All calls through hvm_funcs are fully altcall'd. Harden all function pointer
targets.
This optimises away 106 targets.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>
---
xen/arch/x86/hvm/hvm.c | 2 +-
xen/arch/x86/hvm/svm/svm.c | 2 +-
xen/arch/x86/hvm/vmx/vmx.c | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index cdd1529014f2..709a4191efe8 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -88,7 +88,7 @@ unsigned int opt_hvm_debug_level __read_mostly;
integer_param("hvm_debug", opt_hvm_debug_level);
#endif
-struct hvm_function_table hvm_funcs __read_mostly;
+struct hvm_function_table __ro_after_init hvm_funcs;
/*
* The I/O permission bitmap is globally shared by all HVM guests except
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 63535a74b504..b80d4af6cb90 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -2513,7 +2513,7 @@ static void cf_check svm_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
}
}
-static struct hvm_function_table __initdata svm_function_table = {
+static struct hvm_function_table __initdata_cf_clobber svm_function_table = {
.name = "SVM",
.cpu_up_prepare = svm_cpu_up_prepare,
.cpu_dead = svm_cpu_dead,
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 41db538a9e3d..758df3321884 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2473,7 +2473,7 @@ static void cf_check vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
vmx_vmcs_exit(v);
}
-static struct hvm_function_table __initdata vmx_function_table = {
+static struct hvm_function_table __initdata_cf_clobber vmx_function_table = {
.name = "VMX",
.cpu_up_prepare = vmx_cpu_up_prepare,
.cpu_dead = vmx_cpu_dead,
--
2.11.0
On 14.02.2022 13:56, Andrew Cooper wrote:
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -88,7 +88,7 @@ unsigned int opt_hvm_debug_level __read_mostly;
> integer_param("hvm_debug", opt_hvm_debug_level);
> #endif
>
> -struct hvm_function_table hvm_funcs __read_mostly;
> +struct hvm_function_table __ro_after_init hvm_funcs;
Strictly speaking this is an unrelated change. I'm fine with it living here,
but half a sentence would be nice in the description.
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -2513,7 +2513,7 @@ static void cf_check svm_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
> }
> }
>
> -static struct hvm_function_table __initdata svm_function_table = {
> +static struct hvm_function_table __initdata_cf_clobber svm_function_table = {
> .name = "SVM",
> .cpu_up_prepare = svm_cpu_up_prepare,
> .cpu_dead = svm_cpu_dead,
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 41db538a9e3d..758df3321884 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2473,7 +2473,7 @@ static void cf_check vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
> vmx_vmcs_exit(v);
> }
>
> -static struct hvm_function_table __initdata vmx_function_table = {
> +static struct hvm_function_table __initdata_cf_clobber vmx_function_table = {
> .name = "VMX",
> .cpu_up_prepare = vmx_cpu_up_prepare,
> .cpu_dead = vmx_cpu_dead,
While I'd like to re-raise my concern regarding the non-pointer fields
in these structure instances (just consider a sequence of enough bool
bitfields, which effectively can express any value, including ones
which would appear like pointers into .text), since for now all is okay
afaict:
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Jan
On 14/02/2022 13:10, Jan Beulich wrote:
> On 14.02.2022 13:56, Andrew Cooper wrote:
>> --- a/xen/arch/x86/hvm/hvm.c
>> +++ b/xen/arch/x86/hvm/hvm.c
>> @@ -88,7 +88,7 @@ unsigned int opt_hvm_debug_level __read_mostly;
>> integer_param("hvm_debug", opt_hvm_debug_level);
>> #endif
>>
>> -struct hvm_function_table hvm_funcs __read_mostly;
>> +struct hvm_function_table __ro_after_init hvm_funcs;
> Strictly speaking this is an unrelated change. I'm fine with it living here,
> but half a sentence would be nice in the description.
I could split it out, but we could probably make 200 patches of
"sprinkle some __ro_after_init around, now that it exists".
>
>> --- a/xen/arch/x86/hvm/svm/svm.c
>> +++ b/xen/arch/x86/hvm/svm/svm.c
>> @@ -2513,7 +2513,7 @@ static void cf_check svm_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
>> }
>> }
>>
>> -static struct hvm_function_table __initdata svm_function_table = {
>> +static struct hvm_function_table __initdata_cf_clobber svm_function_table = {
>> .name = "SVM",
>> .cpu_up_prepare = svm_cpu_up_prepare,
>> .cpu_dead = svm_cpu_dead,
>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
>> index 41db538a9e3d..758df3321884 100644
>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>> @@ -2473,7 +2473,7 @@ static void cf_check vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
>> vmx_vmcs_exit(v);
>> }
>>
>> -static struct hvm_function_table __initdata vmx_function_table = {
>> +static struct hvm_function_table __initdata_cf_clobber vmx_function_table = {
>> .name = "VMX",
>> .cpu_up_prepare = vmx_cpu_up_prepare,
>> .cpu_dead = vmx_cpu_dead,
> While I'd like to re-raise my concern regarding the non-pointer fields
> in these structure instances (just consider a sequence of enough bool
> bitfields, which effectively can express any value, including ones
> which would appear like pointers into .text), since for now all is okay
> afaict:
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
I should probably put something in the commit message too. It is a
theoretical risk, but not (IMO) a practical one.
~Andrew
On 14/02/2022 13:35, Andrew Cooper wrote:
> On 14/02/2022 13:10, Jan Beulich wrote:
>> On 14.02.2022 13:56, Andrew Cooper wrote:
>>> --- a/xen/arch/x86/hvm/hvm.c
>>> +++ b/xen/arch/x86/hvm/hvm.c
>>> @@ -88,7 +88,7 @@ unsigned int opt_hvm_debug_level __read_mostly;
>>> integer_param("hvm_debug", opt_hvm_debug_level);
>>> #endif
>>>
>>> -struct hvm_function_table hvm_funcs __read_mostly;
>>> +struct hvm_function_table __ro_after_init hvm_funcs;
>> Strictly speaking this is an unrelated change. I'm fine with it living here,
>> but half a sentence would be nice in the description.
> I could split it out, but we could probably make 200 patches of
> "sprinkle some __ro_after_init around, now that it exists".
>
>>> --- a/xen/arch/x86/hvm/svm/svm.c
>>> +++ b/xen/arch/x86/hvm/svm/svm.c
>>> @@ -2513,7 +2513,7 @@ static void cf_check svm_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
>>> }
>>> }
>>>
>>> -static struct hvm_function_table __initdata svm_function_table = {
>>> +static struct hvm_function_table __initdata_cf_clobber svm_function_table = {
>>> .name = "SVM",
>>> .cpu_up_prepare = svm_cpu_up_prepare,
>>> .cpu_dead = svm_cpu_dead,
>>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
>>> index 41db538a9e3d..758df3321884 100644
>>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>>> @@ -2473,7 +2473,7 @@ static void cf_check vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
>>> vmx_vmcs_exit(v);
>>> }
>>>
>>> -static struct hvm_function_table __initdata vmx_function_table = {
>>> +static struct hvm_function_table __initdata_cf_clobber vmx_function_table = {
>>> .name = "VMX",
>>> .cpu_up_prepare = vmx_cpu_up_prepare,
>>> .cpu_dead = vmx_cpu_dead,
>> While I'd like to re-raise my concern regarding the non-pointer fields
>> in these structure instances (just consider a sequence of enough bool
>> bitfields, which effectively can express any value, including ones
>> which would appear like pointers into .text), since for now all is okay
>> afaict:
>> Reviewed-by: Jan Beulich <jbeulich@suse.com>
> I should probably put something in the commit message too. It is a
> theoretical risk, but not (IMO) a practical one.
Updated commit message:
x86/hvm: Use __initdata_cf_clobber for hvm_funcs
Now that all calls through hvm_funcs are fully altcall'd, harden all the svm
and vmx function pointer targets. This drops 106 endbr64 instructions.
Clobbering does come with a theoretical risk. The non-pointer fields of
{svm,vmx}_function_table can in theory happen to form a bit pattern
matching a
pointer into .text at a legal endbr64 instruction, but this is expected
to be
implausible for anything liable to pass code review.
While at it, move hvm_funcs into __ro_after_init now that this exists.
~Andrew
On 14.02.2022 17:39, Andrew Cooper wrote:
> On 14/02/2022 13:35, Andrew Cooper wrote:
>> On 14/02/2022 13:10, Jan Beulich wrote:
>>> On 14.02.2022 13:56, Andrew Cooper wrote:
>>>> --- a/xen/arch/x86/hvm/hvm.c
>>>> +++ b/xen/arch/x86/hvm/hvm.c
>>>> @@ -88,7 +88,7 @@ unsigned int opt_hvm_debug_level __read_mostly;
>>>> integer_param("hvm_debug", opt_hvm_debug_level);
>>>> #endif
>>>>
>>>> -struct hvm_function_table hvm_funcs __read_mostly;
>>>> +struct hvm_function_table __ro_after_init hvm_funcs;
>>> Strictly speaking this is an unrelated change. I'm fine with it living here,
>>> but half a sentence would be nice in the description.
>> I could split it out, but we could probably make 200 patches of
>> "sprinkle some __ro_after_init around, now that it exists".
>>
>>>> --- a/xen/arch/x86/hvm/svm/svm.c
>>>> +++ b/xen/arch/x86/hvm/svm/svm.c
>>>> @@ -2513,7 +2513,7 @@ static void cf_check svm_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
>>>> }
>>>> }
>>>>
>>>> -static struct hvm_function_table __initdata svm_function_table = {
>>>> +static struct hvm_function_table __initdata_cf_clobber svm_function_table = {
>>>> .name = "SVM",
>>>> .cpu_up_prepare = svm_cpu_up_prepare,
>>>> .cpu_dead = svm_cpu_dead,
>>>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
>>>> index 41db538a9e3d..758df3321884 100644
>>>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>>>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>>>> @@ -2473,7 +2473,7 @@ static void cf_check vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
>>>> vmx_vmcs_exit(v);
>>>> }
>>>>
>>>> -static struct hvm_function_table __initdata vmx_function_table = {
>>>> +static struct hvm_function_table __initdata_cf_clobber vmx_function_table = {
>>>> .name = "VMX",
>>>> .cpu_up_prepare = vmx_cpu_up_prepare,
>>>> .cpu_dead = vmx_cpu_dead,
>>> While I'd like to re-raise my concern regarding the non-pointer fields
>>> in these structure instances (just consider a sequence of enough bool
>>> bitfields, which effectively can express any value, including ones
>>> which would appear like pointers into .text), since for now all is okay
>>> afaict:
>>> Reviewed-by: Jan Beulich <jbeulich@suse.com>
>> I should probably put something in the commit message too. It is a
>> theoretical risk, but not (IMO) a practical one.
>
> Updated commit message:
>
> x86/hvm: Use __initdata_cf_clobber for hvm_funcs
>
> Now that all calls through hvm_funcs are fully altcall'd, harden all the svm
> and vmx function pointer targets. This drops 106 endbr64 instructions.
>
> Clobbering does come with a theoretical risk. The non-pointer fields of
> {svm,vmx}_function_table can in theory happen to form a bit pattern
> matching a
> pointer into .text at a legal endbr64 instruction, but this is expected
> to be
> implausible for anything liable to pass code review.
>
> While at it, move hvm_funcs into __ro_after_init now that this exists.
SGTM, thanks.
Jan
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