linux-kernel - [PATCH v8 2/4] mm: Introduce memblock_isolate

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Message-Id: <20230316131711.1284451-3-alexghiti@rivosinc.com>
Date:   Thu, 16 Mar 2023 14:17:09 +0100
From:   Alexandre Ghiti <alexghiti@...osinc.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anup Patel <anup@...infault.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-mm@...ck.org
Cc:     Alexandre Ghiti <alexghiti@...osinc.com>
Subject: [PATCH v8 2/4] mm: Introduce memblock_isolate_memory

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 <alexghiti@...osinc.com>
Reviewed-by: Anup Patel <anup@...infault.org>
Tested-by: Anup Patel <anup@...infault.org>
---
 include/linux/memblock.h |  1 +
 mm/memblock.c            | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

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..e8c651a37012 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -805,6 +805,26 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
 	return 0;
 }
 
+/**
+ * memblock_isolate_memory - isolate given range in memblock.memory
+ * @base: base of range to isolate
+ * @size: size of range to isolate
+ *
+ * Isolates the given range in memblock.memory so that it does not share any
+ * region with other ranges.
+ *
+ * Return:
+ * 0 on success, -errno on failure.
+ */
+
+int __init_memblock memblock_isolate_memory(phys_addr_t base, phys_addr_t size)
+{
+	int start_rgn, end_rgn;
+
+	return memblock_isolate_range(&memblock.memory, base, size,
+				      &start_rgn, &end_rgn);
+}
+
 static int __init_memblock memblock_remove_range(struct memblock_type *type,
 					  phys_addr_t base, phys_addr_t size)
 {
-- 
2.37.2