linux-kernel - [PATCH 06/11] x86/xip: after paging trampoline, discard PMDs above

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 23 Mar 2015 00:46:35 -0700
From:	Jim Kukunas <james.t.kukunas@...ux.intel.com>
To:	Linux Kernel <linux-kernel@...r.kernel.org>,
	tom.zanussi@...ux.intel.com
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, tglx@...utronix.de,
	mingo@...hat.com, x86@...nel.org
Subject: [PATCH 06/11] x86/xip: after paging trampoline, discard PMDs above _brk

In the likely case that XIP_BASE is above PAGE_OFFSET, we
want to discard any early identity mappings. So rather than
keeping every PMD above PAGE_OFFSET, only copy the ones from
PAGE_OFFSET to the last PMD of _end. At this point, the linear
address space should look normal.

Signed-off-by: Jim Kukunas <james.t.kukunas@...ux.intel.com>
---
 arch/x86/include/asm/pgtable.h | 7 +++++++
 arch/x86/kernel/setup.c        | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index a0c35bf..5eaba7d 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -660,6 +660,13 @@ static inline int pgd_none(pgd_t pgd)
 #define KERNEL_PGD_BOUNDARY	pgd_index(PAGE_OFFSET)
 #define KERNEL_PGD_PTRS		(PTRS_PER_PGD - KERNEL_PGD_BOUNDARY)
 
+#ifdef CONFIG_XIP_KERNEL
+#define BOOT_PGD_COPY_PTRS \
+	((pgd_index((unsigned long)_end)  - pgd_index(PAGE_OFFSET)) + 4)
+#else
+#define BOOT_PGD_COPY_PTRS	KERNEL_PGD_PTRS
+#endif
+
 #ifndef __ASSEMBLY__
 
 extern int direct_gbpages;
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index e2d85c4..d276ebf 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -894,7 +894,7 @@ void __init setup_arch(char **cmdline_p)
 	 */
 	clone_pgd_range(swapper_pg_dir     + KERNEL_PGD_BOUNDARY,
 			initial_page_table + KERNEL_PGD_BOUNDARY,
-			KERNEL_PGD_PTRS);
+			BOOT_PGD_COPY_PTRS);
 
 	load_cr3(swapper_pg_dir);
 	/*
-- 
2.1.0

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/