[ofa-general] [PATCH][RFC] IB/umad: Fix bit ordering and 32-on-64 problems on big endian systems
Roland Dreier
rdreier at cisco.com
Mon Oct 1 20:49:32 PDT 2007
[ I just added this to my for-2.6.24 branch... it should only change
behavior for big-endian 32-on-64 systems, so I think this is the fix
that causes the least breakage. Anyway, as usual, comments
appreciated. ]
The declaration of struct ib_user_mad_reg_req.method_mask[] exported
to userspace was an array of __u32, but the kernel internally treated
it as a bitmap made up of longs. This makes a difference for 64-bit
big-endian kernels, where numbering the bits in an array of__u32 gives:
|31.....0|63....31|95....64|127...96|
while numbering the bits in an array of longs gives:
|63..............0|127............64|
64-bit userspace can handle this by just treating method_mask[] as an
array of longs, but 32-bit userspace is really stuck: the meaning of
the bits in method_mask[] depends on whether the kernel is 32-bit or
64-bit, and there's no sane way for userspace to know that.
Fix this by updating <rdma/ib_user_mad.h> to make it clear that
method_mask[] is an array of longs, and using a compat_ioctl method to
convert to an array of 64-bit longs to handle the 32-on-64 problem.
This fixes the interface description to match existing behavior (so
working binaries continue to work) in almost all situations, and gives
consistent semantics in the case of 32-bit userspace that can run on
either a 32-bit or 64-bit kernel, so that the same binary can work for
both 32-on-32 and 32-on-64 systems.
Signed-off-by: Roland Dreier <rolandd at cisco.com>
---
drivers/infiniband/core/user_mad.c | 49 +++++++++++++++++++++++++++++------
include/rdma/ib_user_mad.h | 22 +++++++++++++++-
2 files changed, 61 insertions(+), 10 deletions(-)
diff --git a/drivers/infiniband/core/user_mad.c b/drivers/infiniband/core/user_mad.c
index aee2913..b53eac4 100644
--- a/drivers/infiniband/core/user_mad.c
+++ b/drivers/infiniband/core/user_mad.c
@@ -44,6 +44,7 @@
#include <linux/poll.h>
#include <linux/rwsem.h>
#include <linux/kref.h>
+#include <linux/compat.h>
#include <asm/uaccess.h>
#include <asm/semaphore.h>
@@ -607,7 +608,8 @@ static unsigned int ib_umad_poll(struct file *filp, struct poll_table_struct *wa
return mask;
}
-static int ib_umad_reg_agent(struct ib_umad_file *file, unsigned long arg)
+static int ib_umad_reg_agent(struct ib_umad_file *file, void __user *arg,
+ int compat_method_mask)
{
struct ib_user_mad_reg_req ureq;
struct ib_mad_reg_req req;
@@ -622,7 +624,7 @@ static int ib_umad_reg_agent(struct ib_umad_file *file, unsigned long arg)
goto out;
}
- if (copy_from_user(&ureq, (void __user *) arg, sizeof ureq)) {
+ if (copy_from_user(&ureq, arg, sizeof ureq)) {
ret = -EFAULT;
goto out;
}
@@ -643,8 +645,18 @@ found:
if (ureq.mgmt_class) {
req.mgmt_class = ureq.mgmt_class;
req.mgmt_class_version = ureq.mgmt_class_version;
- memcpy(req.method_mask, ureq.method_mask, sizeof req.method_mask);
- memcpy(req.oui, ureq.oui, sizeof req.oui);
+ memcpy(req.oui, ureq.oui, sizeof req.oui);
+
+ if (compat_method_mask) {
+ u32 *umm = (u32 *) ureq.method_mask;
+ int i;
+
+ for (i = 0; i < BITS_TO_LONGS(IB_MGMT_MAX_METHODS); ++i)
+ req.method_mask[i] =
+ umm[i * 2] | ((u64) umm[i * 2 + 1] << 32);
+ } else
+ memcpy(req.method_mask, ureq.method_mask,
+ sizeof req.method_mask);
}
agent = ib_register_mad_agent(file->port->ib_dev, file->port->port_num,
@@ -682,13 +694,13 @@ out:
return ret;
}
-static int ib_umad_unreg_agent(struct ib_umad_file *file, unsigned long arg)
+static int ib_umad_unreg_agent(struct ib_umad_file *file, u32 __user *arg)
{
struct ib_mad_agent *agent = NULL;
u32 id;
int ret = 0;
- if (get_user(id, (u32 __user *) arg))
+ if (get_user(id, arg))
return -EFAULT;
down_write(&file->port->mutex);
@@ -729,9 +741,9 @@ static long ib_umad_ioctl(struct file *filp, unsigned int cmd,
{
switch (cmd) {
case IB_USER_MAD_REGISTER_AGENT:
- return ib_umad_reg_agent(filp->private_data, arg);
+ return ib_umad_reg_agent(filp->private_data, (void __user *) arg, 0);
case IB_USER_MAD_UNREGISTER_AGENT:
- return ib_umad_unreg_agent(filp->private_data, arg);
+ return ib_umad_unreg_agent(filp->private_data, (__u32 __user *) arg);
case IB_USER_MAD_ENABLE_PKEY:
return ib_umad_enable_pkey(filp->private_data);
default:
@@ -739,6 +751,23 @@ static long ib_umad_ioctl(struct file *filp, unsigned int cmd,
}
}
+#ifdef CONFIG_COMPAT
+static long ib_umad_compat_ioctl(struct file *filp, unsigned int cmd,
+ unsigned long arg)
+{
+ switch (cmd) {
+ case IB_USER_MAD_REGISTER_AGENT:
+ return ib_umad_reg_agent(filp->private_data, compat_ptr(arg), 1);
+ case IB_USER_MAD_UNREGISTER_AGENT:
+ return ib_umad_unreg_agent(filp->private_data, compat_ptr(arg));
+ case IB_USER_MAD_ENABLE_PKEY:
+ return ib_umad_enable_pkey(filp->private_data);
+ default:
+ return -ENOIOCTLCMD;
+ }
+}
+#endif
+
static int ib_umad_open(struct inode *inode, struct file *filp)
{
struct ib_umad_port *port;
@@ -826,7 +855,9 @@ static const struct file_operations umad_fops = {
.write = ib_umad_write,
.poll = ib_umad_poll,
.unlocked_ioctl = ib_umad_ioctl,
- .compat_ioctl = ib_umad_ioctl,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = ib_umad_compat_ioctl,
+#endif
.open = ib_umad_open,
.release = ib_umad_close
};
diff --git a/include/rdma/ib_user_mad.h b/include/rdma/ib_user_mad.h
index 2a32043..29d2c72 100644
--- a/include/rdma/ib_user_mad.h
+++ b/include/rdma/ib_user_mad.h
@@ -147,6 +147,26 @@ struct ib_user_mad {
__u64 data[0];
};
+/*
+ * Earlier versions of this interface definition declared the
+ * method_mask[] member as an array of __u32 but treated it as a
+ * bitmap made up of longs in the kernel. This ambiguity meant that
+ * 32-bit big-endian applications that can run on both 32-bit and
+ * 64-bit kernels had no consistent ABI to rely on, and 64-bit
+ * big-endian applications that treated method_mask as being made up
+ * of 32-bit words would have their bitmap misinterpreted.
+ *
+ * To clear up this confusion, we change the declaration of
+ * method_mask[] to use unsigned long and handle the conversion from
+ * 32-bit userspace to 64-bit kernel for big-endian systems in the
+ * compat_ioctl method. Unfortunately, to keep the structure layout
+ * the same, we need the method_mask[] array to be aligned only to 4
+ * bytes even when long is 64 bits, which forces us into this ugly
+ * typedef.
+ */
+typedef unsigned long __attribute__((aligned(4))) packed_ulong;
+#define IB_USER_MAD_LONGS_PER_METHOD_MASK (128 / (8 * sizeof (long)))
+
/**
* ib_user_mad_reg_req - MAD registration request
* @id - Set by the kernel; used to identify agent in future requests.
@@ -165,7 +185,7 @@ struct ib_user_mad {
*/
struct ib_user_mad_reg_req {
__u32 id;
- __u32 method_mask[4];
+ packed_ulong method_mask[IB_USER_MAD_LONGS_PER_METHOD_MASK];
__u8 qpn;
__u8 mgmt_class;
__u8 mgmt_class_version;
--
1.5.3.2
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