linux-kernel - [PATCH 1/2] mips: vdso: prefer do_mmap() to mmap

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Message-ID: <ef076e381570f709e5c2c142dc030ec5b3309a0e.1735819274.git.lorenzo.stoakes@oracle.com>
Date: Thu,  2 Jan 2025 12:10:51 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org
Subject: [PATCH 1/2] mips: vdso: prefer do_mmap() to mmap_region()

mmap_region() is an internal memory management implementation detail that
is not intended to be used outside of the memory management subsystem.

Map the delay slot emulation page using do_mmap() which makes use of the
already-held mmap write lock and bypasses unneeded populate and userfaultfd
logic.

This should have the precise same behaviour as the existing logic.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 arch/mips/kernel/vdso.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
index 4c8e3c0aa210..75c9d3618f58 100644
--- a/arch/mips/kernel/vdso.c
+++ b/arch/mips/kernel/vdso.c
@@ -11,6 +11,7 @@
 #include <linux/ioport.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
+#include <linux/mman.h>
 #include <linux/random.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
@@ -97,11 +98,12 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 		return -EINTR;
 
 	if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
+		unsigned long unused;
+
 		/* Map delay slot emulation page */
-		base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
-				VM_READ | VM_EXEC |
-				VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
-				0, NULL);
+		base = do_mmap(NULL, STACK_TOP, PAGE_SIZE, PROT_READ | PROT_EXEC,
+			       MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, 0, 0, &unused,
+			       NULL);
 		if (IS_ERR_VALUE(base)) {
 			ret = base;
 			goto out;
-- 
2.47.1