Make sv48 the default address space for mmap as some applications
currently depend on this assumption. Users can now select a
desired address space using a non-zero hint address to mmap. Previously,
requesting the default address space from mmap by passing zero as the hint
address would result in using the largest address space possible. Some
applications depend on empty bits in the virtual address space, like Go and
Java, so this patch provides more flexibility for application developers.
-Charlie
---
v9:
- Raise the mmap_end default to STACK_TOP_MAX to allow the address space to grow
beyond the default of sv48 on sv57 machines as suggested by Alexandre
- Some of the mmap macros had unnecessary conditionals that I have removed
v8:
- Fix RV32 and the RV32 compat mode of RV64 (suggested by Conor)
- Extract out addr and base from the mmap macros (suggested by Alexandre)
v7:
- Changing RLIMIT_STACK inside of an executing program does not trigger
arch_pick_mmap_layout(), so rewrite tests to change RLIMIT_STACK from a
script before executing tests. RLIMIT_STACK of infinity forces bottomup
mmap allocation.
- Make arch_get_mmap_base macro more readible by extracting out the rnd
calculation.
- Use MMAP_MIN_VA_BITS in TASK_UNMAPPED_BASE to support case when mmap
attempts to allocate address smaller than DEFAULT_MAP_WINDOW.
- Fix incorrect wording in documentation.
v6:
- Rebase onto the correct base
v5:
- Minor wording change in documentation
- Change some parenthesis in arch_get_mmap_ macros
- Added case for addr==0 in arch_get_mmap_ because without this, programs would
crash if RLIMIT_STACK was modified before executing the program. This was
tested using the libhugetlbfs tests.
v4:
- Split testcases/document patch into test cases, in-code documentation, and
formal documentation patches
- Modified the mmap_base macro to be more legible and better represent memory
layout
- Fixed documentation to better reflect the implmentation
- Renamed DEFAULT_VA_BITS to MMAP_VA_BITS
- Added additional test case for rlimit changes
---
Charlie Jenkins (4):
RISC-V: mm: Restrict address space for sv39,sv48,sv57
RISC-V: mm: Add tests for RISC-V mm
RISC-V: mm: Update pgtable comment documentation
RISC-V: mm: Document mmap changes
Documentation/riscv/vm-layout.rst | 22 +++++++
arch/riscv/include/asm/elf.h | 2 +-
arch/riscv/include/asm/pgtable.h | 29 +++++++--
arch/riscv/include/asm/processor.h | 52 +++++++++++++--
tools/testing/selftests/riscv/Makefile | 2 +-
tools/testing/selftests/riscv/mm/.gitignore | 2 +
tools/testing/selftests/riscv/mm/Makefile | 15 +++++
.../riscv/mm/testcases/mmap_bottomup.c | 35 ++++++++++
.../riscv/mm/testcases/mmap_default.c | 35 ++++++++++
.../selftests/riscv/mm/testcases/mmap_test.h | 64 +++++++++++++++++++
.../selftests/riscv/mm/testcases/run_mmap.sh | 12 ++++
11 files changed, 258 insertions(+), 12 deletions(-)
create mode 100644 tools/testing/selftests/riscv/mm/.gitignore
create mode 100644 tools/testing/selftests/riscv/mm/Makefile
create mode 100644 tools/testing/selftests/riscv/mm/testcases/mmap_bottomup.c
create mode 100644 tools/testing/selftests/riscv/mm/testcases/mmap_default.c
create mode 100644 tools/testing/selftests/riscv/mm/testcases/mmap_test.h
create mode 100755 tools/testing/selftests/riscv/mm/testcases/run_mmap.sh
--
2.34.1
The behavior of mmap is modified with this patch series, so explain the
changes to the mmap hint address behavior.
Signed-off-by: Charlie Jenkins <[email protected]>
Reviewed-by: Alexandre Ghiti <[email protected]>
---
Documentation/riscv/vm-layout.rst | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/Documentation/riscv/vm-layout.rst b/Documentation/riscv/vm-layout.rst
index 5462c84f4723..69ff6da1dbf8 100644
--- a/Documentation/riscv/vm-layout.rst
+++ b/Documentation/riscv/vm-layout.rst
@@ -133,3 +133,25 @@ 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. A hint address passed to mmap will cause the largest
+address space that fits entirely into the hint to be used, unless there is no
+space left in the address space. If there is no space available in the requested
+address space, an address in the next smallest available address space will be
+returned.
+
+For example, in order to obtain 48-bit VA space, a hint address greater than
+:code:`1 << 47` must be provided. Note that this is 47 due to sv48 userspace
+ending at :code:`1 << 47` and the addresses beyond this are reserved for the
+kernel. Similarly, to obtain 57-bit VA space addresses, a hint address greater
+than or equal to :code:`1 << 56` must be provided.
--
2.34.1
Add tests that enforce mmap hint address behavior. mmap should default
to sv48. mmap will provide an address at the highest address space that
can fit into the hint address, unless the hint address is less than sv39
and not 0, then it will return a sv39 address.
These tests are split into two files: mmap_default.c and mmap_bottomup.c
because a new process must be exec'd in order to change the mmap layout.
The run_mmap.sh script sets the stack to be unlimited for the
mmap_bottomup.c test which triggers a bottomup layout.
Signed-off-by: Charlie Jenkins <[email protected]>
---
tools/testing/selftests/riscv/Makefile | 2 +-
tools/testing/selftests/riscv/mm/.gitignore | 2 +
tools/testing/selftests/riscv/mm/Makefile | 15 +++++
.../riscv/mm/testcases/mmap_bottomup.c | 35 ++++++++++
.../riscv/mm/testcases/mmap_default.c | 35 ++++++++++
.../selftests/riscv/mm/testcases/mmap_test.h | 64 +++++++++++++++++++
.../selftests/riscv/mm/testcases/run_mmap.sh | 12 ++++
7 files changed, 164 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/riscv/mm/.gitignore
create mode 100644 tools/testing/selftests/riscv/mm/Makefile
create mode 100644 tools/testing/selftests/riscv/mm/testcases/mmap_bottomup.c
create mode 100644 tools/testing/selftests/riscv/mm/testcases/mmap_default.c
create mode 100644 tools/testing/selftests/riscv/mm/testcases/mmap_test.h
create mode 100755 tools/testing/selftests/riscv/mm/testcases/run_mmap.sh
diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile
index f4b3d5c9af5b..4a9ff515a3a0 100644
--- a/tools/testing/selftests/riscv/Makefile
+++ b/tools/testing/selftests/riscv/Makefile
@@ -5,7 +5,7 @@
ARCH ?= $(shell uname -m 2>/dev/null || echo not)
ifneq (,$(filter $(ARCH),riscv))
-RISCV_SUBTARGETS ?= hwprobe vector
+RISCV_SUBTARGETS ?= hwprobe vector mm
else
RISCV_SUBTARGETS :=
endif
diff --git a/tools/testing/selftests/riscv/mm/.gitignore b/tools/testing/selftests/riscv/mm/.gitignore
new file mode 100644
index 000000000000..5c2c57cb950c
--- /dev/null
+++ b/tools/testing/selftests/riscv/mm/.gitignore
@@ -0,0 +1,2 @@
+mmap_bottomup
+mmap_default
diff --git a/tools/testing/selftests/riscv/mm/Makefile b/tools/testing/selftests/riscv/mm/Makefile
new file mode 100644
index 000000000000..11e0f0568923
--- /dev/null
+++ b/tools/testing/selftests/riscv/mm/Makefile
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2021 ARM Limited
+# Originally tools/testing/arm64/abi/Makefile
+
+# Additional include paths needed by kselftest.h and local headers
+CFLAGS += -D_GNU_SOURCE -std=gnu99 -I.
+
+TEST_GEN_FILES := testcases/mmap_default testcases/mmap_bottomup
+
+TEST_PROGS := testcases/run_mmap.sh
+
+include ../../lib.mk
+
+$(OUTPUT)/mm: testcases/mmap_default.c testcases/mmap_bottomup.c testcases/mmap_tests.h
+ $(CC) -o$@ $(CFLAGS) $(LDFLAGS) $^
diff --git a/tools/testing/selftests/riscv/mm/testcases/mmap_bottomup.c b/tools/testing/selftests/riscv/mm/testcases/mmap_bottomup.c
new file mode 100644
index 000000000000..b29379f7e478
--- /dev/null
+++ b/tools/testing/selftests/riscv/mm/testcases/mmap_bottomup.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <sys/mman.h>
+#include <testcases/mmap_test.h>
+
+#include "../../kselftest_harness.h"
+
+TEST(infinite_rlimit)
+{
+// Only works on 64 bit
+#if __riscv_xlen == 64
+ struct addresses mmap_addresses;
+
+ EXPECT_EQ(BOTTOM_UP, memory_layout());
+
+ do_mmaps(&mmap_addresses);
+
+ EXPECT_NE(MAP_FAILED, mmap_addresses.no_hint);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_37_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_38_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_46_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_47_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_55_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_56_addr);
+
+ EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.no_hint);
+ EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_37_addr);
+ EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_38_addr);
+ EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_46_addr);
+ EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_47_addr);
+ EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_55_addr);
+ EXPECT_GT(1UL << 56, (unsigned long)mmap_addresses.on_56_addr);
+#endif
+}
+
+TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/riscv/mm/testcases/mmap_default.c b/tools/testing/selftests/riscv/mm/testcases/mmap_default.c
new file mode 100644
index 000000000000..d1accb91b726
--- /dev/null
+++ b/tools/testing/selftests/riscv/mm/testcases/mmap_default.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <sys/mman.h>
+#include <testcases/mmap_test.h>
+
+#include "../../kselftest_harness.h"
+
+TEST(default_rlimit)
+{
+// Only works on 64 bit
+#if __riscv_xlen == 64
+ struct addresses mmap_addresses;
+
+ EXPECT_EQ(TOP_DOWN, memory_layout());
+
+ do_mmaps(&mmap_addresses);
+
+ EXPECT_NE(MAP_FAILED, mmap_addresses.no_hint);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_37_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_38_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_46_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_47_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_55_addr);
+ EXPECT_NE(MAP_FAILED, mmap_addresses.on_56_addr);
+
+ EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.no_hint);
+ EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_37_addr);
+ EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_38_addr);
+ EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_46_addr);
+ EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_47_addr);
+ EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_55_addr);
+ EXPECT_GT(1UL << 56, (unsigned long)mmap_addresses.on_56_addr);
+#endif
+}
+
+TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/riscv/mm/testcases/mmap_test.h b/tools/testing/selftests/riscv/mm/testcases/mmap_test.h
new file mode 100644
index 000000000000..9b8434f62f57
--- /dev/null
+++ b/tools/testing/selftests/riscv/mm/testcases/mmap_test.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _TESTCASES_MMAP_TEST_H
+#define _TESTCASES_MMAP_TEST_H
+#include <sys/mman.h>
+#include <sys/resource.h>
+#include <stddef.h>
+
+#define TOP_DOWN 0
+#define BOTTOM_UP 1
+
+struct addresses {
+ int *no_hint;
+ int *on_37_addr;
+ int *on_38_addr;
+ int *on_46_addr;
+ int *on_47_addr;
+ int *on_55_addr;
+ int *on_56_addr;
+};
+
+static inline void do_mmaps(struct addresses *mmap_addresses)
+{
+ /*
+ * Place all of the hint addresses on the boundaries of mmap
+ * sv39, sv48, sv57
+ * User addresses end at 1<<38, 1<<47, 1<<56 respectively
+ */
+ void *on_37_bits = (void *)(1UL << 37);
+ void *on_38_bits = (void *)(1UL << 38);
+ void *on_46_bits = (void *)(1UL << 46);
+ void *on_47_bits = (void *)(1UL << 47);
+ void *on_55_bits = (void *)(1UL << 55);
+ void *on_56_bits = (void *)(1UL << 56);
+
+ int prot = PROT_READ | PROT_WRITE;
+ int flags = MAP_PRIVATE | MAP_ANONYMOUS;
+
+ mmap_addresses->no_hint =
+ mmap(NULL, 5 * sizeof(int), prot, flags, 0, 0);
+ mmap_addresses->on_37_addr =
+ mmap(on_37_bits, 5 * sizeof(int), prot, flags, 0, 0);
+ mmap_addresses->on_38_addr =
+ mmap(on_38_bits, 5 * sizeof(int), prot, flags, 0, 0);
+ mmap_addresses->on_46_addr =
+ mmap(on_46_bits, 5 * sizeof(int), prot, flags, 0, 0);
+ mmap_addresses->on_47_addr =
+ mmap(on_47_bits, 5 * sizeof(int), prot, flags, 0, 0);
+ mmap_addresses->on_55_addr =
+ mmap(on_55_bits, 5 * sizeof(int), prot, flags, 0, 0);
+ mmap_addresses->on_56_addr =
+ mmap(on_56_bits, 5 * sizeof(int), prot, flags, 0, 0);
+}
+
+static inline int memory_layout(void)
+{
+ int prot = PROT_READ | PROT_WRITE;
+ int flags = MAP_PRIVATE | MAP_ANONYMOUS;
+
+ void *value1 = mmap(NULL, sizeof(int), prot, flags, 0, 0);
+ void *value2 = mmap(NULL, sizeof(int), prot, flags, 0, 0);
+
+ return value2 > value1;
+}
+#endif /* _TESTCASES_MMAP_TEST_H */
diff --git a/tools/testing/selftests/riscv/mm/testcases/run_mmap.sh b/tools/testing/selftests/riscv/mm/testcases/run_mmap.sh
new file mode 100755
index 000000000000..ca5ad7c48bad
--- /dev/null
+++ b/tools/testing/selftests/riscv/mm/testcases/run_mmap.sh
@@ -0,0 +1,12 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+original_stack_limit=$(ulimit -s)
+
+./mmap_default
+
+# Force mmap_bottomup to be ran with bottomup memory due to
+# the unlimited stack
+ulimit -s unlimited
+./mmap_bottomup
+ulimit -s $original_stack_limit
--
2.34.1
sv57 is supported in the kernel so pgtable.h should reflect that.
Signed-off-by: Charlie Jenkins <[email protected]>
Reviewed-by: Alexandre Ghiti <[email protected]>
---
arch/riscv/include/asm/pgtable.h | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 2611c1324a7c..76907b95109a 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -849,14 +849,16 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
* Task size is 0x4000000000 for RV64 or 0x9fc00000 for RV32.
* Note that PGDIR_SIZE must evenly divide TASK_SIZE.
* Task size is:
- * - 0x9fc00000 (~2.5GB) for RV32.
- * - 0x4000000000 ( 256GB) for RV64 using SV39 mmu
- * - 0x800000000000 ( 128TB) for RV64 using SV48 mmu
+ * - 0x9fc00000 (~2.5GB) for RV32.
+ * - 0x4000000000 ( 256GB) for RV64 using SV39 mmu
+ * - 0x800000000000 ( 128TB) for RV64 using SV48 mmu
+ * - 0x100000000000000 ( 64PB) for RV64 using SV57 mmu
*
* Note that PGDIR_SIZE must evenly divide TASK_SIZE since "RISC-V
* Instruction Set Manual Volume II: Privileged Architecture" states that
* "load and store effective addresses, which are 64bits, must have bits
* 63–48 all equal to bit 47, or else a page-fault exception will occur."
+ * Similarly for SV57, bits 63–57 must be equal to bit 56.
*/
#ifdef CONFIG_64BIT
#define TASK_SIZE_64 (PGDIR_SIZE * PTRS_PER_PGD / 2)
--
2.34.1
On Tue, Aug 08, 2023 at 06:51:06PM -0700, Charlie Jenkins wrote:
> Make sv48 the default address space for mmap as some applications
> currently depend on this assumption. Users can now select a
> desired address space using a non-zero hint address to mmap. Previously,
> requesting the default address space from mmap by passing zero as the hint
> address would result in using the largest address space possible. Some
> applications depend on empty bits in the virtual address space, like Go and
> Java, so this patch provides more flexibility for application developers.
This still does not build:
../fs/binfmt_flat.c:900:30: error: call to undeclared function 'is_compat_task'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
Reproduceable with allmodconfig.
On Wed, Aug 09, 2023 at 08:42:58AM +0100, Conor Dooley wrote:
> On Tue, Aug 08, 2023 at 06:51:06PM -0700, Charlie Jenkins wrote:
> > Make sv48 the default address space for mmap as some applications
> > currently depend on this assumption. Users can now select a
> > desired address space using a non-zero hint address to mmap. Previously,
> > requesting the default address space from mmap by passing zero as the hint
> > address would result in using the largest address space possible. Some
> > applications depend on empty bits in the virtual address space, like Go and
> > Java, so this patch provides more flexibility for application developers.
>
> This still does not build:
> ../fs/binfmt_flat.c:900:30: error: call to undeclared function 'is_compat_task'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>
> Reproduceable with allmodconfig.
>
There is some weird interaction with compat.h. Moving the definitions
in pgtable.h into the #ifndef __ASSEMBLY__ guarded section resolves
the compile error. I will send out another version with this change.
-Charlie
On Wed, Aug 09, 2023 at 03:45:31PM -0700, Charlie Jenkins wrote:
> On Wed, Aug 09, 2023 at 08:42:58AM +0100, Conor Dooley wrote:
> > On Tue, Aug 08, 2023 at 06:51:06PM -0700, Charlie Jenkins wrote:
> > > Make sv48 the default address space for mmap as some applications
> > > currently depend on this assumption. Users can now select a
> > > desired address space using a non-zero hint address to mmap. Previously,
> > > requesting the default address space from mmap by passing zero as the hint
> > > address would result in using the largest address space possible. Some
> > > applications depend on empty bits in the virtual address space, like Go and
> > > Java, so this patch provides more flexibility for application developers.
> >
> > This still does not build:
> > ../fs/binfmt_flat.c:900:30: error: call to undeclared function 'is_compat_task'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> >
> > Reproduceable with allmodconfig.
> >
> There is some weird interaction with compat.h. Moving the definitions
> in pgtable.h into the #ifndef __ASSEMBLY__ guarded section resolves
> the compile error. I will send out another version with this change.
Just be sure to run an allmodconfig build this time before doing so ;)