diff options
| -rw-r--r-- | include/libelfu/modelops.h | 1 | ||||
| -rw-r--r-- | include/options.h | 2 | ||||
| -rw-r--r-- | src/main.c | 4 | ||||
| -rw-r--r-- | src/model/insert.c | 106 | ||||
| -rw-r--r-- | src/options.c | 21 |
5 files changed, 129 insertions, 5 deletions
diff --git a/include/libelfu/modelops.h b/include/libelfu/modelops.h index c89630f..d256b07 100644 --- a/include/libelfu/modelops.h +++ b/include/libelfu/modelops.h @@ -19,5 +19,6 @@ ElfuElf* elfu_mFromElf(Elf *e); GElf_Xword elfu_mInsertBefore(ElfuElf *me, GElf_Off off, GElf_Xword size); +GElf_Xword elfu_mInsertAfter(ElfuElf *me, GElf_Off off, GElf_Xword size); #endif diff --git a/include/options.h b/include/options.h index ee9d612..f92298f 100644 --- a/include/options.h +++ b/include/options.h @@ -10,6 +10,8 @@ typedef struct { int printSections; unsigned insertBeforeOffs; unsigned insertBeforeSz; + unsigned insertAfterOffs; + unsigned insertAfterSz; } CLIOpts; @@ -74,6 +74,10 @@ int main(int argc, char **argv) elfu_mInsertBefore(me, opts.insertBeforeOffs, opts.insertBeforeSz); } + if (opts.insertAfterSz) { + elfu_mInsertAfter(me, opts.insertAfterOffs, opts.insertAfterSz); + } + elfu_mCheck(me); printf("Output model checked.\n"); elfu_mToElf(me, hOut.e); diff --git a/src/model/insert.c b/src/model/insert.c index 2086c6e..b299391 100644 --- a/src/model/insert.c +++ b/src/model/insert.c @@ -4,6 +4,9 @@ #include <libelfu/libelfu.h> +// TODO: Take p_align into account + + /* * Insert space at a given position in the file by moving everything @@ -24,8 +27,6 @@ GElf_Xword elfu_mInsertBefore(ElfuElf *me, GElf_Off off, GElf_Xword size) assert(me); - // TODO: Take p_align into account - /* Move SHDRs and PHDRs */ if (me->ehdr.e_shoff >= off) { me->ehdr.e_shoff += size; @@ -46,8 +47,6 @@ GElf_Xword elfu_mInsertBefore(ElfuElf *me, GElf_Off off, GElf_Xword size) /* mp->phdr.p_offset < off */ if (off < end) { - /* Mark this as a modified area */ - /* Insertion in the middle of PHDR, so let it span the new data */ mp->phdr.p_filesz += size; mp->phdr.p_memsz += size; @@ -109,3 +108,102 @@ GElf_Xword elfu_mInsertBefore(ElfuElf *me, GElf_Off off, GElf_Xword size) return size; } + + + +/* + * Insert space at a given position in the file by moving everything + * after it towards the end of the file, and towards higher memory + * regions where it is mapped. + * + * off must not be in the middle of any data structure, such as + * PHDRs, SHDRs, or sections. Behaviour is undefined if it is. + * + * PHDRs will be patched such that everything AFTER off is shifted to + * higher addresses, making space for the new data in-between. + */ +GElf_Xword elfu_mInsertAfter(ElfuElf *me, GElf_Off off, GElf_Xword size) +{ + ElfuScn *ms; + ElfuPhdr *mp; + + assert(me); + +/* Move SHDRs and PHDRs */ + if (me->ehdr.e_shoff >= off) { + me->ehdr.e_shoff += size; + } + + if (me->ehdr.e_phoff >= off) { + me->ehdr.e_phoff += size; + } + + /* Patch PHDRs to include new data */ + CIRCLEQ_FOREACH(mp, &me->phdrList, elem) { + GElf_Off end = mp->phdr.p_offset + mp->phdr.p_filesz; + + if (mp->phdr.p_offset >= off) { + /* Insertion before PHDR's content, so it's shifted. */ + mp->phdr.p_offset += size; + + /* It may also need to be remapped. See second pass below. */ + } else { + /* mp->phdr.p_offset < off */ + + if (off < end) { + /* Insertion in the middle of PHDR, so let it span the new data */ + mp->phdr.p_filesz += size; + mp->phdr.p_memsz += size; + } else { + /* Insertion after PHDR's content. Nothing to do. */ + } + } + } + + /* For each LOAD header, find clashing headers that need to be + remapped to lower memory areas. + */ + CIRCLEQ_FOREACH(mp, &me->phdrList, elem) { + if (mp->phdr.p_type == PT_LOAD) { + ElfuPhdr *mp2; + + CIRCLEQ_FOREACH(mp2, &me->phdrList, elem) { + if (mp2->phdr.p_type != PT_LOAD + && mp2->phdr.p_offset + mp2->phdr.p_filesz > off) { + /* The PHDR now ends in the file after the injection site */ + GElf_Off vend1 = mp->phdr.p_vaddr + mp->phdr.p_memsz; + GElf_Off pend1 = mp->phdr.p_paddr + mp->phdr.p_memsz; + GElf_Off vend2 = mp2->phdr.p_vaddr + mp2->phdr.p_memsz; + GElf_Off pend2 = mp2->phdr.p_paddr + mp2->phdr.p_memsz; + + /* If mp and mp2 now overlap in memory */ + if ((mp2->phdr.p_vaddr < vend1 && vend2 > mp->phdr.p_vaddr) + || (mp2->phdr.p_paddr < pend1 && pend2 > mp->phdr.p_paddr)) { + /* Move mp2 up in memory, as mp has been resized. + Maintaining the relative offset between them is the best + guess at maintaining consistency. + */ + + mp2->phdr.p_vaddr += size; + mp2->phdr.p_paddr += size; + } + } + } + } + } + + /* Move the sections themselves */ + CIRCLEQ_FOREACH(ms, &me->scnList, elem) { + if (ms->shdr.sh_offset >= off) { + ms->shdr.sh_offset += size; + + /* If this was in a LOAD segment, it has been adjusted there + and this synchronises it. + If not, it doesn't matter anyway. + */ + ms->shdr.sh_addr += size; + } + } + + return size; +} diff --git a/src/options.c b/src/options.c index 55a91c5..c728d40 100644 --- a/src/options.c +++ b/src/options.c @@ -14,11 +14,19 @@ static void printUsage(char *progname) " -h, --help Print this help message\n" " -o, --output Where to write the modified ELF file to\n" "\n" + "ELF dump:\n" " --print-header Print ELF header\n" " --print-segments Print program headers\n" " --print-sections Print sections\n" "\n" - " --insert-before off,sz Insert spacing at given offset\n" + "Space insertion:\n" + " off: File offset, not within any structure (headers or sections).\n" + " sz: A multiple of the maximum alignment of all PHDRs.\n" + "\n" + " --insert-before off,sz Insert spacing at given offset,\n" + " mapping everything before it to lower mem addresses.\n" + " --insert-after off,sz Insert spacing at given offset,\n" + " mapping everything after it to higher mem addresses.\n" "\n"); } @@ -38,6 +46,7 @@ void parseOptions(CLIOpts *opts, int argc, char **argv) {"print-segments", 0, 0, 10002}, {"print-sections", 0, 0, 10003}, {"insert-before", 1, 0, 10004}, + {"insert-after", 1, 0, 10005}, {NULL, 0, NULL, 0} }; @@ -69,6 +78,16 @@ void parseOptions(CLIOpts *opts, int argc, char **argv) goto USAGE; } break; + case 10005: + opts->insertAfterOffs = strtoul(optarg, &endptr, 0); + if (endptr[0] != ',') { + goto USAGE; + } + opts->insertAfterSz = strtoul(endptr + 1, &endptr, 0); + if (endptr[0] != '\0' || opts->insertAfterSz == 0) { + goto USAGE; + } + break; case '?': default: goto USAGE; |