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TDA4VM: Cannot access memory at address 0xffff8aaeb000

Part Number: TDA4VM

hi TI expert,

     I can't access some virtual address when i use GDB to debug my code on TDA4VM platform. 

     first, i map a vximage which get from a objectArray

              status = vxMapImagePatch(obj.onScreenImage[0], &rect, 0, &map_id, &image_addr, &data_ptr, VX_WRITE_ONLY, VX_MEMORY_TYPE_HOST,VX_NOGAP_X);

     second, i set a breakpoint after vxMapImagePatch successful and run to this breakpoint, then i use print to show the data in the data_ptr, the whole operation as below:

               (gdb) p data_ptr
                        $7 = (vx_uint8 *) 0xffff8aaeb000 <error: Cannot access memory at address 0xffff8aaeb000>

               (gdb) p *0xffff8aaeb000
                       Cannot access memory at address 0xffff8aaeb000 

               (gdb) p *0xffff8c003000
                        $8 = 0

               (gdb) info proc map
                      process 2648
                      Mapped address spaces:

                      Start Addr End Addr Size Offset objfile

                       ...................................
                      0x3f3000 0xaeb4000 0xaac1000 0x0 [heap]
                      0xffff89d6b000 0xffff8a1a3000 0x438000 0x0 /dmabuf:
                      0xffff8a1a3000 0xffff8a5db000 0x438000 0x0 /dmabuf:
                      0xffff8a5db000 0xffff8aa13000 0x438000 0x0 /dmabuf:
                      0xffff8aa13000 0xffff8aaeb000 0xd8000 0x0 /dmabuf:
                      0xffff8aaeb000 0xffff8af23000 0x438000 0x0 /dmabuf:
                      0xffff8af23000 0xffff8b35b000 0x438000 0x0 /dmabuf:
                      0xffff8b35b000 0xffff8b793000 0x438000 0x0 /dmabuf:
                      0xffff8b793000 0xffff8bbcb000 0x438000 0x0 /dmabuf:
                      0xffff8bbcb000 0xffff8c003000 0x438000 0x0 /dmabuf:
                      0xffff8c003000 0xffff8c013000 0x10000 0x0
                      0xffff8c013000 0xffff8c813000 0x800000 0x0
                      0xffff8c813000 0xffff8c823000 0x10000 0x0

                       ...............................
               
                    according to my test, the virtual addr named dambuf  can't be accessed and others can be accessed, why ? waiting for your help, Thanks.