From 0fd9c19c5d66a380ad4b2b881881ce7fba9a6d27 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sat, 21 May 2022 18:26:54 +0200
Subject: syscall/memflag: implement freeing memory
---
src/kernel/arch/i386/pagedir.c | 50 ++++++++++++++++++++++++++----------------
1 file changed, 31 insertions(+), 19 deletions(-)
(limited to 'src/kernel/arch/i386')
diff --git a/src/kernel/arch/i386/pagedir.c b/src/kernel/arch/i386/pagedir.c
index 00539b7..28608dc 100644
--- a/src/kernel/arch/i386/pagedir.c
+++ b/src/kernel/arch/i386/pagedir.c
@@ -68,6 +68,25 @@ void pagedir_free(struct pagedir *dir) {
page_free(dir, 1);
}
+static struct pagetable_entry*
+get_entry(struct pagedir *dir, const void __user *virt) {
+ uint32_t pd_idx = ((uintptr_t)virt) >> 22;
+ uint32_t pt_idx = ((uintptr_t)virt) >> 12 & 0x03FF;
+ struct pagetable_entry *pagetable;
+
+ if (!dir->e[pd_idx].present) return NULL;
+
+ pagetable = (void*)(dir->e[pd_idx].address << 11);
+ return &pagetable[pt_idx];
+}
+
+void *pagedir_unmap(struct pagedir *dir, void __user *virt) {
+ void *phys = pagedir_virt2phys(dir, virt, false, false);
+ struct pagetable_entry *page = get_entry(dir, virt);
+ page->present = false;
+ return phys;
+}
+
void pagedir_map(struct pagedir *dir, void __user *virt, void *phys,
bool user, bool writeable)
{
@@ -146,29 +165,22 @@ struct pagedir *pagedir_copy(const struct pagedir *orig) {
return clone;
}
+bool pagedir_iskern(struct pagedir *dir, const void __user *virt) {
+ struct pagetable_entry *page = get_entry(dir, virt);
+ return page && page->present && !page->user;
+}
+
void *pagedir_virt2phys(struct pagedir *dir, const void __user *virt,
bool user, bool writeable)
{
- uintptr_t virt_cast = (uintptr_t) virt;
+ struct pagetable_entry *page;
uintptr_t phys;
- uint32_t pd_idx = virt_cast >> 22;
- uint32_t pt_idx = virt_cast >> 12 & 0x03FF;
- struct pagetable_entry *pagetable, page;
-
- /* DOESN'T CHECK PERMISSIONS ON PAGE DIRS, TODO
- * while i don't currently see a reason to set permissions
- * directly on page dirs, i might see one in the future.
- * leaving this as-is would be a security bug */
- if (!dir->e[pd_idx].present) return NULL;
-
- pagetable = (void*)(dir->e[pd_idx].address << 11);
- page = pagetable[pt_idx];
-
- if (!page.present) return NULL;
- if (user && !page.user) return NULL;
- if (writeable && !page.writeable) return NULL;
+ page = get_entry(dir, virt);
+ if (!page || !page->present) return NULL;
+ if (user && !page->user) return NULL;
+ if (writeable && !page->writeable) return NULL;
- phys = page.address << 11;
- phys |= virt_cast & 0xFFF;
+ phys = page->address << 11;
+ phys |= ((uintptr_t)virt) & 0xFFF;
return (void*)phys;
}
--
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