Re: [PATCH RFC 16/43] x86-64: Use per-cpu stack canary if supported by compiler

["Hou Wenlong" <houwenlong.hwl@xxxxxxxxxxxx>]

On Thu, May 04, 2023 at 12:31:59PM +0200, Juergen Gross wrote:
> On 28.04.23 11:50, Hou Wenlong wrote:
> >From: Brian Gerst <brgerst@xxxxxxxxx>
> >
> >From: Brian Gerst <brgerst@xxxxxxxxx>
> >
> >If the compiler supports it, use a standard per-cpu variable for the
> >stack protector instead of the old fixed location.  Keep the fixed
> >location code for compatibility with older compilers.
> >
> >[Hou Wenlong: Disable it on Clang, adapt new code change and adapt
> >missing GS set up path in pvh_start_xen()]
> >
> >Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
> >Co-developed-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
> >Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
> >Cc: Thomas Garnier <thgarnie@xxxxxxxxxxxx>
> >Cc: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
> >Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> >---
> >  arch/x86/Kconfig                      | 12 ++++++++++++
> >  arch/x86/Makefile                     | 21 ++++++++++++++-------
> >  arch/x86/entry/entry_64.S             |  6 +++++-
> >  arch/x86/include/asm/processor.h      | 17 ++++++++++++-----
> >  arch/x86/include/asm/stackprotector.h | 16 +++++++---------
> >  arch/x86/kernel/asm-offsets_64.c      |  2 +-
> >  arch/x86/kernel/cpu/common.c          | 15 +++++++--------
> >  arch/x86/kernel/head_64.S             | 16 ++++++++++------
> >  arch/x86/kernel/vmlinux.lds.S         |  4 +++-
> >  arch/x86/platform/pvh/head.S          |  8 ++++++++
> >  arch/x86/xen/xen-head.S               | 14 +++++++++-----
> >  11 files changed, 88 insertions(+), 43 deletions(-)
> >
> 
> ...
> 
> >diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
> >index 643d02900fbb..09eaf59e8066 100644
> >--- a/arch/x86/xen/xen-head.S
> >+++ b/arch/x86/xen/xen-head.S
> >@@ -51,15 +51,19 @@ SYM_CODE_START(startup_xen)
> >     leaq    (__end_init_task - PTREGS_SIZE)(%rip), %rsp
> >-    /* Set up %gs.
> >-     *
> >-     * The base of %gs always points to fixed_percpu_data.  If the
> >-     * stack protector canary is enabled, it is located at %gs:40.
> >+    /*
> >+     * Set up GS base.
> >      * Note that, on SMP, the boot cpu uses init data section until
> >      * the per cpu areas are set up.
> >      */
> >     movl    $MSR_GS_BASE,%ecx
> >-    movq    $INIT_PER_CPU_VAR(fixed_percpu_data),%rax
> >+#if defined(CONFIG_STACKPROTECTOR_FIXED)
> >+    leaq    INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
> >+#elif defined(CONFIG_SMP)
> >+    movabs  $__per_cpu_load, %rdx
> 
> Shouldn't above 2 targets be %rax?
>
Ah yes, my mistake. I didn't test it on XEN guest, sorry,
I'll test XEN guest before the next submission.

Thanks.

> >+#else
> >+    xorl    %eax, %eax
> >+#endif
> >     cdq
> >     wrmsr
> 
> 
> Juergen

> pub  2048R/28BF132F 2014-06-02 Juergen Gross <jg@xxxxxxxxx>
> uid                            Juergen Gross <jgross@xxxxxxxx>
> uid                            Juergen Gross <jgross@xxxxxxxxxx>
> uid                            Juergen Gross <jgross@xxxxxxx>
> sub  2048R/16375B53 2014-06-02