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Luffy-tsai
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LoongArch: Check PC-relative relocations for shared libraries
Building shared libraries should not be allowed for PC-relative relocations against external symbols. Currently LoongArch has no corresponding checks and silently generates wrong shared libraries. However, In the first version of the medium cmodel, pcalau12i+jirl was used for function calls, in which case PC-relative relocations were allowed.
1 parent 7721dca commit 4cb7776

11 files changed

+80
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lines changed

‎bfd/elfnn-loongarch.c‎

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@@ -1079,6 +1079,18 @@ loongarch_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
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h->non_got_ref = 1;
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break;
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/* Since shared library global symbols interpose, any
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PC-relative relocations against external symbols
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should not be used to build shared libraries. */
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case R_LARCH_PCREL20_S2:
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if (bfd_link_pic (info)
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&& (sec->flags & SEC_ALLOC) != 0
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&& (sec->flags & SEC_READONLY) != 0
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&& ! LARCH_REF_LOCAL (info, h))
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return bad_static_reloc (abfd, rel, sec, r_type, h, NULL);
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break;
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/* For normal cmodel, pcalau12i + addi.d/w used to data.
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For first version medium cmodel, pcalau12i + jirl are used to
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function call, it need to creat PLT entry for STT_FUNC and
@@ -1096,6 +1108,15 @@ loongarch_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
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h->pointer_equality_needed = 1;
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}
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/* PC-relative relocations are allowed For first version
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medium cmodel function call. */
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if (h != NULL && !h->needs_plt
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&& bfd_link_pic (info)
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&& (sec->flags & SEC_ALLOC) != 0
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&& (sec->flags & SEC_READONLY) != 0
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&& ! LARCH_REF_LOCAL (info, h))
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return bad_static_reloc (abfd, rel, sec, r_type, h, NULL);
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break;
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case R_LARCH_B16:

‎ld/testsuite/ld-loongarch-elf/bad_pcala_hi20_global.d‎

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#name: PC-relative relocation making shared
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#source: bad_pcala_hi20_global.s
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#target: [check_shared_lib_support]
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#ld: -shared --defsym global_a=0x10 --defsym global_b=0x20
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#error: .*: relocation R_LARCH_PCALA_HI20 against `global_b` can not be used when making a shared object; recompile with -fPIC

‎ld/testsuite/ld-loongarch-elf/bad_pcala_hi20_global.s‎

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.hidden global_a
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.text
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.align 2
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main:
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# Symbols defined .hidden are bound local and
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# the linker should differenciate them.
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la.pcrel $a0, global_a
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la.pcrel $a0, global_b

‎ld/testsuite/ld-loongarch-elf/bad_pcala_hi20_weak.d‎

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#name: PC-relative relocation making shared
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#source: bad_pcala_hi20_weak.s
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#target: [check_shared_lib_support]
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#ld: -shared --defsym global_a=0x10 --defsym global_b=0x20
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#error: .*: relocation R_LARCH_PCALA_HI20 against `global_b` can not be used when making a shared object; recompile with -fPIC

‎ld/testsuite/ld-loongarch-elf/bad_pcala_hi20_weak.s‎

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.hidden global_a
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.weak global_b
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.text
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.align 2
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main:
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# Symbols defined .hidden are bound local and
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# the linker should differenciate them.
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la.pcrel $a0, global_a
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la.pcrel $a0, global_b

‎ld/testsuite/ld-loongarch-elf/bad_pcrel20_s2_global.d‎

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#name: PC-relative relocation making shared
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#source: bad_pcrel20_s2_global.s
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#target: [check_shared_lib_support]
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#ld: -shared --defsym global_a=0x10 --defsym global_b=0x20
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#error: .*: relocation R_LARCH_PCREL20_S2 against `global_b` can not be used when making a shared object; recompile with -fPIC

‎ld/testsuite/ld-loongarch-elf/bad_pcrel20_s2_global.s‎

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.hidden global_a
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.text
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.align 2
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main:
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# Symbols defined .hidden are bound local and
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# the linker should differenciate them.
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pcaddi $a0, %pcrel_20(global_a)
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pcaddi $a0, %pcrel_20(global_b)

‎ld/testsuite/ld-loongarch-elf/bad_pcrel20_s2_weak.d‎

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#name: PC-relative relocation making shared
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#source: bad_pcrel20_s2_weak.s
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#target: [check_shared_lib_support]
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#ld: -shared --defsym global_a=0x10 --defsym global_b=0x20
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#error: .*: relocation R_LARCH_PCREL20_S2 against `global_b` can not be used when making a shared object; recompile with -fPIC

‎ld/testsuite/ld-loongarch-elf/bad_pcrel20_s2_weak.s‎

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.hidden global_a
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.weak global_b
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.text
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.align 2
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main:
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# Symbols defined .hidden are bound local and
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# the linker should differenciate them.
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pcaddi $a0, %pcrel_20(global_a)
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pcaddi $a0, %pcrel_20(global_b)

‎ld/testsuite/ld-loongarch-elf/data-plt.s‎

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@@ -2,6 +2,7 @@
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# R_LARCH_PCALA_HI20 only need to generate PLT entry for function symbols.
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.text
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.globl a
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.hidden a
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.data
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.align 2

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