linux_dsm_epyc7002/arch/x86/entry
Denys Vlasenko 778843f934 x86/asm/entry/32: Simplify pushes of zeroed pt_regs->REGs
Use of a temporary R8 register here seems to be unnecessary.

"push %r8" is a two-byte insn (it needs REX prefix to specify R8),
"push $0" is two-byte too. It seems just using the latter would be
no worse.

Thus, code had an unnecessary "xorq %r8,%r8" insn.
It probably costs nothing in execution time here since we are probably
limited by store bandwidth at this point, but still.

Run-tested under QEMU: 32-bit calls still work:

 / # ./test_syscall_vdso32
 [RUN]	Executing 6-argument 32-bit syscall via VDSO
 [OK]	Arguments are preserved across syscall
 [NOTE]	R11 has changed:0000000000200ed7 - assuming clobbered by SYSRET insn
 [OK]	R8..R15 did not leak kernel data
 [RUN]	Executing 6-argument 32-bit syscall via INT 80
 [OK]	Arguments are preserved across syscall
 [OK]	R8..R15 did not leak kernel data
 [RUN]	Running tests under ptrace
 [RUN]	Executing 6-argument 32-bit syscall via VDSO
 [OK]	Arguments are preserved across syscall
 [NOTE]	R11 has changed:0000000000200ed7 - assuming clobbered by SYSRET insn
 [OK]	R8..R15 did not leak kernel data
 [RUN]	Executing 6-argument 32-bit syscall via INT 80
 [OK]	Arguments are preserved across syscall
 [OK]	R8..R15 did not leak kernel data

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
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: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1462201010-16846-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-05-03 08:19:40 +02:00
..
syscalls x86/syscalls: Wire up compat readv2/writev2 syscalls 2016-04-13 10:31:26 +02:00
vdso x86/vdso: Remove direct HPET access through the vDSO 2016-04-13 10:28:34 +02:00
vsyscall x86/vdso: Disallow vvar access to vclock IO for never-used vclocks 2016-01-12 11:59:35 +01:00
calling.h x86/asm/entry: Remove unused SAVE_ALL/RESTORE_ALL macros for !CONFIG_x86_64 2016-01-19 08:24:03 +01:00
common.c x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall() 2016-04-19 10:44:52 +02:00
entry_32.S x86/entry/32: Change INT80 to be an interrupt gate 2016-03-10 10:53:26 +01:00
entry_64_compat.S x86/asm/entry/32: Simplify pushes of zeroed pt_regs->REGs 2016-05-03 08:19:40 +02:00
entry_64.S x86/segments/64: When load_gs_index fails, clear the base 2016-04-29 11:56:41 +02:00
Makefile objtool: Mark non-standard object files and directories 2016-02-29 08:35:02 +01:00
syscall_32.c x86/syscalls: Add syscall entry qualifiers 2016-01-29 09:46:38 +01:00
syscall_64.c x86/entry/64: Always run ptregs-using syscalls on the slow path 2016-01-29 09:46:38 +01:00
thunk_32.S Merge branch 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-06-22 17:59:09 -07:00
thunk_64.S x86/asm/entry: Create stack frames in thunk functions 2016-02-24 08:35:43 +01:00