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>

1 files changed, 9 insertions, 8 deletions

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 20371d0635e4..8796d1905255 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -37,6 +37,11 @@
         movq    %rax,R8(%rsp)
         .endm
 
+        /*
+         * Reload arg registers from stack in case ptrace changed them.
+         * We don't reload %eax because syscall_trace_enter() returned
+         * the value it wants us to use in the table lookup.
+         */
         .macro LOAD_ARGS32 offset
         movl \offset(%rsp),%r11d
         movl \offset+8(%rsp),%r10d
@@ -46,7 +51,6 @@
         movl \offset+48(%rsp),%edx
         movl \offset+56(%rsp),%esi
         movl \offset+64(%rsp),%edi
-        movl \offset+72(%rsp),%eax
         .endm
         
         .macro CFI_STARTPROC32 simple
@@ -137,13 +141,12 @@ ENTRY(ia32_sysenter_target)
         .previous       
         GET_THREAD_INFO(%r10)
         orl    $TS_COMPAT,TI_status(%r10)
-        testl  $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP), \
-                 TI_flags(%r10)
+        testl  $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
         CFI_REMEMBER_STATE
         jnz  sysenter_tracesys
-sysenter_do_call:       
         cmpl    $(IA32_NR_syscalls-1),%eax
         ja      ia32_badsys
+sysenter_do_call:
         IA32_ARG_FIXUP 1
         call    *ia32_sys_call_table(,%rax,8)
         movq    %rax,RAX-ARGOFFSET(%rsp)
@@ -242,8 +245,7 @@ ENTRY(ia32_cstar_target)
         .previous       
         GET_THREAD_INFO(%r10)
         orl   $TS_COMPAT,TI_status(%r10)
-        testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP), \
-                TI_flags(%r10)
+        testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
         CFI_REMEMBER_STATE
         jnz   cstar_tracesys
 cstar_do_call:  
@@ -336,8 +338,7 @@ ENTRY(ia32_syscall)
         SAVE_ARGS 0,0,1
         GET_THREAD_INFO(%r10)
         orl   $TS_COMPAT,TI_status(%r10)
-        testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP), \
-                TI_flags(%r10)
+        testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
         jnz ia32_tracesys
 ia32_do_syscall:        
         cmpl $(IA32_NR_syscalls-1),%eax