From: Xunlei Pang <xpang@redhat.com> To: Baoquan He <bhe@redhat.com>, xlpang@redhat.com Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org, akpm@linux-foundation.org, Eric Biederman <ebiederm@xmission.com>, Dave Young <dyoung@redhat.com> Subject: Re: [PATCH] kexec: Update vmcoreinfo after crash happened Date: Thu, 16 Mar 2017 21:40:58 +0800 [thread overview] Message-ID: <58CA95EA.1040807@redhat.com> (raw) In-Reply-To: <20170316131809.GC23625@x1> On 03/16/2017 at 09:18 PM, Baoquan He wrote: > On 03/16/17 at 08:36pm, Xunlei Pang wrote: >> On 03/16/2017 at 08:27 PM, Baoquan He wrote: >>> Hi Xunlei, >>> >>> Did you really see this ever happened? Because the vmcore size estimate >>> feature, namely --mem-usage option of makedumpfile, depends on the >>> vmcoreinfo in 1st kernel, your change will break it. >> Hi Baoquan, >> >> I can reproduce it using a kernel module which modifies the vmcoreinfo, >> so it's a problem can actually happen. >> >>> If not, it could be not good to change that. >> That's a good point, then I guess we can keep the crash_save_vmcoreinfo_init(), >> and store again all the vmcoreinfo after crash. What do you think? > Well, then it will make makedumpfile segfault happen too when execute > below command in 1st kernel if it existed: > makedumpfile --mem-usage /proc/kcore Yes, if the initial vmcoreinfo data was modified before "makedumpfile --mem-usage", it might happen, after all the system is going something wrong. And that's why we deploy kdump service at the very beginning when the system has a low possibility of going wrong. But we have to guarantee kdump vmcore can be generated correctly as possible as it can. > > So we still need to face that problem and need fix it. vmcoreinfo_note > is in kernel data area, how does module intrude into this area? And can > we fix the module code? > Bugs always exist in products, we can't know what will happen and fix all the errors, that's why we need kdump. I think the following update should guarantee the correct vmcoreinfo for kdump. --- kernel/kexec_core.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index bfe62d5..0f7b328 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -1367,12 +1367,6 @@ static void update_vmcoreinfo_note(void) final_note(buf); } -void crash_save_vmcoreinfo(void) -{ - vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds()); - update_vmcoreinfo_note(); -} - void vmcoreinfo_append_str(const char *fmt, ...) { va_list args; @@ -1402,7 +1396,7 @@ phys_addr_t __weak paddr_vmcoreinfo_note(void) return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note); } -static int __init crash_save_vmcoreinfo_init(void) +static void do_crash_save_vmcoreinfo_init(void) { VMCOREINFO_OSRELEASE(init_uts_ns.name.release); VMCOREINFO_PAGESIZE(PAGE_SIZE); @@ -1474,6 +1468,20 @@ static int __init crash_save_vmcoreinfo_init(void) #endif arch_crash_save_vmcoreinfo(); +} + +void crash_save_vmcoreinfo(void) +{ + /* Save again to protect vmcoreinfo from being modified */ + vmcoreinfo_size = 0; + do_crash_save_vmcoreinfo_init(); + vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds()); + update_vmcoreinfo_note(); +} + +static int __init crash_save_vmcoreinfo_init(void) +{ + do_crash_save_vmcoreinfo_init(); update_vmcoreinfo_note(); return 0; -- 1.8.3.1
WARNING: multiple messages have this Message-ID (diff)
From: Xunlei Pang <xpang@redhat.com> To: Baoquan He <bhe@redhat.com>, xlpang@redhat.com Cc: Dave Young <dyoung@redhat.com>, akpm@linux-foundation.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Eric Biederman <ebiederm@xmission.com> Subject: Re: [PATCH] kexec: Update vmcoreinfo after crash happened Date: Thu, 16 Mar 2017 21:40:58 +0800 [thread overview] Message-ID: <58CA95EA.1040807@redhat.com> (raw) In-Reply-To: <20170316131809.GC23625@x1> On 03/16/2017 at 09:18 PM, Baoquan He wrote: > On 03/16/17 at 08:36pm, Xunlei Pang wrote: >> On 03/16/2017 at 08:27 PM, Baoquan He wrote: >>> Hi Xunlei, >>> >>> Did you really see this ever happened? Because the vmcore size estimate >>> feature, namely --mem-usage option of makedumpfile, depends on the >>> vmcoreinfo in 1st kernel, your change will break it. >> Hi Baoquan, >> >> I can reproduce it using a kernel module which modifies the vmcoreinfo, >> so it's a problem can actually happen. >> >>> If not, it could be not good to change that. >> That's a good point, then I guess we can keep the crash_save_vmcoreinfo_init(), >> and store again all the vmcoreinfo after crash. What do you think? > Well, then it will make makedumpfile segfault happen too when execute > below command in 1st kernel if it existed: > makedumpfile --mem-usage /proc/kcore Yes, if the initial vmcoreinfo data was modified before "makedumpfile --mem-usage", it might happen, after all the system is going something wrong. And that's why we deploy kdump service at the very beginning when the system has a low possibility of going wrong. But we have to guarantee kdump vmcore can be generated correctly as possible as it can. > > So we still need to face that problem and need fix it. vmcoreinfo_note > is in kernel data area, how does module intrude into this area? And can > we fix the module code? > Bugs always exist in products, we can't know what will happen and fix all the errors, that's why we need kdump. I think the following update should guarantee the correct vmcoreinfo for kdump. --- kernel/kexec_core.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index bfe62d5..0f7b328 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -1367,12 +1367,6 @@ static void update_vmcoreinfo_note(void) final_note(buf); } -void crash_save_vmcoreinfo(void) -{ - vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds()); - update_vmcoreinfo_note(); -} - void vmcoreinfo_append_str(const char *fmt, ...) { va_list args; @@ -1402,7 +1396,7 @@ phys_addr_t __weak paddr_vmcoreinfo_note(void) return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note); } -static int __init crash_save_vmcoreinfo_init(void) +static void do_crash_save_vmcoreinfo_init(void) { VMCOREINFO_OSRELEASE(init_uts_ns.name.release); VMCOREINFO_PAGESIZE(PAGE_SIZE); @@ -1474,6 +1468,20 @@ static int __init crash_save_vmcoreinfo_init(void) #endif arch_crash_save_vmcoreinfo(); +} + +void crash_save_vmcoreinfo(void) +{ + /* Save again to protect vmcoreinfo from being modified */ + vmcoreinfo_size = 0; + do_crash_save_vmcoreinfo_init(); + vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds()); + update_vmcoreinfo_note(); +} + +static int __init crash_save_vmcoreinfo_init(void) +{ + do_crash_save_vmcoreinfo_init(); update_vmcoreinfo_note(); return 0; -- 1.8.3.1 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
next prev parent reply other threads:[~2017-03-16 13:38 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-03-16 12:16 [PATCH] kexec: Update vmcoreinfo after crash happened Xunlei Pang 2017-03-16 12:16 ` Xunlei Pang 2017-03-16 12:27 ` Baoquan He 2017-03-16 12:27 ` Baoquan He 2017-03-16 12:36 ` Xunlei Pang 2017-03-16 12:36 ` Xunlei Pang 2017-03-16 13:18 ` Baoquan He 2017-03-16 13:18 ` Baoquan He 2017-03-16 13:40 ` Xunlei Pang [this message] 2017-03-16 13:40 ` Xunlei Pang 2017-03-18 18:23 ` Petr Tesarik 2017-03-18 18:23 ` Petr Tesarik 2017-03-20 2:17 ` Xunlei Pang 2017-03-20 2:17 ` Xunlei Pang 2017-03-20 13:04 ` Petr Tesarik 2017-03-20 13:04 ` Petr Tesarik 2017-03-20 19:15 ` Eric W. Biederman 2017-03-20 19:15 ` Eric W. Biederman 2017-03-21 2:05 ` Xunlei Pang 2017-03-21 2:05 ` Xunlei Pang
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