[tip: x86/build] x86/vmlinux: Actually use _etext for the end of the text segment

[tip: x86/build] x86/vmlinux: Actually use _etext for the end of the text segment

[tip-bot2 for Kees Cook]

The following commit has been merged into the x86/build branch of tip:

Commit-ID:     b907693883fdcff5b492cf0cd02a0e264623055e
Gitweb:        https://git.kernel.org/tip/b907693883fdcff5b492cf0cd02a0e264623055e
Author:        Kees Cook <keescook@chromium.org>
AuthorDate:    Tue, 29 Oct 2019 14:13:37 -07:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Mon, 04 Nov 2019 17:54:16 +01:00

x86/vmlinux: Actually use _etext for the end of the text segment

Various calculations are using the end of the exception table (which
does not need to be executable) as the end of the text segment. Instead,
in preparation for moving the exception table into RO_DATA, move _etext
after the exception table and update the calculations.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-alpha@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-ia64@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Ross Zwisler <zwisler@chromium.org>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Lendacky <Thomas.Lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Cc: x86-ml <x86@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: https://lkml.kernel.org/r/20191029211351.13243-16-keescook@chromium.org
---
 arch/x86/include/asm/sections.h | 1 -
 arch/x86/kernel/vmlinux.lds.S   | 7 +++----
 arch/x86/mm/init_64.c           | 6 +++---
 arch/x86/mm/pti.c               | 2 +-
 4 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h
index 71b32f2..036c360 100644
--- a/arch/x86/include/asm/sections.h
+++ b/arch/x86/include/asm/sections.h
@@ -6,7 +6,6 @@
 #include <asm/extable.h>
 
 extern char __brk_base[], __brk_limit[];
-extern struct exception_table_entry __stop___ex_table[];
 extern char __end_rodata_aligned[];
 
 #if defined(CONFIG_X86_64)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 41362e9..a1a758e 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -143,15 +143,14 @@ SECTIONS
 		*(.text.__x86.indirect_thunk)
 		__indirect_thunk_end = .;
 #endif
-
-		/* End of text section */
-		_etext = .;
 	} :text = 0x9090
 
 	EXCEPTION_TABLE(16)
 
-	/* .text should occupy whole number of pages */
+	/* End of text section, which should occupy whole number of pages */
+	_etext = .;
 	. = ALIGN(PAGE_SIZE);
+
 	X86_ALIGN_RODATA_BEGIN
 	RO_DATA(PAGE_SIZE)
 	X86_ALIGN_RODATA_END
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index a6b5c65..26299e9 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1263,7 +1263,7 @@ int kernel_set_to_readonly;
 void set_kernel_text_rw(void)
 {
 	unsigned long start = PFN_ALIGN(_text);
-	unsigned long end = PFN_ALIGN(__stop___ex_table);
+	unsigned long end = PFN_ALIGN(_etext);
 
 	if (!kernel_set_to_readonly)
 		return;
@@ -1282,7 +1282,7 @@ void set_kernel_text_rw(void)
 void set_kernel_text_ro(void)
 {
 	unsigned long start = PFN_ALIGN(_text);
-	unsigned long end = PFN_ALIGN(__stop___ex_table);
+	unsigned long end = PFN_ALIGN(_etext);
 
 	if (!kernel_set_to_readonly)
 		return;
@@ -1301,7 +1301,7 @@ void mark_rodata_ro(void)
 	unsigned long start = PFN_ALIGN(_text);
 	unsigned long rodata_start = PFN_ALIGN(__start_rodata);
 	unsigned long end = (unsigned long) &__end_rodata_hpage_align;
-	unsigned long text_end = PFN_ALIGN(&__stop___ex_table);
+	unsigned long text_end = PFN_ALIGN(&_etext);
 	unsigned long rodata_end = PFN_ALIGN(&__end_rodata);
 	unsigned long all_end;
 
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 7f21404..44a9f06 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -574,7 +574,7 @@ static void pti_clone_kernel_text(void)
 	 */
 	unsigned long start = PFN_ALIGN(_text);
 	unsigned long end_clone  = (unsigned long)__end_rodata_aligned;
-	unsigned long end_global = PFN_ALIGN((unsigned long)__stop___ex_table);
+	unsigned long end_global = PFN_ALIGN((unsigned long)_etext);
 
 	if (!pti_kernel_image_global_ok())
 		return;