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https://github.com/frida/tinycc
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Fix PLT creation for i386
i386 target does not have PC relative loads. Its ABI therefore require ebx register to points to the GOT when executing a PLT entry. This means that PLT entry cannot be used transparently, the compiler needs to expect execution of a PLT entry to be able to use one, that is a PLT entry should only be created if the relocation explicitely asks for it (eg. R_386_PLT32). This patch creates a new target macro PCRELATIVE_DLLPLT to indicate whether a target can do a PC relative load in PLT entry when building a dynamic library. Executable do not normally pose a problem because they are loaded at a fixed address and thus the absolute address of GOT can be used. Note that in such a case, if the compiler does not use a PLT aware relocation for external access then the code relocation will fall on the dynamic loader since there is no PLT entry to relocate too.
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@ -15,6 +15,7 @@
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#define ELF_PAGE_SIZE 0x1000
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#define HAVE_SECTION_RELOC
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#define PCRELATIVE_DLLPLT 1
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enum float_abi {
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ARM_SOFTFP_FLOAT,
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@ -14,6 +14,7 @@
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#define ELF_PAGE_SIZE 0x1000
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#define HAVE_SECTION_RELOC
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#define PCRELATIVE_DLLPLT 1
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#else /* !TARGET_DEFS_ONLY */
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@ -15,6 +15,7 @@
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#define ELF_PAGE_SIZE 0x1000
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#define HAVE_SECTION_RELOC
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#define PCRELATIVE_DLLPLT 0
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#else /* !TARGET_DEFS_ONLY */
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@ -15,6 +15,7 @@
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#define ELF_PAGE_SIZE 0x1000
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#define HAVE_SECTION_RELOC
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#define PCRELATIVE_DLLPLT 0
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#else /* !TARGET_DEFS_ONLY */
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12
tccelf.c
12
tccelf.c
@ -1052,7 +1052,8 @@ ST_FUNC void build_got_entries(TCCState *s1)
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/* Proceed with PLT/GOT [entry] creation if any of the following
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condition is met:
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- it is an undefined reference (dynamic relocation needed)
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- symbol is absolute (probably created by tcc_add_symbol)
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- symbol is absolute (probably created by tcc_add_symbol and
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thus might be too far from application code)
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- relocation requires a PLT/GOT (BUILD_GOTPLT_ENTRY or
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ALWAYS_GOTPLT_ENTRY). */
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if (sym->st_shndx != SHN_UNDEF &&
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@ -1060,6 +1061,15 @@ ST_FUNC void build_got_entries(TCCState *s1)
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relocs_info[type].gotplt_entry == AUTO_GOTPLT_ENTRY)
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continue;
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/* Building a dynamic library but target is not capable of PC
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relative PLT entries. It can thus only use PLT entries if
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it expects one to be used (ALWAYS_GOTPLT_ENTRY). */
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if (sym->st_shndx == SHN_UNDEF &&
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s1->output_type == TCC_OUTPUT_DLL &&
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!PCRELATIVE_DLLPLT &&
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relocs_info[type].gotplt_entry == AUTO_GOTPLT_ENTRY)
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continue;
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#ifdef TCC_TARGET_X86_64
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if (type == R_X86_64_PLT32 &&
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ELFW(ST_VISIBILITY)(sym->st_other) != STV_DEFAULT) {
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@ -15,6 +15,7 @@
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#define ELF_PAGE_SIZE 0x200000
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#define HAVE_SECTION_RELOC
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#define PCRELATIVE_DLLPLT 1
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#else /* !TARGET_DEFS_ONLY */
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