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SubjectRe: [PATCH] vsyscall: use __iter_div_u64_rem()
On Thu, Jul 11, 2019 at 2:14 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
>
> Could you please tell me which version of the compiler did you use?
>
> My building command is:
>
> # make mrproper && make CC=clang HOSTCC=clang i386_defconfig && make ARCH=i386
> CC=clang HOSTCC=clang -j56
>

See below for the patch I am using locally to work around this.
That patch is probably wrong, so I have not submitted it yet, but it
gives you a clean build ;-)

Arnd

8<---
Subject: [PATCH] x86: percpu: fix clang 32-bit build

clang does not like an inline assembly with a "=q" contraint for
a 64-bit output:

arch/x86/events/perf_event.h:824:21: error: invalid output size for
constraint '=q'
u64 disable_mask = __this_cpu_read(cpu_hw_events.perf_ctr_virt_mask);
^
include/linux/percpu-defs.h:447:2: note: expanded from macro '__this_cpu_read'
raw_cpu_read(pcp); \
^
include/linux/percpu-defs.h:421:28: note: expanded from macro 'raw_cpu_read'
#define raw_cpu_read(pcp)
__pcpu_size_call_return(raw_cpu_read_, pcp)
^
include/linux/percpu-defs.h:322:23: note: expanded from macro
'__pcpu_size_call_return'
case 1: pscr_ret__ = stem##1(variable); break; \
^
<scratch space>:357:1: note: expanded from here
raw_cpu_read_1
^
arch/x86/include/asm/percpu.h:394:30: note: expanded from macro 'raw_cpu_read_1'
#define raw_cpu_read_1(pcp) percpu_from_op(, "mov", pcp)
^
arch/x86/include/asm/percpu.h:189:15: note: expanded from macro 'percpu_from_op'
: "=q" (pfo_ret__) \
^

According to the commit that introduced the "q" constraint, this was
needed to fix miscompilation, but it gives no further detail.

Using the normal "=r" constraint seems to work so far.

Fixes: 3c598766a2ba ("x86: fix percpu_{to,from}_op()")
Cc: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 2278797c769d..e791fbf4018f 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -99,7 +99,7 @@ do { \
case 1: \
asm qual (op "b %1,"__percpu_arg(0) \
: "+m" (var) \
- : "qi" ((pto_T__)(val))); \
+ : "ri" ((pto_T__)(val))); \
break; \
case 2: \
asm qual (op "w %1,"__percpu_arg(0) \
@@ -144,7 +144,7 @@ do {
\
else \
asm qual ("addb %1, "__percpu_arg(0) \
: "+m" (var) \
- : "qi" ((pao_T__)(val))); \
+ : "ri" ((pao_T__)(val))); \
break; \
case 2: \
if (pao_ID__ == 1) \
@@ -186,7 +186,7 @@ do {
\
switch (sizeof(var)) { \
case 1: \
asm qual (op "b "__percpu_arg(1)",%0" \
- : "=q" (pfo_ret__) \
+ : "=r" (pfo_ret__) \
: "m" (var)); \
break; \
case 2: \
@@ -215,7 +215,7 @@ do {
\
switch (sizeof(var)) { \
case 1: \
asm(op "b "__percpu_arg(P1)",%0" \
- : "=q" (pfo_ret__) \
+ : "=r" (pfo_ret__) \
: "p" (&(var))); \
break; \
case 2: \
\
 
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