Date: Thu, 25 Oct 2018 15:18:54 +0000 (UTC) From: Ed Maste <emaste@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r339726 - stable/12/contrib/elftoolchain/elfcopy Message-ID: <201810251518.w9PFIsjA068402@repo.freebsd.org>
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Author: emaste Date: Thu Oct 25 15:18:54 2018 New Revision: 339726 URL: https://svnweb.freebsd.org/changeset/base/339726 Log: MFC r339451: objcopy: restore behaviour required by GCC's build In r339350 filter_reloc() was removed, to fix the case of stripping statically linked binaries with relocations (which may come from ifunc use, for example). As a side effect this changed the behaviour when stripping object files - the output was broken both before and after r339350, in different ways. Unfortunately GCC's build process relies on the previous behaviour, so: - Revert r339350, restoring filter_reloc(). - Fix an unitialized variable use (commited as r3638 in ELF Tool Chain). - Change filter_reloc() to omit relocations referencing removed symbols, while retaining relocations with no symbol reference. - Retain the entire relocation section if it references the dynamic symbol table (fix from kaiw in D17596). PR: 232176 Approved by: re (gjb, kib) Sponsored by: The FreeBSD Foundation Modified: stable/12/contrib/elftoolchain/elfcopy/sections.c Directory Properties: stable/12/ (props changed) Modified: stable/12/contrib/elftoolchain/elfcopy/sections.c ============================================================================== --- stable/12/contrib/elftoolchain/elfcopy/sections.c Thu Oct 25 15:14:16 2018 (r339725) +++ stable/12/contrib/elftoolchain/elfcopy/sections.c Thu Oct 25 15:18:54 2018 (r339726) @@ -39,6 +39,7 @@ ELFTC_VCSID("$Id: sections.c 3443 2016-04-15 18:57:54Z static void add_gnu_debuglink(struct elfcopy *ecp); static uint32_t calc_crc32(const char *p, size_t len, uint32_t crc); static void check_section_rename(struct elfcopy *ecp, struct section *s); +static void filter_reloc(struct elfcopy *ecp, struct section *s); static int get_section_flags(struct elfcopy *ecp, const char *name); static void insert_sections(struct elfcopy *ecp); static void insert_to_strtab(struct section *t, const char *s); @@ -573,6 +574,14 @@ copy_content(struct elfcopy *ecp) continue; /* + * If strip action is STRIP_ALL, relocation info need + * to be stripped. Skip filtering otherwisw. + */ + if (ecp->strip == STRIP_ALL && + (s->type == SHT_REL || s->type == SHT_RELA)) + filter_reloc(ecp, s); + + /* * The section indices in the SHT_GROUP section needs * to be updated since we might have stripped some * sections and changed section numbering. @@ -661,6 +670,140 @@ update_section_group(struct elfcopy *ecp, struct secti s->sz -= 4; } + s->nocopy = 1; +} + +/* + * Filter relocation entries, only keep those entries whose + * symbol is in the keep list. + */ +static void +filter_reloc(struct elfcopy *ecp, struct section *s) +{ + const char *name; + GElf_Shdr ish; + GElf_Rel rel; + GElf_Rela rela; + Elf32_Rel *rel32; + Elf64_Rel *rel64; + Elf32_Rela *rela32; + Elf64_Rela *rela64; + Elf_Data *id; + uint64_t cap, n, nrels, sym; + int elferr, i; + + if (gelf_getshdr(s->is, &ish) == NULL) + errx(EXIT_FAILURE, "gelf_getehdr() failed: %s", + elf_errmsg(-1)); + + /* We don't want to touch relocation info for dynamic symbols. */ + if ((ecp->flags & SYMTAB_EXIST) == 0) { + /* + * No symbol table in output. If sh_link points to a section + * that exists in the output object, this relocation section + * is for dynamic symbols. Don't touch it. + */ + if (ish.sh_link != 0 && ecp->secndx[ish.sh_link] != 0) + return; + } else { + /* Symbol table exist, check if index equals. */ + if (ish.sh_link != elf_ndxscn(ecp->symtab->is)) + return; + } + +#define COPYREL(REL, SZ) do { \ + if (nrels == 0) { \ + if ((REL##SZ = malloc(cap * \ + sizeof(*REL##SZ))) == NULL) \ + err(EXIT_FAILURE, "malloc failed"); \ + } \ + if (nrels >= cap) { \ + cap *= 2; \ + if ((REL##SZ = realloc(REL##SZ, cap * \ + sizeof(*REL##SZ))) == NULL) \ + err(EXIT_FAILURE, "realloc failed"); \ + } \ + REL##SZ[nrels].r_offset = REL.r_offset; \ + REL##SZ[nrels].r_info = REL.r_info; \ + if (s->type == SHT_RELA) \ + rela##SZ[nrels].r_addend = rela.r_addend; \ + nrels++; \ +} while (0) + + nrels = 0; + cap = 4; /* keep list is usually small. */ + rel32 = NULL; + rel64 = NULL; + rela32 = NULL; + rela64 = NULL; + if ((id = elf_getdata(s->is, NULL)) == NULL) + errx(EXIT_FAILURE, "elf_getdata() failed: %s", + elf_errmsg(-1)); + n = ish.sh_size / ish.sh_entsize; + for(i = 0; (uint64_t)i < n; i++) { + if (s->type == SHT_REL) { + if (gelf_getrel(id, i, &rel) != &rel) + errx(EXIT_FAILURE, "gelf_getrel failed: %s", + elf_errmsg(-1)); + sym = GELF_R_SYM(rel.r_info); + } else { + if (gelf_getrela(id, i, &rela) != &rela) + errx(EXIT_FAILURE, "gelf_getrel failed: %s", + elf_errmsg(-1)); + sym = GELF_R_SYM(rela.r_info); + } + /* + * If a relocation references a symbol and we are omitting + * either that symbol or the entire symbol table we cannot + * produce valid output, and so just omit the relocation. + * Broken output like this is generally not useful, but some + * uses of elfcopy/strip rely on it - for example, GCC's build + * process uses it to check for build reproducibility by + * stripping objects and comparing them. + * + * Relocations that do not reference a symbol are retained. + */ + if (sym != 0) { + if (ish.sh_link == 0 || ecp->secndx[ish.sh_link] == 0) + continue; + name = elf_strptr(ecp->ein, elf_ndxscn(ecp->strtab->is), + sym); + if (name == NULL) + errx(EXIT_FAILURE, "elf_strptr failed: %s", + elf_errmsg(-1)); + if (lookup_symop_list(ecp, name, SYMOP_KEEP) == NULL) + continue; + } + if (ecp->oec == ELFCLASS32) { + if (s->type == SHT_REL) + COPYREL(rel, 32); + else + COPYREL(rela, 32); + } else { + if (s->type == SHT_REL) + COPYREL(rel, 64); + else + COPYREL(rela, 64); + } + } + elferr = elf_errno(); + if (elferr != 0) + errx(EXIT_FAILURE, "elf_getdata() failed: %s", + elf_errmsg(elferr)); + + if (ecp->oec == ELFCLASS32) { + if (s->type == SHT_REL) + s->buf = rel32; + else + s->buf = rela32; + } else { + if (s->type == SHT_REL) + s->buf = rel64; + else + s->buf = rela64; + } + s->sz = gelf_fsize(ecp->eout, (s->type == SHT_REL ? ELF_T_REL : + ELF_T_RELA), nrels, EV_CURRENT); s->nocopy = 1; }
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