Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933755AbbDUQDf (ORCPT ); Tue, 21 Apr 2015 12:03:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46948 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933240AbbDUQDX (ORCPT ); Tue, 21 Apr 2015 12:03:23 -0400 From: Denys Vlasenko To: Ingo Molnar Cc: Denys Vlasenko , Linus Torvalds , Steven Rostedt , Borislav Petkov , "H. Peter Anvin" , Andy Lutomirski , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] x86/asm/entry/32: Update ENOSYS handling to match 64-bit logic Date: Tue, 21 Apr 2015 18:03:14 +0200 Message-Id: <1429632194-13445-2-git-send-email-dvlasenk@redhat.com> In-Reply-To: <1429632194-13445-1-git-send-email-dvlasenk@redhat.com> References: <1429632194-13445-1-git-send-email-dvlasenk@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7172 Lines: 211 Sometime ago Andy changed 64-bit syscall logic so that pt_regs->ax is initially set to -ENOSYS, and on exit from syscall, it is updated with actual return value. This simplified logic there. This patch does the same for 32-bit syscall entry points. The check for %rax being too big is moved to be just before the call insn which dispatches execution through syscall table. There is no way to accidentally skip this check now by jumping to a label after it. This allows to remove redundant checks after e.g. ptrace. If %rax is too big, we just skip over the (call, write %rax to pt_regs->ax) insn pair. pt_regs->ax remains set to -ENOSYS, and it gets returned to userspace. Similar to 64-bit code, this eliminates "ia32_badsys" code path. Run-tested. Signed-off-by: Denys Vlasenko CC: Linus Torvalds CC: Steven Rostedt CC: Ingo Molnar CC: Borislav Petkov CC: "H. Peter Anvin" CC: Andy Lutomirski CC: Oleg Nesterov CC: Frederic Weisbecker CC: Alexei Starovoitov CC: Will Drewry CC: Kees Cook CC: x86@kernel.org CC: linux-kernel@vger.kernel.org --- Changes in v2: fixed an error: changing RAX to ORIG_RAX in movq ORIG_RAX(%rsp),%rax /* reload syscall return value */ was wrong. arch/x86/ia32/ia32entry.S | 44 +++++++++++++++----------------------------- 1 file changed, 15 insertions(+), 29 deletions(-) diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index a821b1c..29ab1c2 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -142,7 +142,7 @@ ENTRY(ia32_sysenter_target) pushq_cfi_reg rsi /* pt_regs->si */ pushq_cfi_reg rdx /* pt_regs->dx */ pushq_cfi_reg rcx /* pt_regs->cx */ - pushq_cfi_reg rax /* pt_regs->ax */ + pushq_cfi $-ENOSYS /* pt_regs->ax */ cld sub $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */ CFI_ADJUST_CFA_OFFSET 10*8 @@ -169,8 +169,6 @@ sysenter_flags_fixed: testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) CFI_REMEMBER_STATE jnz sysenter_tracesys - cmpq $(IA32_NR_syscalls-1),%rax - ja ia32_badsys sysenter_do_call: /* 32bit syscall -> 64bit C ABI argument conversion */ movl %edi,%r8d /* arg5 */ @@ -179,8 +177,11 @@ sysenter_do_call: movl %ebx,%edi /* arg1 */ movl %edx,%edx /* arg3 (zero extension) */ sysenter_dispatch: + cmpq $(IA32_NR_syscalls-1),%rax + ja 1f call *ia32_sys_call_table(,%rax,8) movq %rax,RAX(%rsp) +1: DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) @@ -247,9 +248,7 @@ sysexit_from_sys_call: movl %ebx,%esi /* 2nd arg: 1st syscall arg */ movl %eax,%edi /* 1st arg: syscall number */ call __audit_syscall_entry - movl RAX(%rsp),%eax /* reload syscall number */ - cmpq $(IA32_NR_syscalls-1),%rax - ja ia32_badsys + movl ORIG_RAX(%rsp),%eax /* reload syscall number */ movl %ebx,%edi /* reload 1st syscall arg */ movl RCX(%rsp),%esi /* reload 2nd syscall arg */ movl RDX(%rsp),%edx /* reload 3rd syscall arg */ @@ -300,13 +299,10 @@ sysenter_tracesys: #endif SAVE_EXTRA_REGS CLEAR_RREGS - movq $-ENOSYS,RAX(%rsp)/* ptrace can change this for a bad syscall */ movq %rsp,%rdi /* &pt_regs -> arg1 */ call syscall_trace_enter LOAD_ARGS32 /* reload args from stack in case ptrace changed it */ RESTORE_EXTRA_REGS - cmpq $(IA32_NR_syscalls-1),%rax - ja int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */ jmp sysenter_do_call CFI_ENDPROC ENDPROC(ia32_sysenter_target) @@ -376,7 +372,7 @@ ENTRY(ia32_cstar_target) pushq_cfi_reg rdx /* pt_regs->dx */ pushq_cfi_reg rbp /* pt_regs->cx */ movl %ebp,%ecx - pushq_cfi_reg rax /* pt_regs->ax */ + pushq_cfi $-ENOSYS /* pt_regs->ax */ sub $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */ CFI_ADJUST_CFA_OFFSET 10*8 @@ -392,8 +388,6 @@ ENTRY(ia32_cstar_target) testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) CFI_REMEMBER_STATE jnz cstar_tracesys - cmpq $IA32_NR_syscalls-1,%rax - ja ia32_badsys cstar_do_call: /* 32bit syscall -> 64bit C ABI argument conversion */ movl %edi,%r8d /* arg5 */ @@ -402,8 +396,11 @@ cstar_do_call: movl %ebx,%edi /* arg1 */ movl %edx,%edx /* arg3 (zero extension) */ cstar_dispatch: + cmpq $(IA32_NR_syscalls-1),%rax + ja 1f call *ia32_sys_call_table(,%rax,8) movq %rax,RAX(%rsp) +1: DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) @@ -450,14 +447,11 @@ cstar_tracesys: xchgl %r9d,%ebp SAVE_EXTRA_REGS CLEAR_RREGS r9 - movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */ movq %rsp,%rdi /* &pt_regs -> arg1 */ call syscall_trace_enter LOAD_ARGS32 1 /* reload args from stack in case ptrace changed it */ RESTORE_EXTRA_REGS xchgl %ebp,%r9d - cmpq $(IA32_NR_syscalls-1),%rax - ja int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */ jmp cstar_do_call END(ia32_cstar_target) @@ -516,7 +510,7 @@ ENTRY(ia32_syscall) pushq_cfi_reg rsi /* pt_regs->si */ pushq_cfi_reg rdx /* pt_regs->dx */ pushq_cfi_reg rcx /* pt_regs->cx */ - pushq_cfi_reg rax /* pt_regs->ax */ + pushq_cfi $-ENOSYS /* pt_regs->ax */ cld sub $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */ CFI_ADJUST_CFA_OFFSET 10*8 @@ -524,8 +518,6 @@ ENTRY(ia32_syscall) orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS) testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) jnz ia32_tracesys - cmpq $(IA32_NR_syscalls-1),%rax - ja ia32_badsys ia32_do_call: /* 32bit syscall -> 64bit C ABI argument conversion */ movl %edi,%r8d /* arg5 */ @@ -533,9 +525,12 @@ ia32_do_call: xchg %ecx,%esi /* rsi:arg2, rcx:arg4 */ movl %ebx,%edi /* arg1 */ movl %edx,%edx /* arg3 (zero extension) */ + cmpq $(IA32_NR_syscalls-1),%rax + ja 1f call *ia32_sys_call_table(,%rax,8) # xxx: rip relative ia32_sysret: movq %rax,RAX(%rsp) +1: ia32_ret_from_sys_call: CLEAR_RREGS jmp int_ret_from_sys_call @@ -543,23 +538,14 @@ ia32_ret_from_sys_call: ia32_tracesys: SAVE_EXTRA_REGS CLEAR_RREGS - movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */ movq %rsp,%rdi /* &pt_regs -> arg1 */ call syscall_trace_enter LOAD_ARGS32 /* reload args from stack in case ptrace changed it */ RESTORE_EXTRA_REGS - cmpq $(IA32_NR_syscalls-1),%rax - ja int_ret_from_sys_call /* ia32_tracesys has set RAX(%rsp) */ jmp ia32_do_call + CFI_ENDPROC END(ia32_syscall) -ia32_badsys: - movq $0,ORIG_RAX(%rsp) - movq $-ENOSYS,%rax - jmp ia32_sysret - - CFI_ENDPROC - .macro PTREGSCALL label, func ALIGN GLOBAL(\label) -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/