linux-kernel - [PATCH RFC v2 4/4] selftests/mm: Create MAP_BELOW

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Message-Id: <20240829-patches-below_hint_mmap-v2-4-638a28d9eae0@rivosinc.com>
Date: Thu, 29 Aug 2024 00:16:01 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Arnd Bergmann <arnd@...db.de>, 
 Richard Henderson <richard.henderson@...aro.org>, 
 Ivan Kokshaysky <ink@...assic.park.msu.ru>, 
 Matt Turner <mattst88@...il.com>, Vineet Gupta <vgupta@...nel.org>, 
 Russell King <linux@...linux.org.uk>, Guo Ren <guoren@...nel.org>, 
 Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, 
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
 "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>, 
 Helge Deller <deller@....de>, Michael Ellerman <mpe@...erman.id.au>, 
 Nicholas Piggin <npiggin@...il.com>, 
 Christophe Leroy <christophe.leroy@...roup.eu>, 
 Naveen N Rao <naveen@...nel.org>, 
 Alexander Gordeev <agordeev@...ux.ibm.com>, 
 Gerald Schaefer <gerald.schaefer@...ux.ibm.com>, 
 Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
 Christian Borntraeger <borntraeger@...ux.ibm.com>, 
 Sven Schnelle <svens@...ux.ibm.com>, 
 Yoshinori Sato <ysato@...rs.sourceforge.jp>, Rich Felker <dalias@...c.org>, 
 John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>, 
 "David S. Miller" <davem@...emloft.net>, 
 Andreas Larsson <andreas@...sler.com>, Thomas Gleixner <tglx@...utronix.de>, 
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
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 "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, 
 Peter Zijlstra <peterz@...radead.org>, Muchun Song <muchun.song@...ux.dev>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
 Vlastimil Babka <vbabka@...e.cz>, 
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Shuah Khan <shuah@...nel.org>
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org, 
 linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org, 
 loongarch@...ts.linux.dev, linux-mips@...r.kernel.org, 
 linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, 
 linux-s390@...r.kernel.org, linux-sh@...r.kernel.org, 
 sparclinux@...r.kernel.org, linux-mm@...ck.org, 
 linux-kselftest@...r.kernel.org, Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH RFC v2 4/4] selftests/mm: Create MAP_BELOW_HINT test

Add a selftest for MAP_BELOW_HINT that maps until it runs out of space
below the hint address.

Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
 tools/testing/selftests/mm/Makefile         |  1 +
 tools/testing/selftests/mm/map_below_hint.c | 32 +++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index cfad627e8d94..4e2de85267b5 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -50,6 +50,7 @@ TEST_GEN_FILES += hugepage-shm
 TEST_GEN_FILES += hugepage-vmemmap
 TEST_GEN_FILES += khugepaged
 TEST_GEN_FILES += madv_populate
+TEST_GEN_FILES += map_below_hint
 TEST_GEN_FILES += map_fixed_noreplace
 TEST_GEN_FILES += map_hugetlb
 TEST_GEN_FILES += map_populate
diff --git a/tools/testing/selftests/mm/map_below_hint.c b/tools/testing/selftests/mm/map_below_hint.c
new file mode 100644
index 000000000000..55d6cbf90645
--- /dev/null
+++ b/tools/testing/selftests/mm/map_below_hint.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test the MAP_BELOW_HINT mmap flag.
+ */
+#include <sys/mman.h>
+#include <errno.h>
+#include "../kselftest.h"
+
+#define ADDR (1 << 20)
+#define LENGTH (ADDR / 10000)
+
+#define MAP_BELOW_HINT	  0x8000000	/* Not defined in all libc */
+
+/*
+ * Map memory with MAP_BELOW_HINT until no memory left. Ensure that all returned
+ * addresses are below the hint.
+ */
+int main(int argc, char **argv)
+{
+	void *addr;
+
+	do {
+		addr = mmap((void *)ADDR, LENGTH, PROT_READ | PROT_WRITE,
+			    MAP_PRIVATE | MAP_ANONYMOUS | MAP_BELOW_HINT, -1, 0);
+	} while (addr != MAP_FAILED && (unsigned long)addr <= ADDR);
+
+	if (errno == ENOMEM)
+		ksft_test_result_pass("MAP_BELOW_HINT works\n");
+	else
+		ksft_test_result_fail("mmap returned address above hint with MAP_BELOW_HINT with error: %s\n",
+				      strerror(errno));
+}

-- 
2.45.0