linux-kernel - [PATCH] dma-mapping: Fix tracing dma

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Message-Id: <20241017151055.2806066-1-sean.anderson@linux.dev>
Date: Thu, 17 Oct 2024 11:10:55 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Christoph Hellwig <hch@....de>,
	iommu@...ts.linux.dev
Cc: linux-trace-kernel@...r.kernel.org,
	Robin Murphy <robin.murphy@....com>,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Sean Anderson <sean.anderson@...ux.dev>,
	syzbot+b4bfacdec173efaa8567@...kaller.appspotmail.com
Subject: [PATCH] dma-mapping: Fix tracing dma_alloc/free with vmalloc'd memory

Not all virtual addresses have physical addresses, such as if they were
vmalloc'd. Just trace the virtual address instead of trying to trace a
physical address. This aligns with the API, and is good enough to
associate dma_alloc with dma_free.

Fixes: 038eb433dc14 ("dma-mapping: add tracing for dma-mapping API calls")
Reported-by: syzbot+b4bfacdec173efaa8567@...kaller.appspotmail.com
Closes: https://lore.kernel.org/all/670ebde5.050a0220.d9b66.0154.GAE@google.com/
Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
---
%p obfuscates virtual addresses when tracing just like with printk.

 include/trace/events/dma.h | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h
index 569f86a44aaa..b0f41265191c 100644
--- a/include/trace/events/dma.h
+++ b/include/trace/events/dma.h
@@ -121,7 +121,7 @@ TRACE_EVENT(dma_alloc,
 
 	TP_STRUCT__entry(
 		__string(device, dev_name(dev))
-		__field(u64, phys_addr)
+		__field(void *, virt_addr)
 		__field(u64, dma_addr)
 		__field(size_t, size)
 		__field(gfp_t, flags)
@@ -130,18 +130,18 @@ TRACE_EVENT(dma_alloc,
 
 	TP_fast_assign(
 		__assign_str(device);
-		__entry->phys_addr = virt_to_phys(virt_addr);
+		__entry->virt_addr = virt_addr;
 		__entry->dma_addr = dma_addr;
 		__entry->size = size;
 		__entry->flags = flags;
 		__entry->attrs = attrs;
 	),
 
-	TP_printk("%s dma_addr=%llx size=%zu phys_addr=%llx flags=%s attrs=%s",
+	TP_printk("%s dma_addr=%llx size=%zu virt_addr=%p flags=%s attrs=%s",
 		__get_str(device),
 		__entry->dma_addr,
 		__entry->size,
-		__entry->phys_addr,
+		__entry->virt_addr,
 		show_gfp_flags(__entry->flags),
 		decode_dma_attrs(__entry->attrs))
 );
@@ -153,7 +153,7 @@ TRACE_EVENT(dma_free,
 
 	TP_STRUCT__entry(
 		__string(device, dev_name(dev))
-		__field(u64, phys_addr)
+		__field(void *, virt_addr)
 		__field(u64, dma_addr)
 		__field(size_t, size)
 		__field(unsigned long, attrs)
@@ -161,17 +161,17 @@ TRACE_EVENT(dma_free,
 
 	TP_fast_assign(
 		__assign_str(device);
-		__entry->phys_addr = virt_to_phys(virt_addr);
+		__entry->virt_addr = virt_addr;
 		__entry->dma_addr = dma_addr;
 		__entry->size = size;
 		__entry->attrs = attrs;
 	),
 
-	TP_printk("%s dma_addr=%llx size=%zu phys_addr=%llx attrs=%s",
+	TP_printk("%s dma_addr=%llx size=%zu virt_addr=%p attrs=%s",
 		__get_str(device),
 		__entry->dma_addr,
 		__entry->size,
-		__entry->phys_addr,
+		__entry->virt_addr,
 		decode_dma_attrs(__entry->attrs))
 );
 
-- 
2.35.1.1320.gc452695387.dirty