On 3/12/23 10:35, Mike Rapoport wrote:

Hi Alexandre,

On Fri, Mar 10, 2023 at 10:45:37AM +0100, Alexandre Ghiti wrote:

quoted

This function allows to split a region in memblock.memory and will be
useful when setting up the linear mapping with STRICT_KERNEL_RWX: it
allows to isolate the kernel text/rodata and then avoid to map those
regions with a PUD/P4D/PGD.

Signed-off-by: Alexandre Ghiti <redacted>
---
  include/linux/memblock.h |  1 +
  mm/memblock.c            | 22 +++++++++++++++++++++-
  2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 50ad19662a32..2f7ef97c0da7 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h

@@ -125,6 +125,7 @@ int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
  int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
  int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
  int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
+int memblock_isolate_memory(phys_addr_t base, phys_addr_t size);
  
  void memblock_free_all(void);
  void memblock_free(void *ptr, size_t size);

diff --git a/mm/memblock.c b/mm/memblock.c
index 25fd0626a9e7..d8cf1c9eccf0 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c

@@ -753,7 +753,8 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
  	int idx;
  	struct memblock_region *rgn;
  
-	*start_rgn = *end_rgn = 0;
+	if (start_rgn && end_rgn)
+		*start_rgn = *end_rgn = 0;

Generally, it's possible that either start_rgn or end_rgn will be a valid
pointer and this should be handled here and below.

My preference, though would be to leave memblock_isolate_range() as is and
have unused start_rgn and end_rgn in memblock_isolate_memory().

Sure, I'll do that then.

quoted

  
  	if (!size)
  		return 0;

@@ -795,6 +796,9 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
  					       memblock_get_region_node(rgn),
  					       rgn->flags);
  		} else {
+			if (!end_rgn || !start_rgn)
+				continue;
+
  			/* @rgn is fully contained, record it */
  			if (!*end_rgn)
  				*start_rgn = idx;

@@ -805,6 +809,22 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
  	return 0;
  }
  
+/**
+ * memblock_isolate_memory - isolate given range from memblock.memory

I think it'd better to use "... range in memblock.memory"

Ok

quoted

+ * @base: base of range to isolate
+ * @size: size of range to isolate
+ *
+ * Call memblock_isolate_range on memblock.memory to isolate the given range.

Please elaborate that isolate means that the range does not share regions
with other ranges.

Sure, thanks, I'll come up with a v8 tomorrow along with other fixes 
(rv32 and arm64 comments that I forgot to remove).

Thanks again,

Alex

quoted

+ *
+ * Return:
+ * 0 on success, -errno on failure.
+ */
+
+int __init_memblock memblock_isolate_memory(phys_addr_t base, phys_addr_t size)
+{
+	return memblock_isolate_range(&memblock.memory, base, size, NULL, NULL);
+}
+
  static int __init_memblock memblock_remove_range(struct memblock_type *type,
  					  phys_addr_t base, phys_addr_t size)
  {
-- 
2.37.2

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