add option to map zeroed pages

- add also an option to remap pages without IPIs
- be sure that an IPIs is not required

hermit/arch/x86/include/asm/page.h

@@ -165,9 +165,23 @@ int page_init(void);
  * @param phyaddr Physical address to map from
  * @param npages The region's size in number of pages
  * @param bits Further page flags
+ * @param do_ipi if set, inform via IPI all other cores
  * @return
  */
-int page_map(size_t viraddr, size_t phyaddr, size_t npages, size_t bits);
+int __page_map(size_t viraddr, size_t phyaddr, size_t npages, size_t bits, uint8_t do_ipi);
+
+/** @brief Map a continuous region of pages
+ *
+ * @param viraddr Desired virtual address
+ * @param phyaddr Physical address to map from
+ * @param npages The region's size in number of pages
+ * @param bits Further page flags
+ * @return
+ */
+static inline int page_map(size_t viraddr, size_t phyaddr, size_t npages, size_t bits)
+{
+	return __page_map(viraddr, phyaddr, npages, bits, 1);
+}
 
 /** @brief Unmap a continuous region of pages
  *

hermit/arch/x86/mm/page.c

@@ -112,7 +112,7 @@ int page_set_flags(size_t viraddr, uint32_t npages, int flags)
 	return -EINVAL;
 }
 
-int page_map(size_t viraddr, size_t phyaddr, size_t npages, size_t bits)
+int __page_map(size_t viraddr, size_t phyaddr, size_t npages, size_t bits, uint8_t do_ipi)
 {
 	int lvl, ret = -ENOMEM;
 	long vpn = viraddr >> PAGE_BITS;
@@ -169,7 +169,7 @@ int page_map(size_t viraddr, size_t phyaddr, size_t npages, size_t bits)
 		}
 	}
 
-	if (send_ipi)
+	if (do_ipi && send_ipi)
 		ipi_tlb_flush();
 
 	ret = 0;
@@ -246,8 +246,7 @@ void page_fault_handler(struct state *s)
 		 // on demand userspace heap mapping
 		viraddr &= PAGE_MASK;
 
-		// TODO: a function to get zeroed pages is missing
-		size_t phyaddr = get_page();
+		size_t phyaddr = get_zeroed_page();
 		if (BUILTIN_EXPECT(!phyaddr, 0)) {
 			kprintf("out of memory: task = %u\n", task->id);
 			goto default_handler;
@@ -265,9 +264,6 @@ void page_fault_handler(struct state *s)
 			goto default_handler;
 		}
 
-		// reset page
-		memset(viraddr, 0x00, PAGE_SIZE);
-
 		spinlock_irqsave_unlock(&page_lock);
 
 		return;

hermit/include/hermit/memory.h

@@ -48,6 +48,9 @@ size_t get_pages(size_t npages);
  */
 static inline size_t get_page(void) { return get_pages(1); }
 
+/** @brief Get a single zeroed page */
+size_t get_zeroed_page(void);
+
 /** @brief release physical page frames */
 int put_pages(size_t phyaddr, size_t npages);
 

hermit/mm/memory.c

@@ -30,6 +30,7 @@
 #include <hermit/stdio.h>
 #include <hermit/string.h>
 #include <hermit/spinlock.h>
+#include <hermit/memory.h>
 
 #include <asm/atomic.h>
 #include <asm/page.h>
@@ -104,6 +105,40 @@ out:
 	return ret;
 }
 
+DEFINE_PER_CORE(size_t, ztmp_addr, 0);
+
+size_t get_zeroed_page(void)
+{
+	size_t phyaddr = get_page();
+	size_t viraddr;
+	uint8_t flags;
+
+	if (BUILTIN_EXPECT(!phyaddr, 0))
+		return 0;
+
+	flags = irq_nested_disable();
+
+	viraddr = per_core(ztmp_addr);
+	if (BUILTIN_EXPECT(!viraddr, 0))
+	{
+		viraddr = vma_alloc(PAGE_SIZE, VMA_READ|VMA_WRITE|VMA_CACHEABLE);
+		if (BUILTIN_EXPECT(!viraddr, 0))
+			goto novaddr;
+
+		//kprintf("Core %d uses 0x%zx as temporary address\n", CORE_ID, viraddr);
+		set_per_core(ztmp_addr, viraddr);
+	}
+
+	__page_map(viraddr, phyaddr, 1, PG_GLOBAL|PG_RW|PG_PRESENT, 0);
+
+	memset((void*) viraddr, 0x00, PAGE_SIZE);
+
+novaddr:
+	irq_nested_enable(flags);
+
+	return phyaddr;
+}
+
 /* TODO: reunion of elements is still missing */
 int put_pages(size_t phyaddr, size_t npages)
 {