x86 ptrace: unify syscall tracing

This unifies and cleans up the syscall tracing code on i386 and x86_64.

Using a single function for entry and exit tracing on 32-bit made the
do_syscall_trace() into some terrible spaghetti.  The logic is clear and
simple using separate syscall_trace_enter() and syscall_trace_leave()
functions as on 64-bit.

The unification adds PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support
on x86_64, for 32-bit ptrace() callers and for 64-bit ptrace() callers
tracing either 32-bit or 64-bit tasks.  It behaves just like 32-bit.

Changing syscall_trace_enter() to return the syscall number shortens
all the assembly paths, while adding the SYSEMU feature in a simple way.

Signed-off-by: Roland McGrath <roland@redhat.com>

3 files changed, 17 insertions, 12 deletions

diff --git a/include/asm-x86/calling.h b/include/asm-x86/calling.h
index f13e62e2cb3..2bc162e0ec6 100644
--- a/include/asm-x86/calling.h
+++ b/include/asm-x86/calling.h
@@ -104,7 +104,7 @@
 	.endif
 	.endm
 
-	.macro LOAD_ARGS offset
+	.macro LOAD_ARGS offset, skiprax=0
 	movq \offset(%rsp),    %r11
 	movq \offset+8(%rsp),  %r10
 	movq \offset+16(%rsp), %r9
@@ -113,7 +113,10 @@
 	movq \offset+48(%rsp), %rdx
 	movq \offset+56(%rsp), %rsi
 	movq \offset+64(%rsp), %rdi
+	.if \skiprax
+	.else
 	movq \offset+72(%rsp), %rax
+	.endif
 	.endm
 
 #define REST_SKIP	6*8
@@ -165,4 +168,3 @@
 	.macro icebp
 	.byte 0xf1
 	.endm
-
diff --git a/include/asm-x86/ptrace-abi.h b/include/asm-x86/ptrace-abi.h
index f224eb3c315..72e7b9db29b 100644
--- a/include/asm-x86/ptrace-abi.h
+++ b/include/asm-x86/ptrace-abi.h
@@ -73,11 +73,11 @@
 
 #ifdef __x86_64__
 # define PTRACE_ARCH_PRCTL	  30
-#else
-# define PTRACE_SYSEMU		  31
-# define PTRACE_SYSEMU_SINGLESTEP 32
 #endif
 
+#define PTRACE_SYSEMU		  31
+#define PTRACE_SYSEMU_SINGLESTEP  32
+
 #define PTRACE_SINGLEBLOCK	33	/* resume execution until next branch */
 
 #ifndef __ASSEMBLY__
diff --git a/include/asm-x86/thread_info.h b/include/asm-x86/thread_info.h
index fb8d3cdf143..b2702a1eeac 100644
--- a/include/asm-x86/thread_info.h
+++ b/include/asm-x86/thread_info.h
@@ -75,9 +75,7 @@ struct thread_info {
 #define TIF_NEED_RESCHED	3	/* rescheduling necessary */
 #define TIF_SINGLESTEP		4	/* reenable singlestep on user return*/
 #define TIF_IRET		5	/* force IRET */
-#ifdef CONFIG_X86_32
 #define TIF_SYSCALL_EMU		6	/* syscall emulation active */
-#endif
 #define TIF_SYSCALL_AUDIT	7	/* syscall auditing active */
 #define TIF_SECCOMP		8	/* secure computing */
 #define TIF_MCE_NOTIFY		10	/* notify userspace of an MCE */
@@ -100,11 +98,7 @@ struct thread_info {
 #define _TIF_SINGLESTEP		(1 << TIF_SINGLESTEP)
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
 #define _TIF_IRET		(1 << TIF_IRET)
-#ifdef CONFIG_X86_32
 #define _TIF_SYSCALL_EMU	(1 << TIF_SYSCALL_EMU)
-#else
-#define _TIF_SYSCALL_EMU	0
-#endif
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
 #define _TIF_MCE_NOTIFY		(1 << TIF_MCE_NOTIFY)
@@ -121,11 +115,20 @@ struct thread_info {
 #define _TIF_DS_AREA_MSR	(1 << TIF_DS_AREA_MSR)
 #define _TIF_BTS_TRACE_TS	(1 << TIF_BTS_TRACE_TS)
 
+/* work to do in syscall_trace_enter() */
+#define _TIF_WORK_SYSCALL_ENTRY	\
+	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | \
+	 _TIF_SYSCALL_AUDIT | _TIF_SECCOMP)
+
+/* work to do in syscall_trace_leave() */
+#define _TIF_WORK_SYSCALL_EXIT	\
+	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SINGLESTEP)
+
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK							\
 	(0x0000FFFF &							\
 	 ~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|			\
-	 _TIF_SECCOMP|_TIF_SYSCALL_EMU))
+	   _TIF_SINGLESTEP|_TIF_SECCOMP|_TIF_SYSCALL_EMU))
 
 /* work to do on any return to user space */
 #define _TIF_ALLWORK_MASK (0x0000FFFF & ~_TIF_SECCOMP)