linux-kernel - [PATCH 2/2] arm64/mm: Update create_kpti_ng_temp_pgd() to handle pgtable

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Message-Id: <20250813145607.1612234-3-chaitanyas.prakash@arm.com>
Date: Wed, 13 Aug 2025 20:26:07 +0530
From: Chaitanya S Prakash <chaitanyas.prakash@....com>
To: linux-arm-kernel@...ts.infradead.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: Chaitanya S Prakash <chaitanyas.prakash@....com>,
	Ryan Roberts <ryan.roberts@....com>,
	Yang Shi <yang@...amperecomputing.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Kevin Brodsky <kevin.brodsky@....com>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Zhenhua Huang <quic_zhenhuah@...cinc.com>,
	Joey Gouly <joey.gouly@....com>
Subject: [PATCH 2/2] arm64/mm: Update create_kpti_ng_temp_pgd() to handle pgtable_alloc failure

create_kpti_ng_temp_pgd() was created as an alias for void returning
__create_pgd_mapping_locked() and relied on pgtable_alloc() to BUG_ON()
if an allocation failure occurred. But as __create_pgd_mapping_locked()
has been updated as a part of the error propagation patch to return a
non-void value, update create_kpti_ng_temp_pgd() to act as a wrapper
around __create_pgd_mapping_locked() and BUG_ON() on ret being a non
zero value.

Signed-off-by: Chaitanya S Prakash <chaitanyas.prakash@....com>
---
 arch/arm64/mm/mmu.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index db7f45ef16574..19cbabceb38bd 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -76,6 +76,14 @@ EXPORT_SYMBOL(empty_zero_page);
 static DEFINE_SPINLOCK(swapper_pgdir_lock);
 static DEFINE_MUTEX(fixmap_lock);
 
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+void create_kpti_ng_temp_pgd(pgd_t *pgdir, phys_addr_t phys,
+			     unsigned long virt, phys_addr_t size,
+			     pgprot_t prot,
+			     phys_addr_t (*pgtable_alloc)(enum pgtable_type),
+			     int flags);
+#endif
+
 void noinstr set_swapper_pgd(pgd_t *pgdp, pgd_t pgd)
 {
 	pgd_t *fixmap_pgdp;
@@ -541,11 +549,17 @@ static void ___create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
 }
 
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
-extern __alias(__create_pgd_mapping_locked)
 void create_kpti_ng_temp_pgd(pgd_t *pgdir, phys_addr_t phys, unsigned long virt,
 			     phys_addr_t size, pgprot_t prot,
 			     phys_addr_t (*pgtable_alloc)(enum pgtable_type),
-			     int flags);
+			     int flags)
+{
+	int ret = 0;
+
+	ret = __create_pgd_mapping_locked(pgdir, phys, virt, size, prot,
+					  pgtable_alloc, flags);
+	BUG_ON(ret);
+}
 #endif
 
 static phys_addr_t __pgd_pgtable_alloc(struct mm_struct *mm,
-- 
2.34.1