x86/build: Move _etext to actual end of .text

[ Upstream commit 392bef709659abea614abfe53cf228e7a59876a4 ]

When building x86 with Clang LTO and CFI, CFI jump regions are
automatically added to the end of the .text section late in linking. As a
result, the _etext position was being labelled before the appended jump
regions, causing confusion about where the boundaries of the executable
region actually are in the running kernel, and broke at least the fault
injection code. This moves the _etext mark to outside (and immediately
after) the .text area, as it already the case on other architectures
(e.g. arm64, arm).

Reported-and-tested-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20190423183827.GA4012@beast
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 2384a2ae5ec3e9db7e660d80b45dfc4287cb9139..23df6eebe82f4c0a9938ebd5b23e99f74d7d1d00 100644 (file)
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -131,11 +131,11 @@ SECTIONS
                *(.text.__x86.indirect_thunk)
                __indirect_thunk_end = .;
 #endif
-
-               /* End of text section */
-               _etext = .;
        } :text = 0x9090
 
+       /* End of text section */
+       _etext = .;
+
        NOTES :text :note
 
        EXCEPTION_TABLE(16) :text = 0x9090