xen/arch/x86/smpboot.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
Clang-3.5 from Debian Jessie fails with:
smpboot.c:829:29: error: statement expression not allowed at file scope
BUILD_BUG_ON(sizeof(this_cpu(tss_page)) != PAGE_SIZE);
^
/local/xen.git/xen/include/asm/percpu.h:14:7: note: expanded from macro
'this_cpu'
(*RELOC_HIDE(&per_cpu__##var, get_cpu_info()->per_cpu_offset))
^
/local/xen.git/xen/include/xen/compiler.h:98:3: note: expanded from macro
'RELOC_HIDE'
({ unsigned long __ptr; \
^
/local/xen.git/xen/include/xen/lib.h:26:53: note: expanded from macro
'BUILD_BUG_ON'
#define BUILD_BUG_ON(cond) ((void)BUILD_BUG_ON_ZERO(cond))
^
/local/xen.git/xen/include/xen/lib.h:25:57: note: expanded from macro
'BUILD_BUG_ON_ZERO'
#define BUILD_BUG_ON_ZERO(cond) sizeof(struct { int:-!!(cond); })
^
1 error generated.
/local/xen.git/xen/Rules.mk:202: recipe for target 'smpboot.o' failed
This is obviously a compiler bug because the BUILD_BUG_ON() is not at file
scope. However, it can be worked around by using a local variable.
Spotted by Gitlab CI.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wl@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
xen/arch/x86/smpboot.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 5057109a77..85c81c247e 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -826,9 +826,11 @@ static int setup_cpu_root_pgt(unsigned int cpu)
rc = clone_mapping(idt_tables[cpu], rpt);
if ( !rc )
{
- BUILD_BUG_ON(sizeof(this_cpu(tss_page)) != PAGE_SIZE);
+ struct tss_page *this_tss = &per_cpu(tss_page, cpu);
- rc = clone_mapping(&per_cpu(tss_page, cpu).tss, rpt);
+ BUILD_BUG_ON(sizeof(*this_tss) != PAGE_SIZE);
+
+ rc = clone_mapping(&this_tss->tss, rpt);
}
if ( !rc )
rc = clone_mapping((void *)per_cpu(stubs.addr, cpu), rpt);
--
2.11.0
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https://lists.xenproject.org/mailman/listinfo/xen-develOn Tue, Aug 13, 2019 at 01:01:17PM +0100, Andrew Cooper wrote:
> Clang-3.5 from Debian Jessie fails with:
>
> smpboot.c:829:29: error: statement expression not allowed at file scope
> BUILD_BUG_ON(sizeof(this_cpu(tss_page)) != PAGE_SIZE);
> ^
> /local/xen.git/xen/include/asm/percpu.h:14:7: note: expanded from macro
> 'this_cpu'
> (*RELOC_HIDE(&per_cpu__##var, get_cpu_info()->per_cpu_offset))
> ^
> /local/xen.git/xen/include/xen/compiler.h:98:3: note: expanded from macro
> 'RELOC_HIDE'
> ({ unsigned long __ptr; \
> ^
> /local/xen.git/xen/include/xen/lib.h:26:53: note: expanded from macro
> 'BUILD_BUG_ON'
> #define BUILD_BUG_ON(cond) ((void)BUILD_BUG_ON_ZERO(cond))
> ^
> /local/xen.git/xen/include/xen/lib.h:25:57: note: expanded from macro
> 'BUILD_BUG_ON_ZERO'
> #define BUILD_BUG_ON_ZERO(cond) sizeof(struct { int:-!!(cond); })
> ^
> 1 error generated.
> /local/xen.git/xen/Rules.mk:202: recipe for target 'smpboot.o' failed
>
> This is obviously a compiler bug because the BUILD_BUG_ON() is not at file
> scope. However, it can be worked around by using a local variable.
>
> Spotted by Gitlab CI.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wl@xen.org>
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On 13.08.2019 14:01, Andrew Cooper wrote:
> Clang-3.5 from Debian Jessie fails with:
>
> smpboot.c:829:29: error: statement expression not allowed at file scope
> BUILD_BUG_ON(sizeof(this_cpu(tss_page)) != PAGE_SIZE);
> ^
> /local/xen.git/xen/include/asm/percpu.h:14:7: note: expanded from macro
> 'this_cpu'
> (*RELOC_HIDE(&per_cpu__##var, get_cpu_info()->per_cpu_offset))
> ^
> /local/xen.git/xen/include/xen/compiler.h:98:3: note: expanded from macro
> 'RELOC_HIDE'
> ({ unsigned long __ptr; \
> ^
> /local/xen.git/xen/include/xen/lib.h:26:53: note: expanded from macro
> 'BUILD_BUG_ON'
> #define BUILD_BUG_ON(cond) ((void)BUILD_BUG_ON_ZERO(cond))
> ^
> /local/xen.git/xen/include/xen/lib.h:25:57: note: expanded from macro
> 'BUILD_BUG_ON_ZERO'
> #define BUILD_BUG_ON_ZERO(cond) sizeof(struct { int:-!!(cond); })
> ^
> 1 error generated.
> /local/xen.git/xen/Rules.mk:202: recipe for target 'smpboot.o' failed
>
> This is obviously a compiler bug because the BUILD_BUG_ON() is not at file
> scope. However, it can be worked around by using a local variable.
It can be worked around, yes, but the result is not identical:
> --- a/xen/arch/x86/smpboot.c
> +++ b/xen/arch/x86/smpboot.c
> @@ -826,9 +826,11 @@ static int setup_cpu_root_pgt(unsigned int cpu)
> rc = clone_mapping(idt_tables[cpu], rpt);
> if ( !rc )
> {
> - BUILD_BUG_ON(sizeof(this_cpu(tss_page)) != PAGE_SIZE);
> + struct tss_page *this_tss = &per_cpu(tss_page, cpu);
Whatever type is compatible with struct tss_page * will now be
permitted on the rhs. Hence ...
> - rc = clone_mapping(&per_cpu(tss_page, cpu).tss, rpt);
> + BUILD_BUG_ON(sizeof(*this_tss) != PAGE_SIZE);
... this sizeof() is not necessarily checking the size of the
per-CPU variable. But anyway - the change has been committed
already, and the chances of this going wrong are low enough, so
please don't treat this as an objection or revert request.
Jan
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