linux-hardening - [RFC PATCH v2 10/19] x86/mm: Use alloc_table() for fill

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Message-Id: <20210830235927.6443-11-rick.p.edgecombe@intel.com>
Date:   Mon, 30 Aug 2021 16:59:18 -0700
From:   Rick Edgecombe <rick.p.edgecombe@...el.com>
To:     dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org,
        x86@...nel.org, akpm@...ux-foundation.org, keescook@...omium.org,
        shakeelb@...gle.com, vbabka@...e.cz, rppt@...nel.org
Cc:     Rick Edgecombe <rick.p.edgecombe@...el.com>, linux-mm@...ck.org,
        linux-hardening@...r.kernel.org,
        kernel-hardening@...ts.openwall.com, ira.weiny@...el.com,
        dan.j.williams@...el.com, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v2 10/19] x86/mm: Use alloc_table() for fill_pte(), etc

fill_pte(), set_pte_vaddr(), etc allocate page tables with
spp_getpage(). Use alloc_table() for these allocations in order to get
tables from the cache of protected pages when needed.

Opportunistically, fix a stale comment.

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
---
 arch/x86/mm/init_64.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 3c0323ad99da..de5a785ee89f 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -220,16 +220,19 @@ static void sync_global_pgds(unsigned long start, unsigned long end)
 
 /*
  * NOTE: This function is marked __ref because it calls __init function
- * (alloc_bootmem_pages). It's safe to do it ONLY when after_bootmem == 0.
+ * (memblock_alloc). It's safe to do it ONLY when after_bootmem == 0.
  */
 static __ref void *spp_getpage(void)
 {
 	void *ptr;
 
-	if (after_bootmem)
-		ptr = (void *) get_zeroed_page(GFP_ATOMIC);
-	else
+	if (after_bootmem) {
+		struct page *page = alloc_table(GFP_ATOMIC | __GFP_ZERO);
+
+		ptr = page ? page_address(page) : NULL;
+	} else {
 		ptr = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
+	}
 
 	if (!ptr || ((unsigned long)ptr & ~PAGE_MASK)) {
 		panic("set_pte_phys: cannot allocate page data %s\n",
-- 
2.17.1