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Re: [Xen-devel] [PATCH] x86: fix alternative_callN



Forget about this version, I've updated the subject and commit
message and forgot to re-generate the patch.

On Wed, May 22, 2019 at 05:38:10PM +0100, Roger Pau Monne wrote:
> alternative_callN using inline assemble to generate the alternative
> patch sites should be using the ALTERNATIVE C preprocessor macro
> rather than the ALTERNATIVE assembly macro, the more that using the
> assembly macro in an inline assembly instance causes the following
> error 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:
>                          ^
> 
> Fixes: 67d01cdb5 ("x86: infrastructure to allow converting certain indirect 
> calls to direct ones")
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  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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