This patch is dependent upon the patch 'crash: change
crash_prepare_elf64_headers() to for_each_possible_cpu()'. With that
patch, crash_prepare_elf64_headers() writes out an ELF cpu PT_NOTE
for all possible cpus, thus further cpu changes to the elfcorehdr
are not needed.
This change works for kexec_file_load() and kexec_load() syscalls.
For kexec_file_load(), crash_prepare_elf64_headers() is utilized
directly and thus all ELF cpu PT_NOTEs are in the elfcorehdr already.
This is the kimage->file_mode term.
For kexec_load() syscall, one cpu or memory change will cause the
elfcorehdr to be updated via crash_prepare_elf64_headers() and at
that point all ELF cpu PT_NOTEs are in the elfcorehdr. This is the
kimage->elfcorehdr_updated term.
This code is intentionally *NOT* hoisted into
crash_handle_hotplug_event() as it would prevent the arch-specific
handler from running for cpu changes. This would break PPC, for
example, which needs to update other information besides the
elfcorehdr, on cpu changes.
Signed-off-by: Eric DeVolder <[email protected]>
---
arch/x86/kernel/crash.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index c9aaec9de775..82ea2b1bdc61 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -471,6 +471,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image)
unsigned long mem, memsz;
unsigned long elfsz = 0;
+ /* As crash_prepare_elf64_headers() has already described all
+ * possible cpus, there is no need to update the elfcorehdr
+ * for additional cpu changes. This works for both kexec_load()
+ * and kexec_file_load() syscalls.
+ */
+ if ((image->file_mode || image->elfcorehdr_updated) &&
+ ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
+ (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
+ return;
+
/*
* Create the new elfcorehdr reflecting the changes to CPU and/or
* memory resources.
--
2.31.1
On 06/03/23 21:52, Eric DeVolder wrote:
> This patch is dependent upon the patch 'crash: change
> crash_prepare_elf64_headers() to for_each_possible_cpu()'. With that
> patch, crash_prepare_elf64_headers() writes out an ELF cpu PT_NOTE
> for all possible cpus, thus further cpu changes to the elfcorehdr
> are not needed.
>
> This change works for kexec_file_load() and kexec_load() syscalls.
> For kexec_file_load(), crash_prepare_elf64_headers() is utilized
> directly and thus all ELF cpu PT_NOTEs are in the elfcorehdr already.
> This is the kimage->file_mode term.
> For kexec_load() syscall, one cpu or memory change will cause the
> elfcorehdr to be updated via crash_prepare_elf64_headers() and at
> that point all ELF cpu PT_NOTEs are in the elfcorehdr. This is the
> kimage->elfcorehdr_updated term.
>
> This code is intentionally *NOT* hoisted into
> crash_handle_hotplug_event() as it would prevent the arch-specific
> handler from running for cpu changes. This would break PPC, for
> example, which needs to update other information besides the
> elfcorehdr, on cpu changes.
>
> Signed-off-by: Eric DeVolder <[email protected]>
> ---
> arch/x86/kernel/crash.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index c9aaec9de775..82ea2b1bdc61 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -471,6 +471,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image)
> unsigned long mem, memsz;
> unsigned long elfsz = 0;
>
> + /* As crash_prepare_elf64_headers() has already described all
> + * possible cpus, there is no need to update the elfcorehdr
> + * for additional cpu changes. This works for both kexec_load()
> + * and kexec_file_load() syscalls.
> + */
> + if ((image->file_mode || image->elfcorehdr_updated) &&
> + ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
> + (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
> + return;
I like the idea of having elfcorehdr_updated to track elfcoredhr segment
updates.
It handles the possible CPU thing for kexec_load syscall nicely.
Thanks for incorporating the possible CPU change.
The patch series looks good to me.
Reviewed-by: Sourabh Jain <[email protected]>
- Sourabh Jain
On 3/7/23 03:00, Sourabh Jain wrote:
>
> On 06/03/23 21:52, Eric DeVolder wrote:
>> This patch is dependent upon the patch 'crash: change
>> crash_prepare_elf64_headers() to for_each_possible_cpu()'. With that
>> patch, crash_prepare_elf64_headers() writes out an ELF cpu PT_NOTE
>> for all possible cpus, thus further cpu changes to the elfcorehdr
>> are not needed.
>>
>> This change works for kexec_file_load() and kexec_load() syscalls.
>> For kexec_file_load(), crash_prepare_elf64_headers() is utilized
>> directly and thus all ELF cpu PT_NOTEs are in the elfcorehdr already.
>> This is the kimage->file_mode term.
>> For kexec_load() syscall, one cpu or memory change will cause the
>> elfcorehdr to be updated via crash_prepare_elf64_headers() and at
>> that point all ELF cpu PT_NOTEs are in the elfcorehdr. This is the
>> kimage->elfcorehdr_updated term.
>>
>> This code is intentionally *NOT* hoisted into
>> crash_handle_hotplug_event() as it would prevent the arch-specific
>> handler from running for cpu changes. This would break PPC, for
>> example, which needs to update other information besides the
>> elfcorehdr, on cpu changes.
>>
>> Signed-off-by: Eric DeVolder <[email protected]>
>> ---
>> arch/x86/kernel/crash.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
>> index c9aaec9de775..82ea2b1bdc61 100644
>> --- a/arch/x86/kernel/crash.c
>> +++ b/arch/x86/kernel/crash.c
>> @@ -471,6 +471,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image)
>> unsigned long mem, memsz;
>> unsigned long elfsz = 0;
>> + /* As crash_prepare_elf64_headers() has already described all
>> + * possible cpus, there is no need to update the elfcorehdr
>> + * for additional cpu changes. This works for both kexec_load()
>> + * and kexec_file_load() syscalls.
>> + */
>> + if ((image->file_mode || image->elfcorehdr_updated) &&
>> + ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
>> + (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
>> + return;
>
> I like the idea of having elfcorehdr_updated to track elfcoredhr segment updates.
> It handles the possible CPU thing for kexec_load syscall nicely.
>
> Thanks for incorporating the possible CPU change.
>
> The patch series looks good to me.
> Reviewed-by: Sourabh Jain <[email protected]>
>
> - Sourabh Jain
>
Thanks for the RB! Look for v20 very soon.
eric