From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932390Ab2CZBhm (ORCPT ); Sun, 25 Mar 2012 21:37:42 -0400 Received: from terminus.zytor.com ([198.137.202.10]:46070 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932256Ab2CZBhX (ORCPT ); Sun, 25 Mar 2012 21:37:23 -0400 Message-ID: <4F6FC838.7000904@zytor.com> Date: Sun, 25 Mar 2012 18:36:56 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120209 Thunderbird/10.0.1 MIME-Version: 1.0 To: Borislav Petkov , Thomas Renninger , eric.piel@tremplin-utc.net, vojcek@tlen.pl, dsdt@gaugusch.at, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, Lin Ming , lenb@kernel.org, robert.moore@intel.com, Al Viro Subject: Re: [PATCH] ACPI: Implement overriding of arbitrary ACPI tables via initrd References: <1332512984-79664-1-git-send-email-trenn@suse.de> <201203240242.07724.trenn@suse.de> <4F6D2AF8.3070707@zytor.com> <201203240402.38749.trenn@suse.de> <4F6D50DD.4050306@zytor.com> <20120324092451.GA3352@liondog.tnic> <4F6E1742.6060709@zytor.com> <20120325085420.GA12565@liondog.tnic> In-Reply-To: <20120325085420.GA12565@liondog.tnic> X-Enigmail-Version: 1.4 Content-Type: multipart/mixed; boundary="------------080709060403040904020707" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------080709060403040904020707 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 03/25/2012 01:54 AM, Borislav Petkov wrote: > > One other downside for this approach would be the need to have > initrd/initramfs support always compiled into the kernel in order to do > all those things but, hey, distro kernels already have that so we're > probably stuck with it anyway. > In theory we could make the early stuff independent of the initramfs code in the kernel -- just like we always build in an initramfs. Not that it matters much, at this point the no-initramfs configurations are mostly theoretical. I was able to shave a bit more off the code... optimizing for size can be fun sometimes. The code is now 442 bytes on x86-64 and 413 on i386 when compiled with -O2 -fomit-frame-pointer; with -Os -fomit-frame-pointer it is 372/410... all of that without any library calls or relocations of any kind (which means it should be safe to call from the prepaging environment.) -hpa --------------080709060403040904020707 Content-Type: text/x-csrc; name="findcpio.c" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="findcpio.c" /* * findcpio.c * * Find a specific cpio member; must precede any compressed content. */ #include #include struct cpio_data { void *data; unsigned long size; }; enum cpio_fields { C_MAGIC, C_INO, C_MODE, C_UID, C_GID, C_NLINK, C_MTIME, C_FILESIZE, C_MAJ, C_MIN, C_RMAJ, C_RMIN, C_NAMESIZE, C_CHKSUM, C_NFIELDS }; #if defined(__i386__) || defined(__x86_64__) static size_t strlen(const char *name) { size_t n = -1; asm("repne; scasb" : "+D" (name), "+c" (n) : "a" (0)); return -2 - n; } static int memcmp(const void *p1, const void *p2, size_t n) { unsigned char rv; asm("repe; cmpsb; setne %0" : "=r" (rv), "+S" (p1), "+D" (p2), "+c" (n)); return rv; } #else static size_t strlen(const char *name) { size_t n = 0; while (*name++) n++; return n; } static int memcmp(const void *p1, const void *p2, size_t n) { const unsigned char *u1 = p1; const unsigned char *u2 = p2; int d; while (n--) { d = *u2++ - *u1++; if (d) return d; } return 0; } #endif #define ALIGN4(p) ((void *)(((size_t)p + 3) & ~3)) struct cpio_data find_cpio_data(const char *name, const void *data, size_t len) { const size_t cpio_header_len = 8*C_NFIELDS - 2; struct cpio_data cd = { NULL, 0 }; const char *p, *dptr, *nptr; unsigned int ch[C_NFIELDS], *chp, v; unsigned char c, x; size_t mynamesize = strlen(name) + 1; int i, j; p = data; while (len > cpio_header_len) { if (!*p) { /* All cpio headers need to be 4-byte aligned */ p += 4; len -= 4; continue; } j = 6; /* The magic field is only 6 characters */ chp = ch; for (i = C_NFIELDS; i; i--) { v = 0; while (j--) { v <<= 4; c = *p++; x = c - '0'; if (x < 10) { v += x; continue; } x = (c | 0x20) - 'a'; if (x < 6) { v += x + 10; continue; } goto quit; /* Invalid hexadecimal */ } *chp++ = v; j = 8; /* All other fields are 8 characters */ } if ((ch[C_MAGIC] - 0x070701) > 1) goto quit; /* Invalid magic */ len -= cpio_header_len; dptr = ALIGN4(p + ch[C_NAMESIZE]); nptr = ALIGN4(dptr + ch[C_FILESIZE]); if (nptr > p + len || dptr < p || nptr < dptr) goto quit; /* Buffer overrun */ if ((ch[C_MODE] & 0170000) == 0100000 && ch[C_NAMESIZE] == mynamesize && !memcmp(p, name, mynamesize)) { cd.data = (void *)dptr; cd.size = ch[C_FILESIZE]; return cd; /* Found it! */ } len -= (nptr - p); p = nptr; } quit: return cd; } --------------080709060403040904020707--