Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752418Ab3FQWOa (ORCPT ); Mon, 17 Jun 2013 18:14:30 -0400 Received: from moutng.kundenserver.de ([212.227.17.9]:49301 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752281Ab3FQWOW (ORCPT ); Mon, 17 Jun 2013 18:14:22 -0400 Message-ID: <51BF8A1C.5070403@dawncrow.de> Date: Tue, 18 Jun 2013 00:13:48 +0200 From: =?ISO-8859-1?Q?Andr=E9_Hentschel?= User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: "linux-arch@vger.kernel.org" CC: Russell King - ARM Linux , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "gregkh@linuxfoundation.org" , Will Deacon , Jonathan Austin Subject: [PATCH v6] arm: Preserve the user r/w register TPIDRURW on context, switch and fork Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Provags-ID: V02:K0:PqYa0EJoCsPvsdSrIO62slgbd8qWSU38CyWC4NYuH1r 2AeCd65oucmNJf56Tls08EXnFmJVLQgDwp/YUq5zdtL1kpC8yE NWu0gW2ZMNByMosgZYdGOtA6Q0aJt4ULzpbySPVcKsxz+n9dao nxL68JLwwMA4bAPJ/3Id8JjSyyJcZ0vtdu0/37EZlAQ/zyaB83 1DkrW+WJRD4fvqLsWzg3pqDATAC3HkyhRYfIHDFvMzEtYuy47+ ZkPT1N24EMxGqj8Rwi0GGLEkgLOrkQKIYHu9tAtnODvJmAKfab fPF42SpBF7d98/GnnMN4vvV7LCvFwj9+nKfQOUNm6ysx5UoR0N 8FxmTnJlZQ00NNCYxiRo= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7778 Lines: 220 From: Andr? Hentschel Since commit 6a1c53124aa1 the user writeable TLS register was zeroed to prevent it from being used as a covert channel between two tasks. There are more and more applications coming to Windows RT, Wine could support them, but mostly they expect to have the thread environment block (TEB) in TPIDRURW. This patch preserves that register per thread instead of clearing it. Unlike the TPIDRURO, which is already switched, the TPIDRURW can be updated from userspace so needs careful treatment in the case that we modify TPIDRURW and call fork(). To avoid this we must always read TPIDRURW in copy_thread. Signed-off-by: Andr? Hentschel Signed-off-by: Will Deacon Signed-off-by: Jonathan Austin --- This patch is against Linux 3.10-rc6 (7d132055814ef17a6c7b69f342244c410a5e000f) v2: rework and fixup of v1, based on a suggested patch by Will Deacon v3: total rework and fixup of v2 v4: removed condition on assembler instruction, adapted my code to kernel-style, both based on comments by Will Deacon v5: rebased v4 on 3.10-rc2 and adding this version history v6: moved loading the TLS registers to the macros (fixing the "LDRD is not supported on all the CPUs we have" problem) Why so much Signed-off-bys? Some History: The first patch had performance issues pointed out by Russel King, so Will Deacon jumped in to help me with that. The second one again had performance issues and the missing copy_thread part was uncovered. After some iterations by me, Jonathan Austin proposed a patch and Russel King sent his idea of the assembler part. All this was finally merged and refined into this patch. Thanks to everyone! diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index 1995d1a..214d415 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -58,7 +58,7 @@ struct thread_info { struct cpu_context_save cpu_context; /* cpu context */ __u32 syscall; /* syscall number */ __u8 used_cp[16]; /* thread used copro */ - unsigned long tp_value; + unsigned long tp_value[2]; /* TLS registers */ #ifdef CONFIG_CRUNCH struct crunch_state crunchstate; #endif diff --git a/arch/arm/include/asm/tls.h b/arch/arm/include/asm/tls.h index 73409e6..3742722 100644 --- a/arch/arm/include/asm/tls.h +++ b/arch/arm/include/asm/tls.h @@ -2,27 +2,33 @@ #define __ASMARM_TLS_H #ifdef __ASSEMBLY__ - .macro set_tls_none, tp, tmp1, tmp2 +#include + .macro switch_tls_none, prev, next, tp, tpuser, tmp1, tmp2 .endm - .macro set_tls_v6k, tp, tmp1, tmp2 + .macro switch_tls_v6k, prev, next, tp, tpuser, tmp1, tmp2 + ldrd \tp, \tpuser, [\next, #TI_TP_VALUE] @ get the next TLS and user r/w register + mrc p15, 0, \tmp2, c13, c0, 2 @ get the user r/w register mcr p15, 0, \tp, c13, c0, 3 @ set TLS register - mov \tmp1, #0 - mcr p15, 0, \tmp1, c13, c0, 2 @ clear user r/w TLS register + mcr p15, 0, \tpuser, c13, c0, 2 @ and the user r/w register + str \tmp2, [\prev, #TI_TP_VALUE + 4] @ save it .endm - .macro set_tls_v6, tp, tmp1, tmp2 + .macro switch_tls_v6, prev, next, tp, tpuser, tmp1, tmp2 ldr \tmp1, =elf_hwcap ldr \tmp1, [\tmp1, #0] mov \tmp2, #0xffff0fff + ldr \tp, [\next, #TI_TP_VALUE] @ get the next TLS register tst \tmp1, #HWCAP_TLS @ hardware TLS available? - mcrne p15, 0, \tp, c13, c0, 3 @ yes, set TLS register - movne \tmp1, #0 - mcrne p15, 0, \tmp1, c13, c0, 2 @ clear user r/w TLS register streq \tp, [\tmp2, #-15] @ set TLS value at 0xffff0ff0 + mrcne p15, 0, \tmp2, c13, c0, 2 @ get the previous user r/w register + ldrne \tpuser, [\next, #TI_TP_VALUE + 4] @ get the next user r/w register + mcrne p15, 0, \tp, c13, c0, 3 @ yes, set TLS register + mcrne p15, 0, \tpuser, c13, c0, 2 @ set user r/w register + strne \tmp2, [\prev, #TI_TP_VALUE + 4] @ save it .endm - .macro set_tls_software, tp, tmp1, tmp2 + .macro switch_tls_software, prev, next, tp, tpuser, tmp1, tmp2 mov \tmp1, #0xffff0fff str \tp, [\tmp1, #-15] @ set TLS value at 0xffff0ff0 .endm @@ -31,19 +37,30 @@ #ifdef CONFIG_TLS_REG_EMUL #define tls_emu 1 #define has_tls_reg 1 -#define set_tls set_tls_none +#define switch_tls switch_tls_none #elif defined(CONFIG_CPU_V6) #define tls_emu 0 #define has_tls_reg (elf_hwcap & HWCAP_TLS) -#define set_tls set_tls_v6 +#define switch_tls switch_tls_v6 #elif defined(CONFIG_CPU_32v6K) #define tls_emu 0 #define has_tls_reg 1 -#define set_tls set_tls_v6k +#define switch_tls switch_tls_v6k #else #define tls_emu 0 #define has_tls_reg 0 -#define set_tls set_tls_software +#define switch_tls switch_tls_software #endif +#ifndef __ASSEMBLY__ +static inline unsigned long get_tpuser(void) +{ + unsigned long reg = 0; + + if (has_tls_reg && !tls_emu) + __asm__("mrc p15, 0, %0, c13, c0, 2" : "=r" (reg)); + + return reg; +} +#endif #endif /* __ASMARM_TLS_H */ diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 582b405..1484b59 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -685,7 +685,6 @@ ENTRY(__switch_to) UNWIND(.fnstart ) UNWIND(.cantunwind ) add ip, r1, #TI_CPU_SAVE - ldr r3, [r2, #TI_TP_VALUE] ARM( stmia ip!, {r4 - sl, fp, sp, lr} ) @ Store most regs on stack THUMB( stmia ip!, {r4 - sl, fp} ) @ Store most regs on stack THUMB( str sp, [ip], #4 ) @@ -693,7 +692,7 @@ ENTRY(__switch_to) #ifdef CONFIG_CPU_USE_DOMAINS ldr r6, [r2, #TI_CPU_DOMAIN] #endif - set_tls r3, r4, r5 + switch_tls r1, r2, r4, r5, r3, r7 #if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) ldr r7, [r2, #TI_TASK] ldr r8, =__stack_chk_guard diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 282de48..a24110f 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -39,6 +39,7 @@ #include #include #include +#include #ifdef CONFIG_CC_STACKPROTECTOR #include @@ -343,7 +344,8 @@ copy_thread(unsigned long clone_flags, unsigned long stack_start, clear_ptrace_hw_breakpoint(p); if (clone_flags & CLONE_SETTLS) - thread->tp_value = childregs->ARM_r3; + thread->tp_value[0] = childregs->ARM_r3; + thread->tp_value[1] = get_tpuser(); thread_notify(THREAD_NOTIFY_COPY, thread); diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c index 03deeff..2bc1514 100644 --- a/arch/arm/kernel/ptrace.c +++ b/arch/arm/kernel/ptrace.c @@ -849,7 +849,7 @@ long arch_ptrace(struct task_struct *child, long request, #endif case PTRACE_GET_THREAD_AREA: - ret = put_user(task_thread_info(child)->tp_value, + ret = put_user(task_thread_info(child)->tp_value[0], datap); break; diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index 18b32e8..517bfd4 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -581,7 +581,7 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs) return regs->ARM_r0; case NR(set_tls): - thread->tp_value = regs->ARM_r0; + thread->tp_value[0] = regs->ARM_r0; if (tls_emu) return 0; if (has_tls_reg) { @@ -699,7 +699,7 @@ static int get_tp_trap(struct pt_regs *regs, unsigned int instr) int reg = (instr >> 12) & 15; if (reg == 15) return 1; - regs->uregs[reg] = current_thread_info()->tp_value; + regs->uregs[reg] = current_thread_info()->tp_value[0]; regs->ARM_pc += 4; return 0; } -- 1.8.1.2 -- 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/