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Message-ID: <b3f3a4e5-35e7-2cb4-f754-f425da094f28@oracle.com>
Date: Thu, 12 Jan 2023 11:23:18 -0600
From: Eric DeVolder <eric.devolder@...cle.com>
To: Sourabh Jain <sourabhjain@...ux.ibm.com>,
linux-kernel@...r.kernel.org, x86@...nel.org,
kexec@...ts.infradead.org, ebiederm@...ssion.com,
dyoung@...hat.com, bhe@...hat.com, vgoyal@...hat.com
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, hpa@...or.com,
nramas@...ux.microsoft.com, thomas.lendacky@....com,
robh@...nel.org, efault@....de, rppt@...nel.org, david@...hat.com,
konrad.wilk@...cle.com, boris.ostrovsky@...cle.com
Subject: Re: [PATCH v15 1/7] crash: move crash_prepare_elf64_headers()
On 1/8/23 23:05, Sourabh Jain wrote:
>
> On 09/12/22 21:06, Eric DeVolder wrote:
>> At the outcome of this patch set, the crash_prepare_elf64_headers()
>> is utilized on both the kexec_file_load() and kexec_load() paths. As
>> such, need to move this function out of kexec_file.c and into a
>> common location crash_core.c.
>>
>> No functionality change.
>>
>> Signed-off-by: Eric DeVolder <eric.devolder@...cle.com>
>> Acked-by: Baoquan He <bhe@...hat.com>
>> ---
>> kernel/crash_core.c | 100 ++++++++++++++++++++++++++++++++++++++++++++
>> kernel/kexec_file.c | 99 -------------------------------------------
>> 2 files changed, 100 insertions(+), 99 deletions(-)
>>
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index a0eb4d5cf557..46c160d14045 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -10,6 +10,7 @@
>> #include <linux/utsname.h>
>> #include <linux/vmalloc.h>
>> #include <linux/sizes.h>
>> +#include <linux/kexec.h>
>> #include <asm/page.h>
>> #include <asm/sections.h>
>> @@ -314,6 +315,105 @@ static int __init parse_crashkernel_dummy(char *arg)
>> }
>> early_param("crashkernel", parse_crashkernel_dummy);
>> +int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
>> + void **addr, unsigned long *sz)
>> +{
>> + Elf64_Ehdr *ehdr;
>> + Elf64_Phdr *phdr;
>> + unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
>> + unsigned char *buf;
>> + unsigned int cpu, i;
>> + unsigned long long notes_addr;
>> + unsigned long mstart, mend;
>> +
>> + /* extra phdr for vmcoreinfo ELF note */
>> + nr_phdr = nr_cpus + 1;
>> + nr_phdr += mem->nr_ranges;
>> +
>> + /*
>> + * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping
>> + * area (for example, ffffffff80000000 - ffffffffa0000000 on x86_64).
>> + * I think this is required by tools like gdb. So same physical
>> + * memory will be mapped in two ELF headers. One will contain kernel
>> + * text virtual addresses and other will have __va(physical) addresses.
>> + */
>> +
>> + nr_phdr++;
>> + elf_sz = sizeof(Elf64_Ehdr) + nr_phdr * sizeof(Elf64_Phdr);
>> + elf_sz = ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN);
> Seems like above function is out of CONFIG_KEXEC_FILE but some of the
> structure/attributes like crash_mem and ELF_CORE_HEADER_ALIGN are
> still defined under CONFIG_KEXEC_FILE (look for include/linux/kexec.h).
>
> This leads to kernel build issue when CONFIG_KEXEC_FILE is disabled.
>
> Thanks,
> Sourabh Jain
After looking into this for a bit, to allow hotplug without kexec_file would require quite a bit of
code movement. Why? Because hotplug is basically built on top of (part of) the infrastructure that
was needed for kexec_file.
I'd be inclined to suggest that KEXEC_FILE be a required dependency for CRASH_HOTPLUG, ie:
config CRASH_HOTPLUG
bool "Update the crash elfcorehdr on system configuration changes"
default n
- depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG)
+ depends on CRASH_DUMP && KEXEC_FILE && (HOTPLUG_CPU || MEMORY_HOTPLUG)
If that isn't feasible, then it would appear quite a bit of surgery is needed to properly separate
out the items hotplug needs from kexec_file.
Thoughts?
eric
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