diff mbox series

[v2] selftests/sgx: Use rip relative addressing for encl_stack

Message ID 20220330222834.139769-1-jarkko@kernel.org (mailing list archive)
State New
Headers show
Series [v2] selftests/sgx: Use rip relative addressing for encl_stack | expand

Commit Message

Jarkko Sakkinen March 30, 2022, 10:28 p.m. UTC
Simplify the test_encl_bootstrap.S flow by using RIP-relative addressing.
The compiler automatically puts relative addresses for RIP index addresses.

In order to get a clean and tweakless solution, define separate entry point
for each TCS.

Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v2:
* Based on Reinette's example, make proper structuring with separate
  entry points for each TCS.
---
 .../selftests/sgx/test_encl_bootstrap.S       | 30 +++++++++++--------
 1 file changed, 18 insertions(+), 12 deletions(-)

Comments

Reinette Chatre March 31, 2022, 12:10 a.m. UTC | #1
Hi Jarkko,

On 3/30/2022 3:28 PM, Jarkko Sakkinen wrote:
> Simplify the test_encl_bootstrap.S flow by using RIP-relative addressing.

It is not clear to me how this is simpler. At this point there is no
functional change (except for what appears to be an unintended bug - more below).
At this time the change seems more code utilizing subtle compiler features
to accomplish the same.

Could you please share more about your plans following this change? I need
to understand this better since it is also an area changed by the SGX2 testing
code.

> The compiler automatically puts relative addresses for RIP index addresses.

I was not aware of this. A comment would be helpful to understand the implementation.

> 
> In order to get a clean and tweakless solution, define separate entry point
> for each TCS.
> 
> Cc: Reinette Chatre <reinette.chatre@intel.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> v2:
> * Based on Reinette's example, make proper structuring with separate
>   entry points for each TCS.
> ---
>  .../selftests/sgx/test_encl_bootstrap.S       | 30 +++++++++++--------
>  1 file changed, 18 insertions(+), 12 deletions(-)
> 
> diff --git a/tools/testing/selftests/sgx/test_encl_bootstrap.S b/tools/testing/selftests/sgx/test_encl_bootstrap.S
> index 82fb0dfcbd23..cc2353f38bcc 100644
> --- a/tools/testing/selftests/sgx/test_encl_bootstrap.S
> +++ b/tools/testing/selftests/sgx/test_encl_bootstrap.S
> @@ -10,12 +10,13 @@
>  	.section ".tcs", "aw"
>  	.balign	4096
>  
> +encl_tcs1:
>  	.fill	1, 8, 0			# STATE (set by CPU)
>  	.fill	1, 8, 0			# FLAGS
>  	.quad	encl_ssa_tcs1		# OSSA
>  	.fill	1, 4, 0			# CSSA (set by CPU)
>  	.fill	1, 4, 1			# NSSA
> -	.quad	encl_entry		# OENTRY
> +	.quad	encl_entry1		# OENTRY
>  	.fill	1, 8, 0			# AEP (set by EENTER and ERESUME)
>  	.fill	1, 8, 0			# OFSBASE
>  	.fill	1, 8, 0			# OGSBASE
> @@ -23,13 +24,13 @@
>  	.fill	1, 4, 0xFFFFFFFF	# GSLIMIT
>  	.fill	4024, 1, 0		# Reserved
>  
> -	# TCS2
> +encl_tcs2:
>  	.fill	1, 8, 0			# STATE (set by CPU)
>  	.fill	1, 8, 0			# FLAGS
>  	.quad	encl_ssa_tcs2		# OSSA
>  	.fill	1, 4, 0			# CSSA (set by CPU)
>  	.fill	1, 4, 1			# NSSA
> -	.quad	encl_entry		# OENTRY
> +	.quad	encl_entry2		# OENTRY
>  	.fill	1, 8, 0			# AEP (set by EENTER and ERESUME)
>  	.fill	1, 8, 0			# OFSBASE
>  	.fill	1, 8, 0			# OGSBASE
> @@ -39,15 +40,19 @@
>  
>  	.text
>  
> -encl_entry:
> -	# RBX contains the base address for TCS, which is the first address
> -	# inside the enclave for TCS #1 and one page into the enclave for
> -	# TCS #2. By adding the value of encl_stack to it, we get
> -	# the absolute address for the stack.
> -	lea	(encl_stack)(%rbx), %rax
> +encl_entry1:
> +	lea	(encl_stack1)(%rip), %rax
>  	xchg	%rsp, %rax
>  	push	%rax
> +	jmp	encl_continue
>  
> +encl_entry2:
> +	lea	(encl_stack2)(%rip), %rax
> +	xchg	%rsp, %rax
> +	push	%rax
> +	jmp	encl_continue
> +

The code duplication (xchg and push) is not needed.

> +encl_continue:
>  	push	%rcx # push the address after EENTER
>  	push	%rbx # push the enclave base address
>  
> @@ -84,13 +89,14 @@ encl_entry:
>  
>  encl_ssa_tcs1:
>  	.space 4096
> +
>  encl_ssa_tcs2:
>  	.space 4096
>  
> +encl_stack1:

Stack grows the other way so by placing the entry here the stack of
TCS #1 will clobber the SSA of TCS #2.

>  	.balign 4096
> -	# Stack of TCS #1
>  	.space 4096
> -encl_stack:
> +
> +encl_stack2:

Here the stack of TCS #2 will actually use the stack of TCS #1.

>  	.balign 4096
> -	# Stack of TCS #2
>  	.space 4096

Last page will be unused.

Reinette
Jarkko Sakkinen March 31, 2022, 12:59 a.m. UTC | #2
On Wed, 2022-03-30 at 17:10 -0700, Reinette Chatre wrote:
> Hi Jarkko,
> 
> On 3/30/2022 3:28 PM, Jarkko Sakkinen wrote:
> > Simplify the test_encl_bootstrap.S flow by using RIP-relative addressing.
> 
> It is not clear to me how this is simpler. At this point there is no
> functional change (except for what appears to be an unintended bug - more below).
> At this time the change seems more code utilizing subtle compiler features
> to accomplish the same.
> 
> Could you please share more about your plans following this change? I need
> to understand this better since it is also an area changed by the SGX2 testing
> code.
> 
> > The compiler automatically puts relative addresses for RIP index addresses.
> 
> I was not aware of this. A comment would be helpful to understand the implementation.
> 
> > 
> > In order to get a clean and tweakless solution, define separate entry point
> > for each TCS.
> > 
> > Cc: Reinette Chatre <reinette.chatre@intel.com>
> > Cc: Dave Hansen <dave.hansen@linux.intel.com>
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > v2:
> > * Based on Reinette's example, make proper structuring with separate
> >   entry points for each TCS.
> > ---
> >  .../selftests/sgx/test_encl_bootstrap.S       | 30 +++++++++++--------
> >  1 file changed, 18 insertions(+), 12 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/sgx/test_encl_bootstrap.S b/tools/testing/selftests/sgx/test_encl_bootstrap.S
> > index 82fb0dfcbd23..cc2353f38bcc 100644
> > --- a/tools/testing/selftests/sgx/test_encl_bootstrap.S
> > +++ b/tools/testing/selftests/sgx/test_encl_bootstrap.S
> > @@ -10,12 +10,13 @@
> >         .section ".tcs", "aw"
> >         .balign 4096
> >  
> > +encl_tcs1:
> >         .fill   1, 8, 0                 # STATE (set by CPU)
> >         .fill   1, 8, 0                 # FLAGS
> >         .quad   encl_ssa_tcs1           # OSSA
> >         .fill   1, 4, 0                 # CSSA (set by CPU)
> >         .fill   1, 4, 1                 # NSSA
> > -       .quad   encl_entry              # OENTRY
> > +       .quad   encl_entry1             # OENTRY
> >         .fill   1, 8, 0                 # AEP (set by EENTER and ERESUME)
> >         .fill   1, 8, 0                 # OFSBASE
> >         .fill   1, 8, 0                 # OGSBASE
> > @@ -23,13 +24,13 @@
> >         .fill   1, 4, 0xFFFFFFFF        # GSLIMIT
> >         .fill   4024, 1, 0              # Reserved
> >  
> > -       # TCS2
> > +encl_tcs2:
> >         .fill   1, 8, 0                 # STATE (set by CPU)
> >         .fill   1, 8, 0                 # FLAGS
> >         .quad   encl_ssa_tcs2           # OSSA
> >         .fill   1, 4, 0                 # CSSA (set by CPU)
> >         .fill   1, 4, 1                 # NSSA
> > -       .quad   encl_entry              # OENTRY
> > +       .quad   encl_entry2             # OENTRY
> >         .fill   1, 8, 0                 # AEP (set by EENTER and ERESUME)
> >         .fill   1, 8, 0                 # OFSBASE
> >         .fill   1, 8, 0                 # OGSBASE
> > @@ -39,15 +40,19 @@
> >  
> >         .text
> >  
> > -encl_entry:
> > -       # RBX contains the base address for TCS, which is the first address
> > -       # inside the enclave for TCS #1 and one page into the enclave for
> > -       # TCS #2. By adding the value of encl_stack to it, we get
> > -       # the absolute address for the stack.
> > -       lea     (encl_stack)(%rbx), %rax
> > +encl_entry1:
> > +       lea     (encl_stack1)(%rip), %rax
> >         xchg    %rsp, %rax
> >         push    %rax
> > +       jmp     encl_continue
> >  
> > +encl_entry2:
> > +       lea     (encl_stack2)(%rip), %rax
> > +       xchg    %rsp, %rax
> > +       push    %rax
> > +       jmp     encl_continue
> > +
> 
> The code duplication (xchg and push) is not needed.
> 
> > +encl_continue:
> >         push    %rcx # push the address after EENTER
> >         push    %rbx # push the enclave base address
> >  
> > @@ -84,13 +89,14 @@ encl_entry:
> >  
> >  encl_ssa_tcs1:
> >         .space 4096
> > +
> >  encl_ssa_tcs2:
> >         .space 4096
> >  
> > +encl_stack1:
> 
> Stack grows the other way so by placing the entry here the stack of
> TCS #1 will clobber the SSA of TCS #2.
> 
> >         .balign 4096
> > -       # Stack of TCS #1
> >         .space 4096
> > -encl_stack:
> > +
> > +encl_stack2:
> 
> Here the stack of TCS #2 will actually use the stack of TCS #1.
> 
> >         .balign 4096
> > -       # Stack of TCS #2
> >         .space 4096
> 
> Last page will be unused.
> 
> Reinette

Thanks for the remarks. I'll fix the issues.

BR, Jarkko
diff mbox series

Patch

diff --git a/tools/testing/selftests/sgx/test_encl_bootstrap.S b/tools/testing/selftests/sgx/test_encl_bootstrap.S
index 82fb0dfcbd23..cc2353f38bcc 100644
--- a/tools/testing/selftests/sgx/test_encl_bootstrap.S
+++ b/tools/testing/selftests/sgx/test_encl_bootstrap.S
@@ -10,12 +10,13 @@ 
 	.section ".tcs", "aw"
 	.balign	4096
 
+encl_tcs1:
 	.fill	1, 8, 0			# STATE (set by CPU)
 	.fill	1, 8, 0			# FLAGS
 	.quad	encl_ssa_tcs1		# OSSA
 	.fill	1, 4, 0			# CSSA (set by CPU)
 	.fill	1, 4, 1			# NSSA
-	.quad	encl_entry		# OENTRY
+	.quad	encl_entry1		# OENTRY
 	.fill	1, 8, 0			# AEP (set by EENTER and ERESUME)
 	.fill	1, 8, 0			# OFSBASE
 	.fill	1, 8, 0			# OGSBASE
@@ -23,13 +24,13 @@ 
 	.fill	1, 4, 0xFFFFFFFF	# GSLIMIT
 	.fill	4024, 1, 0		# Reserved
 
-	# TCS2
+encl_tcs2:
 	.fill	1, 8, 0			# STATE (set by CPU)
 	.fill	1, 8, 0			# FLAGS
 	.quad	encl_ssa_tcs2		# OSSA
 	.fill	1, 4, 0			# CSSA (set by CPU)
 	.fill	1, 4, 1			# NSSA
-	.quad	encl_entry		# OENTRY
+	.quad	encl_entry2		# OENTRY
 	.fill	1, 8, 0			# AEP (set by EENTER and ERESUME)
 	.fill	1, 8, 0			# OFSBASE
 	.fill	1, 8, 0			# OGSBASE
@@ -39,15 +40,19 @@ 
 
 	.text
 
-encl_entry:
-	# RBX contains the base address for TCS, which is the first address
-	# inside the enclave for TCS #1 and one page into the enclave for
-	# TCS #2. By adding the value of encl_stack to it, we get
-	# the absolute address for the stack.
-	lea	(encl_stack)(%rbx), %rax
+encl_entry1:
+	lea	(encl_stack1)(%rip), %rax
 	xchg	%rsp, %rax
 	push	%rax
+	jmp	encl_continue
 
+encl_entry2:
+	lea	(encl_stack2)(%rip), %rax
+	xchg	%rsp, %rax
+	push	%rax
+	jmp	encl_continue
+
+encl_continue:
 	push	%rcx # push the address after EENTER
 	push	%rbx # push the enclave base address
 
@@ -84,13 +89,14 @@  encl_entry:
 
 encl_ssa_tcs1:
 	.space 4096
+
 encl_ssa_tcs2:
 	.space 4096
 
+encl_stack1:
 	.balign 4096
-	# Stack of TCS #1
 	.space 4096
-encl_stack:
+
+encl_stack2:
 	.balign 4096
-	# Stack of TCS #2
 	.space 4096