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Message-Id: <20171004212003.28296-14-thgarnie@google.com>
Date: Wed, 4 Oct 2017 14:19:49 -0700
From: Thomas Garnier <thgarnie@...gle.com>
To: Herbert Xu <herbert@...dor.apana.org.au>,
"David S . Miller" <davem@...emloft.net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Thomas Garnier <thgarnie@...gle.com>,
Arnd Bergmann <arnd@...db.de>,
Kees Cook <keescook@...omium.org>,
Matthias Kaehlcke <mka@...omium.org>,
Tom Lendacky <thomas.lendacky@....com>,
Andy Lutomirski <luto@...nel.org>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Borislav Petkov <bp@...e.de>,
"Rafael J . Wysocki" <rjw@...ysocki.net>,
Len Brown <len.brown@...el.com>,
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Juergen Gross <jgross@...e.com>,
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Masahiro Yamada <yamada.masahiro@...ionext.com>,
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Daniel Borkmann <daniel@...earbox.net>,
Markus Trippelsdorf <markus@...ppelsdorf.de>,
Paolo Bonzini <pbonzini@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Joerg Roedel <joro@...tes.org>,
Rik van Riel <riel@...hat.com>,
David Howells <dhowells@...hat.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Waiman Long <longman@...hat.com>,
Kyle Huey <me@...ehuey.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Jonathan Corbet <corbet@....net>,
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Peter Foley <pefoley2@...oley.com>,
Paul Bolle <pebolle@...cali.nl>,
Jiri Kosina <jkosina@...e.cz>,
Rob Landley <rob@...dley.net>,
"H . J . Lu" <hjl.tools@...il.com>,
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Cc: x86@...nel.org,
linux-crypto@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
xen-devel@...ts.xenproject.org,
linux-arch@...r.kernel.org,
linux-sparse@...r.kernel.org,
kvm@...r.kernel.org,
linux-doc@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: [RFC v3 13/27] x86/boot/64: Use _text in a global for PIE support
By default PIE generated code create only relative references so _text
points to the temporary virtual address. Instead use a global variable
so the relocation is done as expected.
Position Independent Executable (PIE) support will allow to extended the
KASLR randomization range below the -2G memory limit.
Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
---
arch/x86/kernel/head64.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index bab4fa579450..675f1dba3b21 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -45,8 +45,14 @@ static void __head *fixup_pointer(void *ptr, unsigned long physaddr)
return ptr - (void *)_text + (void *)physaddr;
}
-unsigned long __head __startup_64(unsigned long physaddr,
- struct boot_params *bp)
+/*
+ * Use a global variable to properly calculate _text delta on PIE. By default
+ * a PIE binary do a RIP relative difference instead of the relocated address.
+ */
+unsigned long _text_offset = (unsigned long)(_text - __START_KERNEL_map);
+
+unsigned long __head notrace __startup_64(unsigned long physaddr,
+ struct boot_params *bp)
{
unsigned long load_delta, *p;
unsigned long pgtable_flags;
@@ -65,7 +71,7 @@ unsigned long __head __startup_64(unsigned long physaddr,
* Compute the delta between the address I am compiled to run at
* and the address I am actually running at.
*/
- load_delta = physaddr - (unsigned long)(_text - __START_KERNEL_map);
+ load_delta = physaddr - _text_offset;
/* Is the address not 2M aligned? */
if (load_delta & ~PMD_PAGE_MASK)
--
2.14.2.920.gcf0c67979c-goog
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