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[PATCH v2 00/10] x86: Rewrite 64-bit syscall code

Started byAndy Lutomirski <luto@kernel.org>
First post2016-01-29 00:20 +0100
Last post2016-01-29 12:40 +0100
Articles 7 — 2 participants

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Contents

  [PATCH v2 00/10] x86: Rewrite 64-bit syscall code Andy Lutomirski <luto@kernel.org> - 2016-01-29 00:20 +0100
    [PATCH v2 08/10] x86/entry/64: Call all native slow-path syscalls with full pt-regs Andy Lutomirski <luto@kernel.org> - 2016-01-29 00:20 +0100
      [tip:x86/asm] x86/entry/64:   Call all native slow-path syscalls with full pt-regs tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-01-29 12:40 +0100
    [PATCH v2 05/10] x86/syscalls: Move compat syscall entry handling into syscalltbl.sh Andy Lutomirski <luto@kernel.org> - 2016-01-29 00:20 +0100
      [tip:x86/asm] x86/syscalls:   Move compat syscall entry handling into syscalltbl.sh tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-01-29 12:40 +0100
    [PATCH v2 02/10] selftests/x86: Add check_initial_reg_state Andy Lutomirski <luto@kernel.org> - 2016-01-29 00:20 +0100
      [tip:x86/asm] selftests/x86: Add check_initial_reg_state() tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-01-29 12:40 +0100

#1321141 — [PATCH v2 00/10] x86: Rewrite 64-bit syscall code

FromAndy Lutomirski <luto@kernel.org>
Date2016-01-29 00:20 +0100
Subject[PATCH v2 00/10] x86: Rewrite 64-bit syscall code
Message-ID<qW413-2cO-7@gated-at.bofh.it>
This is kind of like the 32-bit and compat code, except that I
preserved the fast path this time.  I was unable to measure any
significant performance change on my laptop in the fast path.

Changes from v1:
 - Various tidying up.
 - Remove duplicate tables (folded in, so the fastpath table isn't in this set).
 - Rebased to 4.5-rc1
 - Remove enter_from_user_mode stuff -- let's get the basics in first.

Andy Lutomirski (10):
  selftests/x86: Extend Makefile to allow 64-bit-only tests
  selftests/x86: Add check_initial_reg_state
  x86/syscalls: Refactor syscalltbl.sh
  x86/syscalls: Remove __SYSCALL_COMMON and __SYSCALL_X32
  x86/syscalls: Move compat syscall entry handling into syscalltbl.sh
  x86/syscalls: Add syscall entry qualifiers
  x86/entry/64: Always run ptregs-using syscalls on the slow path
  x86/entry/64: Call all native slow-path syscalls with full pt-regs
  x86/entry/64: Stop using int_ret_from_sys_call in ret_from_fork
  x86/entry/64: Migrate the 64-bit syscall slow path to C

 arch/x86/entry/common.c                            |  26 ++
 arch/x86/entry/entry_64.S                          | 271 +++++++--------------
 arch/x86/entry/syscall_32.c                        |  10 +-
 arch/x86/entry/syscall_64.c                        |  13 +-
 arch/x86/entry/syscalls/syscall_64.tbl             |  18 +-
 arch/x86/entry/syscalls/syscalltbl.sh              |  58 ++++-
 arch/x86/kernel/asm-offsets_32.c                   |   2 +-
 arch/x86/kernel/asm-offsets_64.c                   |  10 +-
 arch/x86/um/sys_call_table_32.c                    |   4 +-
 arch/x86/um/sys_call_table_64.c                    |   7 +-
 arch/x86/um/user-offsets.c                         |   6 +-
 tools/testing/selftests/x86/Makefile               |  14 +-
 .../selftests/x86/check_initial_reg_state.c        | 109 +++++++++
 13 files changed, 317 insertions(+), 231 deletions(-)
 create mode 100644 tools/testing/selftests/x86/check_initial_reg_state.c

-- 
2.5.0

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#1321142 — [PATCH v2 08/10] x86/entry/64: Call all native slow-path syscalls with full pt-regs

FromAndy Lutomirski <luto@kernel.org>
Date2016-01-29 00:20 +0100
Subject[PATCH v2 08/10] x86/entry/64: Call all native slow-path syscalls with full pt-regs
Message-ID<qW414-2cO-25@gated-at.bofh.it>
In reply to#1321141
This removes all of the remaining asm syscall stubs except for
stub_ptregs_64.  Entries in the main syscall table are now all
callable from C.

The resulting asm is every bit as ridiculous as it looks.  The next
few patches will clean it up.  This patch is here to let reviewers
rest their brains and for bisection.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/entry/entry_64.S              | 79 +---------------------------------
 arch/x86/entry/syscalls/syscall_64.tbl | 18 ++++----
 2 files changed, 10 insertions(+), 87 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index f1c8f150728e..f7050a5d9dbc 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -253,7 +253,6 @@ tracesys:
 	 * the value it wants us to use in the table lookup.
 	 */
 	RESTORE_C_REGS_EXCEPT_RAX
-	RESTORE_EXTRA_REGS
 #if __SYSCALL_MASK == ~0
 	cmpq	$__NR_syscall_max, %rax
 #else
@@ -264,6 +263,7 @@ tracesys:
 	movq	%r10, %rcx			/* fixup for C */
 	call	*sys_call_table(, %rax, 8)
 	movq	%rax, RAX(%rsp)
+	RESTORE_EXTRA_REGS
 1:
 	/* Use IRET because user could have changed pt_regs->foo */
 
@@ -384,83 +384,6 @@ END(ptregs_\func)
 #define __SYSCALL_64(nr, sym, qual) __SYSCALL_64_QUAL_##qual(sym)
 #include <asm/syscalls_64.h>
 
-	.macro FORK_LIKE func
-ENTRY(stub_\func)
-	SAVE_EXTRA_REGS 8
-	jmp	sys_\func
-END(stub_\func)
-	.endm
-
-	FORK_LIKE  clone
-	FORK_LIKE  fork
-	FORK_LIKE  vfork
-
-ENTRY(stub_execve)
-	call	sys_execve
-return_from_execve:
-	testl	%eax, %eax
-	jz	1f
-	/* exec failed, can use fast SYSRET code path in this case */
-	ret
-1:
-	/* must use IRET code path (pt_regs->cs may have changed) */
-	addq	$8, %rsp
-	ZERO_EXTRA_REGS
-	movq	%rax, RAX(%rsp)
-	jmp	int_ret_from_sys_call
-END(stub_execve)
-/*
- * Remaining execve stubs are only 7 bytes long.
- * ENTRY() often aligns to 16 bytes, which in this case has no benefits.
- */
-	.align	8
-GLOBAL(stub_execveat)
-	call	sys_execveat
-	jmp	return_from_execve
-END(stub_execveat)
-
-#if defined(CONFIG_X86_X32_ABI)
-	.align	8
-GLOBAL(stub_x32_execve)
-	call	compat_sys_execve
-	jmp	return_from_execve
-END(stub_x32_execve)
-	.align	8
-GLOBAL(stub_x32_execveat)
-	call	compat_sys_execveat
-	jmp	return_from_execve
-END(stub_x32_execveat)
-#endif
-
-/*
- * sigreturn is special because it needs to restore all registers on return.
- * This cannot be done with SYSRET, so use the IRET return path instead.
- */
-ENTRY(stub_rt_sigreturn)
-	/*
-	 * SAVE_EXTRA_REGS result is not normally needed:
-	 * sigreturn overwrites all pt_regs->GPREGS.
-	 * But sigreturn can fail (!), and there is no easy way to detect that.
-	 * To make sure RESTORE_EXTRA_REGS doesn't restore garbage on error,
-	 * we SAVE_EXTRA_REGS here.
-	 */
-	SAVE_EXTRA_REGS 8
-	call	sys_rt_sigreturn
-return_from_stub:
-	addq	$8, %rsp
-	RESTORE_EXTRA_REGS
-	movq	%rax, RAX(%rsp)
-	jmp	int_ret_from_sys_call
-END(stub_rt_sigreturn)
-
-#ifdef CONFIG_X86_X32_ABI
-ENTRY(stub_x32_rt_sigreturn)
-	SAVE_EXTRA_REGS 8
-	call	sys32_x32_rt_sigreturn
-	jmp	return_from_stub
-END(stub_x32_rt_sigreturn)
-#endif
-
 /*
  * A newly forked process directly context switches into this address.
  *
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 5de342a729d0..dcf107ce2cd4 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -21,7 +21,7 @@
 12	common	brk			sys_brk
 13	64	rt_sigaction		sys_rt_sigaction
 14	common	rt_sigprocmask		sys_rt_sigprocmask
-15	64	rt_sigreturn		stub_rt_sigreturn/ptregs
+15	64	rt_sigreturn		sys_rt_sigreturn/ptregs
 16	64	ioctl			sys_ioctl
 17	common	pread64			sys_pread64
 18	common	pwrite64		sys_pwrite64
@@ -62,10 +62,10 @@
 53	common	socketpair		sys_socketpair
 54	64	setsockopt		sys_setsockopt
 55	64	getsockopt		sys_getsockopt
-56	common	clone			stub_clone/ptregs
-57	common	fork			stub_fork/ptregs
-58	common	vfork			stub_vfork/ptregs
-59	64	execve			stub_execve/ptregs
+56	common	clone			sys_clone/ptregs
+57	common	fork			sys_fork/ptregs
+58	common	vfork			sys_vfork/ptregs
+59	64	execve			sys_execve/ptregs
 60	common	exit			sys_exit
 61	common	wait4			sys_wait4
 62	common	kill			sys_kill
@@ -328,7 +328,7 @@
 319	common	memfd_create		sys_memfd_create
 320	common	kexec_file_load		sys_kexec_file_load
 321	common	bpf			sys_bpf
-322	64	execveat		stub_execveat/ptregs
+322	64	execveat		sys_execveat/ptregs
 323	common	userfaultfd		sys_userfaultfd
 324	common	membarrier		sys_membarrier
 325	common	mlock2			sys_mlock2
@@ -339,14 +339,14 @@
 # for native 64-bit operation.
 #
 512	x32	rt_sigaction		compat_sys_rt_sigaction
-513	x32	rt_sigreturn		stub_x32_rt_sigreturn
+513	x32	rt_sigreturn		sys32_x32_rt_sigreturn
 514	x32	ioctl			compat_sys_ioctl
 515	x32	readv			compat_sys_readv
 516	x32	writev			compat_sys_writev
 517	x32	recvfrom		compat_sys_recvfrom
 518	x32	sendmsg			compat_sys_sendmsg
 519	x32	recvmsg			compat_sys_recvmsg
-520	x32	execve			stub_x32_execve/ptregs
+520	x32	execve			compat_sys_execve/ptregs
 521	x32	ptrace			compat_sys_ptrace
 522	x32	rt_sigpending		compat_sys_rt_sigpending
 523	x32	rt_sigtimedwait		compat_sys_rt_sigtimedwait
@@ -371,4 +371,4 @@
 542	x32	getsockopt		compat_sys_getsockopt
 543	x32	io_setup		compat_sys_io_setup
 544	x32	io_submit		compat_sys_io_submit
-545	x32	execveat		stub_x32_execveat/ptregs
+545	x32	execveat		compat_sys_execveat/ptregs
-- 
2.5.0

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#1321691 — [tip:x86/asm] x86/entry/64: Call all native slow-path syscalls with full pt-regs

Fromtip-bot for Andy Lutomirski <tipbot@zytor.com>
Date2016-01-29 12:40 +0100
Subject[tip:x86/asm] x86/entry/64: Call all native slow-path syscalls with full pt-regs
Message-ID<qWfze-2gW-47@gated-at.bofh.it>
In reply to#1321142
Commit-ID:  46eabf06c04a6847a694a0c1413d4ac57e5b058a
Gitweb:     http://git.kernel.org/tip/46eabf06c04a6847a694a0c1413d4ac57e5b058a
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Thu, 28 Jan 2016 15:11:26 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 29 Jan 2016 09:46:38 +0100

x86/entry/64: Call all native slow-path syscalls with full pt-regs

This removes all of the remaining asm syscall stubs except for
stub_ptregs_64.  Entries in the main syscall table are now all
callable from C.

The resulting asm is every bit as ridiculous as it looks.  The
next few patches will clean it up.  This patch is here to let
reviewers rest their brains and for bisection.

Signed-off-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: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a6b3801be0d505d50aefabda02d3b93efbfc9c73.1454022279.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/entry/entry_64.S              | 79 +---------------------------------
 arch/x86/entry/syscalls/syscall_64.tbl | 18 ++++----
 2 files changed, 10 insertions(+), 87 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index f1c8f15..f7050a5 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -253,7 +253,6 @@ tracesys:
 	 * the value it wants us to use in the table lookup.
 	 */
 	RESTORE_C_REGS_EXCEPT_RAX
-	RESTORE_EXTRA_REGS
 #if __SYSCALL_MASK == ~0
 	cmpq	$__NR_syscall_max, %rax
 #else
@@ -264,6 +263,7 @@ tracesys:
 	movq	%r10, %rcx			/* fixup for C */
 	call	*sys_call_table(, %rax, 8)
 	movq	%rax, RAX(%rsp)
+	RESTORE_EXTRA_REGS
 1:
 	/* Use IRET because user could have changed pt_regs->foo */
 
@@ -384,83 +384,6 @@ END(ptregs_\func)
 #define __SYSCALL_64(nr, sym, qual) __SYSCALL_64_QUAL_##qual(sym)
 #include <asm/syscalls_64.h>
 
-	.macro FORK_LIKE func
-ENTRY(stub_\func)
-	SAVE_EXTRA_REGS 8
-	jmp	sys_\func
-END(stub_\func)
-	.endm
-
-	FORK_LIKE  clone
-	FORK_LIKE  fork
-	FORK_LIKE  vfork
-
-ENTRY(stub_execve)
-	call	sys_execve
-return_from_execve:
-	testl	%eax, %eax
-	jz	1f
-	/* exec failed, can use fast SYSRET code path in this case */
-	ret
-1:
-	/* must use IRET code path (pt_regs->cs may have changed) */
-	addq	$8, %rsp
-	ZERO_EXTRA_REGS
-	movq	%rax, RAX(%rsp)
-	jmp	int_ret_from_sys_call
-END(stub_execve)
-/*
- * Remaining execve stubs are only 7 bytes long.
- * ENTRY() often aligns to 16 bytes, which in this case has no benefits.
- */
-	.align	8
-GLOBAL(stub_execveat)
-	call	sys_execveat
-	jmp	return_from_execve
-END(stub_execveat)
-
-#if defined(CONFIG_X86_X32_ABI)
-	.align	8
-GLOBAL(stub_x32_execve)
-	call	compat_sys_execve
-	jmp	return_from_execve
-END(stub_x32_execve)
-	.align	8
-GLOBAL(stub_x32_execveat)
-	call	compat_sys_execveat
-	jmp	return_from_execve
-END(stub_x32_execveat)
-#endif
-
-/*
- * sigreturn is special because it needs to restore all registers on return.
- * This cannot be done with SYSRET, so use the IRET return path instead.
- */
-ENTRY(stub_rt_sigreturn)
-	/*
-	 * SAVE_EXTRA_REGS result is not normally needed:
-	 * sigreturn overwrites all pt_regs->GPREGS.
-	 * But sigreturn can fail (!), and there is no easy way to detect that.
-	 * To make sure RESTORE_EXTRA_REGS doesn't restore garbage on error,
-	 * we SAVE_EXTRA_REGS here.
-	 */
-	SAVE_EXTRA_REGS 8
-	call	sys_rt_sigreturn
-return_from_stub:
-	addq	$8, %rsp
-	RESTORE_EXTRA_REGS
-	movq	%rax, RAX(%rsp)
-	jmp	int_ret_from_sys_call
-END(stub_rt_sigreturn)
-
-#ifdef CONFIG_X86_X32_ABI
-ENTRY(stub_x32_rt_sigreturn)
-	SAVE_EXTRA_REGS 8
-	call	sys32_x32_rt_sigreturn
-	jmp	return_from_stub
-END(stub_x32_rt_sigreturn)
-#endif
-
 /*
  * A newly forked process directly context switches into this address.
  *
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 5de342a..dcf107c 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -21,7 +21,7 @@
 12	common	brk			sys_brk
 13	64	rt_sigaction		sys_rt_sigaction
 14	common	rt_sigprocmask		sys_rt_sigprocmask
-15	64	rt_sigreturn		stub_rt_sigreturn/ptregs
+15	64	rt_sigreturn		sys_rt_sigreturn/ptregs
 16	64	ioctl			sys_ioctl
 17	common	pread64			sys_pread64
 18	common	pwrite64		sys_pwrite64
@@ -62,10 +62,10 @@
 53	common	socketpair		sys_socketpair
 54	64	setsockopt		sys_setsockopt
 55	64	getsockopt		sys_getsockopt
-56	common	clone			stub_clone/ptregs
-57	common	fork			stub_fork/ptregs
-58	common	vfork			stub_vfork/ptregs
-59	64	execve			stub_execve/ptregs
+56	common	clone			sys_clone/ptregs
+57	common	fork			sys_fork/ptregs
+58	common	vfork			sys_vfork/ptregs
+59	64	execve			sys_execve/ptregs
 60	common	exit			sys_exit
 61	common	wait4			sys_wait4
 62	common	kill			sys_kill
@@ -328,7 +328,7 @@
 319	common	memfd_create		sys_memfd_create
 320	common	kexec_file_load		sys_kexec_file_load
 321	common	bpf			sys_bpf
-322	64	execveat		stub_execveat/ptregs
+322	64	execveat		sys_execveat/ptregs
 323	common	userfaultfd		sys_userfaultfd
 324	common	membarrier		sys_membarrier
 325	common	mlock2			sys_mlock2
@@ -339,14 +339,14 @@
 # for native 64-bit operation.
 #
 512	x32	rt_sigaction		compat_sys_rt_sigaction
-513	x32	rt_sigreturn		stub_x32_rt_sigreturn
+513	x32	rt_sigreturn		sys32_x32_rt_sigreturn
 514	x32	ioctl			compat_sys_ioctl
 515	x32	readv			compat_sys_readv
 516	x32	writev			compat_sys_writev
 517	x32	recvfrom		compat_sys_recvfrom
 518	x32	sendmsg			compat_sys_sendmsg
 519	x32	recvmsg			compat_sys_recvmsg
-520	x32	execve			stub_x32_execve/ptregs
+520	x32	execve			compat_sys_execve/ptregs
 521	x32	ptrace			compat_sys_ptrace
 522	x32	rt_sigpending		compat_sys_rt_sigpending
 523	x32	rt_sigtimedwait		compat_sys_rt_sigtimedwait
@@ -371,4 +371,4 @@
 542	x32	getsockopt		compat_sys_getsockopt
 543	x32	io_setup		compat_sys_io_setup
 544	x32	io_submit		compat_sys_io_submit
-545	x32	execveat		stub_x32_execveat/ptregs
+545	x32	execveat		compat_sys_execveat/ptregs

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#1321143 — [PATCH v2 05/10] x86/syscalls: Move compat syscall entry handling into syscalltbl.sh

FromAndy Lutomirski <luto@kernel.org>
Date2016-01-29 00:20 +0100
Subject[PATCH v2 05/10] x86/syscalls: Move compat syscall entry handling into syscalltbl.sh
Message-ID<qW414-2cO-31@gated-at.bofh.it>
In reply to#1321141
Rather than duplicating the compat entry handling in all consumers
of syscalls_BITS.h, handle it directly in syscalltbl.sh.  Now we
generate entries in syscalls_32.h like:

__SYSCALL_I386(5, sys_open)
__SYSCALL_I386(5, compat_sys_open)

and all of its consumers implicitly get the right entry point.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/entry/syscall_32.c           | 10 ++--------
 arch/x86/entry/syscall_64.c           |  4 ++--
 arch/x86/entry/syscalls/syscalltbl.sh | 22 ++++++++++++++++++----
 arch/x86/kernel/asm-offsets_32.c      |  2 +-
 arch/x86/kernel/asm-offsets_64.c      |  4 ++--
 arch/x86/um/sys_call_table_32.c       |  4 ++--
 arch/x86/um/sys_call_table_64.c       |  4 ++--
 arch/x86/um/user-offsets.c            |  4 ++--
 8 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/arch/x86/entry/syscall_32.c b/arch/x86/entry/syscall_32.c
index 9a6649857106..3e2829759da2 100644
--- a/arch/x86/entry/syscall_32.c
+++ b/arch/x86/entry/syscall_32.c
@@ -6,17 +6,11 @@
 #include <asm/asm-offsets.h>
 #include <asm/syscall.h>
 
-#ifdef CONFIG_IA32_EMULATION
-#define SYM(sym, compat) compat
-#else
-#define SYM(sym, compat) sym
-#endif
-
-#define __SYSCALL_I386(nr, sym, compat) extern asmlinkage long SYM(sym, compat)(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
+#define __SYSCALL_I386(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
 #include <asm/syscalls_32.h>
 #undef __SYSCALL_I386
 
-#define __SYSCALL_I386(nr, sym, compat) [nr] = SYM(sym, compat),
+#define __SYSCALL_I386(nr, sym) [nr] = sym,
 
 extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 
diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c
index 974fd89ac806..3781989b180e 100644
--- a/arch/x86/entry/syscall_64.c
+++ b/arch/x86/entry/syscall_64.c
@@ -6,11 +6,11 @@
 #include <asm/asm-offsets.h>
 #include <asm/syscall.h>
 
-#define __SYSCALL_64(nr, sym, compat) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
+#define __SYSCALL_64(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
 #include <asm/syscalls_64.h>
 #undef __SYSCALL_64
 
-#define __SYSCALL_64(nr, sym, compat) [nr] = sym,
+#define __SYSCALL_64(nr, sym) [nr] = sym,
 
 extern long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 
diff --git a/arch/x86/entry/syscalls/syscalltbl.sh b/arch/x86/entry/syscalls/syscalltbl.sh
index 5ebeaf1041e7..b81479c8c5fb 100644
--- a/arch/x86/entry/syscalls/syscalltbl.sh
+++ b/arch/x86/entry/syscalls/syscalltbl.sh
@@ -8,10 +8,24 @@ emit() {
     nr="$2"
     entry="$3"
     compat="$4"
-    if [ -n "$compat" ]; then
-	echo "__SYSCALL_${abi}($nr, $entry, $compat)"
-    elif [ -n "$entry" ]; then
-	echo "__SYSCALL_${abi}($nr, $entry, $entry)"
+
+    if [ "$abi" == "64" -a -n "$compat" ]; then
+	echo "a compat entry for a 64-bit syscall makes no sense" >&2
+	exit 1
+    fi
+
+    if [ -z "$compat" ]; then
+	if [ -n "$entry" ]; then
+	    echo "__SYSCALL_${abi}($nr, $entry)"
+	fi
+    else
+	echo "#ifdef CONFIG_X86_32"
+	if [ -n "$entry" ]; then
+	    echo "__SYSCALL_${abi}($nr, $entry)"
+	fi
+	echo "#else"
+	echo "__SYSCALL_${abi}($nr, $compat)"
+	echo "#endif"
     fi
 }
 
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index 6ce39025f467..abec4c9f1c97 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -7,7 +7,7 @@
 #include <linux/lguest.h>
 #include "../../../drivers/lguest/lg.h"
 
-#define __SYSCALL_I386(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_I386(nr, sym) [nr] = 1,
 static char syscalls[] = {
 #include <asm/syscalls_32.h>
 };
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index 29db3b3f550c..9677bf9a616f 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -4,11 +4,11 @@
 
 #include <asm/ia32.h>
 
-#define __SYSCALL_64(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_64(nr, sym) [nr] = 1,
 static char syscalls_64[] = {
 #include <asm/syscalls_64.h>
 };
-#define __SYSCALL_I386(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_I386(nr, sym) [nr] = 1,
 static char syscalls_ia32[] = {
 #include <asm/syscalls_32.h>
 };
diff --git a/arch/x86/um/sys_call_table_32.c b/arch/x86/um/sys_call_table_32.c
index 439c0994b696..d4669a679fd0 100644
--- a/arch/x86/um/sys_call_table_32.c
+++ b/arch/x86/um/sys_call_table_32.c
@@ -25,11 +25,11 @@
 
 #define old_mmap sys_old_mmap
 
-#define __SYSCALL_I386(nr, sym, compat) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
+#define __SYSCALL_I386(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
 #include <asm/syscalls_32.h>
 
 #undef __SYSCALL_I386
-#define __SYSCALL_I386(nr, sym, compat) [ nr ] = sym,
+#define __SYSCALL_I386(nr, sym) [ nr ] = sym,
 
 extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 
diff --git a/arch/x86/um/sys_call_table_64.c b/arch/x86/um/sys_call_table_64.c
index 71a497cde921..6ee5268beb05 100644
--- a/arch/x86/um/sys_call_table_64.c
+++ b/arch/x86/um/sys_call_table_64.c
@@ -35,11 +35,11 @@
 #define stub_execveat sys_execveat
 #define stub_rt_sigreturn sys_rt_sigreturn
 
-#define __SYSCALL_64(nr, sym, compat) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
+#define __SYSCALL_64(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
 #include <asm/syscalls_64.h>
 
 #undef __SYSCALL_64
-#define __SYSCALL_64(nr, sym, compat) [ nr ] = sym,
+#define __SYSCALL_64(nr, sym) [ nr ] = sym,
 
 extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 
diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
index 5edf4f4bbf53..6c9a9c1eae32 100644
--- a/arch/x86/um/user-offsets.c
+++ b/arch/x86/um/user-offsets.c
@@ -9,12 +9,12 @@
 #include <asm/types.h>
 
 #ifdef __i386__
-#define __SYSCALL_I386(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_I386(nr, sym) [nr] = 1,
 static char syscalls[] = {
 #include <asm/syscalls_32.h>
 };
 #else
-#define __SYSCALL_64(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_64(nr, sym) [nr] = 1,
 static char syscalls[] = {
 #include <asm/syscalls_64.h>
 };
-- 
2.5.0

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#1321686 — [tip:x86/asm] x86/syscalls: Move compat syscall entry handling into syscalltbl.sh

Fromtip-bot for Andy Lutomirski <tipbot@zytor.com>
Date2016-01-29 12:40 +0100
Subject[tip:x86/asm] x86/syscalls: Move compat syscall entry handling into syscalltbl.sh
Message-ID<qWfzd-2gW-37@gated-at.bofh.it>
In reply to#1321143
Commit-ID:  3e65654e3db6df6aba9c5b895f8b8e6a8d8eb508
Gitweb:     http://git.kernel.org/tip/3e65654e3db6df6aba9c5b895f8b8e6a8d8eb508
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Thu, 28 Jan 2016 15:11:23 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 29 Jan 2016 09:46:37 +0100

x86/syscalls: Move compat syscall entry handling into syscalltbl.sh

Rather than duplicating the compat entry handling in all
consumers of syscalls_BITS.h, handle it directly in
syscalltbl.sh.  Now we generate entries in syscalls_32.h like:

__SYSCALL_I386(5, sys_open)
__SYSCALL_I386(5, compat_sys_open)

and all of its consumers implicitly get the right entry point.

Signed-off-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: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/b7c2b501dc0e6e43050e916b95807c3e2e16e9bb.1454022279.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/entry/syscall_32.c           | 10 ++--------
 arch/x86/entry/syscall_64.c           |  4 ++--
 arch/x86/entry/syscalls/syscalltbl.sh | 22 ++++++++++++++++++----
 arch/x86/kernel/asm-offsets_32.c      |  2 +-
 arch/x86/kernel/asm-offsets_64.c      |  4 ++--
 arch/x86/um/sys_call_table_32.c       |  4 ++--
 arch/x86/um/sys_call_table_64.c       |  4 ++--
 arch/x86/um/user-offsets.c            |  4 ++--
 8 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/arch/x86/entry/syscall_32.c b/arch/x86/entry/syscall_32.c
index 9a66498..3e28297 100644
--- a/arch/x86/entry/syscall_32.c
+++ b/arch/x86/entry/syscall_32.c
@@ -6,17 +6,11 @@
 #include <asm/asm-offsets.h>
 #include <asm/syscall.h>
 
-#ifdef CONFIG_IA32_EMULATION
-#define SYM(sym, compat) compat
-#else
-#define SYM(sym, compat) sym
-#endif
-
-#define __SYSCALL_I386(nr, sym, compat) extern asmlinkage long SYM(sym, compat)(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
+#define __SYSCALL_I386(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
 #include <asm/syscalls_32.h>
 #undef __SYSCALL_I386
 
-#define __SYSCALL_I386(nr, sym, compat) [nr] = SYM(sym, compat),
+#define __SYSCALL_I386(nr, sym) [nr] = sym,
 
 extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 
diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c
index 974fd89..3781989 100644
--- a/arch/x86/entry/syscall_64.c
+++ b/arch/x86/entry/syscall_64.c
@@ -6,11 +6,11 @@
 #include <asm/asm-offsets.h>
 #include <asm/syscall.h>
 
-#define __SYSCALL_64(nr, sym, compat) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
+#define __SYSCALL_64(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
 #include <asm/syscalls_64.h>
 #undef __SYSCALL_64
 
-#define __SYSCALL_64(nr, sym, compat) [nr] = sym,
+#define __SYSCALL_64(nr, sym) [nr] = sym,
 
 extern long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 
diff --git a/arch/x86/entry/syscalls/syscalltbl.sh b/arch/x86/entry/syscalls/syscalltbl.sh
index 5ebeaf1..b81479c 100644
--- a/arch/x86/entry/syscalls/syscalltbl.sh
+++ b/arch/x86/entry/syscalls/syscalltbl.sh
@@ -8,10 +8,24 @@ emit() {
     nr="$2"
     entry="$3"
     compat="$4"
-    if [ -n "$compat" ]; then
-	echo "__SYSCALL_${abi}($nr, $entry, $compat)"
-    elif [ -n "$entry" ]; then
-	echo "__SYSCALL_${abi}($nr, $entry, $entry)"
+
+    if [ "$abi" == "64" -a -n "$compat" ]; then
+	echo "a compat entry for a 64-bit syscall makes no sense" >&2
+	exit 1
+    fi
+
+    if [ -z "$compat" ]; then
+	if [ -n "$entry" ]; then
+	    echo "__SYSCALL_${abi}($nr, $entry)"
+	fi
+    else
+	echo "#ifdef CONFIG_X86_32"
+	if [ -n "$entry" ]; then
+	    echo "__SYSCALL_${abi}($nr, $entry)"
+	fi
+	echo "#else"
+	echo "__SYSCALL_${abi}($nr, $compat)"
+	echo "#endif"
     fi
 }
 
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index 6ce3902..abec4c9 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -7,7 +7,7 @@
 #include <linux/lguest.h>
 #include "../../../drivers/lguest/lg.h"
 
-#define __SYSCALL_I386(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_I386(nr, sym) [nr] = 1,
 static char syscalls[] = {
 #include <asm/syscalls_32.h>
 };
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index 29db3b3..9677bf9 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -4,11 +4,11 @@
 
 #include <asm/ia32.h>
 
-#define __SYSCALL_64(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_64(nr, sym) [nr] = 1,
 static char syscalls_64[] = {
 #include <asm/syscalls_64.h>
 };
-#define __SYSCALL_I386(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_I386(nr, sym) [nr] = 1,
 static char syscalls_ia32[] = {
 #include <asm/syscalls_32.h>
 };
diff --git a/arch/x86/um/sys_call_table_32.c b/arch/x86/um/sys_call_table_32.c
index 439c099..d4669a6 100644
--- a/arch/x86/um/sys_call_table_32.c
+++ b/arch/x86/um/sys_call_table_32.c
@@ -25,11 +25,11 @@
 
 #define old_mmap sys_old_mmap
 
-#define __SYSCALL_I386(nr, sym, compat) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
+#define __SYSCALL_I386(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
 #include <asm/syscalls_32.h>
 
 #undef __SYSCALL_I386
-#define __SYSCALL_I386(nr, sym, compat) [ nr ] = sym,
+#define __SYSCALL_I386(nr, sym) [ nr ] = sym,
 
 extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 
diff --git a/arch/x86/um/sys_call_table_64.c b/arch/x86/um/sys_call_table_64.c
index 71a497c..6ee5268 100644
--- a/arch/x86/um/sys_call_table_64.c
+++ b/arch/x86/um/sys_call_table_64.c
@@ -35,11 +35,11 @@
 #define stub_execveat sys_execveat
 #define stub_rt_sigreturn sys_rt_sigreturn
 
-#define __SYSCALL_64(nr, sym, compat) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
+#define __SYSCALL_64(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long) ;
 #include <asm/syscalls_64.h>
 
 #undef __SYSCALL_64
-#define __SYSCALL_64(nr, sym, compat) [ nr ] = sym,
+#define __SYSCALL_64(nr, sym) [ nr ] = sym,
 
 extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 
diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
index 5edf4f4..6c9a9c1 100644
--- a/arch/x86/um/user-offsets.c
+++ b/arch/x86/um/user-offsets.c
@@ -9,12 +9,12 @@
 #include <asm/types.h>
 
 #ifdef __i386__
-#define __SYSCALL_I386(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_I386(nr, sym) [nr] = 1,
 static char syscalls[] = {
 #include <asm/syscalls_32.h>
 };
 #else
-#define __SYSCALL_64(nr, sym, compat) [nr] = 1,
+#define __SYSCALL_64(nr, sym) [nr] = 1,
 static char syscalls[] = {
 #include <asm/syscalls_64.h>
 };

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#1321145 — [PATCH v2 02/10] selftests/x86: Add check_initial_reg_state

FromAndy Lutomirski <luto@kernel.org>
Date2016-01-29 00:20 +0100
Subject[PATCH v2 02/10] selftests/x86: Add check_initial_reg_state
Message-ID<qW414-2cO-33@gated-at.bofh.it>
In reply to#1321141
This checks that ELF binaries are started with an appropriately
blank register state.

(There's currently a nasty special case in the entry asm to arrange
 for this.  I'm planning on removing the special case, and this will
 help make sure I don't break it.)

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 tools/testing/selftests/x86/Makefile               |   9 +-
 .../selftests/x86/check_initial_reg_state.c        | 109 +++++++++++++++++++++
 2 files changed, 117 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/x86/check_initial_reg_state.c

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 9c81f263a396..df4f767f48da 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -4,7 +4,8 @@ include ../lib.mk
 
 .PHONY: all all_32 all_64 warn_32bit_failure clean
 
-TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall
+TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall \
+			check_initial_reg_state
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault sigreturn test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
 			ldt_gdt \
@@ -66,3 +67,9 @@ endif
 sysret_ss_attrs_64: thunks.S
 ptrace_syscall_32: raw_syscall_helper_32.S
 test_syscall_vdso_32: thunks_32.S
+
+# check_initial_reg_state is special: it needs a custom entry, and it
+# needs to be static so that its interpreter doesn't destroy its initial
+# state.
+check_initial_reg_state_32: CFLAGS += -Wl,-ereal_start -static
+check_initial_reg_state_64: CFLAGS += -Wl,-ereal_start -static
diff --git a/tools/testing/selftests/x86/check_initial_reg_state.c b/tools/testing/selftests/x86/check_initial_reg_state.c
new file mode 100644
index 000000000000..6aaed9b85baf
--- /dev/null
+++ b/tools/testing/selftests/x86/check_initial_reg_state.c
@@ -0,0 +1,109 @@
+/*
+ * check_initial_reg_state.c - check that execve sets the correct state
+ * Copyright (c) 2014-2016 Andrew Lutomirski
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+
+unsigned long ax, bx, cx, dx, si, di, bp, sp, flags;
+unsigned long r8, r9, r10, r11, r12, r13, r14, r15;
+
+asm (
+	".pushsection .text\n\t"
+	".type real_start, @function\n\t"
+	".global real_start\n\t"
+	"real_start:\n\t"
+#ifdef __x86_64__
+	"mov %rax, ax\n\t"
+	"mov %rbx, bx\n\t"
+	"mov %rcx, cx\n\t"
+	"mov %rdx, dx\n\t"
+	"mov %rsi, si\n\t"
+	"mov %rdi, di\n\t"
+	"mov %rbp, bp\n\t"
+	"mov %rsp, sp\n\t"
+	"mov %r8, r8\n\t"
+	"mov %r9, r9\n\t"
+	"mov %r10, r10\n\t"
+	"mov %r11, r11\n\t"
+	"mov %r12, r12\n\t"
+	"mov %r13, r13\n\t"
+	"mov %r14, r14\n\t"
+	"mov %r15, r15\n\t"
+	"pushfq\n\t"
+	"popq flags\n\t"
+#else
+	"mov %eax, ax\n\t"
+	"mov %ebx, bx\n\t"
+	"mov %ecx, cx\n\t"
+	"mov %edx, dx\n\t"
+	"mov %esi, si\n\t"
+	"mov %edi, di\n\t"
+	"mov %ebp, bp\n\t"
+	"mov %esp, sp\n\t"
+	"pushfl\n\t"
+	"popl flags\n\t"
+#endif
+	"jmp _start\n\t"
+	".size real_start, . - real_start\n\t"
+	".popsection");
+
+int main()
+{
+	int nerrs = 0;
+
+	if (sp == 0) {
+		printf("[FAIL]\tTest was built incorrectly\n");
+		return 1;
+	}
+
+	if (ax || bx || cx || dx || si || di || bp
+#ifdef __x86_64__
+	    || r8 || r9 || r10 || r11 || r12 || r13 || r14 || r15
+#endif
+		) {
+		printf("[FAIL]\tAll GPRs except SP should be 0\n");
+#define SHOW(x) printf("\t" #x " = 0x%lx\n", x);
+		SHOW(ax);
+		SHOW(bx);
+		SHOW(cx);
+		SHOW(dx);
+		SHOW(si);
+		SHOW(di);
+		SHOW(bp);
+		SHOW(sp);
+#ifdef __x86_64__
+		SHOW(r8);
+		SHOW(r9);
+		SHOW(r10);
+		SHOW(r11);
+		SHOW(r12);
+		SHOW(r13);
+		SHOW(r14);
+		SHOW(r15);
+#endif
+		nerrs++;
+	} else {
+		printf("[OK]\tAll GPRs except SP are 0\n");
+	}
+
+	if (flags != 0x202) {
+		printf("[FAIL]\tFLAGS is 0x%lx, but it should be 0x202\n", flags);
+		nerrs++;
+	} else {
+		printf("[OK]\tFLAGS is 0x202\n");
+	}
+
+	return nerrs ? 1 : 0;
+}
-- 
2.5.0

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#1321683 — [tip:x86/asm] selftests/x86: Add check_initial_reg_state()

Fromtip-bot for Andy Lutomirski <tipbot@zytor.com>
Date2016-01-29 12:40 +0100
Subject[tip:x86/asm] selftests/x86: Add check_initial_reg_state()
Message-ID<qWfzd-2gW-33@gated-at.bofh.it>
In reply to#1321145
Commit-ID:  e21d50f3864e2a8995f5d2a41dea3f0fa07758b4
Gitweb:     http://git.kernel.org/tip/e21d50f3864e2a8995f5d2a41dea3f0fa07758b4
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Thu, 28 Jan 2016 15:11:20 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 29 Jan 2016 09:46:37 +0100

selftests/x86: Add check_initial_reg_state()

This checks that ELF binaries are started with an appropriately
blank register state.

( There's currently a nasty special case in the entry asm to
  arrange for this. I'm planning on removing the special case,
  and this will help make sure I don't break it. )

Signed-off-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: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/ef54f8d066b30a3eb36bbf26300eebb242185700.1454022279.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/testing/selftests/x86/Makefile               |   9 +-
 .../selftests/x86/check_initial_reg_state.c        | 109 +++++++++++++++++++++
 2 files changed, 117 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 9c81f26..df4f767 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -4,7 +4,8 @@ include ../lib.mk
 
 .PHONY: all all_32 all_64 warn_32bit_failure clean
 
-TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall
+TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall \
+			check_initial_reg_state
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault sigreturn test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
 			ldt_gdt \
@@ -66,3 +67,9 @@ endif
 sysret_ss_attrs_64: thunks.S
 ptrace_syscall_32: raw_syscall_helper_32.S
 test_syscall_vdso_32: thunks_32.S
+
+# check_initial_reg_state is special: it needs a custom entry, and it
+# needs to be static so that its interpreter doesn't destroy its initial
+# state.
+check_initial_reg_state_32: CFLAGS += -Wl,-ereal_start -static
+check_initial_reg_state_64: CFLAGS += -Wl,-ereal_start -static
diff --git a/tools/testing/selftests/x86/check_initial_reg_state.c b/tools/testing/selftests/x86/check_initial_reg_state.c
new file mode 100644
index 0000000..6aaed9b
--- /dev/null
+++ b/tools/testing/selftests/x86/check_initial_reg_state.c
@@ -0,0 +1,109 @@
+/*
+ * check_initial_reg_state.c - check that execve sets the correct state
+ * Copyright (c) 2014-2016 Andrew Lutomirski
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+
+unsigned long ax, bx, cx, dx, si, di, bp, sp, flags;
+unsigned long r8, r9, r10, r11, r12, r13, r14, r15;
+
+asm (
+	".pushsection .text\n\t"
+	".type real_start, @function\n\t"
+	".global real_start\n\t"
+	"real_start:\n\t"
+#ifdef __x86_64__
+	"mov %rax, ax\n\t"
+	"mov %rbx, bx\n\t"
+	"mov %rcx, cx\n\t"
+	"mov %rdx, dx\n\t"
+	"mov %rsi, si\n\t"
+	"mov %rdi, di\n\t"
+	"mov %rbp, bp\n\t"
+	"mov %rsp, sp\n\t"
+	"mov %r8, r8\n\t"
+	"mov %r9, r9\n\t"
+	"mov %r10, r10\n\t"
+	"mov %r11, r11\n\t"
+	"mov %r12, r12\n\t"
+	"mov %r13, r13\n\t"
+	"mov %r14, r14\n\t"
+	"mov %r15, r15\n\t"
+	"pushfq\n\t"
+	"popq flags\n\t"
+#else
+	"mov %eax, ax\n\t"
+	"mov %ebx, bx\n\t"
+	"mov %ecx, cx\n\t"
+	"mov %edx, dx\n\t"
+	"mov %esi, si\n\t"
+	"mov %edi, di\n\t"
+	"mov %ebp, bp\n\t"
+	"mov %esp, sp\n\t"
+	"pushfl\n\t"
+	"popl flags\n\t"
+#endif
+	"jmp _start\n\t"
+	".size real_start, . - real_start\n\t"
+	".popsection");
+
+int main()
+{
+	int nerrs = 0;
+
+	if (sp == 0) {
+		printf("[FAIL]\tTest was built incorrectly\n");
+		return 1;
+	}
+
+	if (ax || bx || cx || dx || si || di || bp
+#ifdef __x86_64__
+	    || r8 || r9 || r10 || r11 || r12 || r13 || r14 || r15
+#endif
+		) {
+		printf("[FAIL]\tAll GPRs except SP should be 0\n");
+#define SHOW(x) printf("\t" #x " = 0x%lx\n", x);
+		SHOW(ax);
+		SHOW(bx);
+		SHOW(cx);
+		SHOW(dx);
+		SHOW(si);
+		SHOW(di);
+		SHOW(bp);
+		SHOW(sp);
+#ifdef __x86_64__
+		SHOW(r8);
+		SHOW(r9);
+		SHOW(r10);
+		SHOW(r11);
+		SHOW(r12);
+		SHOW(r13);
+		SHOW(r14);
+		SHOW(r15);
+#endif
+		nerrs++;
+	} else {
+		printf("[OK]\tAll GPRs except SP are 0\n");
+	}
+
+	if (flags != 0x202) {
+		printf("[FAIL]\tFLAGS is 0x%lx, but it should be 0x202\n", flags);
+		nerrs++;
+	} else {
+		printf("[OK]\tFLAGS is 0x202\n");
+	}
+
+	return nerrs ? 1 : 0;
+}

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