2019-05-20 23:22:32

by Thomas Garnier

Subject: [PATCH v7 11/12] x86/paravirt: Adapt assembly for PIE support

From: Thomas Garnier <[email protected]>

if PIE is enabled, switch the paravirt assembly constraints to be
compatible. The %c/i constrains generate smaller code so is kept by
default.

Position Independent Executable (PIE) support will allow to extend the
KASLR randomization range below 0xffffffff80000000.

Signed-off-by: Thomas Garnier <[email protected]>
---
arch/x86/include/asm/paravirt_types.h | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 2474e434a6f7..93be18bdb63e 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -343,9 +343,17 @@ extern struct paravirt_patch_template pv_ops;
#define PARAVIRT_PATCH(x) \
(offsetof(struct paravirt_patch_template, x) / sizeof(void *))

+#ifdef CONFIG_X86_PIE
+#define paravirt_opptr_call "a"
+#define paravirt_opptr_type "p"
+#else
+#define paravirt_opptr_call "c"
+#define paravirt_opptr_type "i"
+#endif
+
#define paravirt_type(op) \
[paravirt_typenum] "i" (PARAVIRT_PATCH(op)), \
- [paravirt_opptr] "i" (&(pv_ops.op))
+ [paravirt_opptr] paravirt_opptr_type (&(pv_ops.op))
#define paravirt_clobber(clobber) \
[paravirt_clobber] "i" (clobber)

@@ -393,7 +401,7 @@ int paravirt_disable_iospace(void);
*/
#define PARAVIRT_CALL \
ANNOTATE_RETPOLINE_SAFE \
- "call *%c[paravirt_opptr];"
+ "call *%" paravirt_opptr_call "[paravirt_opptr];"

/*
* These macros are intended to wrap calls through one of the paravirt
--
2.21.0.1020.gf2820cf01a-goog

2019-05-27 05:50:59

by Juergen Gross

Subject: Re: [PATCH v7 11/12] x86/paravirt: Adapt assembly for PIE support

On 21/05/2019 01:19, Thomas Garnier wrote:
> From: Thomas Garnier <[email protected]>
>
> if PIE is enabled, switch the paravirt assembly constraints to be
> compatible. The %c/i constrains generate smaller code so is kept by
> default.
>
> Position Independent Executable (PIE) support will allow to extend the
> KASLR randomization range below 0xffffffff80000000.
>
> Signed-off-by: Thomas Garnier <[email protected]>

Acked-by: Juergen Gross <[email protected]>


Juergen

2019-05-29 15:52:09

by Thomas Garnier

Subject: Re: [PATCH v7 11/12] x86/paravirt: Adapt assembly for PIE support

On Sun, May 26, 2019 at 10:47 PM Juergen Gross <[email protected]> wrote:
>
> On 21/05/2019 01:19, Thomas Garnier wrote:
> > From: Thomas Garnier <[email protected]>
> >
> > if PIE is enabled, switch the paravirt assembly constraints to be
> > compatible. The %c/i constrains generate smaller code so is kept by
> > default.
> >
> > Position Independent Executable (PIE) support will allow to extend the
> > KASLR randomization range below 0xffffffff80000000.
> >
> > Signed-off-by: Thomas Garnier <[email protected]>
>
> Acked-by: Juergen Gross <[email protected]>

Thanks Juergen.

>
>
> Juergen