From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936867AbYEUS7s (ORCPT ); Wed, 21 May 2008 14:59:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S936335AbYEUS6o (ORCPT ); Wed, 21 May 2008 14:58:44 -0400 Received: from [198.99.130.12] ([198.99.130.12]:51708 "EHLO saraswathi.solana.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S936274AbYEUS6m (ORCPT ); Wed, 21 May 2008 14:58:42 -0400 Date: Wed, 21 May 2008 13:58:29 -0400 From: Jeff Dike To: Tom Spink Cc: "linux-os (Dick Johnson)" , LKML Subject: Re: UML fails to locate address space Message-ID: <20080521175829.GA10648@c2.user-mode-linux.org> References: <7b9198260805200408k1d6b70a8xc7e4c24106e5020f@mail.gmail.com> <20080520135238.GB6990@c2.user-mode-linux.org> <20080520173503.GA10811@c2.user-mode-linux.org> <20080521021502.GB16212@c2.user-mode-linux.org> <7b9198260805210502i316c9e38lcc9b5561045dd5d@mail.gmail.com> <7b9198260805210504h278f014s5aba720360ac02ab@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7b9198260805210504h278f014s5aba720360ac02ab@mail.gmail.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 21, 2008 at 01:04:21PM +0100, Tom Spink wrote: > Oh No! I forgot to get rid of those nasty includes.... Take 2.... This is actually supposed to return the address space top, not the size, so I changed the name and return value accordingly. Other than that, this is fine. The final result is below... Jeff -- Work email - jdike at linux dot intel dot com From: Tom Spink This patch makes os_get_task_size locate the bottom of the address space, as well as the top. This is for systems which put a lower limit on mmap addresses. It works by manually scanning pages from zero onwards until a valid page is found. Because the bottom of the address space may not be zero, it's not sufficient to assume the top of the address space is the size of the address space. The size is the difference between the top address and bottom address. [ jdike@addtoit.com - Changed the name to reflect that this function is supposed to return the top of the process address space, not its size and changed the return value to reflect that. Also some minor formatting changes ] Signed-off-by: Tom Spink Signed-off-by: Jeff Dike --- arch/um/include/os.h | 2 - arch/um/kernel/um_arch.c | 2 - arch/um/os-Linux/sys-i386/task_size.c | 35 +++++++++++++++++++++----------- arch/um/os-Linux/sys-x86_64/task_size.c | 2 - 4 files changed, 27 insertions(+), 14 deletions(-) Index: linux-2.6.22/arch/um/include/os.h =================================================================== --- linux-2.6.22.orig/arch/um/include/os.h 2008-05-21 13:48:23.000000000 -0400 +++ linux-2.6.22/arch/um/include/os.h 2008-05-21 13:48:47.000000000 -0400 @@ -299,6 +299,6 @@ extern int os_arch_prctl(int pid, int co extern int get_pty(void); /* sys-$ARCH/task_size.c */ -extern unsigned long os_get_task_size(void); +extern unsigned long os_get_top_address(void); #endif Index: linux-2.6.22/arch/um/kernel/um_arch.c =================================================================== --- linux-2.6.22.orig/arch/um/kernel/um_arch.c 2008-04-24 13:22:09.000000000 -0400 +++ linux-2.6.22/arch/um/kernel/um_arch.c 2008-05-21 13:46:56.000000000 -0400 @@ -274,7 +274,7 @@ int __init linux_main(int argc, char **a if (have_root == 0) add_arg(DEFAULT_COMMAND_LINE); - host_task_size = os_get_task_size(); + host_task_size = os_get_top_address(); /* * TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps * out Index: linux-2.6.22/arch/um/os-Linux/sys-i386/task_size.c =================================================================== --- linux-2.6.22.orig/arch/um/os-Linux/sys-i386/task_size.c 2008-04-23 13:07:23.000000000 -0400 +++ linux-2.6.22/arch/um/os-Linux/sys-i386/task_size.c 2008-05-21 13:54:47.000000000 -0400 @@ -63,7 +63,7 @@ static int page_ok(unsigned long page) return ok; } -unsigned long os_get_task_size(void) +unsigned long os_get_top_address(void) { struct sigaction sa, old; unsigned long bottom = 0; @@ -76,9 +76,9 @@ unsigned long os_get_task_size(void) * hosts, but shouldn't hurt otherwise. */ unsigned long top = 0xffffd000 >> UM_KERN_PAGE_SHIFT; - unsigned long test; + unsigned long test, original; - printf("Locating the top of the address space ... "); + printf("Locating the bottom of the address space ... "); fflush(stdout); /* @@ -89,16 +89,30 @@ unsigned long os_get_task_size(void) sigemptyset(&sa.sa_mask); sa.sa_flags = SA_NODEFER; if (sigaction(SIGSEGV, &sa, &old)) { - perror("os_get_task_size"); + perror("os_get_top_address"); exit(1); } - if (!page_ok(bottom)) { - fprintf(stderr, "Address 0x%x no good?\n", - bottom << UM_KERN_PAGE_SHIFT); + /* Manually scan the address space, bottom-up, until we find + * the first valid page (or run out of them). + */ + for (bottom = 0; bottom < top; bottom++) { + if (page_ok(bottom)) + break; + } + + /* If we've got this far, we ran out of pages. */ + if (bottom == top) { + fprintf(stderr, "Unable to determine bottom of address " + "space.\n"); exit(1); } + printf("0x%x\n", bottom << UM_KERN_PAGE_SHIFT); + printf("Locating the top of the address space ... "); + fflush(stdout); + + original = bottom; /* This could happen with a 4G/4G split */ if (page_ok(top)) goto out; @@ -114,11 +128,10 @@ unsigned long os_get_task_size(void) out: /* Restore the old SIGSEGV handling */ if (sigaction(SIGSEGV, &old, NULL)) { - perror("os_get_task_size"); + perror("os_get_top_address"); exit(1); } - top <<= UM_KERN_PAGE_SHIFT; - printf("0x%x\n", top); + printf("0x%x\n", top << UM_KERN_PAGE_SHIFT); - return top; + return top << UM_KERN_PAGE_SHIFT; } Index: linux-2.6.22/arch/um/os-Linux/sys-x86_64/task_size.c =================================================================== --- linux-2.6.22.orig/arch/um/os-Linux/sys-x86_64/task_size.c 2008-02-18 11:53:51.000000000 -0500 +++ linux-2.6.22/arch/um/os-Linux/sys-x86_64/task_size.c 2008-05-21 13:49:59.000000000 -0400 @@ -1,4 +1,4 @@ -unsigned long os_get_task_size(unsigned long shift) +unsigned long os_get_top_address(unsigned long shift) { /* The old value of CONFIG_TOP_ADDR */ return 0x7fc0000000;