Merge patch series "riscv: mm: Do not restrict mmap address based on hint"

Charlie Jenkins <charlie@rivosinc.com> says:

There have been a couple of reports that using the hint address to
restrict the address returned by mmap hint address has caused issues in
applications. A different solution for restricting addresses returned by
mmap is necessary to avoid breakages.

[Palmer: This also just wasn't doing the right thing in the first place,
as it didn't handle the sv39 cases we were trying to deal with.]

* b4-shazam-merge:
  riscv: mm: Do not restrict mmap address based on hint
  riscv: selftests: Remove mmap hint address checks
  Revert "RISC-V: mm: Document mmap changes"

Link: https://lore.kernel.org/r/20240826-riscv_mmap-v1-0-cd8962afe47f@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Documentation/arch/riscv/vm-layout.rst

@@ -134,19 +134,3 @@ RISC-V Linux Kernel SV57
    ffffffff00000000 |  -4     GB | ffffffff7fffffff |    2 GB | modules, BPF
    ffffffff80000000 |  -2     GB | ffffffffffffffff |    2 GB | kernel
   __________________|____________|__________________|_________|____________________________________________________________
-
-
-Userspace VAs
---------------------
-To maintain compatibility with software that relies on the VA space with a
-maximum of 48 bits the kernel will, by default, return virtual addresses to
-userspace from a 48-bit range (sv48). This default behavior is achieved by
-passing 0 into the hint address parameter of mmap. On CPUs with an address space
-smaller than sv48, the CPU maximum supported address space will be the default.
-
-Software can "opt-in" to receiving VAs from another VA space by providing
-a hint address to mmap. When a hint address is passed to mmap, the returned
-address will never use more bits than the hint address. For example, if a hint
-address of `1 << 40` is passed to mmap, a valid returned address will never use
-bits 41 through 63. If no mappable addresses are available in that range, mmap
-will return `MAP_FAILED`.

arch/riscv/include/asm/processor.h

@@ -14,36 +14,14 @@
 
 #include <asm/ptrace.h>
 
-/*
- * addr is a hint to the maximum userspace address that mmap should provide, so
- * this macro needs to return the largest address space available so that
- * mmap_end < addr, being mmap_end the top of that address space.
- * See Documentation/arch/riscv/vm-layout.rst for more details.
- */
 #define arch_get_mmap_end(addr, len, flags)			\
 ({								\
-	unsigned long mmap_end;					\
+	STACK_TOP_MAX;						\
-	typeof(addr) _addr = (addr);				\
-	if ((_addr) == 0 || is_compat_task() ||			\
-	    ((_addr + len) > BIT(VA_BITS - 1)))			\
-		mmap_end = STACK_TOP_MAX;			\
-	else							\
-		mmap_end = (_addr + len);			\
-	mmap_end;						\
 })
 
 #define arch_get_mmap_base(addr, base)				\
 ({								\
-	unsigned long mmap_base;				\
+	base;							\
-	typeof(addr) _addr = (addr);				\
-	typeof(base) _base = (base);				\
-	unsigned long rnd_gap = DEFAULT_MAP_WINDOW - (_base);	\
-	if ((_addr) == 0 || is_compat_task() || 		\
-	    ((_addr + len) > BIT(VA_BITS - 1)))			\
-		mmap_base = (_base);				\
-	else							\
-		mmap_base = (_addr + len) - rnd_gap;		\
-	mmap_base;						\
 })
 
 #ifdef CONFIG_64BIT

tools/testing/selftests/riscv/mm/mmap_bottomup.c

@@ -7,8 +7,6 @@
 TEST(infinite_rlimit)
 {
 	EXPECT_EQ(BOTTOM_UP, memory_layout());
-
-	TEST_MMAPS;
 }
 
 TEST_HARNESS_MAIN

tools/testing/selftests/riscv/mm/mmap_default.c

@@ -7,8 +7,6 @@
 TEST(default_rlimit)
 {
 	EXPECT_EQ(TOP_DOWN, memory_layout());
-
-	TEST_MMAPS;
 }
 
 TEST_HARNESS_MAIN

tools/testing/selftests/riscv/mm/mmap_test.h

@@ -10,76 +10,9 @@
 #define TOP_DOWN 0
 #define BOTTOM_UP 1
 
-#if __riscv_xlen == 64
-uint64_t random_addresses[] = {
-	0x19764f0d73b3a9f0, 0x016049584cecef59, 0x3580bdd3562f4acd,
-	0x1164219f20b17da0, 0x07d97fcb40ff2373, 0x76ec528921272ee7,
-	0x4dd48c38a3de3f70, 0x2e11415055f6997d, 0x14b43334ac476c02,
-	0x375a60795aff19f6, 0x47f3051725b8ee1a, 0x4e697cf240494a9f,
-	0x456b59b5c2f9e9d1, 0x101724379d63cb96, 0x7fe9ad31619528c1,
-	0x2f417247c495c2ea, 0x329a5a5b82943a5e, 0x06d7a9d6adcd3827,
-	0x327b0b9ee37f62d5, 0x17c7b1851dfd9b76, 0x006ebb6456ec2cd9,
-	0x00836cd14146a134, 0x00e5c4dcde7126db, 0x004c29feadf75753,
-	0x00d8b20149ed930c, 0x00d71574c269387a, 0x0006ebe4a82acb7a,
-	0x0016135df51f471b, 0x00758bdb55455160, 0x00d0bdd949b13b32,
-	0x00ecea01e7c5f54b, 0x00e37b071b9948b1, 0x0011fdd00ff57ab3,
-	0x00e407294b52f5ea, 0x00567748c200ed20, 0x000d073084651046,
-	0x00ac896f4365463c, 0x00eb0d49a0b26216, 0x0066a2564a982a31,
-	0x002e0d20237784ae, 0x0000554ff8a77a76, 0x00006ce07a54c012,
-	0x000009570516d799, 0x00000954ca15b84d, 0x0000684f0d453379,
-	0x00002ae5816302b5, 0x0000042403fb54bf, 0x00004bad7392bf30,
-	0x00003e73bfa4b5e3, 0x00005442c29978e0, 0x00002803f11286b6,
-	0x000073875d745fc6, 0x00007cede9cb8240, 0x000027df84cc6a4f,
-	0x00006d7e0e74242a, 0x00004afd0b836e02, 0x000047d0e837cd82,
-	0x00003b42405efeda, 0x00001531bafa4c95, 0x00007172cae34ac4,
-};
-#else
-uint32_t random_addresses[] = {
-	0x8dc302e0, 0x929ab1e0, 0xb47683ba, 0xea519c73, 0xa19f1c90, 0xc49ba213,
-	0x8f57c625, 0xadfe5137, 0x874d4d95, 0xaa20f09d, 0xcf21ebfc, 0xda7737f1,
-	0xcedf392a, 0x83026c14, 0xccedca52, 0xc6ccf826, 0xe0cd9415, 0x997472ca,
-	0xa21a44c1, 0xe82196f5, 0xa23fd66b, 0xc28d5590, 0xd009cdce, 0xcf0be646,
-	0x8fc8c7ff, 0xe2a85984, 0xa3d3236b, 0x89a0619d, 0xc03db924, 0xb5d4cc1b,
-	0xb96ee04c, 0xd191da48, 0xb432a000, 0xaa2bebbc, 0xa2fcb289, 0xb0cca89b,
-	0xb0c18d6a, 0x88f58deb, 0xa4d42d1c, 0xe4d74e86, 0x99902b09, 0x8f786d31,
-	0xbec5e381, 0x9a727e65, 0xa9a65040, 0xa880d789, 0x8f1b335e, 0xfc821c1e,
-	0x97e34be4, 0xbbef84ed, 0xf447d197, 0xfd7ceee2, 0xe632348d, 0xee4590f4,
-	0x958992a5, 0xd57e05d6, 0xfd240970, 0xc5b0dcff, 0xd96da2c2, 0xa7ae041d,
-};
-#endif
-
-// Only works on 64 bit
-#if __riscv_xlen == 64
 #define PROT (PROT_READ | PROT_WRITE)
 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS)
 
-/* mmap must return a value that doesn't use more bits than the hint address. */
-static inline unsigned long get_max_value(unsigned long input)
-{
-	unsigned long max_bit = (1UL << (((sizeof(unsigned long) * 8) - 1 -
-					  __builtin_clzl(input))));
-
-	return max_bit + (max_bit - 1);
-}
-
-#define TEST_MMAPS                                                            \
-	({                                                                    \
-		void *mmap_addr;                                              \
-		for (int i = 0; i < ARRAY_SIZE(random_addresses); i++) {      \
-			mmap_addr = mmap((void *)random_addresses[i],         \
-					 5 * sizeof(int), PROT, FLAGS, 0, 0); \
-			EXPECT_NE(MAP_FAILED, mmap_addr);                     \
-			EXPECT_GE((void *)get_max_value(random_addresses[i]), \
-				  mmap_addr);                                 \
-			mmap_addr = mmap((void *)random_addresses[i],         \
-					 5 * sizeof(int), PROT, FLAGS, 0, 0); \
-			EXPECT_NE(MAP_FAILED, mmap_addr);                     \
-			EXPECT_GE((void *)get_max_value(random_addresses[i]), \
-				  mmap_addr);                                 \
-		}                                                             \
-	})
-#endif /* __riscv_xlen == 64 */
-
 static inline int memory_layout(void)
 {
 	void *value1 = mmap(NULL, sizeof(int), PROT, FLAGS, 0, 0);