On Nov 29, 2018, at 4:28 AM, Florian Weimer [off-list ref] wrote:

Disclaimer: I'm looking at this patch because Christian requested it.
I'm not a kernel developer.

* Christian Brauner:

quoted

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 3cf7b533b3d1..3f27ffd8ae87 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl

@@ -398,3 +398,4 @@

384    i386    arch_prctl        sys_arch_prctl            __ia32_compat_sys_arch_prctl
385    i386    io_pgetevents        sys_io_pgetevents        __ia32_compat_sys_io_pgetevents
386    i386    rseq            sys_rseq            __ia32_sys_rseq
+387    i386    procfd_signal        sys_procfd_signal        __ia32_compat_sys_procfd_signal

diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index f0b1709a5ffb..8a30cde82450 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl

@@ -343,6 +343,7 @@

332    common    statx            __x64_sys_statx
333    common    io_pgetevents        __x64_sys_io_pgetevents
334    common    rseq            __x64_sys_rseq
+335    64    procfd_signal        __x64_sys_procfd_signal

#
# x32-specific system call numbers start at 512 to avoid cache impact

@@ -386,3 +387,4 @@

545    x32    execveat        __x32_compat_sys_execveat/ptregs
546    x32    preadv2            __x32_compat_sys_preadv64v2
547    x32    pwritev2        __x32_compat_sys_pwritev64v2
+548    x32    procfd_signal        __x32_compat_sys_procfd_signal

Is there a reason why these numbers have to be different?

(See the recent discussion with Andy Lutomirski.)

Hah, I missed this part of the patch.  Let’s not add new x32 syscall numbers.

Also, can we perhaps rework this a bit to get rid of the compat entry point?  The easier way would be to check in_compat_syscall(). The nicer way IMO would be to use the 64-bit structure for 32-bit as well.