linux-kernel - Re: [PATCH v7 2/7] kexec: define functions to map and unmap segments

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Message-ID: <47565966-c735-4758-80a5-523fd93adc72@linux.microsoft.com>
Date: Mon, 10 Feb 2025 09:06:42 -0800
From: steven chen <chenste@...ux.microsoft.com>
To: Mimi Zohar <zohar@...ux.ibm.com>, stefanb@...ux.ibm.com,
 roberto.sassu@...weicloud.com, roberto.sassu@...wei.com,
 eric.snowberg@...cle.com, ebiederm@...ssion.com, paul@...l-moore.com,
 code@...icks.com, bauermann@...abnow.com, linux-integrity@...r.kernel.org,
 kexec@...ts.infradead.org, linux-security-module@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: madvenka@...ux.microsoft.com, nramas@...ux.microsoft.com,
 James.Bottomley@...senPartnership.com
Subject: Re: [PATCH v7 2/7] kexec: define functions to map and unmap segments

On 2/7/2025 11:15 AM, Mimi Zohar wrote:
> Hi Steven,
>
> On Mon, 2025-02-03 at 15:20 -0800, steven chen wrote:
>> Currently, the mechanism to map and unmap segments to the kimage
>> structure is not available to the subsystems outside of kexec.  This
>> functionality is needed when IMA is allocating the memory segments
>> during kexec 'load' operation.  Implement functions to map and unmap
>> segments to kimage.
>>
>> Implement kimage_map_segment() to enable mapping of IMA buffer source
>> pages to the kimage structure post kexec 'load'.  This function,
>> accepting a kimage pointer, an address, and a size, will gather the
>> source pages within the specified address range, create an array of page
>> pointers, and map these to a contiguous virtual address range.  The
>> function returns the start of this range if successful, or NULL if
>> unsuccessful.
>>
>> Implement kimage_unmap_segment() for unmapping segments
>> using vunmap().
>>
>> From: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
>> Author: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
>> Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>
>> Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
> I don't recall previously adding my "Reviewed-by" tag.
>
> Eric, I'd appreciate your reviewing this and the subsequent patch "[PATCH v7 3/7]
> ima: kexec: skip IMA segment validation after kexec soft reboot" in particular.
Hi Eric, Could you help to review this patch as Mimi mentioned? Thanks!
>
>> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
>> Signed-off-by: steven chen <chenste@...ux.microsoft.com>
>> ---
>>   include/linux/kexec.h |  7 ++++++
>>   kernel/kexec_core.c   | 54 +++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 61 insertions(+)
>>
>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
>> index f0e9f8eda7a3..f8413ea5c8c8 100644
>> --- a/include/linux/kexec.h
>> +++ b/include/linux/kexec.h
>> @@ -467,6 +467,9 @@ extern bool kexec_file_dbg_print;
>>   #define kexec_dprintk(fmt, arg...) \
>>           do { if (kexec_file_dbg_print) pr_info(fmt, ##arg); } while (0)
>>   
>> +extern void *kimage_map_segment(struct kimage *image,
>> +					unsigned long addr, unsigned long size);
> scripts/Checkpatch.pl complains about the parenthesis alignment here and elsewhere.
>
> Mimi
>
>> +extern void kimage_unmap_segment(void *buffer);
>>   #else /* !CONFIG_KEXEC_CORE */
>>   struct pt_regs;
>>   struct task_struct;
>> @@ -474,6 +477,10 @@ static inline void __crash_kexec(struct pt_regs *regs) { }
>>   static inline void crash_kexec(struct pt_regs *regs) { }
>>   static inline int kexec_should_crash(struct task_struct *p) { return 0; }
>>   static inline int kexec_crash_loaded(void) { return 0; }
>> +static inline void *kimage_map_segment(struct kimage *image,
>> +					unsigned long addr, unsigned long size)
>> +{ return NULL; }
>> +static inline void kimage_unmap_segment(void *buffer) { }
>>   #define kexec_in_progress false
>>   #endif /* CONFIG_KEXEC_CORE */
>>   

Thanks, Mimi, I will update in next version