ld: Rewrite lang_size_relro_segment_1
1. Compute the desired PT_GNU_RELRO segment base and find the maximum section alignment of sections starting from the PT_GNU_RELRO segment. 2. Find the first preceding load section. 3. Don't add the 1-page gap between the first preceding load section and the relro segment if the maximum page size >= the maximum section alignment. Align the PT_GNU_RELRO segment first. Subtract the maximum page size if therer is still a 1-page gap. PR ld/28743 PR ld/28819 * ldlang.c (lang_size_relro_segment_1): Rewrite. * testsuite/ld-x86-64/pr28743-1.d: New file. * testsuite/ld-x86-64/pr28743-1.s: Likewise. * testsuite/ld-x86-64/x86-64.exp: Run pr28743-1.
This commit is contained in:
H.J. Lu
parent
8357282156
commit
c804c6f98d
4 changed files with 118 additions and 44 deletions
91
ld/ldlang.c
91
ld/ldlang.c
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@ -6370,94 +6370,101 @@ lang_size_segment (seg_align_type *seg)
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static bfd_vma
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lang_size_relro_segment_1 (seg_align_type *seg)
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{
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bfd_vma relro_end, desired_end;
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asection *sec, *prev_sec = NULL;
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bool remove_page_gap = false;
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bfd_vma relro_end, desired_relro_base;
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asection *sec, *relro_sec = NULL;
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unsigned int max_alignment_power = 0;
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bool seen_reloc_section = false;
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bool desired_relro_base_reduced = false;
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/* Compute the expected PT_GNU_RELRO/PT_LOAD segment end. */
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relro_end = ((seg->relro_end + seg->pagesize - 1)
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& ~(seg->pagesize - 1));
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/* Adjust by the offset arg of XXX_SEGMENT_RELRO_END. */
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desired_end = relro_end - seg->relro_offset;
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desired_relro_base = relro_end - seg->relro_offset;
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/* For sections in the relro segment.. */
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/* For sections in the relro segment. */
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for (sec = link_info.output_bfd->section_last; sec; sec = sec->prev)
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if ((sec->flags & SEC_ALLOC) != 0)
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{
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/* Record the maximum alignment for all sections starting from
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the relro segment. */
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if (sec->alignment_power > max_alignment_power)
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max_alignment_power = sec->alignment_power;
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if (sec->vma >= seg->base
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&& sec->vma < seg->relro_end - seg->relro_offset)
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{
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/* Where do we want to put this section so that it ends as
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desired? */
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/* Where do we want to put the relro section so that the
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relro segment ends on the page bounary? */
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bfd_vma start, end, bump;
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end = start = sec->vma;
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if (!IS_TBSS (sec))
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end += TO_ADDR (sec->size);
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bump = desired_end - end;
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bump = desired_relro_base - end;
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/* We'd like to increase START by BUMP, but we must heed
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alignment so the increase might be less than optimum. */
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start += bump;
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start &= ~(((bfd_vma) 1 << sec->alignment_power) - 1);
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/* This is now the desired end for the previous section. */
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desired_end = start;
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prev_sec = sec->prev;
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desired_relro_base = start;
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relro_sec = sec;
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seen_reloc_section = true;
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}
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}
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seg->phase = exp_seg_relro_adjust;
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ASSERT (desired_end >= seg->base);
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for (; prev_sec; prev_sec = prev_sec->prev)
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if ((prev_sec->flags & SEC_ALLOC) != 0)
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else if (seen_reloc_section)
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{
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if (prev_sec->alignment_power > max_alignment_power)
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max_alignment_power = prev_sec->alignment_power;
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if (prev_sec->size != 0)
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{
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/* The 1-page gap before the RELRO segment may be removed. */
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remove_page_gap = ((prev_sec->vma + prev_sec->size
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+ seg->maxpagesize) < desired_end);
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/* Stop searching if we see a non-relro section after seeing
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relro sections. */
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break;
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}
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}
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if (remove_page_gap)
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if (relro_sec != NULL
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&& seg->maxpagesize >= (1U << max_alignment_power))
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{
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/* Find the maximum section alignment. */
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for (sec = prev_sec; sec; sec = sec->prev)
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if ((sec->flags & SEC_ALLOC) != 0
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&& sec->alignment_power > max_alignment_power)
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max_alignment_power = sec->alignment_power;
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asection *prev_sec;
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bfd_vma prev_sec_end_plus_1_page;
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/* Remove the 1-page gap before the RELRO segment only if the
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maximum page size >= the maximum section alignment. */
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if (seg->maxpagesize >= (1U << max_alignment_power))
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/* Find the first preceding load section. */
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for (prev_sec = relro_sec->prev;
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prev_sec != NULL;
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prev_sec = prev_sec->prev)
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if ((prev_sec->flags & SEC_ALLOC) != 0)
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break;
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prev_sec_end_plus_1_page = (prev_sec->vma + prev_sec->size
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+ seg->maxpagesize);
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if (prev_sec_end_plus_1_page < desired_relro_base)
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{
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/* If the preceding section size is greater than the maximum
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page size, subtract the maximum page size. Otherwise,
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align the RELRO segment to the maximum page size. */
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if (prev_sec->size > seg->maxpagesize)
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bfd_vma aligned_relro_base;
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desired_relro_base_reduced = true;
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/* Don't add the 1-page gap before the relro segment. Align
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the relro segment first. */
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aligned_relro_base = (desired_relro_base
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& ~(seg->maxpagesize - 1));
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if (prev_sec_end_plus_1_page < aligned_relro_base)
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{
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desired_end -= seg->maxpagesize;
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/* Subtract the maximum page size if therer is still a
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1-page gap. */
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desired_relro_base -= seg->maxpagesize;
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relro_end -= seg->maxpagesize;
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}
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else
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{
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desired_end &= ~(seg->maxpagesize - 1);
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/* Align the relro segment. */
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desired_relro_base = aligned_relro_base;
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relro_end &= ~(seg->maxpagesize - 1);
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}
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}
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}
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seg->base = desired_end;
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seg->phase = exp_seg_relro_adjust;
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ASSERT (desired_relro_base_reduced
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|| desired_relro_base >= seg->base);
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seg->base = desired_relro_base;
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return relro_end;
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}
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50
ld/testsuite/ld-x86-64/pr28743-1.d
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50
ld/testsuite/ld-x86-64/pr28743-1.d
Normal file
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@ -0,0 +1,50 @@
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#as: --64
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#ld: -melf_x86_64 -shared -z relro -z now --hash-style=sysv -z max-page-size=0x1000 -z noseparate-code $NO_DT_RELR_LDFLAGS
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#readelf: -S -l --wide
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#target: x86_64-*-linux*
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There are 17 section headers, starting at offset 0x101228:
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Section Headers:
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\[Nr\] Name Type Address Off Size ES Flg Lk Inf Al
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\[ 0\] NULL 0000000000000000 000000 000000 00 0 0 0
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\[ 1\] .hash HASH 0000000000000120 000120 000018 04 A 2 0 8
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\[ 2\] .dynsym DYNSYM 0000000000000138 000138 000048 18 A 3 1 8
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\[ 3\] .dynstr STRTAB 0000000000000180 000180 00000a 00 A 0 0 1
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\[ 4\] .rela.dyn RELA 0000000000000190 000190 000018 18 A 2 0 8
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\[ 5\] .plt PROGBITS 00000000000001b0 0001b0 000010 10 AX 0 0 16
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\[ 6\] .plt.got PROGBITS 00000000000001c0 0001c0 000008 08 AX 0 0 8
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\[ 7\] .text PROGBITS 00000000000001c8 0001c8 00000c 00 AX 0 0 1
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\[ 8\] .eh_frame PROGBITS 00000000000001d8 0001d8 00006c 00 A 0 0 8
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\[ 9\] .init_array INIT_ARRAY 00000000000ffff8 0ffff8 000004 08 WA 0 0 8
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\[10\] .fini_array FINI_ARRAY 0000000000100000 100000 000100 08 WA 0 0 1048576
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\[11\] .dynamic DYNAMIC 0000000000100100 100100 000150 10 WA 3 0 8
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\[12\] .got PROGBITS 0000000000100250 100250 000020 08 WA 0 0 8
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\[13\] .data PROGBITS 0000000000101000 101000 000100 00 WA 0 0 1
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\[14\] .symtab SYMTAB 0000000000000000 101100 000078 18 15 3 8
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\[15\] .strtab STRTAB 0000000000000000 101178 000029 00 0 0 1
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\[16\] .shstrtab STRTAB 0000000000000000 1011a1 000080 00 0 0 1
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Key to Flags:
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W \(write\), A \(alloc\), X \(execute\), M \(merge\), S \(strings\), I \(info\),
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L \(link order\), O \(extra OS processing required\), G \(group\), T \(TLS\),
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C \(compressed\), x \(unknown\), o \(OS specific\), E \(exclude\),
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D \(mbind\), l \(large\), p \(processor specific\)
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Elf file type is DYN \(Shared object file\)
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Entry point 0x0
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There are 4 program headers, starting at offset 64
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Program Headers:
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Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
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LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x000244 0x000244 R E 0x1000
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LOAD 0x0ffff8 0x00000000000ffff8 0x00000000000ffff8 0x001108 0x001108 RW 0x100000
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DYNAMIC 0x100100 0x0000000000100100 0x0000000000100100 0x000150 0x000150 RW 0x8
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GNU_RELRO 0x0ffff8 0x00000000000ffff8 0x00000000000ffff8 0x001008 0x001008 R 0x1
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Section to Segment mapping:
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Segment Sections...
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00 .hash .dynsym .dynstr .rela.dyn .plt .plt.got .text .eh_frame
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01 .init_array .fini_array .dynamic .got .data
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02 .dynamic
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03 .init_array .fini_array .dynamic .got
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#pass
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16
ld/testsuite/ld-x86-64/pr28743-1.s
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16
ld/testsuite/ld-x86-64/pr28743-1.s
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@ -0,0 +1,16 @@
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.text
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.globl foo
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.type foo, @function
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foo:
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.cfi_startproc
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call func@plt
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movq func@GOTPCREL(%rip), %rax
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.cfi_endproc
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.section .init_array,"aw",@init_array
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.p2align 3
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.zero 0x4
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.section .fini_array,"aw",@fini_array
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.p2align 20
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.zero 0x100
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.data
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.zero 0x100
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@ -511,6 +511,7 @@ run_dump_test "dt-relr-1a"
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run_dump_test "dt-relr-1a-x32"
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run_dump_test "dt-relr-1b"
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run_dump_test "dt-relr-1b-x32"
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run_dump_test "pr28743-1"
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if ![istarget "x86_64-*-linux*"] {
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return
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