[llvm-bugs] [Bug 31196] New: lld -Ttext 0x600 (as used in FreeBSD boot loader) results in 4GB output on i386

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=31196

            Bug ID: 31196
           Summary: lld -Ttext 0x600 (as used in FreeBSD boot loader)
                    results in 4GB output on i386
           Product: lld
           Version: unspecified
          Hardware: PC
                OS: FreeBSD
            Status: NEW
          Severity: normal
          Priority: P
         Component: ELF
          Assignee: unassignedbugs at nondot.org
          Reporter: emaste at freebsd.org
                CC: llvm-bugs at lists.llvm.org
            Blocks: 23214
    Classification: Unclassified

Created attachment 17677
  --> https://llvm.org/bugs/attachment.cgi?id=17677&action=edit
reproducer for large output with -Ttext 0x0600

Found while testing the WIP -N support in https://reviews.llvm.org/D26888

The boot0 boot component is linked with the following command line:

ld --eh-frame-hdr -dynamic-linker /libexec/ld-elf.so.1 --hash-style=both
--enable-new-dtags -m elf_i386_fbsd -o boot0 -L/usr/lib32 -Ttext 0x600 -e start
-N -S --oformat binary boot0.o

This produces 4GB output:

% ls -l boot0
-rwxr-xr-x  1 emaste  emaste  4294903808 28 Nov 18:01 boot0

Outputting as ELF instead by dropping the --oformat binary:

% /tank/emaste/src/llvm/build-debug/bin/ld.lld  --eh-frame-hdr -dynamic-linker
/libexec/ld-elf.so.1 --hash-style=both --enable-new-dtags -m elf_i386_fbsd -o
boot0 -L/usr/lib32 -Ttext 0x600 -e start -N -S boot0.o

lets us see what's going on (note the Off column):

% readelf -S boot0
There are 8 section headers, starting at offset 0xffff0e60:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf
Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0 
0
  [ 1] .text             PROGBITS        00000600 ffff0600 000200 00  AX  0   0
 4
  [ 2] .data             PROGBITS        00000800 ffff0800 000000 00  WA  0   0
 4
  [ 3] .bss              NOBITS          00000800 ffff0800 000000 00  WA  0   0
 4
  [ 4] .comment          PROGBITS        00000000 ffff0800 000055 01  MS  0   0
 1
  [ 5] .symtab           SYMTAB          00000000 ffff0858 0003e0 10      7  61
 4
  [ 6] .shstrtab         STRTAB          00000000 ffff0c38 000035 00      0   0
 1
  [ 7] .strtab           STRTAB          00000000 ffff0c6d 0001f1 00      0   0
 1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

For reference, here's the output when linked by ld.bfd 2.17.50:

% readelf -S boot0
There are 5 section headers, starting at offset 0x278:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf
Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0 
0
  [ 1] .text             PROGBITS        00000600 000054 000200 00 WAX  0   0 
4
  [ 2] .shstrtab         STRTAB          00000000 000254 000021 00      0   0 
1
  [ 3] .symtab           SYMTAB          00000000 000340 000420 10      4  62 
4
  [ 4] .strtab           STRTAB          00000000 000760 000209 00      0   0 
1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

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