[llvm] [llvm-objcopy] Fix file offsets when PT_INTERP/PT_LOAD offsets are equal (PR #80562)

[James Henderson via llvm-commits]

================
@@ -0,0 +1,131 @@
+## When the offset of a non-PT_LOAD segment (e.g. PT_INTERP) equals the offset
+## of a PT_LOAD segment, set the parent of the PT_INTERP segment to the PT_LOAD
+## segment, ensuring that the offset is correctly aligned.
+
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-objcopy %t %t2
+# RUN: llvm-readelf -Sl %t2 | FileCheck %s
+
+# CHECK:       [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
+# CHECK-NEXT:  [ 0]                   NULL            0000000000000000 000000 000000 00      0   0  0
+# CHECK-NEXT:  [ 1] .text             PROGBITS        0000000000201000 001000 000001 00  AX  0   0  4
+# CHECK-NEXT:  [ 2] .interp           PROGBITS        0000000000202000 002000 00001c 00   A  0   0  1
+# CHECK-NEXT:  [ 3] .rodata           PROGBITS        0000000000202020 002020 000001 00   A  0   0  1
+# CHECK-NEXT:  [ 4] .tdata            PROGBITS        0000000000203000 003000 000001 00 WAT  0   0 4096
+# CHECK-NEXT:  [ 5] .relro_padding    NOBITS          0000000000203001 003001 000fff 00  WA  0   0  1
+# CHECK-NEXT:  [ 6] .strtab           STRTAB          0000000000000000 003001 000001 00      0   0  1
+# CHECK-NEXT:  [ 7] .shstrtab         STRTAB          0000000000000000 003002 00003f 00      0   0  1
+
+# CHECK:     Program Headers:
+# CHECK-NEXT:  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
+# CHECK-NEXT:  PHDR           0x000040 0x0000000000200040 0x0000000000200040 0x0001c0 0x0001c0 R   0x8
+# CHECK-NEXT:  INTERP         0x002000 0x0000000000202000 0x0000000000202000 0x00001c 0x00001c R   0x1
+# CHECK-NEXT:      [Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]
+# CHECK-NEXT:  LOAD           0x000000 0x0000000000200000 0x0000000000200000 0x000200 0x000200 R   0x1000
+# CHECK-NEXT:  LOAD           0x001000 0x0000000000201000 0x0000000000201000 0x000001 0x000001 R E 0x1000
+# CHECK-NEXT:  LOAD           0x002000 0x0000000000202000 0x0000000000202000 0x000021 0x000021 R   0x1000
+# CHECK-NEXT:  TLS            0x003000 0x0000000000203000 0x0000000000203000 0x000001 0x001000 R   0x1000
+# CHECK-NEXT:  GNU_RELRO      0x003000 0x0000000000203000 0x0000000000203000 0x000001 0x001000 R   0x1000
+# CHECK-NEXT:  LOAD           0x003000 0x0000000000203000 0x0000000000203000 0x000001 0x001000 RW  0x1000
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_X86_64
+  Entry:           0x201000
+ProgramHeaders:
+  - Type:            PT_PHDR
+    Flags:           [ PF_R ]
+    VAddr:           0x200040
+    Align:           0x8
+    Offset:          0x40
+    FileSize:        0x1c0
+    MemSize:         0x1c0
+  - Type:            PT_INTERP
+    Flags:           [ PF_R ]
+    FirstSec:        .interp
+    LastSec:         .interp
+    ## The address equals the address of its containing PT_LOAD.
+    VAddr:           0x202000
+    Offset:          0x2000
+  - Type:            PT_LOAD
+    Flags:           [ PF_R ]
+    VAddr:           0x200000
+    Align:           0x1000
+    Offset:          0x0
+    FileSize:        0x200
+    MemSize:         0x200
+  - Type:            PT_LOAD
+    Flags:           [ PF_X, PF_R ]
+    FirstSec:        .text
+    LastSec:         .text
+    VAddr:           0x201000
+    Align:           0x1000
+    Offset:          0x1000
+  - Type:            PT_LOAD
+    Flags:           [ PF_R ]
+    FirstSec:        .interp
+    LastSec:         .rodata
+    VAddr:           0x202000
+    Align:           0x1000
+    Offset:          0x2000
+  ## Intentionally place PT_TLS/PT_GNU_RELRO before PT_LOAD to test that we
+  ## correctly set parent segments.
+  - Type:            PT_TLS
+    Flags:           [ PF_R ]
+    FirstSec:        .tdata
+    LastSec:         .relro_padding
+    VAddr:           0x203000
+    Align:           0x1000
+    Offset:          0x3000
+  - Type:            PT_GNU_RELRO
+    Flags:           [ PF_R ]
+    FirstSec:        .tdata
+    LastSec:         .relro_padding
+    VAddr:           0x203000
+    Align:           0x1000
+    Offset:          0x3000
+  - Type:            PT_LOAD
+    Flags:           [ PF_W, PF_R ]
+    FirstSec:        .tdata
+    LastSec:         .relro_padding
+    VAddr:           0x203000
+    Align:           0x1000
+    Offset:          0x3000
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x201000
+    AddressAlign:    0x4
+    Offset:          0x1000
+    Content:         C3
+  - Name:            .interp
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    Address:         0x202000
+    AddressAlign:    0x1
+    Offset:          0x2000
+    Content:         2F6C696236342F6C642D6C696E75782D7838362D36342E736F2E3200
----------------
jh7370 wrote:

That's not really what this test is about though? This test is about making sure the alignment is respected when the higher alignment segment appears after another segment it nests, so it's about the final file offset in program headers. There are already tests that show that segment contents are preserved (see e.g. `preserve-segment-contents.test`).

https://github.com/llvm/llvm-project/pull/80562