From: Eric DeVolder <eric.devolder@oracle.com> To: linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, bhe@redhat.com, vgoyal@redhat.com Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, eric.devolder@oracle.com Subject: [PATCH v4 10/10] crash hp: Add x86 crash hotplug support for kexec_load Date: Wed, 9 Feb 2022 14:57:06 -0500 [thread overview] Message-ID: <20220209195706.51522-11-eric.devolder@oracle.com> (raw) In-Reply-To: <20220209195706.51522-1-eric.devolder@oracle.com> For kexec_file_load support, the loading of the crash kernel occurs entirely within the kernel, and as such the elfcorehdr is readily identified (so that it can be modified upon hotplug events). This change enables support for kexec_load by identifying the elfcorehdr segment in the arch_crash_hotplug_handler(), if it has not already been identified. In general, support for kexec_load requires corresponding changes to the userspace kexec-tools utility. It is the responsibility of the userspace kexec utility to ensure that: - the elfcorehdr segment is sufficiently large enough to accommodate hotplug changes, ala CRASH_HOTPLUG_ELFCOREHDR_SZ. - provides a purgatory that excludes the elfcorehdr from its list of run-time segments to check. These changes to the userspace kexec utility are available, but not yet accepted upstream. Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> --- arch/x86/kernel/crash.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 6215c51919db..1b3e5e4fb965 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -458,6 +458,32 @@ void arch_crash_hotplug_handler(struct kimage *image, void *elfbuf = NULL; unsigned long mem, memsz; + /* + * When the struct kimage is alloced, it is wiped to zero, so + * the elf_index_valid defaults to false. It is set on the + * kexec_file_load path, or here for kexec_load. + */ + if (!image->elf_index_valid) { + unsigned int n; + + for (n = 0; n < image->nr_segments; n++) { + mem = image->segment[n].mem; + memsz = image->segment[n].memsz; + ptr = map_crash_pages(mem, memsz); + if (ptr) { + /* The segment containing elfcorehdr */ + if ((ptr[0] == 0x7F) && + (ptr[1] == 'E') && + (ptr[2] == 'L') && + (ptr[3] == 'F')) { + image->elf_index = (int)n; + image->elf_index_valid = true; + } + } + unmap_crash_pages((void **)&ptr); + } + } + /* Must have valid elfcorehdr index */ if (!image->elf_index_valid) { pr_err("crash hp: unable to locate elfcorehdr segment"); -- 2.27.0
WARNING: multiple messages have this Message-ID (diff)
From: Eric DeVolder <eric.devolder@oracle.com> To: kexec@lists.infradead.org Subject: [PATCH v4 10/10] crash hp: Add x86 crash hotplug support for kexec_load Date: Wed, 9 Feb 2022 14:57:06 -0500 [thread overview] Message-ID: <20220209195706.51522-11-eric.devolder@oracle.com> (raw) In-Reply-To: <20220209195706.51522-1-eric.devolder@oracle.com> For kexec_file_load support, the loading of the crash kernel occurs entirely within the kernel, and as such the elfcorehdr is readily identified (so that it can be modified upon hotplug events). This change enables support for kexec_load by identifying the elfcorehdr segment in the arch_crash_hotplug_handler(), if it has not already been identified. In general, support for kexec_load requires corresponding changes to the userspace kexec-tools utility. It is the responsibility of the userspace kexec utility to ensure that: - the elfcorehdr segment is sufficiently large enough to accommodate hotplug changes, ala CRASH_HOTPLUG_ELFCOREHDR_SZ. - provides a purgatory that excludes the elfcorehdr from its list of run-time segments to check. These changes to the userspace kexec utility are available, but not yet accepted upstream. Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> --- arch/x86/kernel/crash.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 6215c51919db..1b3e5e4fb965 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -458,6 +458,32 @@ void arch_crash_hotplug_handler(struct kimage *image, void *elfbuf = NULL; unsigned long mem, memsz; + /* + * When the struct kimage is alloced, it is wiped to zero, so + * the elf_index_valid defaults to false. It is set on the + * kexec_file_load path, or here for kexec_load. + */ + if (!image->elf_index_valid) { + unsigned int n; + + for (n = 0; n < image->nr_segments; n++) { + mem = image->segment[n].mem; + memsz = image->segment[n].memsz; + ptr = map_crash_pages(mem, memsz); + if (ptr) { + /* The segment containing elfcorehdr */ + if ((ptr[0] == 0x7F) && + (ptr[1] == 'E') && + (ptr[2] == 'L') && + (ptr[3] == 'F')) { + image->elf_index = (int)n; + image->elf_index_valid = true; + } + } + unmap_crash_pages((void **)&ptr); + } + } + /* Must have valid elfcorehdr index */ if (!image->elf_index_valid) { pr_err("crash hp: unable to locate elfcorehdr segment"); -- 2.27.0
next prev parent reply other threads:[~2022-02-09 20:03 UTC|newest] Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-02-09 19:56 [PATCH v4 00/10] crash: Kernel handling of CPU and memory hot un/plug Eric DeVolder 2022-02-09 19:56 ` Eric DeVolder 2022-02-09 19:56 ` [PATCH v4 01/10] crash: fix minor typo/bug in debug message Eric DeVolder 2022-02-09 19:56 ` Eric DeVolder 2022-02-09 19:56 ` [PATCH v4 02/10] crash hp: Introduce CRASH_HOTPLUG configuration options Eric DeVolder 2022-02-09 19:56 ` Eric DeVolder 2022-02-23 3:25 ` Baoquan He 2022-02-23 3:25 ` Baoquan He 2022-03-01 20:04 ` Eric DeVolder 2022-03-01 20:04 ` Eric DeVolder 2022-03-02 9:20 ` David Hildenbrand 2022-03-02 9:20 ` David Hildenbrand 2022-03-03 10:22 ` Baoquan He 2022-03-03 10:22 ` Baoquan He 2022-03-03 11:36 ` David Hildenbrand 2022-03-03 11:36 ` David Hildenbrand 2022-03-03 12:08 ` Baoquan He 2022-03-03 12:08 ` Baoquan He 2022-03-03 15:31 ` Eric DeVolder 2022-03-03 15:31 ` Eric DeVolder 2022-02-09 19:56 ` [PATCH v4 03/10] crash hp: definitions and prototype changes Eric DeVolder 2022-02-09 19:56 ` Eric DeVolder 2022-02-23 3:43 ` Baoquan He 2022-02-23 3:43 ` Baoquan He 2022-03-01 20:04 ` Eric DeVolder 2022-03-01 20:04 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 04/10] crash hp: prototype change for crash_prepare_elf64_headers Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 3:46 ` Baoquan He 2022-02-23 3:46 ` Baoquan He 2022-03-01 20:05 ` Eric DeVolder 2022-03-01 20:05 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 05/10] crash hp: introduce helper functions un/map_crash_pages Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 3:58 ` Baoquan He 2022-02-23 3:58 ` Baoquan He 2022-03-01 20:06 ` Eric DeVolder 2022-03-01 20:06 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 06/10] crash hp: generic crash hotplug support infrastructure Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 3:59 ` Baoquan He 2022-02-23 3:59 ` Baoquan He 2022-03-01 20:07 ` Eric DeVolder 2022-03-01 20:07 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 07/10] crash hp: exclude elfcorehdr from the segment digest Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 4:00 ` Baoquan He 2022-02-23 4:00 ` Baoquan He 2022-03-01 20:07 ` Eric DeVolder 2022-03-01 20:07 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 08/10] crash hp: exclude hot remove cpu from elfcorehdr notes Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 4:04 ` Baoquan He 2022-02-23 4:04 ` Baoquan He 2022-03-01 20:08 ` Eric DeVolder 2022-03-01 20:08 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 09/10] crash hp: Add x86 crash hotplug support for kexec_file_load Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 4:10 ` Baoquan He 2022-02-23 4:10 ` Baoquan He 2022-03-01 20:12 ` Eric DeVolder 2022-03-01 20:12 ` Eric DeVolder 2022-03-03 10:27 ` Baoquan He 2022-03-03 10:27 ` Baoquan He 2022-02-09 19:57 ` Eric DeVolder [this message] 2022-02-09 19:57 ` [PATCH v4 10/10] crash hp: Add x86 crash hotplug support for kexec_load Eric DeVolder 2022-02-21 4:08 ` [PATCH v4 00/10] crash: Kernel handling of CPU and memory hot un/plug Baoquan He 2022-02-21 4:08 ` Baoquan He
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