Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1431354AbdDYNwL (ORCPT ); Tue, 25 Apr 2017 09:52:11 -0400 Received: from mx2.suse.de ([195.135.220.15]:33268 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1430832AbdDYNwC (ORCPT ); Tue, 25 Apr 2017 09:52:02 -0400 Date: Tue, 25 Apr 2017 15:51:50 +0200 From: Borislav Petkov To: Ricardo Neri Cc: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Masami Hiramatsu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S. Tsirkin" , Paul Gortmaker , Vlastimil Babka , Chen Yucong , Alexandre Julliard , Stas Sergeev , Fenghua Yu , "Ravi V. Shankar" , Shuah Khan , linux-kernel@vger.kernel.org, x86@kernel.org, linux-msdos@vger.kernel.org, wine-devel@winehq.org, Adam Buchbinder , Colin Ian King , Lorenzo Stoakes , Qiaowei Ren , Arnaldo Carvalho de Melo , Adrian Hunter , Kees Cook , Thomas Garnier , Dmitry Vyukov Subject: Re: [v6 PATCH 12/21] x86/insn: Support both signed 32-bit and 64-bit effective addresses Message-ID: <20170425135150.5sk4kwaw2qrsxre3@pd.tnic> References: <20170308003254.27833-1-ricardo.neri-calderon@linux.intel.com> <20170308003254.27833-13-ricardo.neri-calderon@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170308003254.27833-13-ricardo.neri-calderon@linux.intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5487 Lines: 164 On Tue, Mar 07, 2017 at 04:32:45PM -0800, Ricardo Neri wrote: > The 32-bit and 64-bit address encodings are identical. This means that we > can use the same function in both cases. In order to reuse the function for > 32-bit address encodings, we must sign-extend our 32-bit signed operands to > 64-bit signed variables (only for 64-bit builds). To decide on whether sign > extension is needed, we rely on the address size as given by the > instruction structure. > > Lastly, before computing the linear address, we must truncate our signed > 64-bit signed effective address if the address size is 32-bit. > > Cc: Dave Hansen > Cc: Adam Buchbinder > Cc: Colin Ian King > Cc: Lorenzo Stoakes > Cc: Qiaowei Ren > Cc: Arnaldo Carvalho de Melo > Cc: Masami Hiramatsu > Cc: Adrian Hunter > Cc: Kees Cook > Cc: Thomas Garnier > Cc: Peter Zijlstra > Cc: Borislav Petkov > Cc: Dmitry Vyukov > Cc: Ravi V. Shankar > Cc: x86@kernel.org > Signed-off-by: Ricardo Neri > --- > arch/x86/lib/insn-eval.c | 44 ++++++++++++++++++++++++++++++++------------ > 1 file changed, 32 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c > index edb360f..a9a1704 100644 > --- a/arch/x86/lib/insn-eval.c > +++ b/arch/x86/lib/insn-eval.c > @@ -559,6 +559,15 @@ int insn_get_reg_offset_sib_index(struct insn *insn, struct pt_regs *regs) > return get_reg_offset(insn, regs, REG_TYPE_INDEX); > } > > +static inline long __to_signed_long(unsigned long val, int long_bytes) > +{ > +#ifdef CONFIG_X86_64 > + return long_bytes == 4 ? (long)((int)((val) & 0xffffffff)) : (long)val; I don't think this always works as expected: --- typedef unsigned int u32; typedef unsigned long u64; int main() { u64 v = 0x1ffffffff; printf("v: %ld, 0x%lx, %ld\n", v, v, (long)((int)((v) & 0xffffffff))); return 0; } -- ... v: 8589934591, 0x1ffffffff, -1 Now, this should not happen on 32-bit because unsigned long is 32-bit there but can that happen on 64-bit? > +#else > + return (long)val; > +#endif > +} > + > /* > * return the address being referenced be instruction > * for rm=3 returning the content of the rm reg > @@ -567,19 +576,21 @@ int insn_get_reg_offset_sib_index(struct insn *insn, struct pt_regs *regs) > void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) > { > unsigned long linear_addr, seg_base_addr; > - long eff_addr, base, indx; > - int addr_offset, base_offset, indx_offset; > + long eff_addr, base, indx, tmp; > + int addr_offset, base_offset, indx_offset, addr_bytes; > insn_byte_t sib; > > insn_get_modrm(insn); > insn_get_sib(insn); > sib = insn->sib.value; > + addr_bytes = insn->addr_bytes; > > if (X86_MODRM_MOD(insn->modrm.value) == 3) { > addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); > if (addr_offset < 0) > goto out_err; > - eff_addr = regs_get_register(regs, addr_offset); > + tmp = regs_get_register(regs, addr_offset); > + eff_addr = __to_signed_long(tmp, addr_bytes); This repeats throughout the function so it begs to be a separate: get_mem_addr() or so. > seg_base_addr = insn_get_seg_base(regs, insn, addr_offset, > false); > } else { > @@ -591,20 +602,24 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) > * in the address computation. > */ > base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE); > - if (unlikely(base_offset == -EDOM)) > + if (unlikely(base_offset == -EDOM)) { > base = 0; > - else if (unlikely(base_offset < 0)) > + } else if (unlikely(base_offset < 0)) { > goto out_err; > - else > - base = regs_get_register(regs, base_offset); > + } else { > + tmp = regs_get_register(regs, base_offset); > + base = __to_signed_long(tmp, addr_bytes); > + } > > indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX); > - if (unlikely(indx_offset == -EDOM)) > + if (unlikely(indx_offset == -EDOM)) { > indx = 0; > - else if (unlikely(indx_offset < 0)) > + } else if (unlikely(indx_offset < 0)) { > goto out_err; > - else > - indx = regs_get_register(regs, indx_offset); > + } else { > + tmp = regs_get_register(regs, indx_offset); > + indx = __to_signed_long(tmp, addr_bytes); > + } > > eff_addr = base + indx * (1 << X86_SIB_SCALE(sib)); > seg_base_addr = insn_get_seg_base(regs, insn, > @@ -625,13 +640,18 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) > } else if (addr_offset < 0) { > goto out_err; > } else { > - eff_addr = regs_get_register(regs, addr_offset); > + tmp = regs_get_register(regs, addr_offset); > + eff_addr = __to_signed_long(tmp, addr_bytes); > } > seg_base_addr = insn_get_seg_base(regs, insn, > addr_offset, false); > } > eff_addr += insn->displacement.value; > } > + /* truncate to 4 bytes for 32-bit effective addresses */ > + if (addr_bytes == 4) > + eff_addr &= 0xffffffff; Why again? -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --