On 05/28/2018 02:17 PM, Christophe Leroy wrote:
Latest GCC version emit many warnings similar to the following one.
Oops, forgot to include the failure text:
In file included from arch/powerpc/kernel/syscalls.c:24:
./include/linux/syscalls.h:233:18: warning: 'sys_mmap2' alias between
functions of incompatible types 'long int(long unsigned int, size_t,
long unsigned int, long unsigned int, long unsigned int, long
unsigned int)' {aka 'long int(long unsigned int, unsigned int, long
unsigned int, long unsigned int, long unsigned int, long unsigned
int)'} and 'long int(long int, long int, long int, long int, long
int, long int)' [-Wattribute-alias]
asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:65:1: note: in expansion of macro
'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:65:1: note: in expansion of macro
'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
^~~~~~~~~~~~~~~
./include/linux/syscalls.h:233:18: warning: 'sys_mmap' alias between
functions of incompatible types 'long int(long unsigned int, size_t,
long unsigned int, long unsigned int, long unsigned int, off_t)' {aka
'long int(long unsigned int, unsigned int, long unsigned int, long
unsigned int, long unsigned int, long int)'} and 'long int(long int,
long int, long int, long int, long int, long int)' [-Wattribute-alias]
asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:72:1: note: in expansion of macro
'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:72:1: note: in expansion of macro
'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
^~~~~~~~~~~~~~~
CC arch/powerpc/kernel/irq.o
CC arch/powerpc/kernel/align.o
CC arch/powerpc/kernel/signal_32.o
In file included from arch/powerpc/kernel/signal_32.c:29:
./include/linux/syscalls.h:233:18: warning: 'sys_swapcontext' alias
between functions of incompatible types 'long int(struct ucontext *,
struct ucontext *, long int)' and 'long int(long int, long int, long
int)' [-Wattribute-alias]
asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:213:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/signal_32.c:1044:1: note: in expansion of macro
'SYSCALL_DEFINE3'
SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:213:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/signal_32.c:1044:1: note: in expansion of macro
'SYSCALL_DEFINE3'
SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
^~~~~~~~~~~~~~~
./include/linux/syscalls.h:233:18: warning: 'sys_debug_setcontext' alias
between functions of incompatible types 'long int(struct ucontext *,
int, struct sig_dbg_op *)' and 'long int(long int, long int, long
int)' [-Wattribute-alias]
asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:213:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/signal_32.c:1232:1: note: in expansion of macro
'SYSCALL_DEFINE3'
SYSCALL_DEFINE3(debug_setcontext, struct ucontext __user *, ctx,
^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:213:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/signal_32.c:1232:1: note: in expansion of macro
'SYSCALL_DEFINE3'
SYSCALL_DEFINE3(debug_setcontext, struct ucontext __user *, ctx,
^~~~~~~~~~~~~~~
Christophe
quoted hunk
As arch/powerpc code is built with -Werror, this breaks build with
GCC 8.1
This patch inhibits that warning
Signed-off-by: Christophe Leroy <redacted>
---
arch/powerpc/Makefile | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 26ccd0b91512..d6c557530ce8 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -145,6 +145,8 @@ CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mno-pointers-to-nested-functions)
CFLAGS-$(CONFIG_PPC32) := -ffixed-r2 $(MULTIPLEWORD)
CFLAGS-$(CONFIG_PPC32) += $(call cc-option,-mno-readonly-in-sdata)
+CFLAGS-y += $(call cc-option,-Wno-attribute-alias)
+
ifeq ($(CONFIG_PPC_BOOK3S_64),y)
ifeq ($(CONFIG_CPU_LITTLE_ENDIAN),y)
CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=power8
Le 28/05/2018 à 16:37, Segher Boessenkool a écrit :
On Mon, May 28, 2018 at 02:17:49PM +0000, Christophe Leroy wrote:
quoted
Latest GCC version emit many warnings similar to the following one.
You didn't actually show an example?
Yes I forgot:
In file included from arch/powerpc/kernel/syscalls.c:24:
./include/linux/syscalls.h:233:18: warning: 'sys_mmap2' alias between
functions of incompatible types 'long int(long unsigned int, size_t,
long unsigned int, long unsigned int, long unsigned int, long
unsigned int)' {aka 'long int(long unsigned int, unsigned int, long
unsigned int, long unsigned int, long unsigned int, long unsigned
int)'} and 'long int(long int, long int, long int, long int, long
int, long int)' [-Wattribute-alias]
asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:65:1: note: in expansion of macro
'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:65:1: note: in expansion of macro
'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
^~~~~~~~~~~~~~~
This warning should detect serious problems, so don't disable it without
first investigating please.
It's been a discussion on this topic, ref
https://lkml.org/lkml/2017/12/5/581
It says "The new warning seems reasonable in principle, but it doesn't
help us here, since we rely on the type mismatch to sanitize the
system call arguments. After I reported this as GCC PR82435, a new
-Wno-attribute-alias option was added that could be used to turn the
warning off globally on the command line, but I'd prefer to do it a
little more fine-grained"
What do you call "latest version", btw? Trunk, aka 9.0? Or the most
advanced release, 8.1? Or the latest release (which also is 8.1 :-) )
I encounter it with 8.1
According the refered discusion, it linked to GCC 8
Christophe
Segher
On Mon, May 28, 2018 at 02:39:37PM +0000, Christophe Leroy wrote:
In file included from arch/powerpc/kernel/syscalls.c:24:
./include/linux/syscalls.h:233:18: warning: 'sys_mmap2' alias between
functions of incompatible types 'long int(long unsigned int, size_t,
long unsigned int, long unsigned int, long unsigned int, long
unsigned int)' {aka 'long int(long unsigned int, unsigned int, long
unsigned int, long unsigned int, long unsigned int, long unsigned
int)'} and 'long int(long int, long int, long int, long int, long
int, long int)' [-Wattribute-alias]
So yes, these are actually different (int vs. long).
In file included from arch/powerpc/kernel/signal_32.c:29:
./include/linux/syscalls.h:233:18: warning: 'sys_swapcontext' alias
between functions of incompatible types 'long int(struct ucontext *,
struct ucontext *, long int)' and 'long int(long int, long int, long
int)' [-Wattribute-alias]
And this one is quite spectacularly different.
Try putting this before the wacko aliases:
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wattribute-alias"
and this after:
#pragma GCC diagnostic pop
so that you will get this quite useful warning for all other code.
Segher