[PATCH] tests/x86emul: Annotate test blobs as executable code

[PATCH] tests/x86emul: Annotate test blobs as executable code

[Andrew Cooper]

This causes objdump to disassemble them, rather than rendering them as
straight hex data.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 tools/tests/x86_emulator/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/tests/x86_emulator/Makefile b/tools/tests/x86_emulator/Makefile
index 970ec3e..b54603d 100644
--- a/tools/tests/x86_emulator/Makefile
+++ b/tools/tests/x86_emulator/Makefile
@@ -149,7 +149,7 @@ $(addsuffix .h,$(TESTCASES)): %.h: %.c testcase.mk Makefile
 		(echo 'static const unsigned int __attribute__((section(".test, \"ax\", @progbits #")))' \
 		      "$${prefix}_$(arch)$${flavor}[] = {"; \
 		 od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 's/$$/,/'; \
-		 echo "};") >>$@.new; \
+		 echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, STT_FUNC;\");") >>$@.new; \
 		rm -f $*.bin; \
 	    done; \
 	)
@@ -165,7 +165,7 @@ $(addsuffix -opmask.h,$(OPMASK)): %.h: opmask.S testcase.mk Makefile
 		(echo 'static const unsigned int __attribute__((section(".test, \"ax\", @progbits #")))' \
 		      "$${prefix}_$(arch)$${flavor}[] = {"; \
 		 od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 's/$$/,/'; \
-		 echo "};") >>$@.new; \
+		 echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, STT_FUNC;\");") >>$@.new; \
 		rm -f $*.bin; \
 	    done; \
 	)
-- 
2.1.4


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

[Xen-devel] [PATCH] tests/x86emul: Annotate test blobs as executable code

[Andrew Cooper]

This causes objdump to disassemble them, rather than rendering them as
straight hex data.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 tools/tests/x86_emulator/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/tests/x86_emulator/Makefile b/tools/tests/x86_emulator/Makefile
index 970ec3e..b54603d 100644
--- a/tools/tests/x86_emulator/Makefile
+++ b/tools/tests/x86_emulator/Makefile
@@ -149,7 +149,7 @@ $(addsuffix .h,$(TESTCASES)): %.h: %.c testcase.mk Makefile
 		(echo 'static const unsigned int __attribute__((section(".test, \"ax\", @progbits #")))' \
 		      "$${prefix}_$(arch)$${flavor}[] = {"; \
 		 od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 's/$$/,/'; \
-		 echo "};") >>$@.new; \
+		 echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, STT_FUNC;\");") >>$@.new; \
 		rm -f $*.bin; \
 	    done; \
 	)
@@ -165,7 +165,7 @@ $(addsuffix -opmask.h,$(OPMASK)): %.h: opmask.S testcase.mk Makefile
 		(echo 'static const unsigned int __attribute__((section(".test, \"ax\", @progbits #")))' \
 		      "$${prefix}_$(arch)$${flavor}[] = {"; \
 		 od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 's/$$/,/'; \
-		 echo "};") >>$@.new; \
+		 echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, STT_FUNC;\");") >>$@.new; \
 		rm -f $*.bin; \
 	    done; \
 	)
-- 
2.1.4


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tests/x86emul: Annotate test blobs as executable code

[Jan Beulich]

>>> On 24.05.19 at 17:15, <andrew.cooper3@citrix.com> wrote:
> --- a/tools/tests/x86_emulator/Makefile
> +++ b/tools/tests/x86_emulator/Makefile
> @@ -149,7 +149,7 @@ $(addsuffix .h,$(TESTCASES)): %.h: %.c testcase.mk Makefile
>  		(echo 'static const unsigned int __attribute__((section(".test, \"ax\", @progbits #")))' \
>  		      "$${prefix}_$(arch)$${flavor}[] = {"; \
>  		 od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 's/$$/,/'; \
> -		 echo "};") >>$@.new; \
> +		 echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, STT_FUNC;\");") >>$@.new; \

Hmm, this seems risky to me - I'd expect a decent compiler to mark
them as STT_OBJECT, and a decent assembler to choke on finding
disagreeing .type directives for the same symbol. Current binutils
looks to simply OR together all the values, and then decide in an
adhoc sequence which type to actually emit:

      if ((flags & BSF_THREAD_LOCAL) != 0)
	type = STT_TLS;
      else if ((flags & BSF_GNU_INDIRECT_FUNCTION) != 0)
	type = STT_GNU_IFUNC;
      else if ((flags & BSF_FUNCTION) != 0)
	type = STT_FUNC;
      else if ((flags & BSF_OBJECT) != 0)
	type = STT_OBJECT;
      else if ((flags & BSF_RELC) != 0)
	type = STT_RELC;
      else if ((flags & BSF_SRELC) != 0)
	type = STT_SRELC;
      else
	type = STT_NOTYPE;

I don't think that's sane behavior (albeit it guarantees @function to
win over @object), and hence I'd say it can change at any time.

I wanted to suggest forcing the type change via objcopy, but to
my surprise I couldn't find a respective option.

Jan



_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [Xen-devel] [PATCH] tests/x86emul: Annotate test blobs as executable code

[Jan Beulich]

>>> On 24.05.19 at 17:15, <andrew.cooper3@citrix.com> wrote:
> --- a/tools/tests/x86_emulator/Makefile
> +++ b/tools/tests/x86_emulator/Makefile
> @@ -149,7 +149,7 @@ $(addsuffix .h,$(TESTCASES)): %.h: %.c testcase.mk Makefile
>  		(echo 'static const unsigned int __attribute__((section(".test, \"ax\", @progbits #")))' \
>  		      "$${prefix}_$(arch)$${flavor}[] = {"; \
>  		 od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 's/$$/,/'; \
> -		 echo "};") >>$@.new; \
> +		 echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, STT_FUNC;\");") >>$@.new; \

Hmm, this seems risky to me - I'd expect a decent compiler to mark
them as STT_OBJECT, and a decent assembler to choke on finding
disagreeing .type directives for the same symbol. Current binutils
looks to simply OR together all the values, and then decide in an
adhoc sequence which type to actually emit:

      if ((flags & BSF_THREAD_LOCAL) != 0)
	type = STT_TLS;
      else if ((flags & BSF_GNU_INDIRECT_FUNCTION) != 0)
	type = STT_GNU_IFUNC;
      else if ((flags & BSF_FUNCTION) != 0)
	type = STT_FUNC;
      else if ((flags & BSF_OBJECT) != 0)
	type = STT_OBJECT;
      else if ((flags & BSF_RELC) != 0)
	type = STT_RELC;
      else if ((flags & BSF_SRELC) != 0)
	type = STT_SRELC;
      else
	type = STT_NOTYPE;

I don't think that's sane behavior (albeit it guarantees @function to
win over @object), and hence I'd say it can change at any time.

I wanted to suggest forcing the type change via objcopy, but to
my surprise I couldn't find a respective option.

Jan



_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [Xen-devel] [PATCH] tests/x86emul: Annotate test blobs as executable code

[Jan Beulich]

On 02.08.2019 20:31, Andrew Cooper wrote:
> On 03/07/2019 11:47, Jan Beulich wrote:
>>>>> On 24.05.19 at 17:15, <andrew.cooper3@citrix.com> wrote:
>>> --- a/tools/tests/x86_emulator/Makefile
>>> +++ b/tools/tests/x86_emulator/Makefile
>>> @@ -149,7 +149,7 @@ $(addsuffix .h,$(TESTCASES)): %.h: %.c testcase.mk Makefile
>>>   		(echo 'static const unsigned int __attribute__((section(".test, \"ax\", @progbits #")))' \
>>>   		      "$${prefix}_$(arch)$${flavor}[] = {"; \
>>>   		 od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 's/$$/,/'; \
>>> -		 echo "};") >>$@.new; \
>>> +		 echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, STT_FUNC;\");") >>$@.new; \
>> While I think we've sufficiently agreed on future gas behavior
>> that I'd consider this change fine to make as long as you add
>> an intermediate step going through STT_NOTYPE, I'd like to note
>> that your mileage from this will only be about 50%: While the
>> 64-bit blobs will disassemble fine, I'm afraid the 32-bit ones
>> will be somewhat garbled. Sadly there's no annotation or alike
>> (like Arm's mapping symbols) that one could use to make
>> disassemblers switch bitness for separate blocks of code.
> 
> Thats fine.
> 
> Disassembling twice, once with -mi386 works well, as the symbol names
> still get emitted sensibly.  I even use -m i8086 for bits of Xen's
> trampoline.
> 
> Its rare to need to look at a different disassembly, but its very easy
> to do so if you need to.
> 
> Can I take this reply as an ack for using the STT_NOTYPE intermediate step?

Yes - sorry for not being explicit in this regard.

Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [Xen-devel] [PATCH] tests/x86emul: Annotate test blobs as executable code

[Andrew Cooper]

On 03/07/2019 11:47, Jan Beulich wrote:
>>>> On 24.05.19 at 17:15, <andrew.cooper3@citrix.com> wrote:
>> --- a/tools/tests/x86_emulator/Makefile
>> +++ b/tools/tests/x86_emulator/Makefile
>> @@ -149,7 +149,7 @@ $(addsuffix .h,$(TESTCASES)): %.h: %.c testcase.mk Makefile
>>  		(echo 'static const unsigned int __attribute__((section(".test, \"ax\", @progbits #")))' \
>>  		      "$${prefix}_$(arch)$${flavor}[] = {"; \
>>  		 od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 's/$$/,/'; \
>> -		 echo "};") >>$@.new; \
>> +		 echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, STT_FUNC;\");") >>$@.new; \
> While I think we've sufficiently agreed on future gas behavior
> that I'd consider this change fine to make as long as you add
> an intermediate step going through STT_NOTYPE, I'd like to note
> that your mileage from this will only be about 50%: While the
> 64-bit blobs will disassemble fine, I'm afraid the 32-bit ones
> will be somewhat garbled. Sadly there's no annotation or alike
> (like Arm's mapping symbols) that one could use to make
> disassemblers switch bitness for separate blocks of code.

Thats fine.

Disassembling twice, once with -mi386 works well, as the symbol names
still get emitted sensibly.  I even use -m i8086 for bits of Xen's
trampoline.

Its rare to need to look at a different disassembly, but its very easy
to do so if you need to.

Can I take this reply as an ack for using the STT_NOTYPE intermediate step?

~Andrew

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [Xen-devel] [PATCH] tests/x86emul: Annotate test blobs as executable code

[Jan Beulich]

>>> On 24.05.19 at 17:15, <andrew.cooper3@citrix.com> wrote:
> --- a/tools/tests/x86_emulator/Makefile
> +++ b/tools/tests/x86_emulator/Makefile
> @@ -149,7 +149,7 @@ $(addsuffix .h,$(TESTCASES)): %.h: %.c testcase.mk Makefile
>  		(echo 'static const unsigned int __attribute__((section(".test, \"ax\", @progbits #")))' \
>  		      "$${prefix}_$(arch)$${flavor}[] = {"; \
>  		 od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 's/$$/,/'; \
> -		 echo "};") >>$@.new; \
> +		 echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, STT_FUNC;\");") >>$@.new; \

While I think we've sufficiently agreed on future gas behavior
that I'd consider this change fine to make as long as you add
an intermediate step going through STT_NOTYPE, I'd like to note
that your mileage from this will only be about 50%: While the
64-bit blobs will disassemble fine, I'm afraid the 32-bit ones
will be somewhat garbled. Sadly there's no annotation or alike
(like Arm's mapping symbols) that one could use to make
disassemblers switch bitness for separate blocks of code.

Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel