Revision 4dc2287c1805e7fe8a7cb90bbcd44abee8cdb914 authored by Bjorn Helgaas on 16 December 2010, 17:38:56 UTC, committed by Jesse Barnes on 17 December 2010, 18:01:24 UTC
When we allocate address space, e.g., to assign it to a PCI device, don't
allocate anything mentioned in the BIOS E820 memory map.

On recent machines (2008 and newer), we assign PCI resources from the
windows described by the ACPI PCI host bridge _CRS.  On many Dell
machines, these windows overlap some E820 reserved areas, e.g.,

    BIOS-e820: 00000000bfe4dc00 - 00000000c0000000 (reserved)
    pci_root PNP0A03:00: host bridge window [mem 0xbff00000-0xdfffffff]

If we put devices at 0xbff00000, they don't work, probably because
that's really RAM, not I/O memory.  This patch prevents that by removing
the 0xbfe4dc00-0xbfffffff area from the "available" resource.

I'm not very happy with this solution because Windows solves the problem
differently (it seems to ignore E820 reserved areas and it allocates
top-down instead of bottom-up; details at comment 45 of the bugzilla
below).  That means we're vulnerable to BIOS defects that Windows would not
trip over.  For example, if BIOS described a device in ACPI but didn't
mention it in E820, Windows would work fine but Linux would fail.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=16228
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
1 parent 30919b0
Raw File
syscall.c
/*
 * sys_ipc() is the old de-multiplexer for the SysV IPC calls.
 *
 * This is really horribly ugly, and new architectures should just wire up
 * the individual syscalls instead.
 */
#include <linux/unistd.h>

#ifdef __ARCH_WANT_SYS_IPC
#include <linux/errno.h>
#include <linux/ipc.h>
#include <linux/shm.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>

SYSCALL_DEFINE6(ipc, unsigned int, call, int, first, unsigned long, second,
		unsigned long, third, void __user *, ptr, long, fifth)
{
	int version, ret;

	version = call >> 16; /* hack for backward compatibility */
	call &= 0xffff;

	switch (call) {
	case SEMOP:
		return sys_semtimedop(first, (struct sembuf __user *)ptr,
				      second, NULL);
	case SEMTIMEDOP:
		return sys_semtimedop(first, (struct sembuf __user *)ptr,
				      second,
				      (const struct timespec __user *)fifth);

	case SEMGET:
		return sys_semget(first, second, third);
	case SEMCTL: {
		union semun fourth;
		if (!ptr)
			return -EINVAL;
		if (get_user(fourth.__pad, (void __user * __user *) ptr))
			return -EFAULT;
		return sys_semctl(first, second, third, fourth);
	}

	case MSGSND:
		return sys_msgsnd(first, (struct msgbuf __user *) ptr,
				  second, third);
	case MSGRCV:
		switch (version) {
		case 0: {
			struct ipc_kludge tmp;
			if (!ptr)
				return -EINVAL;

			if (copy_from_user(&tmp,
					   (struct ipc_kludge __user *) ptr,
					   sizeof(tmp)))
				return -EFAULT;
			return sys_msgrcv(first, tmp.msgp, second,
					   tmp.msgtyp, third);
		}
		default:
			return sys_msgrcv(first,
					   (struct msgbuf __user *) ptr,
					   second, fifth, third);
		}
	case MSGGET:
		return sys_msgget((key_t) first, second);
	case MSGCTL:
		return sys_msgctl(first, second, (struct msqid_ds __user *)ptr);

	case SHMAT:
		switch (version) {
		default: {
			unsigned long raddr;
			ret = do_shmat(first, (char __user *)ptr,
				       second, &raddr);
			if (ret)
				return ret;
			return put_user(raddr, (unsigned long __user *) third);
		}
		case 1:
			/*
			 * This was the entry point for kernel-originating calls
			 * from iBCS2 in 2.2 days.
			 */
			return -EINVAL;
		}
	case SHMDT:
		return sys_shmdt((char __user *)ptr);
	case SHMGET:
		return sys_shmget(first, second, third);
	case SHMCTL:
		return sys_shmctl(first, second,
				   (struct shmid_ds __user *) ptr);
	default:
		return -ENOSYS;
	}
}
#endif
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