Re: [PATCH v8 5/7] powerpc/64: make buildable without CONFIG_COMPAT

On Thu, 12 Sep 2019 21:36:11 +0200
Christophe Leroy [off-list ref] wrote:

Le 12/09/2019 à 20:26, Michal Suchánek a écrit :

quoted

On Thu, 12 Sep 2019 20:02:16 +0200
Christophe Leroy [off-list ref] wrote:
  

quoted

Le 12/09/2019 à 19:26, Michal Suchanek a écrit :  

quoted

There are numerous references to 32bit functions in generic and 64bit
code so ifdef them out.

Signed-off-by: Michal Suchanek <redacted>
---
v2:
- fix 32bit ifdef condition in signal.c
- simplify the compat ifdef condition in vdso.c - 64bit is redundant
- simplify the compat ifdef condition in callchain.c - 64bit is redundant
v3:
- use IS_ENABLED and maybe_unused where possible
- do not ifdef declarations
- clean up Makefile
v4:
- further makefile cleanup
- simplify is_32bit_task conditions
- avoid ifdef in condition by using return
v5:
- avoid unreachable code on 32bit
- make is_current_64bit constant on !COMPAT
- add stub perf_callchain_user_32 to avoid some ifdefs
v6:
- consolidate current_is_64bit
v7:
- remove leftover perf_callchain_user_32 stub from previous series version
v8:
- fix build again - too trigger-happy with stub removal
- remove a vdso.c hunk that causes warning according to kbuild test robot
---
   arch/powerpc/include/asm/thread_info.h |  4 +--
   arch/powerpc/kernel/Makefile           |  7 ++---
   arch/powerpc/kernel/entry_64.S         |  2 ++
   arch/powerpc/kernel/signal.c           |  3 +-
   arch/powerpc/kernel/syscall_64.c       |  6 ++--
   arch/powerpc/kernel/vdso.c             |  3 +-
   arch/powerpc/perf/callchain.c          | 39 ++++++++++++++------------
   7 files changed, 33 insertions(+), 31 deletions(-)

diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 8e1d0195ac36..c128d8a48ea3 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h

@@ -144,10 +144,10 @@ static inline bool test_thread_local_flags(unsigned int flags)
   	return (ti->local_flags & flags) != 0;
   }
   
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_COMPAT
   #define is_32bit_task()	(test_thread_flag(TIF_32BIT))
   #else
-#define is_32bit_task()	(1)
+#define is_32bit_task()	(IS_ENABLED(CONFIG_PPC32))
   #endif
   
   #if defined(CONFIG_PPC64)  

[...]
 

quoted

+static inline int current_is_64bit(void)
+{
+	if (!IS_ENABLED(CONFIG_COMPAT))
+		return IS_ENABLED(CONFIG_PPC64);
+	/*
+	 * We can't use test_thread_flag() here because we may be on an
+	 * interrupt stack, and the thread flags don't get copied over
+	 * from the thread_info on the main stack to the interrupt stack.
+	 */
+	return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
+}  

Since at least commit ed1cd6deb013 ("powerpc: Activate
CONFIG_THREAD_INFO_IN_TASK")
[https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ed1cd6d]
the above comment is wrong and current_is_64bit() is equivalent to
!is_32bit_task()

See https://github.com/linuxppc/issues/issues/275

Christophe  

I aim at changing the code as little as possible here. A separate patch
on top removing this function would be ok?  

Yes I agree. By making prior to this patch a separate patch which drops 
current_is_64bit() would be good. And it would reduce the size of this 
patch by approximately one third.

Indeed, removing it before makes this patch much cleaner.

Thanks

Michal