Re: linux-user/elfload.c: Seeing a segfault in qemu with a binary with no data section

[Stephen Long]

I think that a variant of that patch made it into master:

            /*
             * Some segments may be completely empty without any backing file
             * segment, in that case just let zero_bss allocate an empty buffer
             * for it.
             */
            if (eppnt->p_filesz != 0) {
                error = target_mmap(vaddr_ps, vaddr_len, elf_prot,
                                    MAP_PRIVATE | MAP_FIXED,
                                    image_fd, eppnt->p_offset - vaddr_po);

                if (error == -1) {
                    goto exit_perror;
                }
            }

            vaddr_ef = vaddr + eppnt->p_filesz;

In the case of my elf, it is letting zero_bss() allocate the empty buffer. But 
since there is no data segment before it, the memset in zero_bss() segfaults. 
zero_bss()'s mapping starts at host_map_start.
Here's the output of "readelf -l" on my elf:

Elf file type is EXEC (Executable file)
Entry point 0x2102e8
There are 8 program headers, starting at offset 64

Program Headers:
  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz 
  Flg Align
  PHDR           0x000040 0x0000000000200040 0x0000000000200040 0x0001c0 
0x0001c0 R   0x8
  LOAD           0x000000 0x0000000000200000 0x0000000000200000 0x0002e4 
0x0002e4 R   0x10000
  LOAD           0x0002e8 0x00000000002102e8 0x00000000002102e8 0x000c88 
0x000c88 R E 0x10000
  LOAD           0x000f70 0x0000000000220f70 0x0000000000220f70 0x000068 
0x000068 RW  0x10000
  LOAD           0x000fd8 0x0000000000230fd8 0x0000000000230fd8 0x000000 
0x000278 RW  0x10000
  GNU_RELRO      0x000f70 0x0000000000220f70 0x0000000000220f70 0x000068 
0x000090 R   0x1
  GNU_EH_FRAME   0x000224 0x0000000000200224 0x0000000000200224 0x00002c 
0x00002c R   0x4
  GNU_STACK      0x000000 0x0000000000000000 0x0000000000000000 0x000000 
0x000000 RW  0

 Section to Segment mapping:
  Segment Sections...
   00
   01     .rodata .eh_frame_hdr .eh_frame
   02     .text .init .fini
   03     .init_array .got
   04     .bss
   05     .init_array .got
   06     .eh_frame_hdr
   07