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linux-next/arch/x86/ia32
Denys Vlasenko 3f5159a922 x86/asm/entry/32: Update -ENOSYS handling to match the 64-bit logic
Recently Andy changed the 64-bit syscall logic so that
pt_regs->ax is initially set to -ENOSYS, and on syscall exit,
it is updated with the actual return value. This simplified
the logic there.

This patch does the same for 32-bit syscall entry points.

The check for %rax being too big is moved to be just before
the call instruction which dispatches execution through the
syscall table.

There is no way to accidentally skip this check now by jumping
to a label after it. This allows us to remove redundant checks
after ptrace et al.

If %rax is too big, we just skip over the (call, write %rax to
pt_regs->ax) instruction pair. pt_regs->ax remains set to -ENOSYS,
and it gets returned to userspace.

Similar to 64-bit code, this eliminates the "ia32_badsys" code path.

Run-tested.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1429632194-13445-2-git-send-email-dvlasenk@redhat.com
[ Changelog massage. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-04-22 08:41:44 +02:00
..
audit.c x86: hook up execveat system call 2014-12-13 12:42:51 -08:00
ia32_aout.c assorted conversions to %p[dD] 2014-11-19 13:01:20 -05:00
ia32_signal.c x86/signal: Remove pax argument from restore_sigcontext 2015-04-06 09:06:39 +02:00
ia32entry.S x86/asm/entry/32: Update -ENOSYS handling to match the 64-bit logic 2015-04-22 08:41:44 +02:00
Makefile x86/compat: Merge native and compat 32-bit syscall tables 2015-03-04 06:16:21 +01:00
sys_ia32.c x86/compat: Remove sys32_vm86_warning 2015-03-04 06:16:21 +01:00