linux-kernel - [PATCH v2] riscv/mm/fault: add show

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Message-Id: <20240722042037.27934-1-cuiyunhui@bytedance.com>
Date: Mon, 22 Jul 2024 12:20:37 +0800
From: Yunhui Cui <cuiyunhui@...edance.com>
To: punit.agrawal@...edance.com,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	akpm@...ux-foundation.org,
	surenb@...gle.com,
	peterx@...hat.com,
	alexghiti@...osinc.com,
	willy@...radead.org,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: Yunhui Cui <cuiyunhui@...edance.com>
Subject: [PATCH v2] riscv/mm/fault: add show_pte() before die()

When the kernel displays "Unable to handle kernel paging request at
virtual address", we would like to confirm the status of the virtual
address in the page table. So add show_pte() before die().

Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>
---
 arch/riscv/mm/fault.c | 53 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 5224f3733802..666d282a8bf4 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -22,6 +22,58 @@
 
 #include "../kernel/head.h"
 
+static void show_pte(unsigned long addr)
+{
+	pgd_t *pgdp, pgd;
+	p4d_t *p4dp, p4d;
+	pud_t *pudp, pud;
+	pmd_t *pmdp, pmd;
+	pte_t *ptep, pte;
+	struct mm_struct *mm = current->mm;
+
+	if (!mm)
+		mm = &init_mm;
+
+	pr_alert("Current %s pgtable: %luK pagesize, %d-bit VAs, pgdp=0x%016lx\n",
+		 current->comm, PAGE_SIZE/SZ_1K, VA_BITS,
+		 (mm == &init_mm ? __pa_symbol(mm->pgd) :
+		 (unsigned long)virt_to_phys(mm->pgd)));
+
+	pgdp = pgd_offset(mm, addr);
+	pgd = pgdp_get(pgdp);
+	pr_alert("[%016lx] pgd=%016lx", addr, pgd_val(pgd));
+	if (pgd_none(pgd) || pgd_bad(pgd) || pgd_leaf(pgd))
+		goto out;
+
+	p4dp = p4d_offset(pgdp, addr);
+	p4d = p4dp_get(p4dp);
+	pr_cont(", p4d=%016lx", p4d_val(p4d));
+	if (p4d_none(p4d) || p4d_bad(p4d) || p4d_leaf(p4d))
+		goto out;
+
+	pudp = pud_offset(p4dp, addr);
+	pud = pudp_get(pudp);
+	pr_cont(", pud=%016lx", pud_val(pud));
+	if (pud_none(pud) || pud_bad(pud) || pud_leaf(pud))
+		goto out;
+
+	pmdp = pmd_offset(pudp, addr);
+	pmd = pmdp_get(pmdp);
+	pr_cont(", pmd=%016lx", pmd_val(pmd));
+	if (pmd_none(pmd) || pmd_bad(pmd) || pmd_leaf(pmd))
+		goto out;
+
+	ptep = pte_offset_map(pmdp, addr);
+	if (!ptep)
+		goto out;
+
+	pte = ptep_get(ptep);
+	pr_cont(", pte=%016lx", pte_val(pte));
+	pte_unmap(ptep);
+out:
+	pr_cont("\n");
+}
+
 static void die_kernel_fault(const char *msg, unsigned long addr,
 		struct pt_regs *regs)
 {
@@ -31,6 +83,7 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
 		addr);
 
 	bust_spinlocks(0);
+	show_pte(addr);
 	die(regs, "Oops");
 	make_task_dead(SIGKILL);
 }
-- 
2.39.2