)
 	 */
-	/*
-	movl	$USER_CODE, CPU_CS(%eax)
-	movl	$USER_DATA, CPU_DS(%eax)
-	movl	$USER_DATA, CPU_ES(%eax)
-	movl	$USER_DATA, CPU_FS(%eax)
-	movl	$USER_DATA, CPU_GS(%eax)
-	movl	$USER_DATA, CPU_SS(%eax)
-	*/
+	addl	$8, %ecx
+	movl	%ecx, CPU_DS(%eax)
+	movl	%ecx, CPU_ES(%eax)
+	movl	%ecx, CPU_FS(%eax)
+	movl	%ecx, CPU_GS(%eax)
+	movl	%ecx, CPU_SS(%eax)
+
 	movl	OFFSET_CR3(%edi), %ecx
 
 	/* check if we can avoid writing to cr3, which would clear the TLB */
diff --git a/kernel/include/arch.h b/kernel/include/arch.h
index 43064fd..7503a2b 100644
--- a/kernel/include/arch.h
+++ b/kernel/include/arch.h
@@ -27,6 +27,7 @@ struct task {
 	u32_t t_sp;
 	u32_t t_pgdir;
 	void *t_kstack;
+	u32_t t_privl;
 } __attribute__((packed));
 
 int     cpu_get_id(void);
@@ -35,7 +36,7 @@ u64_t   cpu_timestamp(void);
 
 u32_t   cpu_set_pstate(int pstate);
 
-int     process_create(process_t**);
+int     process_create(process_t**, u32_t);
 
 int     task_prepare(struct task*, u32_t cr3, u32_t eip, u32_t esp0, u32_t esp, u32_t priv);
 int     task_switch(struct task*);