From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from s3.sipsolutions.net ([2a01:4f8:191:4433::2] helo=sipsolutions.net) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lHTqx-005UJF-2P for linux-um@lists.infradead.org; Wed, 03 Mar 2021 15:56:06 +0000 From: Benjamin Berg Subject: [PATCH 04/27] um: Drop NULL check from start_userspace Date: Wed, 3 Mar 2021 16:55:00 +0100 Message-Id: <20210303155523.124277-5-benjamin@sipsolutions.net> In-Reply-To: <20210303155523.124277-1-benjamin@sipsolutions.net> References: <20210303155523.124277-1-benjamin@sipsolutions.net> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: linux-um@lists.infradead.org Cc: Benjamin Berg start_userspace is only called from exactly one location, and the passed pointer for the userspace process stack cannot be NULL. Remove the check, without changing the control flow. Signed-off-by: Benjamin Berg --- arch/um/os-Linux/skas/process.c | 53 +++++++++++++++------------------ 1 file changed, 24 insertions(+), 29 deletions(-) diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c index d30c96b599ac..1c31f833a7ed 100644 --- a/arch/um/os-Linux/skas/process.c +++ b/arch/um/os-Linux/skas/process.c @@ -188,7 +188,7 @@ extern char __syscall_stub_start[]; /** * userspace_tramp() - userspace trampoline - * @stack: pointer to the new userspace stack page, can be NULL, if? FIXME: + * @stack: pointer to the new userspace stack page * * The userspace trampoline is used to setup a new userspace process in start_userspace() after it was clone()'ed. * This function will run on a temporary stack page. @@ -203,9 +203,13 @@ extern char __syscall_stub_start[]; */ static int userspace_tramp(void *stack) { + struct sigaction sa; void *addr; int fd; unsigned long long offset; + unsigned long segv_handler = STUB_CODE + + (unsigned long) stub_segv_handler - + (unsigned long) __syscall_stub_start; ptrace(PTRACE_TRACEME, 0, 0, 0); @@ -221,34 +225,25 @@ static int userspace_tramp(void *stack) exit(1); } - if (stack != NULL) { - fd = phys_mapping(to_phys(stack), &offset); - addr = mmap((void *) STUB_DATA, - UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE, - MAP_FIXED | MAP_SHARED, fd, offset); - if (addr == MAP_FAILED) { - printk(UM_KERN_ERR "mapping segfault stack at 0x%lx failed, errno = %d\n", - STUB_DATA, errno); - exit(1); - } + fd = phys_mapping(to_phys(stack), &offset); + addr = mmap((void *) STUB_DATA, + UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE, + MAP_FIXED | MAP_SHARED, fd, offset); + if (addr == MAP_FAILED) { + printk(UM_KERN_ERR "mapping segfault stack at 0x%lx failed, errno = %d\n", + STUB_DATA, errno); + exit(1); } - if (stack != NULL) { - struct sigaction sa; - - unsigned long v = STUB_CODE + - (unsigned long) stub_segv_handler - - (unsigned long) __syscall_stub_start; - - set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE); - sigemptyset(&sa.sa_mask); - sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO; - sa.sa_sigaction = (void *) v; - sa.sa_restorer = NULL; - if (sigaction(SIGSEGV, &sa, NULL) < 0) { - printk(UM_KERN_ERR "%s - setting SIGSEGV handler failed - errno = %d\n", - __func__, errno); - exit(1); - } + + set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE); + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO; + sa.sa_sigaction = (void *) segv_handler; + sa.sa_restorer = NULL; + if (sigaction(SIGSEGV, &sa, NULL) < 0) { + printk(UM_KERN_ERR "%s - setting SIGSEGV handler failed - errno = %d\n", + __func__, errno); + exit(1); } kill(os_getpid(), SIGSTOP); @@ -260,7 +255,7 @@ int kill_userspace_mm[NR_CPUS]; /** * start_userspace() - prepare a new userspace process - * @stub_stack: pointer to the stub stack. Can be NULL, if? FIXME: + * @stub_stack: pointer to the stub stack. * * Setups a new temporary stack page that is used while userspace_tramp() runs * Clones the kernel process into a new userspace process, with FDs only. -- 2.29.2 _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um