* [PATCH v2] riscv: Make mmap allocation top-down by default
@ 2019-01-28 17:49 Alexandre Ghiti
2019-02-11 8:27 ` Christoph Hellwig
0 siblings, 1 reply; 3+ messages in thread
From: Alexandre Ghiti @ 2019-01-28 17:49 UTC (permalink / raw)
To: Palmer Dabbelt, Albert Ou, hch, linux-riscv; +Cc: Alexandre Ghiti
In order to avoid wasting user address space by using bottom-up mmap
allocation scheme, prefer top-down scheme when possible.
This patch is based on arm64 implementation.
Before:
root@qemuriscv64:~# cat /proc/176/maps
00010000-000be000 r-xp 00000000 fe:00 6355 /bin/bash.bash
000be000-000bf000 r--p 000ad000 fe:00 6355 /bin/bash.bash
000bf000-000c8000 rw-p 000ae000 fe:00 6355 /bin/bash.bash
000c8000-00114000 rw-p 00000000 00:00 0 [heap]
2000000000-2000017000 r-xp 00000000 fe:00 7193 /lib/ld-2.28.so
2000017000-2000018000 r--p 00016000 fe:00 7193 /lib/ld-2.28.so
2000018000-2000019000 rw-p 00017000 fe:00 7193 /lib/ld-2.28.so
2000019000-200001a000 rw-p 00000000 00:00 0
200001a000-200001c000 r-xp 00000000 00:00 0 [vdso]
200001e000-2000020000 rw-p 00000000 00:00 0
2000020000-2000041000 r-xp 00000000 fe:00 7176 /lib/libtinfo.so.5.9
2000041000-2000045000 r--p 00020000 fe:00 7176 /lib/libtinfo.so.5.9
2000045000-2000046000 rw-p 00024000 fe:00 7176 /lib/libtinfo.so.5.9
2000046000-2000048000 r-xp 00000000 fe:00 7112 /lib/libdl-2.28.so
2000048000-2000049000 r--p 00001000 fe:00 7112 /lib/libdl-2.28.so
2000049000-200004a000 rw-p 00002000 fe:00 7112 /lib/libdl-2.28.so
200004a000-2000148000 r-xp 00000000 fe:00 7187 /lib/libc-2.28.so
2000148000-200014c000 r--p 000fd000 fe:00 7187 /lib/libc-2.28.so
200014c000-200014e000 rw-p 00101000 fe:00 7187 /lib/libc-2.28.so
200014e000-2000154000 rw-p 00000000 00:00 0
2000154000-2000159000 r-xp 00000000 fe:00 7100 /lib/libnss_compat-2.28.so
2000159000-200015a000 r--p 00004000 fe:00 7100 /lib/libnss_compat-2.28.so
200015a000-200015b000 rw-p 00005000 fe:00 7100 /lib/libnss_compat-2.28.so
3fff9a4000-3fff9c5000 rw-p 00000000 00:00 0 [stack]
After:
root@qemuriscv64:~# cat /proc/173/maps
00010000-000be000 r-xp 00000000 fe:00 6355 /bin/bash.bash
000be000-000bf000 r--p 000ad000 fe:00 6355 /bin/bash.bash
000bf000-000c8000 rw-p 000ae000 fe:00 6355 /bin/bash.bash
000c8000-00114000 rw-p 00000000 00:00 0 [heap]
3fdd8d0000-3fdd8d5000 r-xp 00000000 fe:00 7100 /lib/libnss_compat-2.28.so
3fdd8d5000-3fdd8d6000 r--p 00004000 fe:00 7100 /lib/libnss_compat-2.28.so
3fdd8d6000-3fdd8d7000 rw-p 00005000 fe:00 7100 /lib/libnss_compat-2.28.so
3fdd8d7000-3fdd8d9000 rw-p 00000000 00:00 0
3fdd8d9000-3fdd9d7000 r-xp 00000000 fe:00 7187 /lib/libc-2.28.so
3fdd9d7000-3fdd9db000 r--p 000fd000 fe:00 7187 /lib/libc-2.28.so
3fdd9db000-3fdd9dd000 rw-p 00101000 fe:00 7187 /lib/libc-2.28.so
3fdd9dd000-3fdd9e1000 rw-p 00000000 00:00 0
3fdd9e1000-3fdd9e3000 r-xp 00000000 fe:00 7112 /lib/libdl-2.28.so
3fdd9e3000-3fdd9e4000 r--p 00001000 fe:00 7112 /lib/libdl-2.28.so
3fdd9e4000-3fdd9e5000 rw-p 00002000 fe:00 7112 /lib/libdl-2.28.so
3fdd9e5000-3fdda06000 r-xp 00000000 fe:00 7176 /lib/libtinfo.so.5.9
3fdda06000-3fdda0a000 r--p 00020000 fe:00 7176 /lib/libtinfo.so.5.9
3fdda0a000-3fdda0b000 rw-p 00024000 fe:00 7176 /lib/libtinfo.so.5.9
3fdda0b000-3fdda0d000 rw-p 00000000 00:00 0
3fdda0f000-3fdda11000 r-xp 00000000 00:00 0 [vdso]
3fdda11000-3fdda28000 r-xp 00000000 fe:00 7193 /lib/ld-2.28.so
3fdda28000-3fdda29000 r--p 00016000 fe:00 7193 /lib/ld-2.28.so
3fdda29000-3fdda2a000 rw-p 00017000 fe:00 7193 /lib/ld-2.28.so
3fdda2a000-3fdda2b000 rw-p 00000000 00:00 0
3ffff8e000-3ffffaf000 rw-p 00000000 00:00 0 [stack]
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
---
Changes in v2:
- Rebased on top of previous patch "riscv: Adjust mmap base address
at a third of task size"
arch/riscv/Kconfig | 12 ++++++
arch/riscv/include/asm/processor.h | 1 +
arch/riscv/mm/Makefile | 1 +
arch/riscv/mm/mmap.c | 69 ++++++++++++++++++++++++++++++
4 files changed, 83 insertions(+)
create mode 100644 arch/riscv/mm/mmap.c
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index e0d7d61779a6..684f3e00e9f8 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -47,6 +47,18 @@ config RISCV
select GENERIC_IRQ_MULTI_HANDLER
select ARCH_HAS_PTE_SPECIAL
+config HAVE_ARCH_MMAP_RND_BITS
+ def_bool y
+
+config ARCH_MMAP_RND_BITS_MIN
+ default 18
+
+# max bits determined by the following formula:
+# VA_BITS - PAGE_SHIFT - 3
+config ARCH_MMAP_RND_BITS_MAX
+ default 33 if 64BIT # SV48 based
+ default 18
+
config MMU
def_bool y
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index ce70bceb8872..8ed27e0ab125 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -23,6 +23,7 @@
* space during mmap's.
*/
#define TASK_UNMAPPED_BASE PAGE_ALIGN(TASK_SIZE / 3)
+#define HAVE_ARCH_PICK_MMAP_LAYOUT
#define STACK_TOP TASK_SIZE
#define STACK_TOP_MAX STACK_TOP
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index eb22ab49b3e0..0eb23b10d0bd 100644
--- a/arch/riscv/mm/Makefile
+++ b/arch/riscv/mm/Makefile
@@ -3,3 +3,4 @@ obj-y += fault.o
obj-y += extable.o
obj-y += ioremap.o
obj-y += cacheflush.o
+obj-y += mmap.o
diff --git a/arch/riscv/mm/mmap.c b/arch/riscv/mm/mmap.c
new file mode 100644
index 000000000000..d182ac66d2e7
--- /dev/null
+++ b/arch/riscv/mm/mmap.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/mm.h>
+#include <linux/sched/mm.h>
+#include <linux/sizes.h>
+#include <linux/personality.h>
+#include <linux/random.h>
+
+/*
+ * Leave enough space between the mmap area and the stack to honour ulimit in
+ * the face of randomisation.
+ */
+#define MIN_GAP (SZ_128M)
+#define MAX_GAP (TASK_SIZE / 6 * 5)
+
+static int mmap_is_legacy(struct rlimit *rlim_stack)
+{
+ if (current->personality & ADDR_COMPAT_LAYOUT)
+ return 1;
+
+ if (rlim_stack->rlim_cur == RLIM_INFINITY)
+ return 1;
+
+ return sysctl_legacy_va_layout;
+}
+
+static unsigned long arch_mmap_rnd(void)
+{
+ unsigned long rnd;
+
+ rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
+
+ return rnd << PAGE_SHIFT;
+}
+
+static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
+{
+ unsigned long gap = rlim_stack->rlim_cur;
+
+ if (gap < MIN_GAP)
+ gap = MIN_GAP;
+ else if (gap > MAX_GAP)
+ gap = MAX_GAP;
+
+ return PAGE_ALIGN(TASK_SIZE - gap - rnd);
+}
+
+/*
+ * This function, called very early during the creation of a new process VM
+ * image, sets up which VM layout function to use:
+ */
+void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+{
+ unsigned long random_factor = 0UL;
+
+ if (current->flags & PF_RANDOMIZE)
+ random_factor = arch_mmap_rnd();
+
+ /*
+ * Fall back to the standard layout if the personality bit is set, or
+ * if the expected stack growth is unlimited:
+ */
+ if (mmap_is_legacy(rlim_stack)) {
+ mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
+ mm->get_unmapped_area = arch_get_unmapped_area;
+ } else {
+ mm->mmap_base = mmap_base(random_factor, rlim_stack);
+ mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+ }
+}
--
2.20.1
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^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH v2] riscv: Make mmap allocation top-down by default
2019-01-28 17:49 [PATCH v2] riscv: Make mmap allocation top-down by default Alexandre Ghiti
@ 2019-02-11 8:27 ` Christoph Hellwig
2019-02-11 12:09 ` Alexandre Ghiti
0 siblings, 1 reply; 3+ messages in thread
From: Christoph Hellwig @ 2019-02-11 8:27 UTC (permalink / raw)
To: Alexandre Ghiti; +Cc: hch, linux-riscv, Palmer Dabbelt, Albert Ou
On Mon, Jan 28, 2019 at 12:49:02PM -0500, Alexandre Ghiti wrote:
> In order to avoid wasting user address space by using bottom-up mmap
> allocation scheme, prefer top-down scheme when possible.
>
> This patch is based on arm64 implementation.
Any chance you could lift the arm64 code into a generic top-down library
and reuse that instead of duplicating it?
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] riscv: Make mmap allocation top-down by default
2019-02-11 8:27 ` Christoph Hellwig
@ 2019-02-11 12:09 ` Alexandre Ghiti
0 siblings, 0 replies; 3+ messages in thread
From: Alexandre Ghiti @ 2019-02-11 12:09 UTC (permalink / raw)
To: Christoph Hellwig; +Cc: linux-riscv, Palmer Dabbelt, Albert Ou
On 02/11/2019 09:27 AM, Christoph Hellwig wrote:
> On Mon, Jan 28, 2019 at 12:49:02PM -0500, Alexandre Ghiti wrote:
>> In order to avoid wasting user address space by using bottom-up mmap
>> allocation scheme, prefer top-down scheme when possible.
>>
>> This patch is based on arm64 implementation.
> Any chance you could lift the arm64 code into a generic top-down library
> and reuse that instead of duplicating it?
Of course, I'm on it.
Thanks for your answer,
Alex
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
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^ permalink raw reply [flat|nested] 3+ messages in thread
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