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[RFC PATCH v3 0/2] selftests/x86: sysret_rip update for FRED system

Ammar Faizi posted 2 patches 3 years ago 
tools/testing/selftests/x86/sysret_rip.c | 120 ++++++++++++++++++++++-
1 file changed, 119 insertions(+), 1 deletion(-)
[RFC PATCH v3 0/2] selftests/x86: sysret_rip update for FRED system
Posted by Ammar Faizi 3 years ago 
From: Ammar Faizi <ammarfaizi2@gnuweeb.org>

This is an RFC patchset v3:
sysret_rip test update for Intel FRED architecture. 

Xin Li reported sysret_rip test fails at:

        assert(ctx->uc_mcontext.gregs[REG_EFL] ==
               ctx->uc_mcontext.gregs[REG_R11]);

in a FRED system. Let's handle the FRED system scenario too. The
'syscall' instruction in a FRED system doesn't set %r11=%rflags.

There are two patches in this series.

How to test this:

  $ make -C tools/testing/selftests/x86
  $ tools/testing/selftests/x86/sysret_rip_64

Link: https://lore.kernel.org/lkml/5d4ad3e3-034f-c7da-d141-9c001c2343af@intel.com
Fixes: 660602140103 ("selftests/x86: Add a selftest for SYSRET to noncanonical addresses")
Link: https://lore.kernel.org/lkml/25b96960-a07e-a952-5c23-786b55054126@zytor.com
Reported-by: Xin Li <xin3.li@intel.com>
Co-developed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---

## Changelog v3:

   - Test that we don't get a mix of REGS_SAVED and REGS_SYSRET,
     which is a major part of the point (hpa).

## Changelog v2:

   - Use "+r"(rsp) as the right way to avoid redzone problems
     per Andrew's comment (hpa).
     (Ref: https://lore.kernel.org/lkml/8f5c24df-514d-5d89-f58f-ec8c3eb1e049@zytor.com )

---

Ammar Faizi (2):
  selftests/x86: sysret_rip: Handle syscall in a FRED system
  selftests/x86: sysret_rip: Add more syscall tests with respect to `%rcx` and `%r11`

 tools/testing/selftests/x86/sysret_rip.c | 120 ++++++++++++++++++++++-
 1 file changed, 119 insertions(+), 1 deletion(-)


base-commit: e12ad468c22065a2826b2fc4c11d2113a7975301
-- 
Ammar Faizi
RE: [RFC PATCH v3 0/2] selftests/x86: sysret_rip update for FRED system
Posted by Li, Xin3 3 years ago 
> From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
> 
> This is an RFC patchset v3:
> sysret_rip test update for Intel FRED architecture.
> 
> Xin Li reported sysret_rip test fails at:
> 
>         assert(ctx->uc_mcontext.gregs[REG_EFL] ==
>                ctx->uc_mcontext.gregs[REG_R11]);

On FRED systems, flags is 0x200a93 and r11 is 0xfeedfacedeadbeef here.

We need to remove or change this assertion, maybe:
  assert(ctx->uc_mcontext.gregs[REG_EFL] == ctx->uc_mcontext.gregs[REG_R11] ||
         r11_sentinel == ctx->uc_mcontext.gregs[REG_R11]);

> 
> in a FRED system. Let's handle the FRED system scenario too. The 'syscall'
> instruction in a FRED system doesn't set %r11=%rflags.
> 
> There are two patches in this series.
> 
> How to test this:
> 
>   $ make -C tools/testing/selftests/x86
>   $ tools/testing/selftests/x86/sysret_rip_64
> 
> Link: https://lore.kernel.org/lkml/5d4ad3e3-034f-c7da-d141-
> 9c001c2343af@intel.com
> Fixes: 660602140103 ("selftests/x86: Add a selftest for SYSRET to noncanonical
> addresses")
> Link: https://lore.kernel.org/lkml/25b96960-a07e-a952-5c23-
> 786b55054126@zytor.com
> Reported-by: Xin Li <xin3.li@intel.com>
> Co-developed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
> ---
> 
> ## Changelog v3:
> 
>    - Test that we don't get a mix of REGS_SAVED and REGS_SYSRET,
>      which is a major part of the point (hpa).
> 
> ## Changelog v2:
> 
>    - Use "+r"(rsp) as the right way to avoid redzone problems
>      per Andrew's comment (hpa).
>      (Ref: https://lore.kernel.org/lkml/8f5c24df-514d-5d89-f58f-
> ec8c3eb1e049@zytor.com )
> 
> ---
> 
> Ammar Faizi (2):
>   selftests/x86: sysret_rip: Handle syscall in a FRED system
>   selftests/x86: sysret_rip: Add more syscall tests with respect to `%rcx` and `%r11`
> 
>  tools/testing/selftests/x86/sysret_rip.c | 120 ++++++++++++++++++++++-
>  1 file changed, 119 insertions(+), 1 deletion(-)
> 
> 
> base-commit: e12ad468c22065a2826b2fc4c11d2113a7975301
> --
> Ammar Faizi
RE: [RFC PATCH v3 0/2] selftests/x86: sysret_rip update for FRED system
Posted by H. Peter Anvin 3 years ago 
On January 24, 2023 1:32:14 PM PST, "Li, Xin3" <xin3.li@intel.com> wrote:
>> From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
>> 
>> This is an RFC patchset v3:
>> sysret_rip test update for Intel FRED architecture.
>> 
>> Xin Li reported sysret_rip test fails at:
>> 
>>         assert(ctx->uc_mcontext.gregs[REG_EFL] ==
>>                ctx->uc_mcontext.gregs[REG_R11]);
>
>On FRED systems, flags is 0x200a93 and r11 is 0xfeedfacedeadbeef here.
>
>We need to remove or change this assertion, maybe:
>  assert(ctx->uc_mcontext.gregs[REG_EFL] == ctx->uc_mcontext.gregs[REG_R11] ||
>         r11_sentinel == ctx->uc_mcontext.gregs[REG_R11]);
>
>> 
>> in a FRED system. Let's handle the FRED system scenario too. The 'syscall'
>> instruction in a FRED system doesn't set %r11=%rflags.
>> 
>> There are two patches in this series.
>> 
>> How to test this:
>> 
>>   $ make -C tools/testing/selftests/x86
>>   $ tools/testing/selftests/x86/sysret_rip_64
>> 
>> Link: https://lore.kernel.org/lkml/5d4ad3e3-034f-c7da-d141-
>> 9c001c2343af@intel.com
>> Fixes: 660602140103 ("selftests/x86: Add a selftest for SYSRET to noncanonical
>> addresses")
>> Link: https://lore.kernel.org/lkml/25b96960-a07e-a952-5c23-
>> 786b55054126@zytor.com
>> Reported-by: Xin Li <xin3.li@intel.com>
>> Co-developed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
>> Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
>> Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>
>> Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
>> ---
>> 
>> ## Changelog v3:
>> 
>>    - Test that we don't get a mix of REGS_SAVED and REGS_SYSRET,
>>      which is a major part of the point (hpa).
>> 
>> ## Changelog v2:
>> 
>>    - Use "+r"(rsp) as the right way to avoid redzone problems
>>      per Andrew's comment (hpa).
>>      (Ref: https://lore.kernel.org/lkml/8f5c24df-514d-5d89-f58f-
>> ec8c3eb1e049@zytor.com )
>> 
>> ---
>> 
>> Ammar Faizi (2):
>>   selftests/x86: sysret_rip: Handle syscall in a FRED system
>>   selftests/x86: sysret_rip: Add more syscall tests with respect to `%rcx` and `%r11`
>> 
>>  tools/testing/selftests/x86/sysret_rip.c | 120 ++++++++++++++++++++++-
>>  1 file changed, 119 insertions(+), 1 deletion(-)
>> 
>> 
>> base-commit: e12ad468c22065a2826b2fc4c11d2113a7975301
>> --
>> Ammar Faizi
>
>

This should use check_regs_result() – which is exactly the reason I made that a separate function.
Re: [RFC PATCH v3 0/2] selftests/x86: sysret_rip update for FRED system
Posted by Ammar Faizi 3 years ago 
On Tue, Jan 24, 2023 at 01:37:43PM -0800, H. Peter Anvin wrote:
> On January 24, 2023 1:32:14 PM PST, "Li, Xin3" <xin3.li@intel.com> wrote:
> >> From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
> >> 
> >> This is an RFC patchset v3:
> >> sysret_rip test update for Intel FRED architecture.
> >> 
> >> Xin Li reported sysret_rip test fails at:
> >> 
> >>         assert(ctx->uc_mcontext.gregs[REG_EFL] ==
> >>                ctx->uc_mcontext.gregs[REG_R11]);
> >
> >On FRED systems, flags is 0x200a93 and r11 is 0xfeedfacedeadbeef here.
> >
> >We need to remove or change this assertion, maybe:
> >  assert(ctx->uc_mcontext.gregs[REG_EFL] == ctx->uc_mcontext.gregs[REG_R11] ||
> >         r11_sentinel == ctx->uc_mcontext.gregs[REG_R11]);
> >
>
> This should use check_regs_result() – which is exactly the reason I made that a separate function.

Fixed in v4.

-- 
Ammar Faizi
RE: [RFC PATCH v3 0/2] selftests/x86: sysret_rip update for FRED system
Posted by Li, Xin3 3 years ago 
> >>
> >> Xin Li reported sysret_rip test fails at:
> >>
> >>         assert(ctx->uc_mcontext.gregs[REG_EFL] ==
> >>                ctx->uc_mcontext.gregs[REG_R11]);
> >
> >On FRED systems, flags is 0x200a93 and r11 is 0xfeedfacedeadbeef here.
> >
> >We need to remove or change this assertion, maybe:
> >  assert(ctx->uc_mcontext.gregs[REG_EFL] == ctx->uc_mcontext.gregs[REG_R11] ||
> >         r11_sentinel == ctx->uc_mcontext.gregs[REG_R11]);
> >
> >>
> >> in a FRED system. Let's handle the FRED system scenario too. The 'syscall'
> >> instruction in a FRED system doesn't set %r11=%rflags.
> >>
> 
> This should use check_regs_result() – which is exactly the reason I made that a
> separate function.

Exactly.
Re: [RFC PATCH v3 0/2] selftests/x86: sysret_rip update for FRED system
Posted by Andrew Cooper 3 years ago 
On 24/01/2023 9:32 pm, Li, Xin3 wrote:
>> From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
>>
>> This is an RFC patchset v3:
>> sysret_rip test update for Intel FRED architecture.
>>
>> Xin Li reported sysret_rip test fails at:
>>
>>         assert(ctx->uc_mcontext.gregs[REG_EFL] ==
>>                ctx->uc_mcontext.gregs[REG_R11]);
> On FRED systems, flags is 0x200a93 and r11 is 0xfeedfacedeadbeef here.

Is this under SIMICS, or elsewhere?  It's doubly weird that flags/%r11
match, but %rip/%rcx don't.

~Andrew
RE: [RFC PATCH v3 0/2] selftests/x86: sysret_rip update for FRED system
Posted by Li, Xin3 3 years ago 
> >>         assert(ctx->uc_mcontext.gregs[REG_EFL] ==
> >>                ctx->uc_mcontext.gregs[REG_R11]);
> > On FRED systems, flags is 0x200a93 and r11 is 0xfeedfacedeadbeef here.
> 
> Is this under SIMICS, or elsewhere?  It's doubly weird that flags/%r11 match, but
> %rip/%rcx don't.

This is on Intel Simics, with FRED enabled.

Flags and %r11 don’t match on FRED, and %rip and %rcx also don't match.

I think it's expected.

Xin

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