[PATCH] add description for jumping back to the original kernel in man page

[Gi-Oh Kim]

On Thu, Feb 15, 2018 at 7:54 PM, Bhupesh SHARMA <bhupesh.linux at gmail.com> wrote:
> Hi,
>
> Some nitpicks inline..

I thank you again for your review.
I'll send the second version patch soon.

>
> On Thu, Feb 15, 2018 at 5:14 PM, Gioh Kim <gi-oh.kim at profitbricks.com> wrote:
>> "--load-preserve-context", "--load-jump-back-helper" and "--entry"
>> options are described separately but there is not any description
>> how to use them.
>>
>> Signed-off-by: Gioh Kim <gi-oh.kim at profitbricks.com>
>> ---
>>  kexec/kexec.8 | 30 ++++++++++++++++++++++++++++++
>>  1 file changed, 30 insertions(+)
>>
>> diff --git a/kexec/kexec.8 b/kexec/kexec.8
>> index e0131b4..b7ac028 100644
>> --- a/kexec/kexec.8
>> +++ b/kexec/kexec.8
>> @@ -30,6 +30,9 @@ when configuring the kernel. The
>>  option enables the
>>  .B kexec
>>  system call.
>> +After booting into another kernel, you can jump back to the first kernel with enabling
>
> I would suggest using the already prevalent naming conventions - primary kernel
> and secondary kernel for the two kernels.
>
>> +.B CONFIG_KEXEC_JUMP
>> +option (x86 only).
>
> I think this is also supported on sh architecture, so may be you can
> reword this to something like:
> (currently only x86 and sh architectures are supported).
>
>>  .SH USAGE
>>  Using
>>  .B kexec
>> @@ -102,6 +105,30 @@ command:
>>  .BR kexec \ \-e
>>  .RE
>>
>> +After booting the kernel, you can jump back to the first kernel if you enable
>> +.B CONFIG_KEXEC_JUMP
>> +kernel option and specify \-\-load\-preserve\-context option.
>
> Do we need to repeat the details of CONFIG_KEXEC_JUMP here and below,
> as we have already the captured the same above.
>
>> +You can see
>
>                      ^^^ specify (instead of see)
>
>> +.BR "kexec_jump_back_entry=<address>"
>> +kernel parameter in /proc/cmdline file, for example:
>> +
>> +.RS
>> +.BR "kexec_jump_back_entry=0x00000000000810d2"
>
> Better to specify literal addr instead of specifying a value here.
>
>> +.RE
>> +
>> +Frist you need to prepare jump with \-\-load\-jump\-back\-helper and \-\-entry options.
>
>      ^^^ First (rather than Frist)
>
>> +
>> +.RS
>> +.B kexec
>> +.RB \-\-load\-jump\-back\-helper \-\-entry=0x810d2
>
> Better to use literal addr instead of specifying a particular value
> here, to keep the man page generic.
>
> Regards,
> Bhupesh
>
>> +.RE
>> +
>> +Then the first kernel can be rebooted using the command:
>> +
>> +.RS
>> +.BR kexec \ \-e
>> +.RE
>> +
>>  .SH OPTIONS
>>  .TP
>>  .B \-d\ (\-\-debug)
>> @@ -173,6 +200,9 @@ Specify the jump back address. (0 means it's not jump back or preserve context)
>>  .TP
>>  .BI \-\-load\-preserve\-context
>>  Load the new kernel and preserve context of current kernel during kexec.
>> +(kexec returns error if
>> +.B CONFIG_KEXEC_JUMP
>> +is not enabled)
>>  .TP
>>  .BI \-\-load\-jump\-back\-helper
>>  Load a helper image to jump back to original kernel.
>> --
>> 2.14.1
>>



-- 
GIOH KIM
Linux Kernel Entwickler

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