Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753950Ab3F0Tck (ORCPT ); Thu, 27 Jun 2013 15:32:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:17520 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752622Ab3F0Tcj (ORCPT ); Thu, 27 Jun 2013 15:32:39 -0400 Date: Thu, 27 Jun 2013 15:32:02 -0400 From: Vivek Goyal To: Michael Holzheu Cc: HATAYAMA Daisuke , Jan Willeke , Martin Schwidefsky , Heiko Carstens , linux-kernel@vger.kernel.org, kexec@lists.infradead.org Subject: Re: [PATCH v5 1/5] vmcore: Introduce ELF header in new memory feature Message-ID: <20130627193202.GK4899@redhat.com> References: <1370624161-2298-1-git-send-email-holzheu@linux.vnet.ibm.com> <1370624161-2298-2-git-send-email-holzheu@linux.vnet.ibm.com> <20130614185401.GL12023@redhat.com> <20130621161703.751b5f23@holzheu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130621161703.751b5f23@holzheu> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8069 Lines: 240 On Fri, Jun 21, 2013 at 04:17:03PM +0200, Michael Holzheu wrote: > On Fri, 14 Jun 2013 14:54:02 -0400 > Vivek Goyal wrote: > > > On Fri, Jun 07, 2013 at 06:55:57PM +0200, Michael Holzheu wrote: > > > > [..] > > > @@ -935,10 +967,17 @@ static int __init vmcore_init(void) > > > { > > > int rc = 0; > > > > > > - /* If elfcorehdr= has been passed in cmdline, then capture the dump.*/ > > > - if (!(is_vmcore_usable())) > > > - return rc; > > > + /* > > > + * If elfcorehdr= has not been passed in cmdline, try to get the > > > + * header from 2nd kernel, then capture the dump. > > > + */ > > > + if (!(is_vmcore_usable())) { > > > + rc = elfcorehdr_alloc(); > > > + if (rc) > > > + return rc; > > > + } > > > > Hi Michael, > > > > Patch description says that elfcorehdr_alloc() returns the addr and > > size of elf headers. But that does not seem to be the case here. Has > > it been modified in later patches. > > Sorry, that is a relict of one of my previous experiments where I tried > to implement elfcorehdr_addr() similar to the way as you suggest it now. > Because elfcorehdr_addr is a global variable, I decided to not pass > it in the functions. But of course I can change that again if you prefer > that. > > > Also will it be better if we call elfcorehdr_alloc() always and then > > check for is_vmcore_usable(). > > > > Something like. > > > > elfcorehdr_addr = elfcorehdr_alloc() > > if (elfcorehdr_addr < ) > > return elfcorehdr_addr > > > > if (!(is_vmcore_usable())) > > return error > > Ok, but then I think elfcorehdr_alloc() should also return > the elfcorehdr_size. > > So what about the following patch: This patch looks good to me. There are little ugly pieces w.r.t not setting elfcorehdr_addr null after calling free() as there are other pieces depdendent on elfcorehdr_addr. I think sometime later we can have a separate variable to track track whether this is kdump kernel and remove dependency on elfcorehdr_addr being set. So I am fine with this patch. Vivek > --- > fs/proc/vmcore.c | 65 +++++++++++++++++++++++++++++++++++++-------- > include/linux/crash_dump.h | 6 ++++ > 2 files changed, 60 insertions(+), 11 deletions(-) > > --- a/fs/proc/vmcore.c > +++ b/fs/proc/vmcore.c > @@ -123,6 +123,36 @@ static ssize_t read_from_oldmem(char *bu > return read; > } > > +/* > + * Architectures may override this function to allocate ELF header in 2nd kernel > + */ > +int __weak elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size) > +{ > + return 0; > +} > + > +/* > + * Architectures may override this function to free header > + */ > +void __weak elfcorehdr_free(unsigned long long addr) > +{} > + > +/* > + * Architectures may override this function to read from ELF header > + */ > +ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos) > +{ > + return read_from_oldmem(buf, count, ppos, 0); > +} > + > +/* > + * Architectures may override this function to read from notes sections > + */ > +ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos) > +{ > + return read_from_oldmem(buf, count, ppos, 0); > +} > + > /* Read from the ELF header and then the crash dump. On error, negative value is > * returned otherwise number of bytes read are returned. > */ > @@ -322,7 +352,7 @@ static int __init update_note_header_siz > notes_section = kmalloc(max_sz, GFP_KERNEL); > if (!notes_section) > return -ENOMEM; > - rc = read_from_oldmem(notes_section, max_sz, &offset, 0); > + rc = elfcorehdr_read_notes(notes_section, max_sz, &offset); > if (rc < 0) { > kfree(notes_section); > return rc; > @@ -409,7 +439,8 @@ static int __init copy_notes_elf64(const > if (phdr_ptr->p_type != PT_NOTE) > continue; > offset = phdr_ptr->p_offset; > - rc = read_from_oldmem(notes_buf, phdr_ptr->p_memsz, &offset, 0); > + rc = elfcorehdr_read_notes(notes_buf, phdr_ptr->p_memsz, > + &offset); > if (rc < 0) > return rc; > notes_buf += phdr_ptr->p_memsz; > @@ -510,7 +541,7 @@ static int __init update_note_header_siz > notes_section = kmalloc(max_sz, GFP_KERNEL); > if (!notes_section) > return -ENOMEM; > - rc = read_from_oldmem(notes_section, max_sz, &offset, 0); > + rc = elfcorehdr_read_notes(notes_section, max_sz, &offset); > if (rc < 0) { > kfree(notes_section); > return rc; > @@ -597,7 +628,8 @@ static int __init copy_notes_elf32(const > if (phdr_ptr->p_type != PT_NOTE) > continue; > offset = phdr_ptr->p_offset; > - rc = read_from_oldmem(notes_buf, phdr_ptr->p_memsz, &offset, 0); > + rc = elfcorehdr_read_notes(notes_buf, phdr_ptr->p_memsz, > + &offset); > if (rc < 0) > return rc; > notes_buf += phdr_ptr->p_memsz; > @@ -793,7 +825,7 @@ static int __init parse_crash_elf64_head > addr = elfcorehdr_addr; > > /* Read Elf header */ > - rc = read_from_oldmem((char*)&ehdr, sizeof(Elf64_Ehdr), &addr, 0); > + rc = elfcorehdr_read((char *)&ehdr, sizeof(Elf64_Ehdr), &addr); > if (rc < 0) > return rc; > > @@ -820,7 +852,7 @@ static int __init parse_crash_elf64_head > if (!elfcorebuf) > return -ENOMEM; > addr = elfcorehdr_addr; > - rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz_orig, &addr, 0); > + rc = elfcorehdr_read(elfcorebuf, elfcorebuf_sz_orig, &addr); > if (rc < 0) > goto fail; > > @@ -849,7 +881,7 @@ static int __init parse_crash_elf32_head > addr = elfcorehdr_addr; > > /* Read Elf header */ > - rc = read_from_oldmem((char*)&ehdr, sizeof(Elf32_Ehdr), &addr, 0); > + rc = elfcorehdr_read((char *)&ehdr, sizeof(Elf32_Ehdr), &addr); > if (rc < 0) > return rc; > > @@ -875,7 +907,7 @@ static int __init parse_crash_elf32_head > if (!elfcorebuf) > return -ENOMEM; > addr = elfcorehdr_addr; > - rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz_orig, &addr, 0); > + rc = elfcorehdr_read(elfcorebuf, elfcorebuf_sz_orig, &addr); > if (rc < 0) > goto fail; > > @@ -902,7 +934,7 @@ static int __init parse_crash_elf_header > int rc=0; > > addr = elfcorehdr_addr; > - rc = read_from_oldmem(e_ident, EI_NIDENT, &addr, 0); > + rc = elfcorehdr_read(e_ident, EI_NIDENT, &addr); > if (rc < 0) > return rc; > if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) { > @@ -935,7 +967,14 @@ static int __init vmcore_init(void) > { > int rc = 0; > > - /* If elfcorehdr= has been passed in cmdline, then capture the dump.*/ > + /* Allow architectures to allocate ELF header in 2nd kernel */ > + rc = elfcorehdr_alloc(&elfcorehdr_addr, &elfcorehdr_size); > + if (rc) > + return rc; > + /* > + * If elfcorehdr= has been passed in cmdline or created in 2nd kernel, > + * then capture the dump. > + */ > if (!(is_vmcore_usable())) > return rc; > rc = parse_crash_elf_headers(); > @@ -943,7 +982,11 @@ static int __init vmcore_init(void) > pr_warn("Kdump: vmcore not initialized\n"); > return rc; > } > - > + elfcorehdr_free(elfcorehdr_addr); > + /* > + * elfcorehdr_addr must not be set to NULL here to keep > + * is_kdump_kernel() working. > + */ > proc_vmcore = proc_create("vmcore", S_IRUSR, NULL, &proc_vmcore_operations); > if (proc_vmcore) > proc_vmcore->size = vmcore_size; > --- a/include/linux/crash_dump.h > +++ b/include/linux/crash_dump.h > @@ -12,6 +12,12 @@ > extern unsigned long long elfcorehdr_addr; > extern unsigned long long elfcorehdr_size; > > +extern int __weak elfcorehdr_alloc(unsigned long long *addr, > + unsigned long long *size); > +extern void __weak elfcorehdr_free(unsigned long long addr); > +extern ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos); > +extern ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos); > + > extern ssize_t copy_oldmem_page(unsigned long, char *, size_t, > unsigned long, int); > -- 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/