Elfedit: file sizes not aligned with page boundaries

pmeunier

May 8, 2025, 5:19 PM

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Dependencies

• [2] Z43EQIWN Elfedit: edit to file
• [3] AR2X3TLA Initial commit: introducing elfedit
• [4] 5PJAXSZ7 Elfedit: correct reallocation of dynstr/dynamic
• [5] ZV57M4VN Debugging
• [6] VZTI2E23 Elfedit: handling the case where we move the same section we're adding

Change contents

• replacement in elfedit/src/lib.rs at line 1084
  [3.7629]→[3.7629:7706](∅→∅)
  − let rounded_last_vaddr = align_next(last_vaddr as usize, page_size);
  [3.7629]

  [3.24241]
  + let mut rounded_last_vaddr = align_next(last_vaddr as usize, page_size);
• edit in elfedit/src/lib.rs at line 1146
  [3.9990]→[3.9990:9991](∅→∅),[3.9991]→[3.2413:2549](∅→∅),[3.2549]→[3.10063:10088](∅→∅),[3.10063]→[3.10063:10088](∅→∅)
  −

  − // Combien de sections du début du fichier doit-on

  − // déplacer à la fin pour ajouter notre nouveau header de

  − // segment ?
• edit in elfedit/src/lib.rs at line 1161
  [3.10470]

  [3.10470]
  + // Can we add a new LOAD segment (i.e. is there space

  + // immediately after the program header table?)
• replacement in elfedit/src/lib.rs at line 1164
  [3.10548]→[3.10548:10802](∅→∅)
  − // In the absolute worst case, we need 3 new LOAD

  − // segments: our new one, and then one for each end of

  − // the sequence of sections we need to move to make

  − // room for the program headers.
  [3.10548]

  [3.10802]
  + // No space. We will move enough sections to the end

  + // of the file, in order to make room.

  + //

  + // In the worst global case of patching, we need 3 new

  + // LOAD segments:

  + //

  + // - two new ones (interp + dynstr)

  + // - possibly an extra one for the initial segments we

  + // need to move

  +
• edit in elfedit/src/lib.rs at line 1244
  [3.13746]

  [3.13746]
  + rounded_last_vaddr = rounded_last_vaddr + rounded_moved as usize;
• edit in elfedit/src/lib.rs at line 1246
  [3.13767]

  [2.421]
  + // There is space after the program header table, no

  + // need to move anything.
• replacement in elfedit/src/lib.rs at line 1287
  [3.14561]→[3.14561:14658](∅→∅)
  − self.add_load_segment(id, new_offset, new.len(), last_vaddr as usize, 4, page_size);
  [3.14561]

  [3.26107]
  + self.add_load_segment(id, new_offset, new.len(), rounded_last_vaddr as usize, 6, page_size);