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[81.157.241.155]) by smtp.gmail.com with ESMTPSA id v12sm49438wrr.87.2019.08.22.09.30.09 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 22 Aug 2019 09:30:10 -0700 (PDT) Subject: Re: [RFC v4 01/18] objtool: Add abstraction for computation of symbols offsets To: Raphael Gault , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, jpoimboe@redhat.com Cc: peterz@infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, raph.gault+kdev@gmail.com References: <20190816122403.14994-1-raphael.gault@arm.com> <20190816122403.14994-2-raphael.gault@arm.com> From: Julien Message-ID: <7bdc1178-e916-7d21-eb54-bea27fcadc17@gmail.com> Date: Thu, 22 Aug 2019 17:30:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <20190816122403.14994-2-raphael.gault@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Raphaël, On 16/08/19 13:23, Raphael Gault wrote: > The jump destination and relocation offset used previously are only > reliable on x86_64 architecture. We abstract these computations by calling > arch-dependent implementations. > > Signed-off-by: Raphael Gault > --- > tools/objtool/arch.h | 6 ++++++ > tools/objtool/arch/x86/decode.c | 11 +++++++++++ > tools/objtool/check.c | 15 ++++++++++----- > 3 files changed, 27 insertions(+), 5 deletions(-) > > diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h > index ced3765c4f44..a9a50a25ca66 100644 > --- a/tools/objtool/arch.h > +++ b/tools/objtool/arch.h > @@ -66,6 +66,8 @@ struct stack_op { > struct op_src src; > }; > > +struct instruction; > + > void arch_initial_func_cfi_state(struct cfi_state *state); > > int arch_decode_instruction(struct elf *elf, struct section *sec, > @@ -75,4 +77,8 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, > > bool arch_callee_saved_reg(unsigned char reg); > > +unsigned long arch_jump_destination(struct instruction *insn); > + > +unsigned long arch_dest_rela_offset(int addend); > + > #endif /* _ARCH_H */ > diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c > index 0567c47a91b1..fa33b3465722 100644 > --- a/tools/objtool/arch/x86/decode.c > +++ b/tools/objtool/arch/x86/decode.c > @@ -11,6 +11,7 @@ > #include "lib/inat.c" > #include "lib/insn.c" > > +#include "../../check.h" > #include "../../elf.h" > #include "../../arch.h" > #include "../../warn.h" > @@ -66,6 +67,11 @@ bool arch_callee_saved_reg(unsigned char reg) > } > } > > +unsigned long arch_dest_rela_offset(int addend) > +{ > + return addend + 4; > +} > + > int arch_decode_instruction(struct elf *elf, struct section *sec, > unsigned long offset, unsigned int maxlen, > unsigned int *len, enum insn_type *type, > @@ -497,3 +503,8 @@ void arch_initial_func_cfi_state(struct cfi_state *state) > state->regs[16].base = CFI_CFA; > state->regs[16].offset = -8; > } > + > +unsigned long arch_jump_destination(struct instruction *insn) > +{ > + return insn->offset + insn->len + insn->immediate; > +} > diff --git a/tools/objtool/check.c b/tools/objtool/check.c > index 176f2f084060..479fab46b656 100644 > --- a/tools/objtool/check.c > +++ b/tools/objtool/check.c > @@ -563,7 +563,7 @@ static int add_jump_destinations(struct objtool_file *file) > insn->len); > if (!rela) { > dest_sec = insn->sec; > - dest_off = insn->offset + insn->len + insn->immediate; > + dest_off = arch_jump_destination(insn); > } else if (rela->sym->type == STT_SECTION) { > dest_sec = rela->sym->sec; > dest_off = rela->addend + 4; > @@ -659,7 +659,7 @@ static int add_call_destinations(struct objtool_file *file) > rela = find_rela_by_dest_range(insn->sec, insn->offset, > insn->len); > if (!rela) { > - dest_off = insn->offset + insn->len + insn->immediate; > + dest_off = arch_jump_destination(insn); > insn->call_dest = find_symbol_by_offset(insn->sec, > dest_off); > > @@ -672,14 +672,19 @@ static int add_call_destinations(struct objtool_file *file) > } > > } else if (rela->sym->type == STT_SECTION) { > + /* > + * the original x86_64 code adds 4 to the rela->addend > + * which is not needed on arm64 architecture. > + */ I'm not sure this is worth mentioning in generic code. You might include it in the commit message to justify the change. > + dest_off = arch_dest_rela_offset(rela->addend); > insn->call_dest = find_symbol_by_offset(rela->sym->sec, > - rela->addend+4); > + dest_off); > if (!insn->call_dest || > insn->call_dest->type != STT_FUNC) { > - WARN_FUNC("can't find call dest symbol at %s+0x%x", > + WARN_FUNC("can't find call dest symbol at %s+0x%lx", > insn->sec, insn->offset, > rela->sym->sec->name, > - rela->addend + 4); > + dest_off); > return -1; > } > } else > Otherwise, the change looks good to me. Thanks, -- Julien Thierry