Also consider RO data for start of flash

[pekangas]

Take read-only data segments into account when determining where flash contents start. This is specifically important if the Tock CRT0 header is in a separate data section before the start of .text.

The change is trivial and fixes #92 for me, but would benefit from someone else thinking the logic through in case I missed some unintended consequences. I am not entirely clear on why elf2tab does some of the things it does...

[bradjc]

I'm looking at blink compiled for riscv:

readelf.py -e examples/blink/build/rv32imc/rv32imc.0x00080080.0x40008000.elf
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           <unknown>
  Version:                           0x1
  Entry point address:               0x800a8
  Start of program headers:          52 (bytes into file)
  Start of section headers:          241876 (bytes into file)
  Flags:                             0x1
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         4
  Size of section headers:           40 (bytes)
  Number of section headers:         25
  Section header string table index: 24

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .got              PROGBITS        40008800 00485c 000000 00  WA  0   0  1
  [ 2] .crt0_header      PROGBITS        00080080 001080 000028 00   A  0   0  1
  [ 3] .data             PROGBITS        40008800 004800 00005c 00  WA  0   0  4
  [ 4] .GCC.command.line PROGBITS        00000000 00485c 0000a7 01  MS  0   0  1
  [ 5] .comment          PROGBITS        00000000 004903 000051 01  MS  0   0  1
  [ 6] .riscv.attributes ARM_ATTRIBUTES  00000000 004954 00002f 00      0   0  1
  [ 7] .wfr.app_state    PROGBITS        000800a8 004983 000000 00   W  0   0  1
  [ 8] .text             PROGBITS        000800a8 0010a8 002ca8 00  AX  0   0  4
  [ 9] .stack            NOBITS          40008000 005000 000800 00  WA  0   0  1
  [10] .bss              NOBITS          4000885c 00485c 0002ac 00  WA  0   0  4
  [11] .debug_info       PROGBITS        00000000 004983 017764 00      0   0  1
  [12] .debug_abbrev     PROGBITS        00000000 01c0e7 005bf8 00      0   0  1
  [13] .debug_loc        PROGBITS        00000000 021cdf 002e32 00      0   0  1
  [14] .debug_aranges    PROGBITS        00000000 024b18 000a40 00      0   0  8
  [15] .debug_ranges     PROGBITS        00000000 025558 000580 00      0   0  1
  [16] .debug_line       PROGBITS        00000000 025ad8 00aec1 00      0   0  1
  [17] .debug_str        PROGBITS        00000000 030999 002374 01  MS  0   0  1
  [18] .debug_frame      PROGBITS        00000000 032d10 001598 00      0   0  4
  [19] .debug_line_str   PROGBITS        00000000 0342a8 000d1e 01  MS  0   0  1
  [20] .debug_loclists   PROGBITS        00000000 034fc6 003c46 00      0   0  1
  [21] .debug_rnglists   PROGBITS        00000000 038c0c 000829 00      0   0  1
  [22] .symtab           SYMTAB          00000000 039438 0012f0 10     23 195  4
  [23] .strtab           STRTAB          00000000 03a728 000892 00      0   0  1
  [24] .shstrtab         STRTAB          00000000 03afba 000117 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  <unknown>      0x004954 0x00000000 0x00000000 0x0002f 0x00000 R   0x1
  LOAD           0x001080 0x00080080 0x00080080 0x02cd0 0x02cd0 R E 0x1000
  LOAD           0x004800 0x40008800 0x00082d50 0x0005c 0x00308 RW  0x1000
  LOAD           0x000000 0x40008000 0x40008000 0x00000 0x00800 RW  0x1000

 Section to Segment mapping:
  Segment Sections...
   00     .riscv.attributes
   01     .crt0_header .text
   02     .data .bss
   03     .stack

There is this "unknown" segment which is only R but isn't anything we want.

[bradjc]

This is specifically important if the Tock CRT0 header is in a separate data section before the start of .text.

Do you mean in a separate data segment? I think the crt0 header has always been in its own section before .text.