linux-kernel - [PATCH] mm/debug: Replace __pa() with __pa_symbol() in debug_vm

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Date:   Thu, 27 Feb 2020 09:30:31 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-mm@...ck.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mm/debug: Replace __pa() with __pa_symbol() in debug_vm_pgtable()

Replace __pa() with __pa_symbol() in debug_vm_pgtable() while accessing the
physical address for 'start_kernel' which is a kernel text symbol, else it
might trigger the following warning on some platforms when DEBUG_VIRTUAL is
enabled.

[   23.123852] ------------[ cut here ]------------
[   23.124486] virt_to_phys used for non-linear address: (____ptrval____) (start_kernel+0x0/0x424)
[   23.125663] WARNING: CPU: 11 PID: 1 at arch/arm64/mm/physaddr.c:15 __virt_to_phys+0x60/0x98
[   23.126877] Modules linked in:
[   23.127390] CPU: 11 PID: 1 Comm: swapper/0 Tainted: G        W 5.6.0-rc3-next-20200226-00001-g306225cc6ffd #163
[   23.129139] Hardware name: linux,dummy-virt (DT)
[   23.129898] pstate: 60400005 (nZCv daif +PAN -UAO)
[   23.130693] pc : __virt_to_phys+0x60/0x98
[   23.131359] lr : __virt_to_phys+0x60/0x98
[   23.132022] sp : ffff800011e6be10
[   23.132575] x29: ffff800011e6be10 x28: 0000000000000000
[   23.133447] x27: 0000000000000000 x26: 0000000000000000
[   23.134319] x25: 0000000000000000 x24: 0020000000000fd3
[   23.135197] x23: fffffe000bd27700 x22: ffff0002fcae8000
[   23.136069] x21: ffff800011a47000 x20: 0000000000000001
[   23.136941] x19: ffff800011350a14 x18: 0000000000000010
[   23.137815] x17: 000000006bb8910e x16: 00000000a1fdc699
[   23.138693] x15: ffffffffffffffff x14: 6c656e72656b5f74
[   23.139567] x13: 726174732820295f x12: 5f5f5f6c61767274
[   23.140441] x11: 705f5f5f5f28203a x10: 7373657264646120
[   23.141314] x9 : 7261656e696c2d6e x8 : ffff8000106b4e70
[   23.142189] x7 : 00000000000002a1 x6 : ffff800011a58bba
[   23.143067] x5 : 001fffffffffffff x4 : 0000000000000000
[   23.143939] x3 : 00000000ffffffff x2 : ffff800011881bf8
[   23.144810] x1 : 16ee3f9cb03efc00 x0 : 0000000000000000
[   23.145682] Call trace:
[   23.146097]  __virt_to_phys+0x60/0x98
[   23.146710]  debug_vm_pgtable+0xd0/0x440
[   23.147362]  kernel_init+0x18/0x100
[   23.147944]  ret_from_fork+0x10/0x18
[   23.148539] ---[ end trace fc4ccb3cb35ff225 ]---

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org
Reported-by: Qian Cai <cai@....pw>
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
This applies on linux-next (next-20200226). Tested on arm64 and x86
platforms. Build tested on several others.

 mm/debug_vm_pgtable.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index cdfab040c1f6..9d1c8570fa00 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -585,7 +585,7 @@ void __init debug_vm_pgtable(void)
 	 * helps avoid large memory block allocations to be used for mapping
 	 * at higher page table levels.
 	 */
-	paddr = __pa(&start_kernel);
+	paddr = __pa_symbol(&start_kernel);
 
 	pte_aligned = (paddr & PAGE_MASK) >> PAGE_SHIFT;
 	pmd_aligned = (paddr & PMD_MASK) >> PAGE_SHIFT;
-- 
2.20.1