From: Roger Pau Monne <roger.pau@citrix.com>
To: xen-devel@lists.xenproject.org
Cc: Roger Pau Monne <roger.pau@citrix.com>,
Jan Beulich <jbeulich@suse.com>,
Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>
Subject: [PATCH] x86/altcall: always use a temporary parameter stashing variable
Date: Wed, 28 Feb 2024 14:59:08 +0100 [thread overview]
Message-ID: <20240228135908.13319-1-roger.pau@citrix.com> (raw)
The usage in ALT_CALL_ARG() on clang of:
register union {
typeof(arg) e;
const unsigned long r;
} ...
When `arg` is the first argument to alternative_{,v}call() and
const_vlapic_vcpu() is used results in clang 3.5.0 complaining with:
arch/x86/hvm/vlapic.c:141:47: error: non-const static data member must be initialized out of line
alternative_call(hvm_funcs.test_pir, const_vlapic_vcpu(vlapic), vec) )
Workaround this by pulling `arg1` into a local variable, like it's done for
further arguments (arg2, arg3...)
Originally arg1 wasn't pulled into a variable because for the a1_ register
local variable the possible clobbering as a result of operators on other
variables don't matter:
https://gcc.gnu.org/onlinedocs/gcc/Local-Register-Variables.html#Local-Register-Variables
Note clang version 3.8.1 seems to already be fixed and don't require the
workaround, but since it's harmless do it uniformly everywhere.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Fixes: 2ce562b2a413 ('x86/altcall: use a union as register type for function parameters on clang')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Gitlab CI seems OK on both the 4.17 and staging branches with this applied:
4.17: https://gitlab.com/xen-project/people/royger/xen/-/pipelines/1193801183
staging: https://gitlab.com/xen-project/people/royger/xen/-/pipelines/1193801881
---
xen/arch/x86/include/asm/alternative.h | 36 +++++++++++++++++---------
1 file changed, 24 insertions(+), 12 deletions(-)
diff --git a/xen/arch/x86/include/asm/alternative.h b/xen/arch/x86/include/asm/alternative.h
index 3c14db5078ba..0d3697f1de49 100644
--- a/xen/arch/x86/include/asm/alternative.h
+++ b/xen/arch/x86/include/asm/alternative.h
@@ -253,21 +253,24 @@ extern void alternative_branches(void);
})
#define alternative_vcall1(func, arg) ({ \
- ALT_CALL_ARG(arg, 1); \
+ typeof(arg) v1_ = (arg); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_NO_ARG2; \
(void)sizeof(func(arg)); \
(void)alternative_callN(1, int, func); \
})
#define alternative_call1(func, arg) ({ \
- ALT_CALL_ARG(arg, 1); \
+ typeof(arg) v1_ = (arg); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_NO_ARG2; \
alternative_callN(1, typeof(func(arg)), func); \
})
#define alternative_vcall2(func, arg1, arg2) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_NO_ARG3; \
(void)sizeof(func(arg1, arg2)); \
@@ -275,17 +278,19 @@ extern void alternative_branches(void);
})
#define alternative_call2(func, arg1, arg2) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_NO_ARG3; \
alternative_callN(2, typeof(func(arg1, arg2)), func); \
})
#define alternative_vcall3(func, arg1, arg2, arg3) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
typeof(arg3) v3_ = (arg3); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_ARG(v3_, 3); \
ALT_CALL_NO_ARG4; \
@@ -294,9 +299,10 @@ extern void alternative_branches(void);
})
#define alternative_call3(func, arg1, arg2, arg3) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
typeof(arg3) v3_ = (arg3); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_ARG(v3_, 3); \
ALT_CALL_NO_ARG4; \
@@ -305,10 +311,11 @@ extern void alternative_branches(void);
})
#define alternative_vcall4(func, arg1, arg2, arg3, arg4) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
typeof(arg3) v3_ = (arg3); \
typeof(arg4) v4_ = (arg4); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_ARG(v3_, 3); \
ALT_CALL_ARG(v4_, 4); \
@@ -318,10 +325,11 @@ extern void alternative_branches(void);
})
#define alternative_call4(func, arg1, arg2, arg3, arg4) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
typeof(arg3) v3_ = (arg3); \
typeof(arg4) v4_ = (arg4); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_ARG(v3_, 3); \
ALT_CALL_ARG(v4_, 4); \
@@ -332,11 +340,12 @@ extern void alternative_branches(void);
})
#define alternative_vcall5(func, arg1, arg2, arg3, arg4, arg5) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
typeof(arg3) v3_ = (arg3); \
typeof(arg4) v4_ = (arg4); \
typeof(arg5) v5_ = (arg5); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_ARG(v3_, 3); \
ALT_CALL_ARG(v4_, 4); \
@@ -347,11 +356,12 @@ extern void alternative_branches(void);
})
#define alternative_call5(func, arg1, arg2, arg3, arg4, arg5) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
typeof(arg3) v3_ = (arg3); \
typeof(arg4) v4_ = (arg4); \
typeof(arg5) v5_ = (arg5); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_ARG(v3_, 3); \
ALT_CALL_ARG(v4_, 4); \
@@ -363,12 +373,13 @@ extern void alternative_branches(void);
})
#define alternative_vcall6(func, arg1, arg2, arg3, arg4, arg5, arg6) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
typeof(arg3) v3_ = (arg3); \
typeof(arg4) v4_ = (arg4); \
typeof(arg5) v5_ = (arg5); \
typeof(arg6) v6_ = (arg6); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_ARG(v3_, 3); \
ALT_CALL_ARG(v4_, 4); \
@@ -379,12 +390,13 @@ extern void alternative_branches(void);
})
#define alternative_call6(func, arg1, arg2, arg3, arg4, arg5, arg6) ({ \
+ typeof(arg1) v1_ = (arg1); \
typeof(arg2) v2_ = (arg2); \
typeof(arg3) v3_ = (arg3); \
typeof(arg4) v4_ = (arg4); \
typeof(arg5) v5_ = (arg5); \
typeof(arg6) v6_ = (arg6); \
- ALT_CALL_ARG(arg1, 1); \
+ ALT_CALL_ARG(v1_, 1); \
ALT_CALL_ARG(v2_, 2); \
ALT_CALL_ARG(v3_, 3); \
ALT_CALL_ARG(v4_, 4); \
--
2.44.0
next reply other threads:[~2024-02-28 13:59 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-28 13:59 Roger Pau Monne [this message]
2024-02-28 14:28 ` [PATCH] x86/altcall: always use a temporary parameter stashing variable Jan Beulich
2024-02-28 16:56 ` Roger Pau Monné
2024-02-29 6:52 ` Jan Beulich
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