[PATCH v2 0/6] Use generic code for randomization of virtual address of x86

[sxwjean]

From: Xiongwei Song <sxwjean@xxxxxxxxx>

Hello,

This patchset are to use generic code for randomization of virtual address
of x86. Since the basic code logic of x86 is same as generic code, so no
need to implement these functions on x86.

Patch 1~3 are prepared to change the generic code to apply to x86.

Patch 4 is to switch to generic arch_pick_mmap_layout() with 
ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT enabled. Also provided basically
test and the result was put in commit message too.

Patch 5~6 are used to handle the legacy things.

Test programs(to verify if the entropy of return value of mmap is kept
after applying the patchset):
- C code for mmap test:
	#include <stdio.h>
	#include <stdlib.h>
	#include <sys/mman.h>

	int main(int argc, char *argv[])
	{
		unsigned long *addr;

		addr = mmap(NULL, 4096, PROT_READ, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
		if (addr == MAP_FAILED) {
			printf("NULL\n");
		} else {
			printf("%lx\n", (unsigned long)addr);
			munmap(addr, 4096);
		}

		return 0;
	}

- Shell script for collecting output of C progarm above and give a
  statistics:
	#!/bin/bash
	declare -a COUNT

	if [ "$1" == "" ]; then
	    echo "Please give a test number!"
	    exit 1
	fi
	number=$1

	for ((i=0; i<$number; i++))
	do
	    addr=$(mmaptest)
	    addr=$(((16#$addr&0xf000000000)>>36))
	    COUNT[$addr]=$((COUNT[$addr]+1))
	done

	echo "    Virtual Address Range     |   hit times   "
	echo "----------------------------------------"
	for ((i=0; i<16; i++))
	do
	    j=`echo "obase=16; $i" | bc`
	    echo "0x7f${j,,}000000000 - 0x7f${j,,}ffffff000 |   ${COUNT[i]}"
	done

Run 10 thousands times C progam, collect the output with shell script, get
the test results below:
	Before the patchset:
            Virtual Address Range       | hit times
        ----------------------------------------
        0x7f0000000000 - 0x7f0ffffff000 |   655 
        0x7f1000000000 - 0x7f1ffffff000 |   617 
        0x7f2000000000 - 0x7f2ffffff000 |   636 
        0x7f3000000000 - 0x7f3ffffff000 |   625 
        0x7f4000000000 - 0x7f4ffffff000 |   651 
        0x7f5000000000 - 0x7f5ffffff000 |   591 
        0x7f6000000000 - 0x7f6ffffff000 |   623 
        0x7f7000000000 - 0x7f7ffffff000 |   627 
        0x7f8000000000 - 0x7f8ffffff000 |   638 
        0x7f9000000000 - 0x7f9ffffff000 |   586 
        0x7fa000000000 - 0x7faffffff000 |   637 
        0x7fb000000000 - 0x7fbffffff000 |   607 
        0x7fc000000000 - 0x7fcffffff000 |   618 
        0x7fd000000000 - 0x7fdffffff000 |   656 
        0x7fe000000000 - 0x7feffffff000 |   614 
        0x7ff000000000 - 0x7ffffffff000 |   619 

	After the patchset:
            Virtual Address Range       | hit times
        ----------------------------------------
        0x7f0000000000 - 0x7f0ffffff000 |   661 
        0x7f1000000000 - 0x7f1ffffff000 |   645 
        0x7f2000000000 - 0x7f2ffffff000 |   609 
        0x7f3000000000 - 0x7f3ffffff000 |   594 
        0x7f4000000000 - 0x7f4ffffff000 |   616 
        0x7f5000000000 - 0x7f5ffffff000 |   622 
        0x7f6000000000 - 0x7f6ffffff000 |   617 
        0x7f7000000000 - 0x7f7ffffff000 |   582 
        0x7f8000000000 - 0x7f8ffffff000 |   618 
        0x7f9000000000 - 0x7f9ffffff000 |   629 
        0x7fa000000000 - 0x7faffffff000 |   635 
        0x7fb000000000 - 0x7fbffffff000 |   625 
        0x7fc000000000 - 0x7fcffffff000 |   614 
        0x7fd000000000 - 0x7fdffffff000 |   610 
        0x7fe000000000 - 0x7feffffff000 |   648
        0x7ff000000000 - 0x7ffffffff000 |   675

v1 -> v2:
- Spilt the patch 2 of v1 as Kees suggested.
- Drop patch 1 of v1, which renamed TIF_ADDR32 to TIF_32BIT, which is
  unreasonable for x86. Because in x86, 64bit process can call 32bit
  syscall. Thanks Peterz for pointing this out. 

v1:
- https://lkml.org/lkml/2021/9/21/482
- https://lkml.org/lkml/2021/9/21/484
- https://lkml.org/lkml/2021/9/27/688

Please review.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: Yazen Ghannam <yazen.ghannam@xxxxxxx>
Cc: Kim Phillips <kim.phillips@xxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Balbir Singh <sblbir@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: sxwjean@xxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

Xiongwei Song (6):
  mm/util: Assign a meaningful value to mmap_legacy_base
  mm/util: Allow to pass a specific task size when getting mmapping base
  mm/util: Support CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
  x86/mm: Randomize VA with generit arch_pick_mmap_layout()
  x86/mm: Discard the defination of HAVE_ARCH_PICK_MMAP_LAYOUT
  x86/elf: Discard ARCH_HAS_ELF_RANDOMIZE selection

 arch/x86/Kconfig                 |   2 +-
 arch/x86/include/asm/compat.h    |   5 ++
 arch/x86/include/asm/processor.h |   5 +-
 arch/x86/mm/mmap.c               | 112 -------------------------------
 mm/util.c                        |  35 +++++++---
 5 files changed, 37 insertions(+), 122 deletions(-)

-- 
2.30.2