[v2,06/13] parisc: use generic sys_fanotify_mark implementation

  From: Arnd Bergmann <arnd@arndb.de>

The sys_fanotify_mark() syscall on parisc uses the reverse word order
for the two halves of the 64-bit argument compared to all syscalls on
all 32-bit architectures. As far as I can tell, the problem is that
the function arguments on parisc are sorted backwards (26, 25, 24, 23,
...) compared to everyone else, so the calling conventions of using an
even/odd register pair in native word order result in the lower word
coming first in function arguments, matching the expected behavior
on little-endian architectures. The system call conventions however
ended up matching what the other 32-bit architectures do.

A glibc cleanup in 2020 changed the userspace behavior in a way that
handles all architectures consistently, but this inadvertently broke
parisc32 by changing to the same method as everyone else.

The change made it into glibc-2.35 and subsequently into debian 12
(bookworm), which is the latest stable release. This means we
need to choose between reverting the glibc change or changing the
kernel to match it again, but either hange will leave some systems
broken.

Pick the option that is more likely to help current and future
users and change the kernel to match current glibc. This also
means the behavior is now consistent across architectures, but
it breaks running new kernels with old glibc builds before 2.35.

Link: https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=d150181d73d9
Link: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/arch/parisc/kernel/sys_parisc.c?h=57b1dfbd5b4a39d
Cc: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Tested-by: Helge Deller <deller@gmx.de>
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
I found this through code inspection, please double-check to make
sure I got the bug and the fix right.

The alternative is to fix this by reverting glibc back to the
unusual behavior.
---
 arch/parisc/Kconfig                     | 1 +
 arch/parisc/kernel/sys_parisc32.c       | 9 ---------
 arch/parisc/kernel/syscalls/syscall.tbl | 2 +-
 3 files changed, 2 insertions(+), 10 deletions(-)
  

On Mon, Jun 24, 2024 at 06:37:04PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> The sys_fanotify_mark() syscall on parisc uses the reverse word order
> for the two halves of the 64-bit argument compared to all syscalls on
> all 32-bit architectures. As far as I can tell, the problem is that
> the function arguments on parisc are sorted backwards (26, 25, 24, 23,
> ...) compared to everyone else, so the calling conventions of using an
> even/odd register pair in native word order result in the lower word
> coming first in function arguments, matching the expected behavior
> on little-endian architectures. The system call conventions however
> ended up matching what the other 32-bit architectures do.
> 
> A glibc cleanup in 2020 changed the userspace behavior in a way that
> handles all architectures consistently, but this inadvertently broke
> parisc32 by changing to the same method as everyone else.
> 
> The change made it into glibc-2.35 and subsequently into debian 12
> (bookworm), which is the latest stable release. This means we
> need to choose between reverting the glibc change or changing the
> kernel to match it again, but either hange will leave some systems
> broken.
> 
> Pick the option that is more likely to help current and future
> users and change the kernel to match current glibc. This also
> means the behavior is now consistent across architectures, but
> it breaks running new kernels with old glibc builds before 2.35.
> 
> Link: https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=d150181d73d9
> Link: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/arch/parisc/kernel/sys_parisc.c?h=57b1dfbd5b4a39d
> Cc: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> Tested-by: Helge Deller <deller@gmx.de>
> Acked-by: Helge Deller <deller@gmx.de>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> I found this through code inspection, please double-check to make
> sure I got the bug and the fix right.
> 

Building parisc:allmodconfig ... failed
--------------
Error log:
In file included from fs/notify/fanotify/fanotify_user.c:14:
include/linux/syscalls.h:248:25: error: conflicting types for 'sys_fanotify_mark'; have 'long int(int,  unsigned int,  u32,  u32,  int,  const char *)' {aka 'long int(int,  unsigned int,  unsigned int,  unsigned int,  int,  const char *)'}
  248 |         asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))       \
      |                         ^~~
include/linux/syscalls.h:234:9: note: in expansion of macro '__SYSCALL_DEFINEx'
  234 |         __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
      |         ^~~~~~~~~~~~~~~~~
include/linux/syscalls.h:228:36: note: in expansion of macro 'SYSCALL_DEFINEx'
  228 | #define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
      |                                    ^~~~~~~~~~~~~~~
include/linux/syscalls.h:287:27: note: in expansion of macro 'SYSCALL_DEFINE6'
  287 | #define SYSCALL32_DEFINE6 SYSCALL_DEFINE6
      |                           ^~~~~~~~~~~~~~~
fs/notify/fanotify/fanotify_user.c:1924:1: note: in expansion of macro 'SYSCALL32_DEFINE6'
 1924 | SYSCALL32_DEFINE6(fanotify_mark,
      | ^~~~~~~~~~~~~~~~~
include/linux/syscalls.h:862:17: note: previous declaration of 'sys_fanotify_mark' with type 'long int(int,  unsigned int,  u64,  int,  const char *)' {aka 'long int(int,  unsigned int,  long long unsigned int,  int,  const char *)'}
  862 | asmlinkage long sys_fanotify_mark(int fanotify_fd, unsigned int flags,
      |                 ^~~~~~~~~~~~~~~~~
make[6]: [scripts/Makefile.build:244: fs/notify/fanotify/fanotify_user.o] Error 1 (ignored)

Guenter
  

On Sat, Jun 29, 2024, at 19:46, Guenter Roeck wrote:

> Building parisc:allmodconfig ... failed
> --------------
> Error log:
> In file included from fs/notify/fanotify/fanotify_user.c:14:
> include/linux/syscalls.h:248:25: error: conflicting types for 
> 'sys_fanotify_mark'; have 'long int(int,  unsigned int,  u32,  u32,  
> int,  const char *)' {aka 'long int(int,  unsigned int,  unsigned int,  
> unsigned int,  int,  const char *)'}
>   248 |         asmlinkage long 
> sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))       \
>       |                         ^~~
> include/linux/syscalls.h:234:9: note: in expansion of macro 
> '__SYSCALL_DEFINEx'
>   234 |         __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
>       |         ^~~~~~~~~~~~~~~~~

Thanks for the report, this has escaped my build testing
since I had fanotify disabled on the parisc build.

Sent a fix now and queued it as a fix in the asm-generic
tree:

https://lore.kernel.org/lkml/20240629210359.94426-1-arnd@kernel.org/T/#u

     Arnd