[PATCH v4 2/7] kexec: define functions to map and unmap segments

[Tushar Sugandhi]

Thanks Stefan for taking a look.

On 1/23/24 09:03, Stefan Berger wrote:
> 
> 
> On 1/22/24 13:37, Tushar Sugandhi wrote:
>> 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().  Relocate 'for_each_kimage_entry()' macro from
>> kexec_core.c to kexec.h for broader accessibility.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu at linux.microsoft.com>
>> ---
>>   include/linux/kexec.h              | 13 +++++++
>>   kernel/kexec_core.c                | 59 +++++++++++++++++++++++++++---
>>   security/integrity/ima/ima_kexec.c |  1 +
>>   3 files changed, 68 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
>> index 22b5cd24f581..e00b8101b53b 100644
>> --- a/include/linux/kexec.h
>> +++ b/include/linux/kexec.h
>> @@ -490,6 +490,15 @@ static inline int 
>> arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, g
>>   static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned 
>> int pages) { }
>>   #endif
>> +#define for_each_kimage_entry(image, ptr, entry) \
>> +    for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE); \
>> +        ptr = (entry & IND_INDIRECTION) ? \
>> +            boot_phys_to_virt((entry & PAGE_MASK)) : ptr + 1)
>> +
>> +extern void *kimage_map_segment(struct kimage *image,
>> +                unsigned long addr, unsigned long size);
>> +extern void kimage_unmap_segment(void *buffer);
>> +
> 
> This series applies to v6.5. You may want to rebase to 6.7.
> 
Will rebase. Thanks for catching this.
>>   #else /* !CONFIG_KEXEC_CORE */
>>   struct pt_regs;
>>   struct task_struct;
>> @@ -497,6 +506,10 @@ 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 */
>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>> index 3d578c6fefee..26978ad02676 100644
>> --- a/kernel/kexec_core.c
>> +++ b/kernel/kexec_core.c
>> @@ -594,11 +594,6 @@ void kimage_terminate(struct kimage *image)
>>       *image->entry = IND_DONE;
>>   }
>> -#define for_each_kimage_entry(image, ptr, entry) \
>> -    for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE); \
>> -        ptr = (entry & IND_INDIRECTION) ? \
>> -            boot_phys_to_virt((entry & PAGE_MASK)) : ptr + 1)
>> -
>>   static void kimage_free_entry(kimage_entry_t entry)
>>   {
>>       struct page *page;
>> @@ -921,6 +916,60 @@ int kimage_load_segment(struct kimage *image,
>>       return result;
>>   }
>> +void *kimage_map_segment(struct kimage *image,
>> +             unsigned long addr, unsigned long size)
>> +{
>> +    unsigned long eaddr = addr + size;
>> +    unsigned long src_page_addr, dest_page_addr;
>> +    unsigned int npages;
>> +    struct page **src_pages;
>> +    int i;
>> +    kimage_entry_t *ptr, entry;
>> +    void *vaddr = NULL;
>> +
>> +    /*
>> +     * Collect the source pages and map them in a contiguous VA range.
>> +     */
>> +    npages = PFN_UP(eaddr) - PFN_DOWN(addr);
>> +    src_pages = kmalloc_array(npages, sizeof(*src_pages), GFP_KERNEL);
>> +    if (!src_pages) {
>> +        pr_err("%s: Could not allocate ima pages array.\n", __func__);
>> +        return NULL;
>> +    }
>> +
>> +    i = 0;
>> +    for_each_kimage_entry(image, ptr, entry) {
>> +        if (entry & IND_DESTINATION)
>> +            dest_page_addr = entry & PAGE_MASK;
>> +        else if (entry & IND_SOURCE) {
>> +            if (dest_page_addr >= addr && dest_page_addr < eaddr) {
>> +                src_page_addr = entry & PAGE_MASK;
>> +                src_pages[i++] =
>> +                    virt_to_page(__va(src_page_addr));
>> +                if (i == npages)
>> +                    break;
>> +                dest_page_addr += PAGE_SIZE;
>> +            }
>> +        }
>> +    }
>> +
>> +    /* Sanity check. */
>> +    WARN_ON(i < npages);
>> +
>> +    vaddr = vmap(src_pages, npages, VM_MAP, PAGE_KERNEL);
>> +    kfree(src_pages);
>> +
>> +    if (!vaddr)
>> +        pr_err("%s: Could not map imap buffer.\n", __func__);
> 
> imap -> ima
> 
Good eye catching this.
Will fix.
>> +
>> +    return vaddr;
>> +}
>> +
>> +void kimage_unmap_segment(void *segment_buffer)
>> +{
>> +    vunmap(segment_buffer);
>> +}
>> +
>>   struct kexec_load_limit {
>>       /* Mutex protects the limit count. */
>>       struct mutex mutex;
>> diff --git a/security/integrity/ima/ima_kexec.c 
>> b/security/integrity/ima/ima_kexec.c
>> index 99daac355c70..4f944c9b4168 100644
>> --- a/security/integrity/ima/ima_kexec.c
>> +++ b/security/integrity/ima/ima_kexec.c
>> @@ -170,6 +170,7 @@ void ima_add_kexec_buffer(struct kimage *image)
>>       pr_debug("kexec measurement buffer for the loaded kernel at 
>> 0x%lx.\n",
>>            kbuf.mem);
>>   }
>> +
> 
> remove
>
Will do.

~Tushar

>>   #endif /* IMA_KEXEC */
>>   /*