Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755019Ab3CEIir (ORCPT ); Tue, 5 Mar 2013 03:38:47 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:12055 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753608Ab3CEIiq convert rfc822-to-8bit (ORCPT ); Tue, 5 Mar 2013 03:38:46 -0500 X-IronPort-AV: E=Sophos;i="4.84,786,1355068800"; d="scan'208";a="6816089" Message-ID: <5135AEA5.7000605@cn.fujitsu.com> Date: Tue, 05 Mar 2013 16:36:53 +0800 From: Zhang Yanfei User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.8) Gecko/20121012 Thunderbird/10.0.8 MIME-Version: 1.0 To: HATAYAMA Daisuke CC: vgoyal@redhat.com, ebiederm@xmission.com, cpw@sgi.com, kumagai-atsushi@mxc.nes.nec.co.jp, lisa.mitchell@hp.com, heiko.carstens@de.ibm.com, akpm@linux-foundation.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 02/20] vmcore: rearrange program headers without assuming consequtive PT_NOTE entries References: <20130302083447.31252.93914.stgit@localhost6.localdomain6> <20130302083559.31252.60341.stgit@localhost6.localdomain6> In-Reply-To: <20130302083559.31252.60341.stgit@localhost6.localdomain6> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/03/05 16:37:42, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/03/05 16:37:43 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7405 Lines: 227 于 2013年03月02日 16:35, HATAYAMA Daisuke 写道: > Current code assumes all PT_NOTE headers are placed at the beginning > of program header table and they are consequtive. But the assumption > could be broken by future changes on either kexec-tools or the 1st > kernel. This patch removes the assumption and rearranges program > headers as the following conditions are satisfied: > > - PT_NOTE entry is unique at the first entry, > > - the order of program headers are unchanged during this > rearrangement, only their positions are changed in positive > direction. > > - unused part that occurs in the bottom of program headers are filled > with 0. > > Also, this patch adds one exceptional case where the number of PT_NOTE > entries is somehow 0. Then, immediately go out of the function. > > Signed-off-by: HATAYAMA Daisuke > --- > > fs/proc/vmcore.c | 92 +++++++++++++++++++++++++++++++++++++++++++----------- > 1 files changed, 74 insertions(+), 18 deletions(-) > > diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c > index abf4f01..b5c9e33 100644 > --- a/fs/proc/vmcore.c > +++ b/fs/proc/vmcore.c > @@ -251,8 +251,7 @@ static u64 __init get_vmcore_size_elf32(char *elfptr) > static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, > struct list_head *vc_list) > { > - int i, nr_ptnote=0, rc=0; > - char *tmp; > + int i, j, nr_ptnote=0, i_ptnote, rc=0; After applying the patch, there are two "j" defined. 251 static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, 252 struct list_head *vc_list) 253 { 254 int i, j, nr_ptnote=0, i_ptnote, rc=0; 255 Elf64_Ehdr *ehdr_ptr; 256 Elf64_Phdr phdr, *phdr_ptr; 257 Elf64_Nhdr *nhdr_ptr; 258 u64 phdr_sz = 0, note_off; 259 260 ehdr_ptr = (Elf64_Ehdr *)elfptr; 261 phdr_ptr = (Elf64_Phdr*)(elfptr + ehdr_ptr->e_phoff); 262 for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) { 263 int j; 264 void *notes_section; 265 struct vmcore *new; line 254 and 263. > Elf64_Ehdr *ehdr_ptr; > Elf64_Phdr phdr, *phdr_ptr; > Elf64_Nhdr *nhdr_ptr; > @@ -302,6 +301,39 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, > kfree(notes_section); > } > > + if (nr_ptnote == 0) > + goto out; > + > + phdr_ptr = (Elf64_Phdr *)(elfptr + ehdr_ptr->e_phoff); > + > + /* Remove unwanted PT_NOTE program headers. */ > + > + /* - 1st pass shifts non-PT_NOTE entries until the first > + PT_NOTE entry. */ > + i_ptnote = -1; > + for (i = 0; i < ehdr_ptr->e_phnum; ++i) { > + if (phdr_ptr[i].p_type == PT_NOTE) { > + i_ptnote = i; > + break; > + } > + } > + BUG_ON(i_ptnote == -1); /* impossible case since nr_ptnote > 0. */ > + memmove(phdr_ptr + 1, phdr_ptr, i_ptnote * sizeof(Elf64_Phdr)); is there any problem with this move? What is the batch bytes for every loop of memmove? if i_ptnode == 2, so we have ------------------------------------- | PT_LOAD 1 | PT_LOAD 2 | PT_NOTE 1 | ------------------------------------- --> ------------------------------------- | | PT_LOAD 1 | PT_LOAD 2 | ------------------------------------- right? In the move, Does PT_LOAD 1 overwrite the original PT_LOAD 2? > + > + /* - 2nd pass moves the remaining non-PT_NOTE entries under > + the first PT_NOTE entry. */ > + for (i = j = i_ptnote + 1; i < ehdr_ptr->e_phnum; i++) { > + if (phdr_ptr[i].p_type != PT_NOTE) { > + memmove(phdr_ptr + j, phdr_ptr + i, > + sizeof(Elf64_Phdr)); > + j++; > + } > + } > + > + /* - Finally, fill unused part with 0. */ > + memset(phdr_ptr + ehdr_ptr->e_phnum - (nr_ptnote - 1), 0, > + (nr_ptnote - 1) * sizeof(Elf64_Phdr)); > + > /* Prepare merged PT_NOTE program header. */ > phdr.p_type = PT_NOTE; > phdr.p_flags = 0; > @@ -313,18 +345,14 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, > phdr.p_align = 0; > > /* Add merged PT_NOTE program header*/ > - tmp = elfptr + ehdr_ptr->e_phoff; > - memcpy(tmp, &phdr, sizeof(phdr)); > - tmp += sizeof(phdr); > + memcpy(phdr_ptr, &phdr, sizeof(Elf64_Phdr)); > > - /* Remove unwanted PT_NOTE program headers. */ > - i = (nr_ptnote - 1) * sizeof(Elf64_Phdr); > - *elfsz = *elfsz - i; > - memmove(tmp, tmp+i, ((*elfsz)-ehdr_ptr->e_phoff-sizeof(Elf64_Phdr))); > + *elfsz = *elfsz - (nr_ptnote - 1) * sizeof(Elf64_Phdr); > > /* Modify e_phnum to reflect merged headers. */ > ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1; > > +out: > return 0; > } > > @@ -332,8 +360,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, > static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz, > struct list_head *vc_list) > { > - int i, nr_ptnote=0, rc=0; > - char *tmp; > + int i, j, nr_ptnote=0, i_ptnote, rc=0; > Elf32_Ehdr *ehdr_ptr; > Elf32_Phdr phdr, *phdr_ptr; > Elf32_Nhdr *nhdr_ptr; > @@ -383,6 +410,39 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz, > kfree(notes_section); > } > > + if (nr_ptnote == 0) > + goto out; > + > + phdr_ptr = (Elf32_Phdr *)(elfptr + ehdr_ptr->e_phoff); > + > + /* Remove unwanted PT_NOTE program headers. */ > + > + /* - 1st pass shifts non-PT_NOTE entries until the first > + PT_NOTE entry. */ > + i_ptnote = -1; > + for (i = 0; i < ehdr_ptr->e_phnum; ++i) { > + if (phdr_ptr[i].p_type == PT_NOTE) { > + i_ptnote = i; > + break; > + } > + } > + BUG_ON(i_ptnote == -1); /* impossible case since nr_ptnote > 0. */ > + memmove(phdr_ptr + 1, phdr_ptr, i_ptnote * sizeof(Elf32_Phdr)); > + > + /* - 2nd pass moves the remaining non-PT_NOTE entries under > + the first PT_NOTE entry. */ > + for (i = j = i_ptnote + 1; i < ehdr_ptr->e_phnum; i++) { > + if (phdr_ptr[i].p_type != PT_NOTE) { > + memmove(phdr_ptr + j, phdr_ptr + i, > + sizeof(Elf32_Phdr)); > + j++; > + } > + } > + > + /* - Finally, fill unused part with 0. */ > + memset(phdr_ptr + ehdr_ptr->e_phnum - (nr_ptnote - 1), 0, > + (nr_ptnote - 1) * sizeof(Elf32_Phdr)); > + > /* Prepare merged PT_NOTE program header. */ > phdr.p_type = PT_NOTE; > phdr.p_flags = 0; > @@ -394,18 +454,14 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz, > phdr.p_align = 0; > > /* Add merged PT_NOTE program header*/ > - tmp = elfptr + ehdr_ptr->e_phoff; > - memcpy(tmp, &phdr, sizeof(phdr)); > - tmp += sizeof(phdr); > + memcpy(phdr_ptr, &phdr, sizeof(Elf32_Phdr)); > > - /* Remove unwanted PT_NOTE program headers. */ > - i = (nr_ptnote - 1) * sizeof(Elf32_Phdr); > - *elfsz = *elfsz - i; > - memmove(tmp, tmp+i, ((*elfsz)-ehdr_ptr->e_phoff-sizeof(Elf32_Phdr))); > + *elfsz = *elfsz - (nr_ptnote - 1) * sizeof(Elf32_Phdr); > > /* Modify e_phnum to reflect merged headers. */ > ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1; > > +out: > return 0; > } > > > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/