On 6/20/24 18:23, Arnd Bergmann wrote:
From: Arnd Bergmann <arnd@xxxxxxxx>
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,
r26 is arg0, r25 is arg1, and so on.
I'm not sure I would call this "sorted backwards".
I think the reason is simply that hppa is the only 32-bit big-endian
arch left...
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.
I appreciate such cleanups to make arches consistent.
But it's bad if breakages aren't noticed or reported then...
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.
Agreed (assuming we have really a problem on parisc).
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@xxxxxxxxxx>
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
I found this through code inspection, please double-check to make
sure I got the bug and the fix right.
The patch looks good at first sight.
I'll pick it up in my parisc git tree and will do some testing the
next few days and then push forward for 6.11 when it opens....
Thank you!!
Helge
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(-)
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index daafeb20f993..dc9b902de8ea 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -16,6 +16,7 @@ config PARISC
select ARCH_HAS_UBSAN
select ARCH_HAS_PTE_SPECIAL
select ARCH_NO_SG_CHAIN
+ select ARCH_SPLIT_ARG64 if !64BIT
select ARCH_SUPPORTS_HUGETLBFS if PA20
select ARCH_SUPPORTS_MEMORY_FAILURE
select ARCH_STACKWALK
diff --git a/arch/parisc/kernel/sys_parisc32.c b/arch/parisc/kernel/sys_parisc32.c
index 2a12a547b447..826c8e51b585 100644
--- a/arch/parisc/kernel/sys_parisc32.c
+++ b/arch/parisc/kernel/sys_parisc32.c
@@ -23,12 +23,3 @@ asmlinkage long sys32_unimplemented(int r26, int r25, int r24, int r23,
current->comm, current->pid, r20);
return -ENOSYS;
}
-
-asmlinkage long sys32_fanotify_mark(compat_int_t fanotify_fd, compat_uint_t flags,
- compat_uint_t mask0, compat_uint_t mask1, compat_int_t dfd,
- const char __user * pathname)
-{
- return sys_fanotify_mark(fanotify_fd, flags,
- ((__u64)mask1 << 32) | mask0,
- dfd, pathname);
-}
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index 39e67fab7515..66dc406b12e4 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -364,7 +364,7 @@
320 common accept4 sys_accept4
321 common prlimit64 sys_prlimit64
322 common fanotify_init sys_fanotify_init
-323 common fanotify_mark sys_fanotify_mark sys32_fanotify_mark
+323 common fanotify_mark sys_fanotify_mark compat_sys_fanotify_mark
324 32 clock_adjtime sys_clock_adjtime32
324 64 clock_adjtime sys_clock_adjtime
325 common name_to_handle_at sys_name_to_handle_at
