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Groups > linux.kernel > #1342137
| From | Boris Ostrovsky <boris.ostrovsky@oracle.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v2] xen/x86: Zero out .bss for PV guests |
| Date | 2016-02-24 16:30 +0100 |
| Message-ID | <r5Jy2-6wc-35@gated-at.bofh.it> (permalink) |
| Organization | linux.* mail to news gateway |
Baremetal kernels clear .bss early in the boot but Xen PV guests don't execute that code. They have been able to run without problems because Xen domain builder happens to give out zeroed pages. However, since this is not really guaranteed, .bss should be explicitly cleared. (Since we introduce macros for specifying 32- and 64-bit registers we can get rid of ifdefs in startup_xen()) Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: stable@vger.kernel.org --- arch/x86/xen/xen-head.S | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index b65f59a..2af87d1 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -35,16 +35,31 @@ #define PVH_FEATURES (0) #endif - __INIT -ENTRY(startup_xen) - cld #ifdef CONFIG_X86_32 - mov %esi,xen_start_info - mov $init_thread_union+THREAD_SIZE,%esp +#define REG(register) %e##register +#define WSIZE_SHIFT 2 +#define STOS stosl #else - mov %rsi,xen_start_info - mov $init_thread_union+THREAD_SIZE,%rsp +#define REG(register) %r##register +#define WSIZE_SHIFT 3 +#define STOS stosq #endif + + __INIT +ENTRY(startup_xen) + cld + + /* Clear .bss */ + xor REG(ax),REG(ax) + mov $__bss_start,REG(di) + mov $__bss_stop,REG(cx) + sub REG(di),REG(cx) + shr $WSIZE_SHIFT,REG(cx) + rep STOS + + mov REG(si),xen_start_info + mov $init_thread_union+THREAD_SIZE,REG(sp) + jmp xen_start_kernel __FINIT -- 2.1.0
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[PATCH v2] xen/x86: Zero out .bss for PV guests Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-02-24 16:30 +0100
Re: [PATCH v2] xen/x86: Zero out .bss for PV guests Brian Gerst <brgerst@gmail.com> - 2016-02-24 17:10 +0100
Re: [PATCH v2] xen/x86: Zero out .bss for PV guests Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-02-24 17:40 +0100
Re: [Xen-devel] [PATCH v2] xen/x86: Zero out .bss for PV guests Andrew Cooper <andrew.cooper3@citrix.com> - 2016-02-24 18:30 +0100
Re: [Xen-devel] [PATCH v2] xen/x86: Zero out .bss for PV guests Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-02-24 18:50 +0100
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