Re: [PATCH v12 3/9] kexec: define functions to map and unmap segments

[Mimi Zohar <zohar@linux.ibm.com>]

On Fri, 2025-04-18 at 12:36 +0800, Baoquan He wrote:
> On 04/15/25 at 07:10pm, steven chen wrote:
> > From: Steven Chen <chenste@linux.microsoft.com>
>  ^^^^^^

As James Bottomley previously explained[1], if you haven't made any changes to
Tushar's patch, then the very first line of the patch description would be
"From: Tushar Sugandhi <tusharsu@linux.microsoft.com>" followed by a blank line.
If there is a minor change, you would add "<your email address>: explanation".
For example:

Steven Chen <chenste@linux.microsoft.com>: modified patch description

[1]
https://lore.kernel.org/lkml/58e70121aaee33679ac295847197c1e5511b2a81.camel@HansenPartnership.com/

> > 
> > Implement kimage_map_segment() to enable IMA to map the measurement log 
> > list to the kimage structure during the kexec 'load' stage. This function
> > gathers the source pages within the specified address range, and maps them
> > to a contiguous virtual address range.
> > 
> > This is a preparation for later usage.
> > 
> > Implement kimage_unmap_segment() for unmapping segments using vunmap().
> > 
> > From: Tushar Sugandhi <tusharsu@linux.microsoft.com>
>   ^^^^^^

Neither "Author:" nor "From:" belong here.  Please remove.

> > Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
>   ^^^^^^^

Having Tushar's "Signed-off-by" tag and yours below indicate that you modified
the original author's patch.

thanks,

Mimi

> > Cc: Eric Biederman <ebiederm@xmission.com>
> > Cc: Baoquan He <bhe@redhat.com> 
> > Cc: Vivek Goyal <vgoyal@redhat.com>
> > Cc: Dave Young <dyoung@redhat.com>
> > Signed-off-by: steven chen <chenste@linux.microsoft.com>
>   ^^^^^
> 
> The signing on this patch is a little confusing. I can't see who is the
> real author, who is the co-author, between you and Tushar. You may need
> to refer to Documentation/process/5.Posting.rst to make that clear.
> 
> > Acked-by: Baoquan He <bhe@redhat.com>
> > ---
> >  include/linux/kexec.h |  6 +++++
> >  kernel/kexec_core.c   | 54 +++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 60 insertions(+)
> > 
> > diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> > index f0e9f8eda7a3..7d6b12f8b8d0 100644
> > --- a/include/linux/kexec.h
> > +++ b/include/linux/kexec.h
> > @@ -467,13 +467,19 @@ 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);
> > +extern void kimage_unmap_segment(void *buffer);
> >  #else /* !CONFIG_KEXEC_CORE */
> >  struct pt_regs;
> >  struct task_struct;
> > +struct kimage;
> >  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 c0bdc1686154..a5e378e1dc7f 100644
> > --- a/kernel/kexec_core.c
> > +++ b/kernel/kexec_core.c
> > @@ -867,6 +867,60 @@ int kimage_load_segment(struct kimage *image,
> >  	return result;
> >  }
> >  
> > +void *kimage_map_segment(struct kimage *image,
> > +			 unsigned long addr, unsigned long size)
> > +{
> > +	unsigned long src_page_addr, dest_page_addr = 0;
> > +	unsigned long eaddr = addr + size;
> > +	kimage_entry_t *ptr, entry;
> > +	struct page **src_pages;
> > +	unsigned int npages;
> > +	void *vaddr = NULL;
> > +	int i;
> > +
> > +	/*
> > +	 * 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("Could not allocate ima pages array.\n");
> > +		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("Could not map ima buffer.\n");
> > +
> > +	return vaddr;
> > +}
> > +
> > +void kimage_unmap_segment(void *segment_buffer)
> > +{
> > +	vunmap(segment_buffer);
> > +}
> > +
> >  struct kexec_load_limit {
> >  	/* Mutex protects the limit count. */
> >  	struct mutex mutex;
> > -- 
> > 2.43.0
> > 
> 
>