From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:38654 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764289AbdEWOrc (ORCPT ); Tue, 23 May 2017 10:47:32 -0400 Subject: Patch "powerpc/64e: Fix hang when debugging programs with relocated kernel" has been added to the 4.11-stable tree To: liu.hailong6@zte.com.cn, gregkh@linuxfoundation.org, huang.jian@zte.com.cn, jiang.biao2@zte.com.cn, jiang.xuexin@zte.com.cn, liu.song11@zte.com.cn, oss@buserror.net Cc: , From: Date: Tue, 23 May 2017 16:45:50 +0200 Message-ID: <1495550750172188@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled powerpc/64e: Fix hang when debugging programs with relocated kernel to the 4.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-64e-fix-hang-when-debugging-programs-with-relocated-kernel.patch and it can be found in the queue-4.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From fd615f69a18a9d4aa5ef02a1dc83f319f75da8e7 Mon Sep 17 00:00:00 2001 From: LiuHailong Date: Tue, 7 Feb 2017 10:35:52 +0800 Subject: powerpc/64e: Fix hang when debugging programs with relocated kernel From: LiuHailong commit fd615f69a18a9d4aa5ef02a1dc83f319f75da8e7 upstream. Debug interrupts can be taken during interrupt entry, since interrupt entry does not automatically turn them off. The kernel will check whether the faulting instruction is between [interrupt_base_book3e, __end_interrupts], and if so clear MSR[DE] and return. However, when the kernel is built with CONFIG_RELOCATABLE, it can't use LOAD_REG_IMMEDIATE(r14,interrupt_base_book3e) and LOAD_REG_IMMEDIATE(r15,__end_interrupts), as they ignore relocation. Thus, if the kernel is actually running at a different address than it was built at, the address comparison will fail, and the exception entry code will hang at kernel_dbg_exc. r2(toc) is also not usable here, as r2 still holds data from the interrupted context, so LOAD_REG_ADDR() doesn't work either. So we use the *name@got* to get the EV of two labels directly. Test programs test.c shows as follows: int main(int argc, char *argv[]) { if (access("/proc/sys/kernel/perf_event_paranoid", F_OK) == -1) printf("Kernel doesn't have perf_event support\n"); } Steps to reproduce the bug, for example: 1) ./gdb ./test 2) (gdb) b access 3) (gdb) r 4) (gdb) s Signed-off-by: Liu Hailong Signed-off-by: Jiang Xuexin Reviewed-by: Jiang Biao Reviewed-by: Liu Song Reviewed-by: Huang Jian [scottwood: cleaned up commit message, and specified bad behavior as a hang rather than an oops to correspond to mainline kernel behavior] Fixes: 1cb6e0649248 ("powerpc/book3e: support CONFIG_RELOCATABLE") Signed-off-by: Scott Wood Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/exceptions-64e.S | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- a/arch/powerpc/kernel/exceptions-64e.S +++ b/arch/powerpc/kernel/exceptions-64e.S @@ -735,8 +735,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC) andis. r15,r14,(DBSR_IC|DBSR_BT)@h beq+ 1f +#ifdef CONFIG_RELOCATABLE + ld r15,PACATOC(r13) + ld r14,interrupt_base_book3e@got(r15) + ld r15,__end_interrupts@got(r15) +#else LOAD_REG_IMMEDIATE(r14,interrupt_base_book3e) LOAD_REG_IMMEDIATE(r15,__end_interrupts) +#endif cmpld cr0,r10,r14 cmpld cr1,r10,r15 blt+ cr0,1f @@ -799,8 +805,14 @@ kernel_dbg_exc: andis. r15,r14,(DBSR_IC|DBSR_BT)@h beq+ 1f +#ifdef CONFIG_RELOCATABLE + ld r15,PACATOC(r13) + ld r14,interrupt_base_book3e@got(r15) + ld r15,__end_interrupts@got(r15) +#else LOAD_REG_IMMEDIATE(r14,interrupt_base_book3e) LOAD_REG_IMMEDIATE(r15,__end_interrupts) +#endif cmpld cr0,r10,r14 cmpld cr1,r10,r15 blt+ cr0,1f Patches currently in stable-queue which might be from liu.hailong6@zte.com.cn are queue-4.11/powerpc-64e-fix-hang-when-debugging-programs-with-relocated-kernel.patch