From f75b1b1bedfb498cc43a992ce4d7ed8df3b1e770 Mon Sep 17 00:00:00 2001 From: Richard Weinberger Date: Sat, 17 Aug 2013 18:46:00 +0200 Subject: um: Implement probe_kernel_read() UML needs it's own probe_kernel_read() to handle kernel mode faults correctly. The implementation uses mincore() on the host side to detect whether a page is owned by the UML kernel process. This fixes also a possible crash when sysrq-t is used. Starting with 3.10 sysrq-t calls probe_kernel_read() to read details from the kernel workers. As kernel worker are completely async pointers may turn NULL while reading them. Cc: Cc: Cc: # 3.10.x Signed-off-by: Richard Weinberger --- arch/um/kernel/Makefile | 2 +- arch/um/kernel/maccess.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+), 1 deletion(-) create mode 100644 arch/um/kernel/maccess.c (limited to 'arch/um/kernel') diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile index babe21826e3e..d8b78a03855c 100644 --- a/arch/um/kernel/Makefile +++ b/arch/um/kernel/Makefile @@ -13,7 +13,7 @@ clean-files := obj-y = config.o exec.o exitcode.o irq.o ksyms.o mem.o \ physmem.o process.o ptrace.o reboot.o sigio.o \ signal.o smp.o syscall.o sysrq.o time.o tlb.o trap.o \ - um_arch.o umid.o skas/ + um_arch.o umid.o maccess.o skas/ obj-$(CONFIG_BLK_DEV_INITRD) += initrd.o obj-$(CONFIG_GPROF) += gprof_syms.o diff --git a/arch/um/kernel/maccess.c b/arch/um/kernel/maccess.c new file mode 100644 index 000000000000..1f3d5c4910d1 --- /dev/null +++ b/arch/um/kernel/maccess.c @@ -0,0 +1,24 @@ +/* + * Copyright (C) 2013 Richard Weinberger + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include +#include +#include + +long probe_kernel_read(void *dst, const void *src, size_t size) +{ + void *psrc = (void *)rounddown((unsigned long)src, PAGE_SIZE); + + if ((unsigned long)src < PAGE_SIZE || size <= 0) + return -EFAULT; + + if (os_mincore(psrc, size + src - psrc) <= 0) + return -EFAULT; + + return __probe_kernel_read(dst, src, size); +} -- cgit v1.2.3