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Subjectusbmon in 2.6.13: peeking into DMA areas
I am not completely confident in this patch, so while the fix is being
requested by users, I would like to have it postponed until 2.6.13.

This code looks at urb->transfer_dma, maps the page and takes the data.
I am looking for volunteers to contribute architectures other than i386
or to develop an architecure-neutral API for it (or point me that it
was done already).

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>

diff -urpN -X dontdiff linux-2.6.13-rc6/drivers/usb/mon/Makefile linux-2.6.13-rc6-lem/drivers/usb/mon/Makefile
--- linux-2.6.13-rc6/drivers/usb/mon/Makefile 2005-08-14 20:57:43.000000000 -0700
+++ linux-2.6.13-rc6-lem/drivers/usb/mon/Makefile 2005-08-15 11:25:32.000000000 -0700
@@ -2,7 +2,7 @@
# Makefile for USB Core files and filesystem
#

-usbmon-objs := mon_main.o mon_stat.o mon_text.o
+usbmon-objs := mon_main.o mon_stat.o mon_text.o mon_dma.o

# This does not use CONFIG_USB_MON because we want this to use a tristate.
obj-$(CONFIG_USB) += usbmon.o
diff -urpN -X dontdiff linux-2.6.13-rc6/drivers/usb/mon/mon_dma.c linux-2.6.13-rc6-lem/drivers/usb/mon/mon_dma.c
--- linux-2.6.13-rc6/drivers/usb/mon/mon_dma.c 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.13-rc6-lem/drivers/usb/mon/mon_dma.c 2005-08-15 16:11:51.000000000 -0700
@@ -0,0 +1,55 @@
+/*
+ * The USB Monitor, inspired by Dave Harding's USBMon.
+ *
+ * mon_dma.c: Library which snoops on DMA areas.
+ *
+ * Copyright (C) 2005 Pete Zaitcev (zaitcev@redhat.com)
+ */
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/highmem.h>
+#include <asm/page.h>
+
+#include <linux/usb.h> /* Only needed for declarations in usb_mon.h */
+#include "usb_mon.h"
+
+#ifdef __i386__ /* CONFIG_ARCH_I386 does not exit */
+#define MON_HAS_UNMAP 1
+
+#define phys_to_page(phys) pfn_to_page((phys) >> PAGE_SHIFT)
+
+char mon_dmapeek(unsigned char *dst, dma_addr_t dma_addr, int len)
+{
+ struct page *pg;
+ unsigned long flags;
+ unsigned char *map;
+ unsigned char *ptr;
+
+ /*
+ * On i386, a DMA handle is the "physical" address of a page.
+ * In other words, the bus address is equal to physical address.
+ * There is no IOMMU.
+ */
+ pg = phys_to_page(dma_addr);
+
+ /*
+ * We are called from hardware IRQs in case of callbacks.
+ * But we can be called from softirq or process context in case
+ * of submissions. In such case, we need to protect KM_IRQ0.
+ */
+ local_irq_save(flags);
+ map = kmap_atomic(pg, KM_IRQ0);
+ ptr = map + (dma_addr & (PAGE_SIZE-1));
+ memcpy(dst, ptr, len);
+ kunmap_atomic(map, KM_IRQ0);
+ local_irq_restore(flags);
+ return 0;
+}
+#endif /* __i386__ */
+
+#ifndef MON_HAS_UNMAP
+char mon_dmapeek(unsigned char *dst, dma_addr_t dma_addr, int len)
+{
+ return 'D';
+}
+#endif
diff -urpN -X dontdiff linux-2.6.13-rc6/drivers/usb/mon/mon_text.c linux-2.6.13-rc6-lem/drivers/usb/mon/mon_text.c
--- linux-2.6.13-rc6/drivers/usb/mon/mon_text.c 2005-08-14 20:57:43.000000000 -0700
+++ linux-2.6.13-rc6-lem/drivers/usb/mon/mon_text.c 2005-08-15 11:44:13.000000000 -0700
@@ -91,25 +91,11 @@ static inline char mon_text_get_data(str
int len, char ev_type)
{
int pipe = urb->pipe;
- unsigned char *data;
-
- /*
- * The check to see if it's safe to poke at data has an enormous
- * number of corner cases, but it seems that the following is
- * more or less safe.
- *
- * We do not even try to look transfer_buffer, because it can
- * contain non-NULL garbage in case the upper level promised to
- * set DMA for the HCD.
- */
- if (urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)
- return 'D';

if (len <= 0)
return 'L';
-
- if ((data = urb->transfer_buffer) == NULL)
- return 'Z'; /* '0' would be not as pretty. */
+ if (len >= DATA_MAX)
+ len = DATA_MAX;

/*
* Bulk is easy to shortcut reliably.
@@ -126,8 +112,21 @@ static inline char mon_text_get_data(str
}
}

- if (len >= DATA_MAX)
- len = DATA_MAX;
+ /*
+ * The check to see if it's safe to poke at data has an enormous
+ * number of corner cases, but it seems that the following is
+ * more or less safe.
+ *
+ * We do not even try to look transfer_buffer, because it can
+ * contain non-NULL garbage in case the upper level promised to
+ * set DMA for the HCD.
+ */
+ if (urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)
+ return mon_dmapeek(ep->data, urb->transfer_dma, len);
+
+ if (urb->transfer_buffer == NULL)
+ return 'Z'; /* '0' would be not as pretty. */
+
memcpy(ep->data, urb->transfer_buffer, len);
return 0;
}
diff -urpN -X dontdiff linux-2.6.13-rc6/drivers/usb/mon/usb_mon.h linux-2.6.13-rc6-lem/drivers/usb/mon/usb_mon.h
--- linux-2.6.13-rc6/drivers/usb/mon/usb_mon.h 2005-06-17 12:48:29.000000000 -0700
+++ linux-2.6.13-rc6-lem/drivers/usb/mon/usb_mon.h 2005-08-15 16:12:42.000000000 -0700
@@ -43,6 +45,10 @@ struct mon_reader {
void mon_reader_add(struct mon_bus *mbus, struct mon_reader *r);
void mon_reader_del(struct mon_bus *mbus, struct mon_reader *r);

+/*
+ */
+extern char mon_dmapeek(unsigned char *dst, dma_addr_t dma_addr, int len);
+
extern struct semaphore mon_lock;

extern struct file_operations mon_fops_text;
-
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