Re: [PATCH 15/21] x86/xen/pvh: Convert indirect jump to retpoline
On Fri, Jan 15, 2021 at 06:24:10AM +0100, Jürgen Groß wrote: > On 14.01.21 20:40, Josh Poimboeuf wrote: > > It's kernel policy to not have (unannotated) indirect jumps because of > > Spectre v2. This one's probably harmless, but better safe than sorry. > > Convert it to a retpoline. > > > > Cc: Boris Ostrovsky > > Cc: Juergen Gross > > Signed-off-by: Josh Poimboeuf > > --- > > arch/x86/platform/pvh/head.S | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S > > index 43b4d864817e..d87cebd08d32 100644 > > --- a/arch/x86/platform/pvh/head.S > > +++ b/arch/x86/platform/pvh/head.S > > @@ -16,6 +16,7 @@ > > #include > > #include > > #include > > +#include > > #include > > __HEAD > > @@ -105,7 +106,7 @@ SYM_CODE_START_LOCAL(pvh_start_xen) > > /* startup_64 expects boot_params in %rsi. */ > > mov $_pa(pvh_bootparams), %rsi > > mov $_pa(startup_64), %rax > > - jmp *%rax > > + JMP_NOSPEC rax > > I'd rather have it annotated only. > > Using ALTERNATIVE in very early boot code is just adding needless > clutter, as the retpoline variant won't ever be active. Yeah, Andy pointed out something similar. I'll be changing this to an annotation. -- Josh
Re: [PATCH 15/21] x86/xen/pvh: Convert indirect jump to retpoline
On 14.01.21 20:40, Josh Poimboeuf wrote: It's kernel policy to not have (unannotated) indirect jumps because of Spectre v2. This one's probably harmless, but better safe than sorry. Convert it to a retpoline. Cc: Boris Ostrovsky Cc: Juergen Gross Signed-off-by: Josh Poimboeuf --- arch/x86/platform/pvh/head.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S index 43b4d864817e..d87cebd08d32 100644 --- a/arch/x86/platform/pvh/head.S +++ b/arch/x86/platform/pvh/head.S @@ -16,6 +16,7 @@ #include #include #include +#include #include __HEAD @@ -105,7 +106,7 @@ SYM_CODE_START_LOCAL(pvh_start_xen) /* startup_64 expects boot_params in %rsi. */ mov $_pa(pvh_bootparams), %rsi mov $_pa(startup_64), %rax - jmp *%rax + JMP_NOSPEC rax I'd rather have it annotated only. Using ALTERNATIVE in very early boot code is just adding needless clutter, as the retpoline variant won't ever be active. Juergen OpenPGP_0xB0DE9DD628BF132F.asc Description: application/pgp-keys OpenPGP_signature Description: OpenPGP digital signature
Re: [PATCH 15/21] x86/xen/pvh: Convert indirect jump to retpoline
On 1/14/21 2:40 PM, Josh Poimboeuf wrote: > It's kernel policy to not have (unannotated) indirect jumps because of > Spectre v2. This one's probably harmless, but better safe than sorry. > Convert it to a retpoline. > > Cc: Boris Ostrovsky > Cc: Juergen Gross > Signed-off-by: Josh Poimboeuf Reviewed-by: Boris Ostrovsky
