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[Xen-devel] [PATCH v3] x86: remove alternative_callN usage of ALTERNATIVE asm macro

Roger Pau Monne posted 1 patch 4 years, 11 months ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/xen tags/patchew/20190529161319.51794-1-roger.pau@citrix.com
xen/include/asm-x86/alternative.h | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
[Xen-devel] [PATCH v3] x86: remove alternative_callN usage of ALTERNATIVE asm macro
Posted by Roger Pau Monne 4 years, 11 months ago 
There is a bug in llvm that needs to be fixed before switching to use
the alternative assembly macros in inline assembly call sites.
Therefore alternative_callN using inline assembly to generate the
alternative patch sites should be using the ALTERNATIVE C preprocessor
macro rather than the ALTERNATIVE assembly macro. Using the assembly
macro in an inline assembly instance triggers the following bug on
llvm based toolchains:

<instantiation>:1:1: error: invalid symbol redefinition
.L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - .L0_repl_s1) - (...
^
<instantiation>:1:37: error: invalid symbol redefinition
.L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - .L0_repl_s1) - (...
                                    ^
<instantiation>:1:60: error: invalid reassignment of non-absolute variable '.L0_diff'
.L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - .L0_repl_s1) - (...
                                                           ^
<inline asm>:1:2: note: while in macro instantiation
        ALTERNATIVE "call *genapic+64(%rip)", "call .", X86_FEATURE_LM
        ^
<instantiation>:1:156: error: invalid symbol redefinition
  ...- (.L0_orig_e - .L0_orig_s); mknops ((-(.L0_diff > 0)) * .L0_diff); .L0_orig_p:
                                                                         ^
<instantiation>:18:5: error: invalid symbol redefinition
    .L0_repl_s1: call .; .L0_repl_e1:
    ^
<instantiation>:18:26: error: invalid symbol redefinition
    .L0_repl_s1: call .; .L0_repl_e1:
                         ^
<instantiation>:1:1: error: invalid symbol redefinition
.L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - .L0_repl_s1) - (...
^
<instantiation>:1:37: error: invalid symbol redefinition
.L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - .L0_repl_s1) - (...
                                    ^
<instantiation>:1:60: error: invalid reassignment of non-absolute variable '.L0_diff'
.L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - .L0_repl_s1) - (...
                                                           ^
<inline asm>:1:2: note: while in macro instantiation
        ALTERNATIVE "call *genapic+64(%rip)", "call .", X86_FEATURE_LM
        ^
<instantiation>:1:156: error: invalid symbol redefinition
  ...- (.L0_orig_e - .L0_orig_s); mknops ((-(.L0_diff > 0)) * .L0_diff); .L0_orig_p:
                                                                         ^
<instantiation>:18:5: error: invalid symbol redefinition
    .L0_repl_s1: call .; .L0_repl_e1:
    ^
<instantiation>:18:26: error: invalid symbol redefinition
    .L0_repl_s1: call .; .L0_repl_e1:
                         ^
<instantiation>:1:1: error: invalid symbol redefinition
.L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - .L0_repl_s1) - (...
^
<instantiation>:1:37: error: invalid symbol redefinition
.L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - .L0_repl_s1) - (...
                                    ^
<instantiation>:1:60: error: invalid reassignment of non-absolute variable '.L0_diff'
.L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - .L0_repl_s1) - (...
                                                           ^
<inline asm>:1:2: note: while in macro instantiation
        ALTERNATIVE "call *genapic+64(%rip)", "call .", X86_FEATURE_LM
        ^
<instantiation>:1:156: error: invalid symbol redefinition
  ...- (.L0_orig_e - .L0_orig_s); mknops ((-(.L0_diff > 0)) * .L0_diff); .L0_orig_p:
                                                                         ^
<instantiation>:18:5: error: invalid symbol redefinition
    .L0_repl_s1: call .; .L0_repl_e1:
    ^
<instantiation>:18:26: error: invalid symbol redefinition
    .L0_repl_s1: call .; .L0_repl_e1:
                         ^

This has been reported to upstream llvm:

https://bugs.llvm.org/show_bug.cgi?id=42034

Fixes: 67d01cdb5 ("x86: infrastructure to allow converting certain indirect calls to direct ones")
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
---
Changes since v2:
 - Further fixes to commit log.

Changes since v1:
 - Fix subject and commit message.
---
 xen/include/asm-x86/alternative.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/xen/include/asm-x86/alternative.h b/xen/include/asm-x86/alternative.h
index 63d0a450ba..92e3581bc2 100644
--- a/xen/include/asm-x86/alternative.h
+++ b/xen/include/asm-x86/alternative.h
@@ -202,9 +202,8 @@ extern void alternative_branches(void);
     rettype ret_;                                                  \
     register unsigned long r10_ asm("r10");                        \
     register unsigned long r11_ asm("r11");                        \
-    asm volatile (__stringify(ALTERNATIVE "call *%c[addr](%%rip)", \
-                                          "call .",                \
-                                          X86_FEATURE_ALWAYS)      \
+    asm volatile (ALTERNATIVE("call *%c[addr](%%rip)", "call .",   \
+                              X86_FEATURE_ALWAYS)                  \
                   : ALT_CALL ## n ## _OUT, "=a" (ret_),            \
                     "=r" (r10_), "=r" (r11_) ASM_CALL_CONSTRAINT   \
                   : [addr] "i" (&(func)), "g" (func)               \
-- 
2.20.1 (Apple Git-117)


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Re: [Xen-devel] [PATCH v3] x86: remove alternative_callN usage of ALTERNATIVE asm macro
Posted by Jan Beulich 4 years, 10 months ago 
>>> On 29.05.19 at 18:13, <roger.pau@citrix.com> wrote:
> There is a bug in llvm that needs to be fixed before switching to use
> the alternative assembly macros in inline assembly call sites.
> Therefore alternative_callN using inline assembly to generate the
> alternative patch sites should be using the ALTERNATIVE C preprocessor
> macro rather than the ALTERNATIVE assembly macro. Using the assembly
> macro in an inline assembly instance triggers the following bug on
> llvm based toolchains:
> 
> <instantiation>:1:1: error: invalid symbol redefinition
> .L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - 
> .L0_repl_s1) - (...
> ^
> <instantiation>:1:37: error: invalid symbol redefinition
> .L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - 
> .L0_repl_s1) - (...
>                                     ^
> <instantiation>:1:60: error: invalid reassignment of non-absolute variable 
> '.L0_diff'
> .L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - 
> .L0_repl_s1) - (...
>                                                            ^
> <inline asm>:1:2: note: while in macro instantiation
>         ALTERNATIVE "call *genapic+64(%rip)", "call .", X86_FEATURE_LM
>         ^
> <instantiation>:1:156: error: invalid symbol redefinition
>   ...- (.L0_orig_e - .L0_orig_s); mknops ((-(.L0_diff > 0)) * .L0_diff); 
> .L0_orig_p:
>                                                                          ^
> <instantiation>:18:5: error: invalid symbol redefinition
>     .L0_repl_s1: call .; .L0_repl_e1:
>     ^
> <instantiation>:18:26: error: invalid symbol redefinition
>     .L0_repl_s1: call .; .L0_repl_e1:
>                          ^
> <instantiation>:1:1: error: invalid symbol redefinition
> .L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - 
> .L0_repl_s1) - (...
> ^
> <instantiation>:1:37: error: invalid symbol redefinition
> .L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - 
> .L0_repl_s1) - (...
>                                     ^
> <instantiation>:1:60: error: invalid reassignment of non-absolute variable 
> '.L0_diff'
> .L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - 
> .L0_repl_s1) - (...
>                                                            ^
> <inline asm>:1:2: note: while in macro instantiation
>         ALTERNATIVE "call *genapic+64(%rip)", "call .", X86_FEATURE_LM
>         ^
> <instantiation>:1:156: error: invalid symbol redefinition
>   ...- (.L0_orig_e - .L0_orig_s); mknops ((-(.L0_diff > 0)) * .L0_diff); 
> .L0_orig_p:
>                                                                          ^
> <instantiation>:18:5: error: invalid symbol redefinition
>     .L0_repl_s1: call .; .L0_repl_e1:
>     ^
> <instantiation>:18:26: error: invalid symbol redefinition
>     .L0_repl_s1: call .; .L0_repl_e1:
>                          ^
> <instantiation>:1:1: error: invalid symbol redefinition
> .L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - 
> .L0_repl_s1) - (...
> ^
> <instantiation>:1:37: error: invalid symbol redefinition
> .L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - 
> .L0_repl_s1) - (...
>                                     ^
> <instantiation>:1:60: error: invalid reassignment of non-absolute variable 
> '.L0_diff'
> .L0_orig_s: call *genapic+64(%rip); .L0_orig_e: .L0_diff = (.L0_repl_e1 - 
> .L0_repl_s1) - (...
>                                                            ^
> <inline asm>:1:2: note: while in macro instantiation
>         ALTERNATIVE "call *genapic+64(%rip)", "call .", X86_FEATURE_LM
>         ^
> <instantiation>:1:156: error: invalid symbol redefinition
>   ...- (.L0_orig_e - .L0_orig_s); mknops ((-(.L0_diff > 0)) * .L0_diff); 
> .L0_orig_p:
>                                                                          ^
> <instantiation>:18:5: error: invalid symbol redefinition
>     .L0_repl_s1: call .; .L0_repl_e1:
>     ^
> <instantiation>:18:26: error: invalid symbol redefinition
>     .L0_repl_s1: call .; .L0_repl_e1:
>                          ^
> 
> This has been reported to upstream llvm:
> 
> https://bugs.llvm.org/show_bug.cgi?id=42034 
> 
> Fixes: 67d01cdb5 ("x86: infrastructure to allow converting certain indirect calls to direct ones")
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Well, hesitantly,
Acked-by: Jan Beulich <jbeulich@suse.com>

Jan


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