[PATCH v5 0/3] Some bug fixes and cleanups related to kexec

[PATCH v5 0/3] Some bug fixes and cleanups related to kexec

[Yuntao Wang]

This series includes some bug fixes and cleanups for kexec.

This v5 series introduces no changes to any patches. I just reorganize the
patches and repost them.

Yuntao Wang (3):
  kexec: modify the meaning of the end parameter in
    kimage_is_destination_range()
  kexec_file: fix incorrect temp_start value in
    locate_mem_hole_top_down()
  x86/kexec: use pr_err() instead of pr_debug() when an error occurs

 arch/x86/kernel/kexec-bzimage64.c | 2 +-
 kernel/kexec_core.c               | 8 ++++----
 kernel/kexec_file.c               | 4 ++--
 mm/highmem.c                      | 2 --
 4 files changed, 7 insertions(+), 9 deletions(-)

-- 
2.43.0


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[PATCH v5 1/3] kexec: modify the meaning of the end parameter in kimage_is_destination_range()

[Yuntao Wang]

The end parameter received by kimage_is_destination_range() should be the
last valid byte address of the target memory segment plus 1. However, in
the locate_mem_hole_bottom_up() and locate_mem_hole_top_down() functions,
the corresponding value passed to kimage_is_destination_range() is the last
valid byte address of the target memory segment, which is 1 less.

There are two ways to fix this bug. We can either correct the logic of the
locate_mem_hole_bottom_up() and locate_mem_hole_top_down() functions, or we
can fix kimage_is_destination_range() by making the end parameter represent
the last valid byte address of the target memory segment. Here, we choose
the second approach.

Due to the modification to kimage_is_destination_range(), we also need to
adjust its callers, such as kimage_alloc_normal_control_pages() and
kimage_alloc_page().

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
v1->v2:
  Fix this issue using the approach suggested by Eric and Baoquan.

v2->v3:
  Modify the assignment of eaddr as suggested by Baoquan.

v3->v4:
  `eaddr = epfn << PAGE_SHIFT - 1` causes a compilation warning, fix it.

v4->v5:
  No changes.

 kernel/kexec_core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index be5642a4ec49..e3b1a699f087 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -276,8 +276,8 @@ int kimage_is_destination_range(struct kimage *image,
 		unsigned long mstart, mend;
 
 		mstart = image->segment[i].mem;
-		mend = mstart + image->segment[i].memsz;
-		if ((end > mstart) && (start < mend))
+		mend = mstart + image->segment[i].memsz - 1;
+		if ((end >= mstart) && (start <= mend))
 			return 1;
 	}
 
@@ -370,7 +370,7 @@ static struct page *kimage_alloc_normal_control_pages(struct kimage *image,
 		pfn   = page_to_boot_pfn(pages);
 		epfn  = pfn + count;
 		addr  = pfn << PAGE_SHIFT;
-		eaddr = epfn << PAGE_SHIFT;
+		eaddr = (epfn << PAGE_SHIFT) - 1;
 		if ((epfn >= (KEXEC_CONTROL_MEMORY_LIMIT >> PAGE_SHIFT)) ||
 			      kimage_is_destination_range(image, addr, eaddr)) {
 			list_add(&pages->lru, &extra_pages);
@@ -716,7 +716,7 @@ static struct page *kimage_alloc_page(struct kimage *image,
 
 		/* If the page is not a destination page use it */
 		if (!kimage_is_destination_range(image, addr,
-						  addr + PAGE_SIZE))
+						  addr + PAGE_SIZE - 1))
 			break;
 
 		/*
-- 
2.43.0


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[PATCH v5 2/3] kexec_file: fix incorrect temp_start value in locate_mem_hole_top_down()

[Yuntao Wang]

temp_end represents the address of the last available byte. Therefore, the
starting address of the memory segment with temp_end as its last available
byte and a size of `kbuf->memsz`, that is, the value of temp_start, should
be `temp_end - kbuf->memsz + 1` instead of `temp_end - kbuf->memsz`.

Additionally, use the ALIGN_DOWN macro instead of open-coding it directly
in locate_mem_hole_top_down() to improve code readability.

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
 kernel/kexec_file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f9a419cd22d4..336d085cbc47 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -426,11 +426,11 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
 	unsigned long temp_start, temp_end;
 
 	temp_end = min(end, kbuf->buf_max);
-	temp_start = temp_end - kbuf->memsz;
+	temp_start = temp_end - kbuf->memsz + 1;
 
 	do {
 		/* align down start */
-		temp_start = temp_start & (~(kbuf->buf_align - 1));
+		temp_start = ALIGN_DOWN(temp_start, kbuf->buf_align);
 
 		if (temp_start < start || temp_start < kbuf->buf_min)
 			return 0;
-- 
2.43.0


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[PATCH v5 3/3] x86/kexec: use pr_err() instead of pr_debug() when an error occurs

[Yuntao Wang]

When an error is detected, use pr_err() instead of pr_debug() to output
log message.

In addition, remove the unnecessary return from set_page_address().

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
 arch/x86/kernel/kexec-bzimage64.c | 2 +-
 mm/highmem.c                      | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index a61c12c01270..472a45dbc79a 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -424,7 +424,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 	 * command line. Make sure it does not overflow
 	 */
 	if (cmdline_len + MAX_ELFCOREHDR_STR_LEN > header->cmdline_size) {
-		pr_debug("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
+		pr_err("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
 		return ERR_PTR(-EINVAL);
 	}
 
diff --git a/mm/highmem.c b/mm/highmem.c
index e19269093a93..bd48ba445dd4 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -799,8 +799,6 @@ void set_page_address(struct page *page, void *virtual)
 		}
 		spin_unlock_irqrestore(&pas->lock, flags);
 	}
-
-	return;
 }
 
 void __init page_address_init(void)
-- 
2.43.0


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Re: [PATCH v5 0/3] Some bug fixes and cleanups related to kexec

[Baoquan He]

On 12/17/23 at 11:35am, Yuntao Wang wrote:
> This series includes some bug fixes and cleanups for kexec.
> 
> This v5 series introduces no changes to any patches. I just reorganize the
> patches and repost them.

LGTM, thx.

Acked-by: Baoquan He <bhe@redhat.com>

> 
> Yuntao Wang (3):
>   kexec: modify the meaning of the end parameter in
>     kimage_is_destination_range()
>   kexec_file: fix incorrect temp_start value in
>     locate_mem_hole_top_down()
>   x86/kexec: use pr_err() instead of pr_debug() when an error occurs
> 
>  arch/x86/kernel/kexec-bzimage64.c | 2 +-
>  kernel/kexec_core.c               | 8 ++++----
>  kernel/kexec_file.c               | 4 ++--
>  mm/highmem.c                      | 2 --
>  4 files changed, 7 insertions(+), 9 deletions(-)
> 
> -- 
> 2.43.0
> 


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Re: [PATCH v5 3/3] x86/kexec: use pr_err() instead of pr_debug() when an error occurs

[Andrew Morton]

On Sun, 17 Dec 2023 11:35:28 +0800 Yuntao Wang <ytcoode@gmail.com> wrote:

> When an error is detected, use pr_err() instead of pr_debug() to output
> log message.
> 
> In addition, remove the unnecessary return from set_page_address().
> 
> ...
>
> --- a/arch/x86/kernel/kexec-bzimage64.c
> +++ b/arch/x86/kernel/kexec-bzimage64.c
> @@ -424,7 +424,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
>  	 * command line. Make sure it does not overflow
>  	 */
>  	if (cmdline_len + MAX_ELFCOREHDR_STR_LEN > header->cmdline_size) {
> -		pr_debug("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
> +		pr_err("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
>  		return ERR_PTR(-EINVAL);
>  	}

https://lkml.kernel.org/r/20231213055747.61826-4-bhe@redhat.com has
already changed this to call kexec_dprintk().  I'll skip this patch.


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[PATCH] x86/kexec: use pr_err() instead of kexec_dprintk() when an error occurs

[Yuntao Wang]

When an error is detected, use pr_err() instead of kexec_dprintk() to
output log message.

In addition, remove the unnecessary return from set_page_address().

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
 arch/x86/kernel/kexec-bzimage64.c | 2 +-
 mm/highmem.c                      | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index e9ae0eac6bf9..4a77d5dd4bce 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -429,7 +429,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 	 * command line. Make sure it does not overflow
 	 */
 	if (cmdline_len + MAX_ELFCOREHDR_STR_LEN > header->cmdline_size) {
-		kexec_dprintk("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
+		pr_err("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
 		return ERR_PTR(-EINVAL);
 	}
 
diff --git a/mm/highmem.c b/mm/highmem.c
index e19269093a93..bd48ba445dd4 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -799,8 +799,6 @@ void set_page_address(struct page *page, void *virtual)
 		}
 		spin_unlock_irqrestore(&pas->lock, flags);
 	}
-
-	return;
 }
 
 void __init page_address_init(void)
-- 
2.43.0


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Re: [PATCH] x86/kexec: use pr_err() instead of kexec_dprintk() when an error occurs

[Andrew Morton]

On Tue, 19 Dec 2023 15:29:01 +0800 Yuntao Wang <ytcoode@gmail.com> wrote:

> When an error is detected, use pr_err() instead of kexec_dprintk() to
> output log message.
>
> In addition, remove the unnecessary return from set_page_address().

The above describes what the code does, which is already quite clear
from looking at the code.

Please write changelogs and code comments which describe *why* the code
does something, rather than *what* it does.

>
>
> --- a/arch/x86/kernel/kexec-bzimage64.c
> +++ b/arch/x86/kernel/kexec-bzimage64.c
> @@ -429,7 +429,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
>  	 * command line. Make sure it does not overflow
>  	 */
>  	if (cmdline_len + MAX_ELFCOREHDR_STR_LEN > header->cmdline_size) {
> -		kexec_dprintk("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
> +		pr_err("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");

ie, what are the reasons for this change?

>  		return ERR_PTR(-EINVAL);
>  	}
>  
> diff --git a/mm/highmem.c b/mm/highmem.c
> index e19269093a93..bd48ba445dd4 100644
> --- a/mm/highmem.c
> +++ b/mm/highmem.c
> @@ -799,8 +799,6 @@ void set_page_address(struct page *page, void *virtual)
>  		}
>  		spin_unlock_irqrestore(&pas->lock, flags);
>  	}
> -
> -	return;
>  }
>  
>  void __init page_address_init(void)
> -- 
> 2.43.0

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[PATCH v2] x86/kexec: use pr_err() instead of kexec_dprintk() when an error occurs

[Yuntao Wang]

When detecting an error, the current code uses kexec_dprintk() to output
log message. This is not quite appropriate as kexec_dprintk() is mainly
used for outputting debugging messages, rather than error messages.

Replace kexec_dprintk() with pr_err(). This also makes the output method
for this error log align with the output method for other error logs in
this function.

Additionally, the last return statement in set_page_address() is
unnecessary, remove it.

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
v1 -> v2: Rewrite changelogs

 arch/x86/kernel/kexec-bzimage64.c | 2 +-
 mm/highmem.c                      | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index e9ae0eac6bf9..4a77d5dd4bce 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -429,7 +429,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 	 * command line. Make sure it does not overflow
 	 */
 	if (cmdline_len + MAX_ELFCOREHDR_STR_LEN > header->cmdline_size) {
-		kexec_dprintk("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
+		pr_err("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
 		return ERR_PTR(-EINVAL);
 	}
 
diff --git a/mm/highmem.c b/mm/highmem.c
index e19269093a93..bd48ba445dd4 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -799,8 +799,6 @@ void set_page_address(struct page *page, void *virtual)
 		}
 		spin_unlock_irqrestore(&pas->lock, flags);
 	}
-
-	return;
 }
 
 void __init page_address_init(void)
-- 
2.43.0


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