* [PATCH] x86emul: correct stub invocation constraints
@ 2017-04-25 9:04 Jan Beulich
2017-04-25 15:00 ` Andrew Cooper
2017-04-26 14:01 ` Boris Ostrovsky
0 siblings, 2 replies; 8+ messages in thread
From: Jan Beulich @ 2017-04-25 9:04 UTC (permalink / raw)
To: xen-devel; +Cc: Andrew Cooper, Julien Grall
[-- Attachment #1: Type: text/plain, Size: 1513 bytes --]
Stub invocations need to have the space the stub occupies as an input,
to prevent the compiler from re-ordering (or omitting) writes to it.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -837,7 +837,8 @@ do{ asm volatile (
".popsection\n\t" \
_ASM_EXTABLE(.Lret%=, .Lfix%=) \
: [exn] "+g" (res_), constraints, \
- [stub] "rm" (stub.func) ); \
+ [stub] "rm" (stub.func), \
+ "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.ptr) ); \
if ( unlikely(~res_.raw) ) \
{ \
gprintk(XENLOG_WARNING, \
@@ -853,7 +854,8 @@ do{ asm volatile (
#else
# define invoke_stub(pre, post, constraints...) \
asm volatile ( pre "\n\tcall *%[stub]\n\t" post \
- : constraints, [stub] "rm" (stub.func) )
+ : constraints, [stub] "rm" (stub.func), \
+ "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.buf) )
#endif
#define emulate_stub(dst, src...) do { \
[-- Attachment #2: x86emul-stub-constraints.patch --]
[-- Type: text/plain, Size: 1555 bytes --]
x86emul: correct stub invocation constraints
Stub invocations need to have the space the stub occupies as an input,
to prevent the compiler from re-ordering (or omitting) writes to it.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -837,7 +837,8 @@ do{ asm volatile (
".popsection\n\t" \
_ASM_EXTABLE(.Lret%=, .Lfix%=) \
: [exn] "+g" (res_), constraints, \
- [stub] "rm" (stub.func) ); \
+ [stub] "rm" (stub.func), \
+ "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.ptr) ); \
if ( unlikely(~res_.raw) ) \
{ \
gprintk(XENLOG_WARNING, \
@@ -853,7 +854,8 @@ do{ asm volatile (
#else
# define invoke_stub(pre, post, constraints...) \
asm volatile ( pre "\n\tcall *%[stub]\n\t" post \
- : constraints, [stub] "rm" (stub.func) )
+ : constraints, [stub] "rm" (stub.func), \
+ "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.buf) )
#endif
#define emulate_stub(dst, src...) do { \
[-- Attachment #3: Type: text/plain, Size: 127 bytes --]
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^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] x86emul: correct stub invocation constraints
2017-04-25 9:04 [PATCH] x86emul: correct stub invocation constraints Jan Beulich
@ 2017-04-25 15:00 ` Andrew Cooper
2017-04-25 16:48 ` Julien Grall
2017-04-26 14:01 ` Boris Ostrovsky
1 sibling, 1 reply; 8+ messages in thread
From: Andrew Cooper @ 2017-04-25 15:00 UTC (permalink / raw)
To: Jan Beulich, xen-devel; +Cc: Julien Grall
On 25/04/17 10:04, Jan Beulich wrote:
> Stub invocations need to have the space the stub occupies as an input,
> to prevent the compiler from re-ordering (or omitting) writes to it.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] x86emul: correct stub invocation constraints
2017-04-25 15:00 ` Andrew Cooper
@ 2017-04-25 16:48 ` Julien Grall
0 siblings, 0 replies; 8+ messages in thread
From: Julien Grall @ 2017-04-25 16:48 UTC (permalink / raw)
To: Andrew Cooper, Jan Beulich, xen-devel
On 25/04/17 16:00, Andrew Cooper wrote:
> On 25/04/17 10:04, Jan Beulich wrote:
>> Stub invocations need to have the space the stub occupies as an input,
>> to prevent the compiler from re-ordering (or omitting) writes to it.
>>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>
> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Julien Grall <julien.grall@arm.com>
>
--
Julien Grall
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] x86emul: correct stub invocation constraints
2017-04-25 9:04 [PATCH] x86emul: correct stub invocation constraints Jan Beulich
2017-04-25 15:00 ` Andrew Cooper
@ 2017-04-26 14:01 ` Boris Ostrovsky
2017-04-26 14:19 ` Jan Beulich
2017-04-27 8:07 ` Jan Beulich
1 sibling, 2 replies; 8+ messages in thread
From: Boris Ostrovsky @ 2017-04-26 14:01 UTC (permalink / raw)
To: Jan Beulich, xen-devel; +Cc: Andrew Cooper, Julien Grall
On 04/25/2017 05:04 AM, Jan Beulich wrote:
> Stub invocations need to have the space the stub occupies as an input,
> to prevent the compiler from re-ordering (or omitting) writes to it.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -837,7 +837,8 @@ do{ asm volatile (
> ".popsection\n\t" \
> _ASM_EXTABLE(.Lret%=, .Lfix%=) \
> : [exn] "+g" (res_), constraints, \
> - [stub] "rm" (stub.func) ); \
> + [stub] "rm" (stub.func), \
> + "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.ptr) ); \
> if ( unlikely(~res_.raw) ) \
> { \
> gprintk(XENLOG_WARNING, \
> @@ -853,7 +854,8 @@ do{ asm volatile (
> #else
> # define invoke_stub(pre, post, constraints...) \
> asm volatile ( pre "\n\tcall *%[stub]\n\t" post \
> - : constraints, [stub] "rm" (stub.func) )
> + : constraints, [stub] "rm" (stub.func), \
> + "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.buf) )
> #endif
>
> #define emulate_stub(dst, src...) do { \
>
This breaks on old compilers:
FC-64
<build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_emulator>
gcc --version
gcc (GCC) 4.4.4 20100503 (Red Hat 4.4.4-2)
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
FC-64
<build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_emulator>
pwd
/home/build/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_emulator
FC-64
<build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_emulator>
gcc -m64 -DBUILD_ID -fno-strict-aliasing -std=gnu99 -Wall
-Wstrict-prototypes -Wdeclaration-after-statement
-Wno-unused-but-set-variable -g3 -O0 -fno-omit-frame-pointer
-D__XEN_INTERFACE_VERSION__=__XEN_LATEST_INTERFACE_VERSION__ -MMD -MF
.x86_emulate.o.d -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
-I/home/build/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_emulator/../../../tools/include
-D__XEN_TOOLS__ -I. -c -o x86_emulate.o x86_emulate.c
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c: In function ‘x86_emulate’:
x86_emulate/x86_emulate.c:4085: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4161: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4226: error: memory input 5 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4229: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4279: error: memory input 5 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4288: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4353: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4402: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4465: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4516: error: memory input 5 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:4522: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:5632: error: memory input 5 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:5679: error: memory input 8 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:5863: error: memory input 3 is not directly
addressable
x86_emulate/x86_emulate.c:6069: error: memory input 4 is not directly
addressable
x86_emulate/x86_emulate.c:6213: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7029: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7178: error: memory input 6 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7328: error: memory input 7 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7362: error: memory input 6 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7482: error: memory input 3 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7603: error: memory input 9 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7607: error: memory input 9 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7676: error: memory input 6 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7715: error: memory input 6 is not directly
addressable
In file included from x86_emulate.c:157:
x86_emulate/x86_emulate.c:7795: error: memory input 4 is not directly
addressable
x86_emulate/x86_emulate.c:7798: error: memory input 3 is not directly
addressable
FC-64
<build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_emulator>
-boris
_______________________________________________
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https://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] x86emul: correct stub invocation constraints
2017-04-26 14:01 ` Boris Ostrovsky
@ 2017-04-26 14:19 ` Jan Beulich
2017-04-26 14:29 ` Boris Ostrovsky
2017-04-27 8:07 ` Jan Beulich
1 sibling, 1 reply; 8+ messages in thread
From: Jan Beulich @ 2017-04-26 14:19 UTC (permalink / raw)
To: Boris Ostrovsky; +Cc: Andrew Cooper, Julien Grall, xen-devel
>>> On 26.04.17 at 16:01, <boris.ostrovsky@oracle.com> wrote:
> On 04/25/2017 05:04 AM, Jan Beulich wrote:
>> Stub invocations need to have the space the stub occupies as an input,
>> to prevent the compiler from re-ordering (or omitting) writes to it.
>>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>>
>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>> @@ -837,7 +837,8 @@ do{ asm volatile (
>> ".popsection\n\t" \
>> _ASM_EXTABLE(.Lret%=, .Lfix%=) \
>> : [exn] "+g" (res_), constraints, \
>> - [stub] "rm" (stub.func) ); \
>> + [stub] "rm" (stub.func), \
>> + "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.ptr) ); \
>> if ( unlikely(~res_.raw) ) \
>> { \
>> gprintk(XENLOG_WARNING, \
>> @@ -853,7 +854,8 @@ do{ asm volatile (
>> #else
>> # define invoke_stub(pre, post, constraints...) \
>> asm volatile ( pre "\n\tcall *%[stub]\n\t" post \
>> - : constraints, [stub] "rm" (stub.func) )
>> + : constraints, [stub] "rm" (stub.func), \
>> + "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.buf) )
>> #endif
>>
>> #define emulate_stub(dst, src...) do { \
>>
>
>
> This breaks on old compilers:
>
> FC-64
> <build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_em
> ulator>
> gcc --version
> gcc (GCC) 4.4.4 20100503 (Red Hat 4.4.4-2)
I did try with 4.3.x, fwiw (but I'm afraid I've lost that machine just
now, and will hardly set it up again using an old distro). Also I can't
immediately see what the compiler dislikes and hence how a fix may
look like (short of adding memory clobbers instead).
Jan
> Copyright (C) 2010 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions. There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>
> FC-64
> <build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_em
> ulator>
> pwd
> /home/build/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_emulator
> FC-64
> <build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_em
> ulator>
> gcc -m64 -DBUILD_ID -fno-strict-aliasing -std=gnu99 -Wall
> -Wstrict-prototypes -Wdeclaration-after-statement
> -Wno-unused-but-set-variable -g3 -O0 -fno-omit-frame-pointer
> -D__XEN_INTERFACE_VERSION__=__XEN_LATEST_INTERFACE_VERSION__ -MMD -MF
> .x86_emulate.o.d -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
> -I/home/build/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_emulat
> or/../../../tools/include
> -D__XEN_TOOLS__ -I. -c -o x86_emulate.o x86_emulate.c
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c: In function ‘x86_emulate’:
> x86_emulate/x86_emulate.c:4085: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4161: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4226: error: memory input 5 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4229: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4279: error: memory input 5 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4288: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4353: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4402: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4465: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4516: error: memory input 5 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:4522: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:5632: error: memory input 5 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:5679: error: memory input 8 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:5863: error: memory input 3 is not directly
> addressable
> x86_emulate/x86_emulate.c:6069: error: memory input 4 is not directly
> addressable
> x86_emulate/x86_emulate.c:6213: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7029: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7178: error: memory input 6 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7328: error: memory input 7 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7362: error: memory input 6 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7482: error: memory input 3 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7603: error: memory input 9 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7607: error: memory input 9 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7676: error: memory input 6 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7715: error: memory input 6 is not directly
> addressable
> In file included from x86_emulate.c:157:
> x86_emulate/x86_emulate.c:7795: error: memory input 4 is not directly
> addressable
> x86_emulate/x86_emulate.c:7798: error: memory input 3 is not directly
> addressable
> FC-64
> <build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_em
> ulator>
>
>
>
> -boris
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^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] x86emul: correct stub invocation constraints
2017-04-26 14:19 ` Jan Beulich
@ 2017-04-26 14:29 ` Boris Ostrovsky
0 siblings, 0 replies; 8+ messages in thread
From: Boris Ostrovsky @ 2017-04-26 14:29 UTC (permalink / raw)
To: Jan Beulich; +Cc: Andrew Cooper, Julien Grall, xen-devel
>> This breaks on old compilers:
>>
>> FC-64
>> <build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_em
>> ulator>
>> gcc --version
>> gcc (GCC) 4.4.4 20100503 (Red Hat 4.4.4-2)
> I did try with 4.3.x, fwiw (but I'm afraid I've lost that machine just
> now, and will hardly set it up again using an old distro). Also I can't
> immediately see what the compiler dislikes and hence how a fix may
> look like (short of adding memory clobbers instead).
This is Fedora 13, if that helps.
I can probably arrange your access to that environment (copying Konrad
who owns it).
-boris
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] x86emul: correct stub invocation constraints
2017-04-26 14:01 ` Boris Ostrovsky
2017-04-26 14:19 ` Jan Beulich
@ 2017-04-27 8:07 ` Jan Beulich
2017-04-27 8:30 ` Jan Beulich
1 sibling, 1 reply; 8+ messages in thread
From: Jan Beulich @ 2017-04-27 8:07 UTC (permalink / raw)
To: Boris Ostrovsky; +Cc: Andrew Cooper, Julien Grall, xen-devel
>>> On 26.04.17 at 16:01, <boris.ostrovsky@oracle.com> wrote:
> On 04/25/2017 05:04 AM, Jan Beulich wrote:
>> Stub invocations need to have the space the stub occupies as an input,
>> to prevent the compiler from re-ordering (or omitting) writes to it.
>>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>>
>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>> @@ -837,7 +837,8 @@ do{ asm volatile (
>> ".popsection\n\t" \
>> _ASM_EXTABLE(.Lret%=, .Lfix%=) \
>> : [exn] "+g" (res_), constraints, \
>> - [stub] "rm" (stub.func) ); \
>> + [stub] "rm" (stub.func), \
>> + "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.ptr) ); \
>> if ( unlikely(~res_.raw) ) \
>> { \
>> gprintk(XENLOG_WARNING, \
>> @@ -853,7 +854,8 @@ do{ asm volatile (
>> #else
>> # define invoke_stub(pre, post, constraints...) \
>> asm volatile ( pre "\n\tcall *%[stub]\n\t" post \
>> - : constraints, [stub] "rm" (stub.func) )
>> + : constraints, [stub] "rm" (stub.func), \
>> + "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.buf) )
>> #endif
>>
>> #define emulate_stub(dst, src...) do { \
>>
>
>
> This breaks on old compilers:
>
> FC-64
> <build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_em
> ulator>
> gcc --version
> gcc (GCC) 4.4.4 20100503 (Red Hat 4.4.4-2)
Btw., I've just realized that I did use an old gcc only on the
hypervisor build. Do you see the same issue there, or is this tools
side specific?
Jan
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^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] x86emul: correct stub invocation constraints
2017-04-27 8:07 ` Jan Beulich
@ 2017-04-27 8:30 ` Jan Beulich
0 siblings, 0 replies; 8+ messages in thread
From: Jan Beulich @ 2017-04-27 8:30 UTC (permalink / raw)
To: Boris Ostrovsky; +Cc: Andrew Cooper, Julien Grall, xen-devel
>>> On 27.04.17 at 10:07, <JBeulich@suse.com> wrote:
>>>> On 26.04.17 at 16:01, <boris.ostrovsky@oracle.com> wrote:
>> On 04/25/2017 05:04 AM, Jan Beulich wrote:
>>> Stub invocations need to have the space the stub occupies as an input,
>>> to prevent the compiler from re-ordering (or omitting) writes to it.
>>>
>>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>>>
>>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>>> @@ -837,7 +837,8 @@ do{ asm volatile (
>>> ".popsection\n\t" \
>>> _ASM_EXTABLE(.Lret%=, .Lfix%=) \
>>> : [exn] "+g" (res_), constraints, \
>>> - [stub] "rm" (stub.func) ); \
>>> + [stub] "rm" (stub.func), \
>>> + "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.ptr) ); \
>>> if ( unlikely(~res_.raw) ) \
>>> { \
>>> gprintk(XENLOG_WARNING, \
>>> @@ -853,7 +854,8 @@ do{ asm volatile (
>>> #else
>>> # define invoke_stub(pre, post, constraints...) \
>>> asm volatile ( pre "\n\tcall *%[stub]\n\t" post \
>>> - : constraints, [stub] "rm" (stub.func) )
>>> + : constraints, [stub] "rm" (stub.func), \
>>> + "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.buf) )
>>> #endif
>>>
>>> #define emulate_stub(dst, src...) do { \
>>>
>>
>>
>> This breaks on old compilers:
>>
>> FC-64
>> <build@build-mk2:~/xtt-x86_64/bootstrap/xen.git/tools/fuzz/x86_instruction_em
>> ulator>
>> gcc --version
>> gcc (GCC) 4.4.4 20100503 (Red Hat 4.4.4-2)
>
> Btw., I've just realized that I did use an old gcc only on the
> hypervisor build. Do you see the same issue there, or is this tools
> side specific?
And now that I've extracted it into a smaller example and thus was
able to try, I can see the issue with 4.3.x. The problem is that with
struct stub {
unsigned long addr;
void *ptr;
unsigned char buf[16];
};
void test(const struct stub*ptr) {
asm("" :: "m" (*(unsigned char(*)[16])ptr->addr));
asm("" :: "m" (*(unsigned char(*)[16])ptr->ptr));
asm("" :: "m" (*(unsigned char(*)[16])ptr->buf));
asm("" :: "m" (*(unsigned char(*)[16])&ptr->buf));
asm("" :: "m" (*(unsigned char(*)[16])&ptr->buf[0]));
}
none of the last three work, so we'll have to resort to using the
first. I'll have to verify that this is good enough for the case
where I did actually observe things to break without the extra
constraint (with a not yet submitted patch).
Jan
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^ permalink raw reply [flat|nested] 8+ messages in thread
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-- links below jump to the message on this page --
2017-04-25 9:04 [PATCH] x86emul: correct stub invocation constraints Jan Beulich
2017-04-25 15:00 ` Andrew Cooper
2017-04-25 16:48 ` Julien Grall
2017-04-26 14:01 ` Boris Ostrovsky
2017-04-26 14:19 ` Jan Beulich
2017-04-26 14:29 ` Boris Ostrovsky
2017-04-27 8:07 ` Jan Beulich
2017-04-27 8:30 ` Jan Beulich
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