From 0bf262864c95e555fbd077b8f30e64652d9113a6 Mon Sep 17 00:00:00 2001 From: Thomas Preud'homme Date: Sat, 10 Dec 2016 09:14:29 +0000 Subject: 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. --- tccelf.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'tccelf.c') diff --git a/tccelf.c b/tccelf.c index 7f1679d..df7375c 100644 --- a/tccelf.c +++ b/tccelf.c @@ -1052,7 +1052,8 @@ ST_FUNC void build_got_entries(TCCState *s1) /* Proceed with PLT/GOT [entry] creation if any of the following condition is met: - it is an undefined reference (dynamic relocation needed) - - symbol is absolute (probably created by tcc_add_symbol) + - symbol is absolute (probably created by tcc_add_symbol and + thus might be too far from application code) - relocation requires a PLT/GOT (BUILD_GOTPLT_ENTRY or ALWAYS_GOTPLT_ENTRY). */ if (sym->st_shndx != SHN_UNDEF && @@ -1060,6 +1061,15 @@ ST_FUNC void build_got_entries(TCCState *s1) relocs_info[type].gotplt_entry == AUTO_GOTPLT_ENTRY) continue; + /* Building a dynamic library but target is not capable of PC + relative PLT entries. It can thus only use PLT entries if + it expects one to be used (ALWAYS_GOTPLT_ENTRY). */ + if (sym->st_shndx == SHN_UNDEF && + s1->output_type == TCC_OUTPUT_DLL && + !PCRELATIVE_DLLPLT && + relocs_info[type].gotplt_entry == AUTO_GOTPLT_ENTRY) + continue; + #ifdef TCC_TARGET_X86_64 if (type == R_X86_64_PLT32 && ELFW(ST_VISIBILITY)(sym->st_other) != STV_DEFAULT) { -- cgit v1.3.1