Hello,
I’m writing to you because your name shows up on this:
commit 45e29d119e9923ff14dfb840e3482bef1667bbfb
Author: Andy Lutomirski <l...@kernel.org>
Date: Wed Jul 3 13:34:05 2019 -0700
x86/syscalls: Make __X32_SYSCALL_BIT be unsigned long
Currently, it's an int. This is bizarre. Fortunately, the code using it
still works: ~__X32_SYSCALL_BIT is also int, so, if nr is unsigned long,
then C kindly sign-extends the ~__X32_SYSCALL_BIT part, and it actually
results in the desired value.
This is far more subtle than it deserves to be. Syscall numbers are, for
all practical purposes, unsigned long, so make __X32_SYSCALL_BIT be
unsigned long.
Signed-off-by: Andy Lutomirski <l...@kernel.org>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Link:
https://lkml.kernel.org/r/99b0d83ad891c67105470a1a6b63243fd63a5061.1562185330.git.l...@kernel.org
This commit changed an uapi header, breaking userspace. Long debugging
story (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=954294 if you
are interested) short, it goes like this:
libseccomp exposes an interface SCMP_SYS() which is designed to expand
to an int and be usable in cpp context. It redirects to the __NR_*
constants from <asm/unistd.h>.
Example: SCMP_SYS(mmap) becomes __NR_mmap or __NR_mmap2 (depending on
the architecture).
Now, most architectures define __NR_mmap as a mere integer number:
asm/unistd_32.h:#define __NR_mmap 90
asm/unistd_64.h:#define __NR_mmap 9
x32 differs:
asm/unistd_x32.h:#define __NR_mmap (__X32_SYSCALL_BIT + 9)
This construct is, thankfully, still usable in something like
#if (__NR_mmap > __NR_somethingelse)
but as __X32_SYSCALL_BIT is no longer int its type also isn’t.
Therefore I ask you to revert this change, bringing x32 closer
to all other architectures.
> Syscall numbers are, for
> all practical purposes, unsigned long
Yes, except for the one purpose of the C data type of the
syscall constants exposed to userspace, they are.
Feel free to handle __X32_SYSCALL_BIT differently in the
kernel (although even there it *will* introduce subtle
differences from other architectures), but please keep it
as int as visible from userspace.
Thanks in advance,
//mirabilos
PS: Please keep both me *and* the Debian bug in Cc, but
feel free to forward to relevant lists and persons;
I’m unsure where exactly to write to about this.
@bwh: commit 45e29d119e9923ff14dfb840e3482bef1667bbfb is
literally just this…
-#define __X32_SYSCALL_BIT 0x40000000
+#define __X32_SYSCALL_BIT 0x40000000UL
… so can you please revert it in Debian in the meantime,
even if you said you won’t spend time on this?
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