linux-kernel - Re: [PATCH v8 27/27] x86/cet/shstk: Add Shadow Stack instructions to opcode map

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Date:   Fri, 8 Nov 2019 15:27:29 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...capital.net>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>
Subject: Re: [PATCH v8 27/27] x86/cet/shstk: Add Shadow Stack instructions to
 opcode map

On 13/08/19 11:52 PM, Yu-cheng Yu wrote:
> Add the following shadow stack management instructions.
> 
> INCSSP:
>     Increment shadow stack pointer by the steps specified.
> 
> RDSSP:
>     Read SSP register into a GPR.
> 
> SAVEPREVSSP:
>     Use "prev ssp" token at top of current shadow stack to
>     create a "restore token" on previous shadow stack.
> 
> RSTORSSP:
>     Restore from a "restore token" pointed by a GPR to SSP.
> 
> WRSS:
>     Write to kernel-mode shadow stack (kernel-mode instruction).
> 
> WRUSS:
>     Write to user-mode shadow stack (kernel-mode instruction).
> 
> SETSSBSY:
>     Verify the "supervisor token" pointed by IA32_PL0_SSP MSR,
>     if valid, set the token to busy, and set SSP to the value
>     of IA32_PL0_SSP MSR.
> 
> CLRSSBSY:
>     Verify the "supervisor token" pointed by a GPR, if valid,
>     clear the busy bit from the token.
> 
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> ---
>  arch/x86/lib/x86-opcode-map.txt               | 26 +++++++++++++------
>  tools/objtool/arch/x86/lib/x86-opcode-map.txt | 26 +++++++++++++------
>  2 files changed, 36 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/lib/x86-opcode-map.txt b/arch/x86/lib/x86-opcode-map.txt
> index e0b85930dd77..c5e825d44766 100644
> --- a/arch/x86/lib/x86-opcode-map.txt
> +++ b/arch/x86/lib/x86-opcode-map.txt
> @@ -366,7 +366,7 @@ AVXcode: 1
>  1b: BNDCN Gv,Ev (F2) | BNDMOV Ev,Gv (66) | BNDMK Gv,Ev (F3) | BNDSTX Ev,Gv
>  1c:
>  1d:
> -1e:
> +1e: RDSSP Rd (F3),REX.W
>  1f: NOP Ev
>  # 0x0f 0x20-0x2f
>  20: MOV Rd,Cd
> @@ -610,7 +610,17 @@ fe: paddd Pq,Qq | vpaddd Vx,Hx,Wx (66),(v1)
>  ff: UD0
>  EndTable
>  
> -Table: 3-byte opcode 1 (0x0f 0x38)
> +Table: 3-byte opcode 1 (0x0f 0x01)
> +Referrer:
> +AVXcode:
> +# Skip 0x00-0xe7
> +e8: SETSSBSY (f3)
> +e9:
> +ea: SAVEPREVSSP (f3)
> +# Skip 0xeb-0xff
> +EndTable
> +
> +Table: 3-byte opcode 2 (0x0f 0x38)
>  Referrer: 3-byte escape 1
>  AVXcode: 2
>  # 0x0f 0x38 0x00-0x0f
> @@ -789,12 +799,12 @@ f0: MOVBE Gy,My | MOVBE Gw,Mw (66) | CRC32 Gd,Eb (F2) | CRC32 Gd,Eb (66&F2)
>  f1: MOVBE My,Gy | MOVBE Mw,Gw (66) | CRC32 Gd,Ey (F2) | CRC32 Gd,Ew (66&F2)
>  f2: ANDN Gy,By,Ey (v)
>  f3: Grp17 (1A)
> -f5: BZHI Gy,Ey,By (v) | PEXT Gy,By,Ey (F3),(v) | PDEP Gy,By,Ey (F2),(v)
> -f6: ADCX Gy,Ey (66) | ADOX Gy,Ey (F3) | MULX By,Gy,rDX,Ey (F2),(v)
> +f5: BZHI Gy,Ey,By (v) | PEXT Gy,By,Ey (F3),(v) | PDEP Gy,By,Ey (F2),(v) | WRUSS Pq,Qq (66),REX.W
> +f6: ADCX Gy,Ey (66) | ADOX Gy,Ey (F3) | MULX By,Gy,rDX,Ey (F2),(v) | WRSS Pq,Qq (66),REX.W
>  f7: BEXTR Gy,Ey,By (v) | SHLX Gy,Ey,By (66),(v) | SARX Gy,Ey,By (F3),(v) | SHRX Gy,Ey,By (F2),(v)
>  EndTable
>  
> -Table: 3-byte opcode 2 (0x0f 0x3a)
> +Table: 3-byte opcode 3 (0x0f 0x3a)
>  Referrer: 3-byte escape 2
>  AVXcode: 3
>  # 0x0f 0x3a 0x00-0xff
> @@ -948,7 +958,7 @@ GrpTable: Grp7
>  2: LGDT Ms | XGETBV (000),(11B) | XSETBV (001),(11B) | VMFUNC (100),(11B) | XEND (101)(11B) | XTEST (110)(11B)
>  3: LIDT Ms
>  4: SMSW Mw/Rv
> -5: rdpkru (110),(11B) | wrpkru (111),(11B)
> +5: rdpkru (110),(11B) | wrpkru (111),(11B) | RSTORSSP Mq (F3)
>  6: LMSW Ew
>  7: INVLPG Mb | SWAPGS (o64),(000),(11B) | RDTSCP (001),(11B)
>  EndTable
> @@ -1019,8 +1029,8 @@ GrpTable: Grp15
>  2: vldmxcsr Md (v1) | WRFSBASE Ry (F3),(11B)
>  3: vstmxcsr Md (v1) | WRGSBASE Ry (F3),(11B)
>  4: XSAVE | ptwrite Ey (F3),(11B)
> -5: XRSTOR | lfence (11B)
> -6: XSAVEOPT | clwb (66) | mfence (11B)
> +5: XRSTOR | lfence (11B) | INCSSP Rd (F3),REX.W
> +6: XSAVEOPT | clwb (66) | mfence (11B) | CLRSSBSY Mq (F3)
>  7: clflush | clflushopt (66) | sfence (11B)
>  EndTable
>  
> diff --git a/tools/objtool/arch/x86/lib/x86-opcode-map.txt b/tools/objtool/arch/x86/lib/x86-opcode-map.txt
> index e0b85930dd77..c5e825d44766 100644
> --- a/tools/objtool/arch/x86/lib/x86-opcode-map.txt
> +++ b/tools/objtool/arch/x86/lib/x86-opcode-map.txt
> @@ -366,7 +366,7 @@ AVXcode: 1
>  1b: BNDCN Gv,Ev (F2) | BNDMOV Ev,Gv (66) | BNDMK Gv,Ev (F3) | BNDSTX Ev,Gv
>  1c:
>  1d:
> -1e:
> +1e: RDSSP Rd (F3),REX.W

RDSSP is in a Grp with ENDBR32 and ENDBR64

>  1f: NOP Ev
>  # 0x0f 0x20-0x2f
>  20: MOV Rd,Cd
> @@ -610,7 +610,17 @@ fe: paddd Pq,Qq | vpaddd Vx,Hx,Wx (66),(v1)
>  ff: UD0
>  EndTable
>  
> -Table: 3-byte opcode 1 (0x0f 0x38)
> +Table: 3-byte opcode 1 (0x0f 0x01)
> +Referrer:
> +AVXcode:
> +# Skip 0x00-0xe7
> +e8: SETSSBSY (f3)
> +e9:
> +ea: SAVEPREVSSP (f3)

SETSSBSY and SAVEPREVSSP should be in Grp7

> +# Skip 0xeb-0xff
> +EndTable
> +
> +Table: 3-byte opcode 2 (0x0f 0x38)
>  Referrer: 3-byte escape 1
>  AVXcode: 2
>  # 0x0f 0x38 0x00-0x0f
> @@ -789,12 +799,12 @@ f0: MOVBE Gy,My | MOVBE Gw,Mw (66) | CRC32 Gd,Eb (F2) | CRC32 Gd,Eb (66&F2)
>  f1: MOVBE My,Gy | MOVBE Mw,Gw (66) | CRC32 Gd,Ey (F2) | CRC32 Gd,Ew (66&F2)
>  f2: ANDN Gy,By,Ey (v)
>  f3: Grp17 (1A)
> -f5: BZHI Gy,Ey,By (v) | PEXT Gy,By,Ey (F3),(v) | PDEP Gy,By,Ey (F2),(v)
> -f6: ADCX Gy,Ey (66) | ADOX Gy,Ey (F3) | MULX By,Gy,rDX,Ey (F2),(v)
> +f5: BZHI Gy,Ey,By (v) | PEXT Gy,By,Ey (F3),(v) | PDEP Gy,By,Ey (F2),(v) | WRUSS Pq,Qq (66),REX.W
> +f6: ADCX Gy,Ey (66) | ADOX Gy,Ey (F3) | MULX By,Gy,rDX,Ey (F2),(v) | WRSS Pq,Qq (66),REX.W

I know already commented on this, but WRSS does not have (66) prefix

Also no other instructions have been annotated with REX.W so maybe omit that

>  f7: BEXTR Gy,Ey,By (v) | SHLX Gy,Ey,By (66),(v) | SARX Gy,Ey,By (F3),(v) | SHRX Gy,Ey,By (F2),(v)
>  EndTable
>  
> -Table: 3-byte opcode 2 (0x0f 0x3a)
> +Table: 3-byte opcode 3 (0x0f 0x3a)
>  Referrer: 3-byte escape 2
>  AVXcode: 3
>  # 0x0f 0x3a 0x00-0xff
> @@ -948,7 +958,7 @@ GrpTable: Grp7
>  2: LGDT Ms | XGETBV (000),(11B) | XSETBV (001),(11B) | VMFUNC (100),(11B) | XEND (101)(11B) | XTEST (110)(11B)
>  3: LIDT Ms
>  4: SMSW Mw/Rv
> -5: rdpkru (110),(11B) | wrpkru (111),(11B)
> +5: rdpkru (110),(11B) | wrpkru (111),(11B) | RSTORSSP Mq (F3)
>  6: LMSW Ew
>  7: INVLPG Mb | SWAPGS (o64),(000),(11B) | RDTSCP (001),(11B)
>  EndTable
> @@ -1019,8 +1029,8 @@ GrpTable: Grp15
>  2: vldmxcsr Md (v1) | WRFSBASE Ry (F3),(11B)
>  3: vstmxcsr Md (v1) | WRGSBASE Ry (F3),(11B)
>  4: XSAVE | ptwrite Ey (F3),(11B)
> -5: XRSTOR | lfence (11B)
> -6: XSAVEOPT | clwb (66) | mfence (11B)
> +5: XRSTOR | lfence (11B) | INCSSP Rd (F3),REX.W
> +6: XSAVEOPT | clwb (66) | mfence (11B) | CLRSSBSY Mq (F3)
>  7: clflush | clflushopt (66) | sfence (11B)
>  EndTable
>  
>