linux-kernel - [PATCH V2] x86/efi: Add EFI_PGT_DUMP support for x86

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Message-Id: <1494530433-19503-1-git-send-email-sai.praneeth.prakhya@intel.com>
Date:   Thu, 11 May 2017 12:20:33 -0700
From:   Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
To:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Sai Praneeth <sai.praneeth.prakhya@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Ricardo Neri <ricardo.neri@...el.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Ravi Shankar <ravi.v.shankar@...el.com>
Subject: [PATCH V2] x86/efi: Add EFI_PGT_DUMP support for x86_32, kexec 

From: Sai Praneeth <sai.praneeth.prakhya@...el.com>

EFI_PGT_DUMP, as the name suggests dumps efi page tables to dmesg during
kernel boot. This feature is very useful while debugging page
faults/null pointer dereferences to efi related addresses. Presently,
this feature is limited only to x86_64, so let's extend it to other efi
configurations like kexec kernel, efi=old_map and to x86_32 as well.
This doesn't effect normal boot path because this config option should
be used only for debug purposes.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Ricardo Neri <ricardo.neri@...el.com>
Cc: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Ravi Shankar <ravi.v.shankar@...el.com>

Changes since v1:
1. Call efi_dump_pagetable() only once from efi_enter_virtual_mode() -
as suggested by Boris

---
 arch/x86/platform/efi/efi.c    | 3 ++-
 arch/x86/platform/efi/efi_32.c | 9 ++++++++-
 arch/x86/platform/efi/efi_64.c | 5 ++++-
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 217dc166c649..87835c97611f 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -1011,7 +1011,6 @@ static void __init __efi_enter_virtual_mode(void)
 	 * necessary relocation fixups for the new virtual addresses.
 	 */
 	efi_runtime_update_mappings();
-	efi_dump_pagetable();
 
 	/* clean DUMMY object */
 	efi_delete_dummy_variable();
@@ -1026,6 +1025,8 @@ void __init efi_enter_virtual_mode(void)
 		kexec_enter_virtual_mode();
 	else
 		__efi_enter_virtual_mode();
+
+	efi_dump_pagetable();
 }
 
 /*
diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index 9b1abcf6e7bb..9477653c78f8 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -44,7 +44,14 @@ int __init efi_alloc_page_tables(void)
 }
 
 void efi_sync_low_kernel_mappings(void) {}
-void __init efi_dump_pagetable(void) {}
+
+void __init efi_dump_pagetable(void)
+{
+#ifdef CONFIG_EFI_PGT_DUMP
+	ptdump_walk_pgd_level(NULL, swapper_pg_dir);
+#endif
+}
+
 int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 {
 	return 0;
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 76e1cd6b74dd..3bde2589fdb9 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -510,7 +510,10 @@ void __init efi_runtime_update_mappings(void)
 void __init efi_dump_pagetable(void)
 {
 #ifdef CONFIG_EFI_PGT_DUMP
-	ptdump_walk_pgd_level(NULL, efi_pgd);
+	if (efi_enabled(EFI_OLD_MEMMAP))
+		ptdump_walk_pgd_level(NULL, swapper_pg_dir);
+	else
+		ptdump_walk_pgd_level(NULL, efi_pgd);
 #endif
 }
 
-- 
2.1.4