Re: [PATCH v4] dmaengine: xilinx: xdma: Fix regmap max_register

[Alexander Stein <alexander.stein@ew.tq-group.com>]

Am Mittwoch, 3. September 2025, 10:56:13 CEST schrieb Anthony Brandon via B4 Relay:
> From: Anthony Brandon <anthony@amarulasolutions.com>
> 
> The max_register field is assigned the size of the register memory
> region instead of the offset of the last register.
> The result is that reading from the regmap via debugfs can cause
> a segmentation fault:
> 
> tail /sys/kernel/debug/regmap/xdma.1.auto/registers
> Unable to handle kernel paging request at virtual address ffff800082f70000
> Mem abort info:
>   ESR = 0x0000000096000007
>   EC = 0x25: DABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x07: level 3 translation fault
> [...]
> Call trace:
>  regmap_mmio_read32le+0x10/0x30
>  _regmap_bus_reg_read+0x74/0xc0
>  _regmap_read+0x68/0x198
>  regmap_read+0x54/0x88
>  regmap_read_debugfs+0x140/0x380
>  regmap_map_read_file+0x30/0x48
>  full_proxy_read+0x68/0xc8
>  vfs_read+0xcc/0x310
>  ksys_read+0x7c/0x120
>  __arm64_sys_read+0x24/0x40
>  invoke_syscall.constprop.0+0x64/0x108
>  do_el0_svc+0xb0/0xd8
>  el0_svc+0x38/0x130
>  el0t_64_sync_handler+0x120/0x138
>  el0t_64_sync+0x194/0x198
> Code: aa1e03e9 d503201f f9400000 8b214000 (b9400000)
> ---[ end trace 0000000000000000 ]---
> note: tail[1217] exited with irqs disabled
> note: tail[1217] exited with preempt_count 1
> Segmentation fault
> 
> Fixes: 17ce252266c7 ("dmaengine: xilinx: xdma: Add xilinx xdma driver")
> Signed-off-by: Anthony Brandon <anthony@amarulasolutions.com>
> Reviewed-by: Lizhi Hou <lizhi.hou@amd.com>
> Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>

Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>

> ---
> Changes in v4:
> - Reorder Reviewed-by
> - Link to v3: https://lore.kernel.org/r/20250902-xdma-max-reg-v3-1-5fa37b8d2b15@amarulasolutions.com
> 
> Changes in v3:
> - Add Fixes tag
> - Link to v2: https://lore.kernel.org/r/20250901-xdma-max-reg-v2-1-fa3723a718cd@amarulasolutions.com
> 
> Changes in v2:
> - Define new constant XDMA_MAX_REG_OFFSET and use that.
> - Link to v1: https://lore.kernel.org/r/20250901-xdma-max-reg-v1-1-b6a04561edb1@amarulasolutions.com
> ---
>  drivers/dma/xilinx/xdma-regs.h | 1 +
>  drivers/dma/xilinx/xdma.c      | 2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/xilinx/xdma-regs.h b/drivers/dma/xilinx/xdma-regs.h
> index 6ad08878e93862b770febb71b8bc85e66813428e..70bca92621aa41b0367d1e236b3e276344a26320 100644
> --- a/drivers/dma/xilinx/xdma-regs.h
> +++ b/drivers/dma/xilinx/xdma-regs.h
> @@ -9,6 +9,7 @@
>  
>  /* The length of register space exposed to host */
>  #define XDMA_REG_SPACE_LEN	65536
> +#define XDMA_MAX_REG_OFFSET	(XDMA_REG_SPACE_LEN - 4)
>  
>  /*
>   * maximum number of DMA channels for each direction:
> diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
> index 0d88b1a670e142dac90d09c515809faa2476a816..5ecf8223c112e468c79ce635398ba393a535b9e0 100644
> --- a/drivers/dma/xilinx/xdma.c
> +++ b/drivers/dma/xilinx/xdma.c
> @@ -38,7 +38,7 @@ static const struct regmap_config xdma_regmap_config = {
>  	.reg_bits = 32,
>  	.val_bits = 32,
>  	.reg_stride = 4,
> -	.max_register = XDMA_REG_SPACE_LEN,
> +	.max_register = XDMA_MAX_REG_OFFSET,
>  };
>  
>  /**
> 
> ---
> base-commit: b320789d6883cc00ac78ce83bccbfe7ed58afcf0
> change-id: 20250901-xdma-max-reg-1649c6459358
> 
> Best regards,
>