kernel/linux.git/include/trace/events/dma.h, branch v6.18.22

tracing/dma: Cap dma_map_sg tracepoint arrays to prevent buffer overflow

2026-02-19T15:31:33+00:00

[ Upstream commit daafcc0ef0b358d9d622b6e3b7c43767aa3814ee ] The dma_map_sg tracepoint can trigger a perf buffer overflow when tracing large scatter-gather lists. With devices like virtio-gpu creating large DRM buffers, nents can exceed 1000 entries, resulting in: phys_addrs: 1000 * 8 bytes = 8,000 bytes dma_addrs: 1000 * 8 bytes = 8,000 bytes lengths: 1000 * 4 bytes = 4,000 bytes Total: ~20,000 bytes This exceeds PERF_MAX_TRACE_SIZE (8192 bytes), causing: WARNING: CPU: 0 PID: 5497 at kernel/trace/trace_event_perf.c:405 perf buffer not large enough, wanted 24620, have 8192 Cap all three dynamic arrays at 128 entries using min() in the array size calculation. This ensures arrays are only as large as needed (up to the cap), avoiding unnecessary memory allocation for small operations while preventing overflow for large ones. The tracepoint now records the full nents/ents counts and a truncated flag so users can see when data has been capped. Changes in v2: - Use min(nents, DMA_TRACE_MAX_ENTRIES) for dynamic array sizing instead of fixed DMA_TRACE_MAX_ENTRIES allocation (feedback from Steven Rostedt) - This allocates only what's needed up to the cap, avoiding waste for small operations Reported-by: syzbot+28cea38c382fd15e751a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=28cea38c382fd15e751a Tested-by: syzbot+28cea38c382fd15e751a@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey Reviwed-by: Sean Anderson Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20260130155215.69737-1-kartikey406@gmail.com Signed-off-by: Sasha Levin

dma-mapping: fix direction in dma_alloc direction traces

2025-10-03T06:45:09+00:00

Set __entry->dir to the actual "dir" parameter of all trace events in dma_alloc_class. This struct member was left uninitialized by mistake. Signed-off-by: Petr Tesarik Fixes: 3afff779a725 ("dma-mapping: trace dma_alloc/free direction") Cc: stable@vger.kernel.org Reviewed-by: Sean Anderson Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20251001061028.412258-1-ptesarik@suse.com

dma-mapping: export new dma_*map_phys() interface

2025-09-11T22:18:21+00:00

Introduce new DMA mapping functions dma_map_phys() and dma_unmap_phys() that operate directly on physical addresses instead of page+offset parameters. This provides a more efficient interface for drivers that already have physical addresses available. The new functions are implemented as the primary mapping layer, with the existing dma_map_page_attrs()/dma_map_resource() and dma_unmap_page_attrs()/dma_unmap_resource() functions converted to simple wrappers around the phys-based implementations. In case dma_map_page_attrs(), the struct page is converted to physical address with help of page_to_phys() function and dma_map_resource() provides physical address as is together with addition of DMA_ATTR_MMIO attribute. The old page-based API is preserved in mapping.c to ensure that existing code won't be affected by changing EXPORT_SYMBOL to EXPORT_SYMBOL_GPL variant for dma_*map_phys(). Reviewed-by: Jason Gunthorpe Reviewed-by: Keith Busch Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/54cc52af91777906bbe4a386113437ba0bcfba9c.1757423202.git.leonro@nvidia.com

dma-mapping: rename trace_dma_map_page to trace_dma_map_phys

2025-09-11T22:18:20+00:00

As a preparation for following map_page -> map_phys API conversion, let's rename trace_dma_*map_page() to be trace_dma_*map_phys(). Reviewed-by: Jason Gunthorpe Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/c0c02d7d8bd4a148072d283353ba227516a76682.1757423202.git.leonro@nvidia.com

dma-mapping: introduce new DMA attribute to indicate MMIO memory

2025-09-11T22:08:07+00:00

This patch introduces the DMA_ATTR_MMIO attribute to mark DMA buffers that reside in memory-mapped I/O (MMIO) regions, such as device BARs exposed through the host bridge, which are accessible for peer-to-peer (P2P) DMA. This attribute is especially useful for exporting device memory to other devices for DMA without CPU involvement, and avoids unnecessary or potentially detrimental CPU cache maintenance calls. DMA_ATTR_MMIO is supposed to provide dma_map_resource() functionality without need to call to special function and perform branching when processing generic containers like bio_vec by the callers. Reviewed-by: Jason Gunthorpe Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/6f058ec395c5348014860dbc2eed348c17975843.1757423202.git.leonro@nvidia.com

dma-mapping: trace more error paths

2024-10-29T07:54:06+00:00

It can be surprising to the user if DMA functions are only traced on success. On failure, it can be unclear what the source of the problem is. Fix this by tracing all functions even when they fail. Cases where we BUG/WARN are skipped, since those should be sufficiently noisy already. Signed-off-by: Sean Anderson Reviewed-by: Steven Rostedt (Google) Signed-off-by: Christoph Hellwig

dma-mapping: use trace_dma_alloc for dma_alloc* instead of using trace_dma_map

2024-10-29T07:54:03+00:00

In some cases, we use trace_dma_map to trace dma_alloc* functions. This generally follows dma_debug. However, this does not record all of the relevant information for allocations, such as GFP flags. Create new dma_alloc tracepoints for these functions. Note that while dma_alloc_noncontiguous may allocate discontiguous pages (from the CPU's point of view), the device will only see one contiguous mapping. Therefore, we just need to trace dma_addr and size. Signed-off-by: Sean Anderson Reviewed-by: Steven Rostedt (Google) Signed-off-by: Christoph Hellwig

dma-mapping: trace dma_alloc/free direction

2024-10-29T07:54:00+00:00

In preparation for using these tracepoints in a few more places, trace the DMA direction as well. For coherent allocations this is always bidirectional. Signed-off-by: Sean Anderson Reviewed-by: Steven Rostedt (Google) Signed-off-by: Christoph Hellwig

dma-mapping: use macros to define events in a class

2024-10-29T07:53:57+00:00

Use a macro to avoid repeating the parameters and arguments for each event in a class. Signed-off-by: Sean Anderson Reviewed-by: Steven Rostedt (Google) Signed-off-by: Christoph Hellwig

dma-mapping: fix tracing dma_alloc/free with vmalloc'd memory

2024-10-17T15:41:29+00:00

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@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/670ebde5.050a0220.d9b66.0154.GAE@google.com/ Signed-off-by: Sean Anderson Signed-off-by: Christoph Hellwig