[RFC 05/22] xen: Adapt assembly for PIE support
From: Thomas Garnier <hidden>
Date: 2017-07-18 22:33:16
Also in:
kvm, linux-arch, linux-crypto, xen-devel
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), xen hypervisor x86 · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Juergen Gross
Change the assembly code to use the new _ASM_GET_PTR macro which get a symbol reference while being PIE compatible. Modify the RELOC macro that was using an assignment generating a non-relative reference. Position Independent Executable (PIE) support will allow to extended the KASLR randomization range below the -2G memory limit. Signed-off-by: Thomas Garnier <redacted> --- arch/x86/xen/xen-asm.h | 3 ++- arch/x86/xen/xen-head.S | 9 +++++---- 2 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/arch/x86/xen/xen-asm.h b/arch/x86/xen/xen-asm.h
index 465276467a47..3b1c8a2e77d8 100644
--- a/arch/x86/xen/xen-asm.h
+++ b/arch/x86/xen/xen-asm.h@@ -2,8 +2,9 @@ #define _XEN_XEN_ASM_H #include <linux/linkage.h> +#include <asm/asm.h> -#define RELOC(x, v) .globl x##_reloc; x##_reloc=v +#define RELOC(x, v) .globl x##_reloc; x##_reloc: _ASM_PTR v #define ENDPATCH(x) .globl x##_end; x##_end=. /* Pseudo-flag used for virtual NMI, which we don't implement yet */
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 72a8e6adebe6..ab2462396bd8 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S@@ -23,14 +23,15 @@ ENTRY(startup_xen) /* Clear .bss */ xor %eax,%eax - mov $__bss_start, %_ASM_DI - mov $__bss_stop, %_ASM_CX + _ASM_GET_PTR(__bss_start, %_ASM_DI) + _ASM_GET_PTR(__bss_stop, %_ASM_CX) sub %_ASM_DI, %_ASM_CX shr $__ASM_SEL(2, 3), %_ASM_CX rep __ASM_SIZE(stos) - mov %_ASM_SI, xen_start_info - mov $init_thread_union+THREAD_SIZE, %_ASM_SP + _ASM_GET_PTR(xen_start_info, %_ASM_AX) + mov %_ASM_SI, (%_ASM_AX) + _ASM_GET_PTR(init_thread_union+THREAD_SIZE, %_ASM_SP) jmp xen_start_kernel
--
2.13.2.932.g7449e964c-goog
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