From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1Eo1lk-0003rZ-Bm for user-mode-linux-devel@lists.sourceforge.net; Sun, 18 Dec 2005 08:52:20 -0800 Received: from host229-46.pool8259.interbusiness.it ([82.59.46.229] helo=zion.home.lan) by mail.sourceforge.net with esmtp (Exim 4.44) id 1Eo1lh-0004BT-O2 for user-mode-linux-devel@lists.sourceforge.net; Sun, 18 Dec 2005 08:52:20 -0800 From: "Paolo 'Blaisorblade' Giarrusso" Message-Id: <20051218165039.441.89463.stgit@zion.home.lan> In-Reply-To: <20051218164916.441.69564.stgit@zion.home.lan> References: <20051218164916.441.69564.stgit@zion.home.lan> Subject: [uml-devel] [PATCH 4/4] uml skas0: stop gcc's insanity Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Sun, 18 Dec 2005 17:50:39 +0100 To: Linus Torvalds Cc: Jeff Dike , linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net From: Jeff Dike , Paolo 'Blaisorblade' Giarrusso UML skas0 stub has been miscompiling for many people (incidentally not the authors), depending on the used GCC versions. I think (and testing on some GCC versions shows) this patch avoids the fundamental issue which is behind this, namely gcc using the stack when we have just replaced it, behind gcc's back. The remapping and storage of the return value is hidden in a blob of asm, hopefully giving gcc no room for creativity. Signed-off-by: Paolo 'Blaisorblade' Giarrusso --- arch/um/include/sysdep-i386/stub.h | 29 ++++++++++++++++------------- arch/um/include/sysdep-x86_64/stub.h | 30 +++++++++++++++++------------- arch/um/kernel/skas/clone.c | 23 +++++++++++++---------- 3 files changed, 46 insertions(+), 36 deletions(-) diff --git a/arch/um/include/sysdep-i386/stub.h b/arch/um/include/sysdep-i386/stub.h index 6ba8cbb..b492b12 100644 --- a/arch/um/include/sysdep-i386/stub.h +++ b/arch/um/include/sysdep-i386/stub.h @@ -6,8 +6,12 @@ #ifndef __SYSDEP_STUB_H #define __SYSDEP_STUB_H +#include #include #include +#include "stub-data.h" +#include "kern_constants.h" +#include "uml-config.h" extern void stub_segv_handler(int sig); extern void stub_clone_handler(void); @@ -76,23 +80,22 @@ static inline long stub_syscall5(long sy return ret; } -static inline long stub_syscall6(long syscall, long arg1, long arg2, long arg3, - long arg4, long arg5, long arg6) +static inline void trap_myself(void) { - long ret; - - __asm__ volatile ("push %%ebp ; movl %%eax,%%ebp ; movl %1,%%eax ; " - "int $0x80 ; pop %%ebp" - : "=a" (ret) - : "g" (syscall), "b" (arg1), "c" (arg2), "d" (arg3), - "S" (arg4), "D" (arg5), "0" (arg6)); - - return ret; + __asm("int3"); } -static inline void trap_myself(void) +static inline void remap_stack(int fd, unsigned long offset) { - __asm("int3"); + __asm__ volatile ("movl %%eax,%%ebp ; movl %0,%%eax ; int $0x80 ;" + "movl %7, %%ebx ; movl %%eax, (%%ebx)" + : : "g" (STUB_MMAP_NR), "b" (UML_CONFIG_STUB_DATA), + "c" (UM_KERN_PAGE_SIZE), + "d" (PROT_READ | PROT_WRITE), + "S" (MAP_FIXED | MAP_SHARED), "D" (fd), + "a" (offset), + "i" (&((struct stub_data *) UML_CONFIG_STUB_DATA)->err) + : "memory"); } #endif diff --git a/arch/um/include/sysdep-x86_64/stub.h b/arch/um/include/sysdep-x86_64/stub.h index c41689c..92e989f 100644 --- a/arch/um/include/sysdep-x86_64/stub.h +++ b/arch/um/include/sysdep-x86_64/stub.h @@ -6,8 +6,12 @@ #ifndef __SYSDEP_STUB_H #define __SYSDEP_STUB_H +#include #include #include +#include "stub-data.h" +#include "kern_constants.h" +#include "uml-config.h" extern void stub_segv_handler(int sig); extern void stub_clone_handler(void); @@ -81,23 +85,23 @@ static inline long stub_syscall5(long sy return ret; } -static inline long stub_syscall6(long syscall, long arg1, long arg2, long arg3, - long arg4, long arg5, long arg6) +static inline void trap_myself(void) { - long ret; - - __asm__ volatile ("movq %5,%%r10 ; movq %6,%%r8 ; " - "movq %7, %%r9; " __syscall : "=a" (ret) - : "0" (syscall), "D" (arg1), "S" (arg2), "d" (arg3), - "g" (arg4), "g" (arg5), "g" (arg6) - : __syscall_clobber, "r10", "r8", "r9" ); - - return ret; + __asm("int3"); } -static inline void trap_myself(void) +static inline void remap_stack(long fd, unsigned long offset) { - __asm("int3"); + __asm__ volatile ("movq %4,%%r10 ; movq %5,%%r8 ; " + "movq %6, %%r9; " __syscall "; movq %7, %%rbx ; " + "movq %%rax, (%%rbx)": + : "a" (STUB_MMAP_NR), "D" (UML_CONFIG_STUB_DATA), + "S" (UM_KERN_PAGE_SIZE), + "d" (PROT_READ | PROT_WRITE), + "g" (MAP_FIXED | MAP_SHARED), "g" (fd), + "g" (offset), + "i" (&((struct stub_data *) UML_CONFIG_STUB_DATA)->err) + : __syscall_clobber, "r10", "r8", "r9" ); } #endif diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c index cb37ce9..47b812b 100644 --- a/arch/um/kernel/skas/clone.c +++ b/arch/um/kernel/skas/clone.c @@ -18,11 +18,10 @@ * on some systems. */ -#define STUB_DATA(field) (((struct stub_data *) UML_CONFIG_STUB_DATA)->field) - void __attribute__ ((__section__ (".__syscall_stub"))) stub_clone_handler(void) { + struct stub_data *data = (struct stub_data *) UML_CONFIG_STUB_DATA; long err; err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD, @@ -35,17 +34,21 @@ stub_clone_handler(void) if(err) goto out; - err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL, - (long) &STUB_DATA(timer), 0); + err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL, + (long) &data->timer, 0); if(err) goto out; - err = stub_syscall6(STUB_MMAP_NR, UML_CONFIG_STUB_DATA, - UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE, - MAP_FIXED | MAP_SHARED, STUB_DATA(fd), - STUB_DATA(offset)); + remap_stack(data->fd, data->offset); + goto done; + out: - /* save current result. Parent: pid; child: retcode of mmap */ - STUB_DATA(err) = err; + /* save current result. + * Parent: pid; + * child: retcode of mmap already saved and it jumps around this + * assignment + */ + data->err = err; + done: trap_myself(); } ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel