Subject: [PATCHv3 2/5] arm64/mm: disable WARN_ON() and BUG_ON() in __create_pgd_mapping() if too early

From: Pingfan Liu <[email-masked]>
Date: Mon, 31 May 2021 04:45:37 -0400

This patch is still one of the preparation for calling
__create_pgd_mapping() from head.S

When calling from head.S, printk() is not ready to work. Hence define
SAFE_BUG_ON()/SAFE_WARN_ON(), wrapping around BUG_ON()/WARN_ON() to
protect against early calling.

Signed-off-by: Pingfan Liu <[email-masked]>
Cc: Catalin Marinas <[email-masked]>
Cc: Will Deacon <[email-masked]>
Cc: Ard Biesheuvel <[email-masked]>
Cc: Marc Zyngier <[email-masked]>
Cc: Kristina Martsenko <[email-masked]>
Cc: James Morse <[email-masked]>
Cc: Steven Price <[email-masked]>
Cc: Jonathan Cameron <[email-masked]>
Cc: Pavel Tatashin <[email-masked]>
Cc: Anshuman Khandual <[email-masked]>
Cc: Atish Patra <[email-masked]>
Cc: Mike Rapoport <[email-masked]>
Cc: Logan Gunthorpe <[email-masked]>
Cc: Mark Brown <[email-masked]>
To: [email-masked]
---
 arch/arm64/mm/mmu.c | 42 ++++++++++++++++++++++++++----------------
 1 file changed, 26 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index f4fc905718ca..fe16f235d1fa 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -40,6 +40,7 @@
 #define NO_BLOCK_MAPPINGS	BIT(0)
 #define NO_CONT_MAPPINGS	BIT(1)
 #define NO_EXEC_MAPPINGS	BIT(2)	/* assumes FEAT_HPDS is not used */
+#define BOOT_HEAD		BIT(3)
 
 u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN);
 u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
@@ -139,6 +140,15 @@ static phys_addr_t __init early_pgtable_alloc(int shift)
 	return phys;
 }
 
+/*
+ * printk is not ready in the very early stage. And this pair macro should be used
+ * instead
+ */
+#define SAFE_BUG_ON(flags, cond)	\
+	do { if (likely(!(flags & BOOT_HEAD))) BUG_ON(cond); } while (0)
+#define SAFE_WARN_ON(flags, cond)	\
+	({ (flags & BOOT_HEAD) ? false : WARN_ON(cond); })
+
 static bool pgattr_change_is_safe(u64 old, u64 new)
 {
 	/*
@@ -174,7 +184,7 @@ static bool pgattr_change_is_safe(u64 old, u64 new)
 }
 
 static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end,
-		     phys_addr_t phys, pgprot_t prot)
+		     phys_addr_t phys, pgprot_t prot, int flags)
 {
 	pte_t *ptep;
 
@@ -188,7 +198,7 @@ static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end,
 		 * After the PTE entry has been populated once, we
 		 * only allow updates to the permission attributes.
 		 */
-		BUG_ON(!pgattr_change_is_safe(pte_val(old_pte),
+		SAFE_BUG_ON(flags, !pgattr_change_is_safe(pte_val(old_pte),
 					      READ_ONCE(pte_val(*ptep))));
 
 		phys += PAGE_SIZE;
@@ -206,19 +216,19 @@ static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr,
 	unsigned long next;
 	pmd_t pmd = READ_ONCE(*pmdp);
 
-	BUG_ON(pmd_sect(pmd));
+	SAFE_BUG_ON(flags, pmd_sect(pmd));
 	if (pmd_none(pmd)) {
 		pmdval_t pmdval = PMD_TYPE_TABLE | PMD_TABLE_UXN;
 		phys_addr_t pte_phys;
 
 		if (flags & NO_EXEC_MAPPINGS)
 			pmdval |= PMD_TABLE_PXN;
-		BUG_ON(!pgtable_alloc);
+		SAFE_BUG_ON(flags, !pgtable_alloc);
 		pte_phys = pgtable_alloc(PAGE_SHIFT);
 		__pmd_populate(pmdp, pte_phys, pmdval);
 		pmd = READ_ONCE(*pmdp);
 	}
-	BUG_ON(pmd_bad(pmd));
+	SAFE_BUG_ON(flags, pmd_bad(pmd));
 
 	do {
 		pgprot_t __prot = prot;
@@ -230,7 +240,7 @@ static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr,
 		    (flags & NO_CONT_MAPPINGS) == 0)
 			__prot = __pgprot(pgprot_val(prot) | PTE_CONT);
 
-		init_pte(pmdp, addr, next, phys, __prot);
+		init_pte(pmdp, addr, next, phys, __prot, flags);
 
 		phys += next - addr;
 	} while (addr = next, addr != end);
@@ -258,13 +268,13 @@ static void init_pmd(pud_t *pudp, unsigned long addr, unsigned long end,
 			 * After the PMD entry has been populated once, we
 			 * only allow updates to the permission attributes.
 			 */
-			BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),
+			SAFE_BUG_ON(flags, !pgattr_change_is_safe(pmd_val(old_pmd),
 						      READ_ONCE(pmd_val(*pmdp))));
 		} else {
 			alloc_init_cont_pte(pmdp, addr, next, phys, prot,
 					    pgtable_alloc, flags);
 
-			BUG_ON(pmd_val(old_pmd) != 0 &&
+			SAFE_BUG_ON(flags, pmd_val(old_pmd) != 0 &&
 			       pmd_val(old_pmd) != READ_ONCE(pmd_val(*pmdp)));
 		}
 		phys += next - addr;
@@ -284,19 +294,19 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr,
 	/*
 	 * Check for initial section mappings in the pgd/pud.
 	 */
-	BUG_ON(pud_sect(pud));
+	SAFE_BUG_ON(flags, pud_sect(pud));
 	if (pud_none(pud)) {
 		pudval_t pudval = PUD_TYPE_TABLE | PUD_TABLE_UXN;
 		phys_addr_t pmd_phys;
 
 		if (flags & NO_EXEC_MAPPINGS)
 			pudval |= PUD_TABLE_PXN;
-		BUG_ON(!pgtable_alloc);
+		SAFE_BUG_ON(flags, !pgtable_alloc);
 		pmd_phys = pgtable_alloc(PMD_SHIFT);
 		__pud_populate(pudp, pmd_phys, pudval);
 		pud = READ_ONCE(*pudp);
 	}
-	BUG_ON(pud_bad(pud));
+	SAFE_BUG_ON(flags, pud_bad(pud));
 
 	do {
 		pgprot_t __prot = prot;
@@ -342,12 +352,12 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
 
 		if (flags & NO_EXEC_MAPPINGS)
 			p4dval |= P4D_TABLE_PXN;
-		BUG_ON(!pgtable_alloc);
+		SAFE_BUG_ON(flags, !pgtable_alloc);
 		pud_phys = pgtable_alloc(PUD_SHIFT);
 		__p4d_populate(p4dp, pud_phys, p4dval);
 		p4d = READ_ONCE(*p4dp);
 	}
-	BUG_ON(p4d_bad(p4d));
+	SAFE_BUG_ON(flags, p4d_bad(p4d));
 
 	pudp = pud_set_fixmap_offset(p4dp, addr);
 	do {
@@ -366,13 +376,13 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
 			 * After the PUD entry has been populated once, we
 			 * only allow updates to the permission attributes.
 			 */
-			BUG_ON(!pgattr_change_is_safe(pud_val(old_pud),
+			SAFE_BUG_ON(flags, !pgattr_change_is_safe(pud_val(old_pud),
 						      READ_ONCE(pud_val(*pudp))));
 		} else {
 			alloc_init_cont_pmd(pudp, addr, next, phys, prot,
 					    pgtable_alloc, flags);
 
-			BUG_ON(pud_val(old_pud) != 0 &&
+			SAFE_BUG_ON(flags, pud_val(old_pud) != 0 &&
 			       pud_val(old_pud) != READ_ONCE(pud_val(*pudp)));
 		}
 		phys += next - addr;
@@ -394,7 +404,7 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
 	 * If the virtual and physical address don't have the same offset
 	 * within a page, we cannot map the region as the caller expects.
 	 */
-	if (WARN_ON((phys ^ virt) & ~PAGE_MASK))
+	if (SAFE_WARN_ON(flags, (phys ^ virt) & ~PAGE_MASK))
 		return;
 
 	phys &= PAGE_MASK;
-- 
2.29.2

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