From c1d19a8489466270bb1c3639dcdabbda1d4c57d7 Mon Sep 17 00:00:00 2001 From: Joseph Huber Date: Thu, 25 Aug 2022 14:00:07 -0500 Subject: [PATCH] [ELF] Provide the GNU hash function in libObject GNU uses a different hashing function compared to the sys-V standard function already provided in libObject. This is already used internally in LLD for generating synthetic sections. This patch simply extracts this definition and makes it availible to other users of `libObject`. This is done in preparation for supporting symbol name lookups via the GNU hash table. Reviewed By: MaskRay, jhenderson Differential Revision: https://reviews.llvm.org/D132696 --- lld/ELF/SyntheticSections.cpp | 7 ------- llvm/include/llvm/Object/ELF.h | 10 ++++++++++ 2 files changed, 10 insertions(+), 7 deletions(-) diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp index c6f749f..4af2de5 100644 --- a/lld/ELF/SyntheticSections.cpp +++ b/lld/ELF/SyntheticSections.cpp @@ -2397,13 +2397,6 @@ void GnuHashTableSection::writeTo(uint8_t *buf) { } } -static uint32_t hashGnu(StringRef name) { - uint32_t h = 5381; - for (uint8_t c : name) - h = (h << 5) + h + c; - return h; -} - // Add symbols to this symbol hash table. Note that this function // destructively sort a given vector -- which is needed because // GNU-style hash table places some sorting requirements. diff --git a/llvm/include/llvm/Object/ELF.h b/llvm/include/llvm/Object/ELF.h index 794d29f..1a987cf 100644 --- a/llvm/include/llvm/Object/ELF.h +++ b/llvm/include/llvm/Object/ELF.h @@ -1223,6 +1223,16 @@ inline unsigned hashSysV(StringRef SymbolName) { return h; } +/// This function returns the hash value for a symbol in the .dynsym section +/// for the GNU hash table. The implementation is defined in the GNU hash ABI. +/// REF : https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=bfd/elf.c#l222 +inline uint32_t hashGnu(StringRef Name) { + uint32_t H = 5381; + for (uint8_t C : Name) + H = (H << 5) + H + C; + return H; +} + } // end namespace object } // end namespace llvm -- 2.7.4