From 55564101a2263650f05502aa43f0d238e3d91e03 Mon Sep 17 00:00:00 2001
From: Matthias Kruk <m@m10k.eu>
Date: Mon, 18 Nov 2019 17:56:38 +0900
Subject: [PATCH] Make use of pg_dir_foreach_region() function in
 process_create() function to clone or map memory regions of the parent
 process, where necessary

---
 kernel/core/process.c | 78 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/kernel/core/process.c b/kernel/core/process.c
index d1c860f..118b977 100644
--- a/kernel/core/process.c
+++ b/kernel/core/process.c
@@ -159,6 +159,70 @@ static inline int DQ(process_t *p)
 	return(ret_val);
 }
 
+int _fork_region(pg_dir_t *parent_dir, region_t *reg, void *data)
+{
+	pg_dir_t *child_dir;
+	int ret_val;
+
+	ret_val = 0;
+	child_dir = (pg_dir_t*)data;
+
+	if(!(reg->reg_flags & REGION_PRIV)) {
+		/* skip regions that are private to the parent */
+
+		switch(reg->reg_type) {
+		case REGION_TEXT:
+		case REGION_BSS:
+		case REGION_DATA:
+		case REGION_RODATA:
+			/* copy the region and its contents */
+			ret_val = pg_dir_clone_region(child_dir, parent_dir, reg);
+			break;
+
+		case REGION_KSTACK:
+		case REGION_STACK:
+		case REGION_HEAP:
+			/* don't clone KSTACK/STACK/HEAP regions */
+		default:
+			break;
+		}
+	}
+
+	return(ret_val);
+}
+
+int _vfork_region(pg_dir_t *parent_dir, region_t *reg, void *data)
+{
+	pg_dir_t *child_dir;
+	int ret_val;
+
+	ret_val = 0;
+	child_dir = (pg_dir_t*)data;
+
+	if(!(reg->reg_flags & REGION_PRIV)) {
+		/* skip private regions */
+
+		switch(reg->reg_type) {
+		case REGION_TEXT:
+		case REGION_BSS:
+		case REGION_DATA:
+		case REGION_RODATA:
+			/* directly map the region into the new page directory */
+			ret_val = pg_dir_map_region(child_dir, parent_dir, reg);
+			break;
+
+		case REGION_KSTACK:
+		case REGION_STACK:
+		case REGION_HEAP:
+			/* don't map these */
+		default:
+			break;
+		}
+	}
+
+	return(ret_val);
+}
+
 int process_create(process_t **dst, pid_t pid, u32_t ppl, void *entry)
 {
 	int ret_val;
@@ -206,6 +270,10 @@ int process_create(process_t **dst, pid_t pid, u32_t ppl, void *entry)
 			goto cleanup;
 		}
 
+		/*
+		 * The new page directory contains only the kernel regions.
+		 */
+
 		pdbr = pg_dir_get_pdbr(proc->p_pgdir);
 		kstack = pg_dir_get_kstack(proc->p_pgdir);
 		ustack = pg_dir_get_ustack(proc->p_pgdir);
@@ -269,6 +337,16 @@ int process_create(process_t **dst, pid_t pid, u32_t ppl, void *entry)
 			cproc = (process_t*)ctask->t_proc;
 			custack = pg_dir_get_ustack(cproc->p_pgdir);
 
+			/*
+			 * The address space of the new process doesn't contain any memory segments
+			 * but those relevant for the kernel. If the process is a fork, clone all non-kernel
+			 * memory segments that are present in the parent's page directory. If it is a vfork,
+			 * directly map the segments into this address space.
+			 */
+			pg_dir_foreach_region(cproc->p_pgdir,
+								  entry == PROC_ENTRY_FORK ? _fork_region : _vfork_region,
+								  proc->p_pgdir);
+
 			/*
 			 * In the case of fork() and vfork() we have to get the address that the
 			 * interrupt is supposed to return to. The stack that the address was pushed
-- 
2.47.3