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

From: Roger Pau Monne <roger.pau@xxxxxxxxxx>

Date: Wed, 29 May 2019 18:13:19 +0200

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Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>

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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@xxxxxxxxxx> --- Cc: Jan Beulich <jbeulich@xxxxxxxx> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Cc: Wei Liu <wei.liu2@xxxxxxxxxx> --- 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) _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel

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