Received: by 2002:a05:6a10:1287:0:0:0:0 with SMTP id d7csp2932939pxv; Sun, 25 Jul 2021 10:23:34 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxieS49lWGM8GMmXrTSatxAbO2EDi95qeGA3AB8S7oGWHn3f1ie6qIiTHcG42tA21NKeoIt X-Received: by 2002:a92:db4e:: with SMTP id w14mr10659120ilq.188.1627233813801; Sun, 25 Jul 2021 10:23:33 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1627233813; cv=none; d=google.com; s=arc-20160816; b=F5T2avOT656Glp6iT4cljrAwQQ6Ojxd0Uu2ZsXbUxpSo0BgOGv9KjG6bhAJoKoOMr+ 66aN6r8G+dMR4Hy8rpou8NpSDCpYriR1RshMZLwDn6+rDunGNG770JYJc6qpoBIu+gTA G9mt+NUq9gntxGGP/5nyqvgYxczmIlFv2IcabzFXkKrLTXeCvX9QDjlia2ighJ/yCk03 DBynDBlEP5BNj6MQ9pJtjSxOK7CqmjlFHqNCxN6xi2amYFvMkA/7vCY0Rqzyhtzw4D/u ckpPPewz/pDjpnziuIactoGHJlV862Pmaj75thcm6F6EZspJjorpYZL24+eFAj9P9APd Ktcw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:in-reply-to:content-disposition :mime-version:references:message-id:subject:cc:to:from:date; bh=dGBm6JGNY9FwaoLPbMG1xE2eVkdr83qpB7s/n6ptLCw=; b=HGdjLkxlOXnvMBaPGR7QbZt3x21SsN4Srf3lNDujPnyrwZOMdjEq1aA8jMYuXuuwX/ DbtysUhQZUKKLNTglw7V2rP2xP6z6AECScoTkEMf2GqrLNpLFPwC+hiHk3tgkme3qQtE Z5fERdn6pcoZjusLy2ZNm20C9xcc9mhyNACkmMWEbWEC4hUfOuBz6q+fwKauScpzbe69 B0n5OmS3IgGePaa1+VxAQZiXtJlpcYKGwdPo9UXD7cza4bVi3A6hw0Mpt1aU8ZROrot9 Z6xvRdyP/rlOpNELsquA3CIIgBL/oNoG5cmvfZxUqGqIUUurTYc4riKotbKEQEk0jtZV bMgg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id b20si32410288jat.16.2021.07.25.10.23.20; Sun, 25 Jul 2021 10:23:33 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231192AbhGYQlx (ORCPT + 99 others); Sun, 25 Jul 2021 12:41:53 -0400 Received: from zeniv-ca.linux.org.uk ([142.44.231.140]:46066 "EHLO zeniv-ca.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229545AbhGYQlx (ORCPT ); Sun, 25 Jul 2021 12:41:53 -0400 Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1m7hnR-003rxN-PU; Sun, 25 Jul 2021 17:20:13 +0000 Date: Sun, 25 Jul 2021 17:20:13 +0000 From: Al Viro To: linux-m68k@lists.linux-m68k.org Cc: Geert Uytterhoeven , Greg Ungerer , linux-kernel@vger.kernel.org Subject: [PATCH 3/3] m68k: leave stack mangling to asm wrapper of sigreturn() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org sigreturn has to deal with an unpleasant problem - exception stack frames have different sizes, depending upon the exception (and processor model, as well) and variable-sized part of exception frame may contain information needed for instruction restart. So when signal handler terminates and calls sigreturn to resume the execution at the place where we'd been when we caught the signal, it has to rearrange the frame at the bottom of kernel stack. Worse, it might need to open a gap in the kernel stack, shifting pt_regs towards lower addresses. Doing that from C is insane - we'd need to shift stack frames (return addresses, local variables, etc.) of C call chain, right under the nose of compiler and hope it won't fall apart horribly. What had been actually done is only slightly less insane - an inline asm in mangle_kernel_stack() moved the stuff around, then reset stack pointer and jumped to label in asm glue. However, we can avoid all that mess if the asm wrapper we have to use anyway would reserve some space on the stack between switch_stack and the C stack frame of do_{rt_,}sigreturn(). Then C part can simply memmove() pt_regs + switch_stack, memcpy() the variable part of exception frame into the opened gap - all of that without inline asm, buggering C call chain, magical jumps to asm labels, etc. Asm wrapper would need to know where the moved switch_stack has ended up - it might have been shifted into the gap we'd reserved before do_rt_sigreturn() call. That's where it needs to set the stack pointer to. So let the C part return just that and be done with that. While we are at it, the call of berr_040cleanup() we need to do when returning via 68040 bus error exception frame can be moved into C part as well. Signed-off-by: Al Viro --- arch/m68k/68000/entry.S | 3 -- arch/m68k/coldfire/entry.S | 3 -- arch/m68k/include/asm/traps.h | 4 ++ arch/m68k/kernel/entry.S | 55 ++++++++++----------- arch/m68k/kernel/signal.c | 111 ++++++++++++++++-------------------------- 5 files changed, 71 insertions(+), 105 deletions(-) diff --git a/arch/m68k/68000/entry.S b/arch/m68k/68000/entry.S index 259b3661b614..cce465e850fe 100644 --- a/arch/m68k/68000/entry.S +++ b/arch/m68k/68000/entry.S @@ -25,7 +25,6 @@ .globl system_call .globl resume .globl ret_from_exception -.globl ret_from_signal .globl sys_call_table .globl bad_interrupt .globl inthandler1 @@ -59,8 +58,6 @@ do_trace: subql #4,%sp /* dummy return address */ SAVE_SWITCH_STACK jbsr syscall_trace_leave - -ret_from_signal: RESTORE_SWITCH_STACK addql #4,%sp jra ret_from_exception diff --git a/arch/m68k/coldfire/entry.S b/arch/m68k/coldfire/entry.S index d43a02795a4a..68adb7b5b296 100644 --- a/arch/m68k/coldfire/entry.S +++ b/arch/m68k/coldfire/entry.S @@ -51,7 +51,6 @@ sw_usp: .globl system_call .globl resume .globl ret_from_exception -.globl ret_from_signal .globl sys_call_table .globl inthandler @@ -98,8 +97,6 @@ ENTRY(system_call) subql #4,%sp /* dummy return address */ SAVE_SWITCH_STACK jbsr syscall_trace_leave - -ret_from_signal: RESTORE_SWITCH_STACK addql #4,%sp diff --git a/arch/m68k/include/asm/traps.h b/arch/m68k/include/asm/traps.h index 4aff3358fbaf..a9d5c1c870d3 100644 --- a/arch/m68k/include/asm/traps.h +++ b/arch/m68k/include/asm/traps.h @@ -267,6 +267,10 @@ struct frame { } un; }; +#ifdef CONFIG_M68040 +asmlinkage void berr_040cleanup(struct frame *fp); +#endif + #endif /* __ASSEMBLY__ */ #endif /* _M68K_TRAPS_H */ diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S index ff9e842cec0f..8fa9822b5922 100644 --- a/arch/m68k/kernel/entry.S +++ b/arch/m68k/kernel/entry.S @@ -78,20 +78,38 @@ ENTRY(__sys_clone3) ENTRY(sys_sigreturn) SAVE_SWITCH_STACK - movel %sp,%sp@- | switch_stack pointer - pea %sp@(SWITCH_STACK_SIZE+4) | pt_regs pointer + movel %sp,%a1 | switch_stack pointer + lea %sp@(SWITCH_STACK_SIZE),%a0 | pt_regs pointer + lea %sp@(-84),%sp | leave a gap + movel %a1,%sp@- + movel %a0,%sp@- jbsr do_sigreturn - addql #8,%sp - RESTORE_SWITCH_STACK - rts + jra 1f | shared with rt_sigreturn() ENTRY(sys_rt_sigreturn) SAVE_SWITCH_STACK - movel %sp,%sp@- | switch_stack pointer - pea %sp@(SWITCH_STACK_SIZE+4) | pt_regs pointer + movel %sp,%a1 | switch_stack pointer + lea %sp@(SWITCH_STACK_SIZE),%a0 | pt_regs pointer + lea %sp@(-84),%sp | leave a gap + movel %a1,%sp@- + movel %a0,%sp@- + | stack contents: + | [original pt_regs address] [original switch_stack address] + | [gap] [switch_stack] [pt_regs] [exception frame] jbsr do_rt_sigreturn - addql #8,%sp + +1: + | stack contents now: + | [original pt_regs address] [original switch_stack address] + | [unused part of the gap] [moved switch_stack] [moved pt_regs] + | [replacement exception frame] + | return value of do_{rt_,}sigreturn() points to moved switch_stack. + + movel %d0,%sp | discard the leftover junk RESTORE_SWITCH_STACK + | stack contents now is just [syscall return address] [pt_regs] [frame] + | return pt_regs.d0 + movel %sp@(PT_OFF_D0+4),%d0 rts ENTRY(buserr) @@ -182,27 +200,6 @@ do_trace_exit: addql #4,%sp jra .Lret_from_exception -ENTRY(ret_from_signal) - movel %curptr@(TASK_STACK),%a1 - tstb %a1@(TINFO_FLAGS+2) - jge 1f - lea %sp@(SWITCH_STACK_SIZE),%a1 - movel %a1,%curptr@(TASK_THREAD+THREAD_ESP0) - jbsr syscall_trace -1: RESTORE_SWITCH_STACK - addql #4,%sp -/* on 68040 complete pending writebacks if any */ -#ifdef CONFIG_M68040 - bfextu %sp@(PT_OFF_FORMATVEC){#0,#4},%d0 - subql #7,%d0 | bus error frame ? - jbne 1f - movel %sp,%sp@- - jbsr berr_040cleanup - addql #4,%sp -1: -#endif - jra .Lret_from_exception - ENTRY(system_call) SAVE_ALL_SYS diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c index cd11eb101eac..338817d0cb3f 100644 --- a/arch/m68k/kernel/signal.c +++ b/arch/m68k/kernel/signal.c @@ -641,56 +641,35 @@ static inline void siginfo_build_tests(void) static int mangle_kernel_stack(struct pt_regs *regs, int formatvec, void __user *fp) { - int fsize = frame_extra_sizes(formatvec >> 12); - if (fsize < 0) { + int extra = frame_extra_sizes(formatvec >> 12); + char buf[sizeof_field(struct frame, un)]; + + if (extra < 0) { /* * user process trying to return with weird frame format */ pr_debug("user process returning with weird frame format\n"); - return 1; + return -1; } - if (!fsize) { - regs->format = formatvec >> 12; - regs->vector = formatvec & 0xfff; - } else { - struct switch_stack *sw = (struct switch_stack *)regs - 1; - /* yes, twice as much as max(sizeof(frame.un.fmt)) */ - unsigned long buf[sizeof_field(struct frame, un) / 2]; - - /* that'll make sure that expansion won't crap over data */ - if (copy_from_user(buf + fsize / 4, fp, fsize)) - return 1; - - /* point of no return */ - regs->format = formatvec >> 12; - regs->vector = formatvec & 0xfff; -#define frame_offset (sizeof(struct pt_regs)+sizeof(struct switch_stack)) - __asm__ __volatile__ ( -#ifdef CONFIG_COLDFIRE - " movel %0,%/sp\n\t" - " bra ret_from_signal\n" -#else - " movel %0,%/a0\n\t" - " subl %1,%/a0\n\t" /* make room on stack */ - " movel %/a0,%/sp\n\t" /* set stack pointer */ - /* move switch_stack and pt_regs */ - "1: movel %0@+,%/a0@+\n\t" - " dbra %2,1b\n\t" - " lea %/sp@(%c3),%/a0\n\t" /* add offset of fmt */ - " lsrl #2,%1\n\t" - " subql #1,%1\n\t" - /* copy to the gap we'd made */ - "2: movel %4@+,%/a0@+\n\t" - " dbra %1,2b\n\t" - " bral ret_from_signal\n" + if (extra && copy_from_user(buf, fp, extra)) + return -1; + regs->format = formatvec >> 12; + regs->vector = formatvec & 0xfff; + if (extra) { + void *p = (struct switch_stack *)regs - 1; + struct frame *new = (void *)regs - extra; + int size = sizeof(struct pt_regs)+sizeof(struct switch_stack); + + memmove(p - extra, p, size); + memcpy(p - extra + size, buf, extra); + current->thread.esp0 = (unsigned long)&new->ptregs; +#ifdef CONFIG_M68040 + /* on 68040 complete pending writebacks if any */ + if (new->ptregs.format == 7) // bus error frame + berr_040cleanup(new); #endif - : /* no outputs, it doesn't ever return */ - : "a" (sw), "d" (fsize), "d" (frame_offset/4-1), - "n" (frame_offset), "a" (buf + fsize/4) - : "a0"); -#undef frame_offset } - return 0; + return extra; } static inline int @@ -698,7 +677,6 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *usc, void __u { int formatvec; struct sigcontext context; - int err = 0; siginfo_build_tests(); @@ -707,7 +685,7 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *usc, void __u /* get previous context */ if (copy_from_user(&context, usc, sizeof(context))) - goto badframe; + return -1; /* restore passed registers */ regs->d0 = context.sc_d0; @@ -720,15 +698,10 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *usc, void __u wrusp(context.sc_usp); formatvec = context.sc_formatvec; - err = restore_fpu_state(&context); - - if (err || mangle_kernel_stack(regs, formatvec, fp)) - goto badframe; - - return 0; + if (restore_fpu_state(&context)) + return -1; -badframe: - return 1; + return mangle_kernel_stack(regs, formatvec, fp); } static inline int @@ -745,7 +718,7 @@ rt_restore_ucontext(struct pt_regs *regs, struct switch_stack *sw, err = __get_user(temp, &uc->uc_mcontext.version); if (temp != MCONTEXT_VERSION) - goto badframe; + return -1; /* restore passed registers */ err |= __get_user(regs->d0, &gregs[0]); err |= __get_user(regs->d1, &gregs[1]); @@ -774,22 +747,17 @@ rt_restore_ucontext(struct pt_regs *regs, struct switch_stack *sw, err |= restore_altstack(&uc->uc_stack); if (err) - goto badframe; - - if (mangle_kernel_stack(regs, temp, &uc->uc_extra)) - goto badframe; + return -1; - return 0; - -badframe: - return 1; + return mangle_kernel_stack(regs, temp, &uc->uc_extra); } -asmlinkage int do_sigreturn(struct pt_regs *regs, struct switch_stack *sw) +asmlinkage void *do_sigreturn(struct pt_regs *regs, struct switch_stack *sw) { unsigned long usp = rdusp(); struct sigframe __user *frame = (struct sigframe __user *)(usp - 4); sigset_t set; + int size; if (!access_ok(frame, sizeof(*frame))) goto badframe; @@ -801,20 +769,22 @@ asmlinkage int do_sigreturn(struct pt_regs *regs, struct switch_stack *sw) set_current_blocked(&set); - if (restore_sigcontext(regs, &frame->sc, frame + 1)) + size = restore_sigcontext(regs, &frame->sc, frame + 1); + if (size < 0) goto badframe; - return regs->d0; + return (void *)sw - size; badframe: force_sig(SIGSEGV); - return 0; + return sw; } -asmlinkage int do_rt_sigreturn(struct pt_regs *regs, struct switch_stack *sw) +asmlinkage void *do_rt_sigreturn(struct pt_regs *regs, struct switch_stack *sw) { unsigned long usp = rdusp(); struct rt_sigframe __user *frame = (struct rt_sigframe __user *)(usp - 4); sigset_t set; + int size; if (!access_ok(frame, sizeof(*frame))) goto badframe; @@ -823,13 +793,14 @@ asmlinkage int do_rt_sigreturn(struct pt_regs *regs, struct switch_stack *sw) set_current_blocked(&set); - if (rt_restore_ucontext(regs, sw, &frame->uc)) + size = rt_restore_ucontext(regs, sw, &frame->uc); + if (size < 0) goto badframe; - return regs->d0; + return (void *)sw - size; badframe: force_sig(SIGSEGV); - return 0; + return sw; } static inline struct pt_regs *rte_regs(struct pt_regs *regs) -- 2.11.0