From: acevest <zhaoyanbai@126.com>
Date: Wed, 24 Nov 2021 13:57:31 +0000 (+0800)
Subject: fix在x86_64的机器上可用的内存地址的低32bit可能出现回绕的问题
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/man.rndc.html?a=commitdiff_plain;h=392004124f627c7b99024b92e320cdd2355f9eea;p=kernel.git

fix在x86_64的机器上可用的内存地址的低32bit可能出现回绕的问题
---

diff --git a/mm/bootmem.c b/mm/bootmem.c
index 8f3088c..9c2d7d5 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -99,6 +99,14 @@ void e820_init_bootmem_data() {
         unsigned long bgn_pfn = PFN_UP(p->addr);
         unsigned long end_pfn = PFN_DW(p->addr + p->size);
 
+        // 在x86_64的机器上低32bit可能出现回绕的情况
+        // 就算物理内存小于4G也可能出现
+        // 这种情况直接忽略
+        if (bgn_pfn < bootmem_data.max_pfn) {
+            break;
+        }
+
+
         if (bootmem_data.min_pfn > bgn_pfn) {
             bootmem_data.min_pfn = bgn_pfn;
         }
@@ -122,6 +130,7 @@ void e820_init_bootmem_data() {
 }
 
 void register_bootmem_pages() {
+    unsigned long max_pfn = 0;
     for (unsigned int i = 0; i < boot_params.e820map.map_cnt; ++i) {
         struct e820_entry *p = boot_params.e820map.map + i;
 
@@ -132,6 +141,16 @@ void register_bootmem_pages() {
         unsigned long bgn_pfn = PFN_UP(p->addr);
         unsigned long end_pfn = PFN_DW(p->addr + p->size);
 
+        // 在x86_64的机器上低32bit可能出现回绕的情况
+        // 就算物理内存小于4G也可能出现
+        // 这种情况直接忽略
+        if (bgn_pfn < max_pfn) {
+            break;
+        }
+        max_pfn = end_pfn;
+
+
+
 #if 1
         // 用一个相对快的方式
         fast_init_bootmem_bitmap(bgn_pfn, end_pfn, 0);