From patchwork series 422629

https://patchwork.ozlabs.org//project/linuxppc-dev/list/?series=422629

Author: Fox Snowpatch

include/uapi/linux/personality.h

@@ -22,6 +22,7 @@ enum {
 	WHOLE_SECONDS =		0x2000000,
 	STICKY_TIMEOUTS	=	0x4000000,
 	ADDR_LIMIT_3GB = 	0x8000000,
+	ADDR_LIMIT_47BIT = 	0x10000000,
 };
 
 /*

mm/mmap.c

@@ -1766,6 +1766,9 @@ unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
 {
 	unsigned long addr;
 
+	if (current->personality & ADDR_LIMIT_47BIT)
+		info->high_limit = MIN(info->high_limit, BIT(47) - 1);
+
 	if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
 		addr = unmapped_area_topdown(info);
 	else

tools/testing/selftests/mm/.gitignore

@@ -32,6 +32,7 @@ mlock-random-test
 virtual_address_range
 gup_test
 va_128TBswitch
+map_47bit_personality
 map_fixed_noreplace
 write_to_hugetlbfs
 hmm-tests

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_47bit_personality
 TEST_GEN_FILES += map_fixed_noreplace
 TEST_GEN_FILES += map_hugetlb
 TEST_GEN_FILES += map_populate

tools/testing/selftests/mm/map_47bit_personality.c

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test the ADDR_LIMIT_47BIT personality flag.
+ */
+#include <sys/syscall.h>
+#include <sys/mman.h>
+#include <errno.h>
+#include "../kselftest.h"
+
+#define LENGTH (100000000)
+
+#define ADDR_LIMIT_47BIT	0x10000000
+#define BIT47			1UL << 47
+
+/*
+ * Map memory with ADDR_LIMIT_47BIT until no memory left. Ensure that all returned
+ * addresses are below 47 bits.
+ */
+int main(int argc, char **argv)
+{
+	void *addr;
+
+	syscall(__NR_personality, ADDR_LIMIT_47BIT);
+
+	do {
+		addr = mmap(0, LENGTH, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	} while (addr != MAP_FAILED && (unsigned long)addr < BIT47);
+
+	if (errno == ENOMEM)
+		ksft_test_result_pass("ADDR_LIMIT_47BIT works\n");
+	else
+		ksft_test_result_fail("mmap returned address above 47 bits with ADDR_LIMIT_47BIT with addr: %p and err: %s\n",
+				      addr, strerror(errno));
+}