strace: add an option for printing syscall numbers

* print_syscall_number.c: New file.
* Makefile.am (libstrace_a_SOURCES): Add it.
* defs.h (struct tcb): Add true_scno field.
(print_syscall_number): New function declaration.
* strace.c: Add -n/--syscall-number option.
(printleader): Call print_syscall_number.
* syscall.c (get_scno): Assign tcp->true_scno.
* tests/options-syntax.test: Check with -c/--summary-only.
* strace.1.in: Document new option.
* NEWS: Mention the new option.

8 files changed, 49 insertions, 3 deletions

diff --git a/Makefile.am b/Makefile.am
index f5447811b..4f7aceec5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -250,6 +250,7 @@ libstrace_a_SOURCES =	\
 	print_sigevent.c \
 	print_statfs.c	\
 	print_struct_stat.c \
+	print_syscall_number.c \
 	print_time.c	\
 	print_timespec.h \
 	print_timespec32.c \
diff --git a/NEWS b/NEWS
index 10039ceb7..81a2c943c 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,7 @@ Noteworthy changes in release ?.? (????-??-??)
 ==============================================
 
 * Improvements
+  * Added -n/--syscall-number option for printing syscall numbers.
 
 * Bug fixes
 
diff --git a/defs.h b/defs.h
index f7ac54f31..3333453fe 100644
--- a/defs.h
+++ b/defs.h
@@ -259,6 +259,7 @@ struct tcb {
 # endif
 	unsigned long u_error;	/* Error code */
 	kernel_ulong_t scno;	/* System call number */
+	kernel_ulong_t true_scno;	/* Same, but without subcall decoding and shuffling */
 	kernel_ulong_t u_arg[MAX_ARGS];	/* System call arguments */
 	kernel_long_t u_rval;	/* Return value */
 	int sys_func_rval;	/* Syscall entry parser's return value */
@@ -508,6 +509,8 @@ extern bool get_instruction_pointer(struct tcb *, kernel_ulong_t *);
 extern bool get_stack_pointer(struct tcb *, kernel_ulong_t *);
 extern void print_instruction_pointer(struct tcb *);
 
+extern void print_syscall_number(struct tcb *);
+
 extern void print_syscall_resume(struct tcb *tcp);
 
 extern int syscall_entering_decode(struct tcb *);
diff --git a/print_syscall_number.c b/print_syscall_number.c
new file mode 100644
index 000000000..5427afb2e
--- /dev/null
+++ b/print_syscall_number.c
@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2020 The strace developers.
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#include "defs.h"
+
+void
+print_syscall_number(struct tcb *tcp)
+{
+	if (tcp->true_scno != (kernel_ulong_t) -1) {
+		tprintf("[%4" PRI_klu "] ", tcp->true_scno);
+	} else {
+		tprintf("[????] ");
+	}
+}
diff --git a/strace.1.in b/strace.1.in
index 3b21caeca..411e159b8 100644
--- a/strace.1.in
+++ b/strace.1.in
@@ -871,6 +871,11 @@ or higher.
 .TQ
 .B \-\-instruction\-pointer
 Print the instruction pointer at the time of the system call.
+.TP
+.B \-n
+.TQ
+.B \-\-syscall\-number
+Print the syscall number.
 .if '@ENABLE_STACKTRACE_FALSE@'#' .TP
 .if '@ENABLE_STACKTRACE_FALSE@'#' .B \-k
 .if '@ENABLE_STACKTRACE_FALSE@'#' .TQ
diff --git a/strace.c b/strace.c
index 4c96a98b0..ce5a46ab5 100644
--- a/strace.c
+++ b/strace.c
@@ -79,6 +79,7 @@ bool Tflag;
 int Tflag_scale = 1000;
 int Tflag_width = 6;
 bool iflag;
+bool nflag;
 bool count_wallclock;
 static int tflag_scale = 1000000000;
 static unsigned tflag_width = 0;
@@ -355,6 +356,8 @@ Output format:\n\
 "
 #endif
 "\
+  -n, --syscall-number\n\
+                 print syscall number\n\
   -o FILE, --output=FILE\n\
                  send trace output to FILE instead of stderr\n\
   -A, --output-append-mode\n\
@@ -811,6 +814,9 @@ printleader(struct tcb *tcp)
 		tprints(tflag_format ? ") " : " ");
 	}
 
+	if (nflag)
+		print_syscall_number(tcp);
+
 	if (iflag)
 		print_instruction_pointer(tcp);
 }
@@ -2013,7 +2019,7 @@ init(int argc, char *argv[])
 	qualify_signals("all");
 
 	static const char optstring[] =
-		"+a:Ab:cCdDe:E:fFhiI:ko:O:p:P:qrs:S:tTu:U:vVwxX:yzZ";
+		"+a:Ab:cCdDe:E:fFhiI:kno:O:p:P:qrs:S:tTu:U:vVwxX:yzZ";
 
 	enum {
 		GETOPT_SECCOMP = 0x100,
@@ -2055,6 +2061,7 @@ init(int argc, char *argv[])
 		{ "instruction-pointer", no_argument,      0, 'i' },
 		{ "interruptible",	required_argument, 0, 'I' },
 		{ "stack-traces",	no_argument,	   0, 'k' },
+		{ "syscall-number",	no_argument,	   0, 'n' },
 		{ "output",		required_argument, 0, 'o' },
 		{ "summary-syscall-overhead", required_argument, 0, 'O' },
 		{ "attach",		required_argument, 0, 'p' },
@@ -2191,6 +2198,9 @@ init(int argc, char *argv[])
 					  "build of strace");
 #endif
 			break;
+		case 'n':
+			nflag = 1;
+			break;
 		case 'o':
 			outfname = optarg;
 			break;
@@ -2465,6 +2475,9 @@ init(int argc, char *argv[])
 		if (stack_trace_enabled)
 			error_msg("-k/--stack-traces has no effect "
 				  "with -c/--summary-only");
+		if (nflag)
+			error_msg("-n/--syscall-number has no effect "
+				  "with -c/--summary-only");
 		if (rflag)
 			error_msg("-r/--relative-timestamps has no effect "
 				  "with -c/--summary-only");
diff --git a/syscall.c b/syscall.c
index bcc87025e..094885de0 100644
--- a/syscall.c
+++ b/syscall.c
@@ -1354,6 +1354,7 @@ get_scno(struct tcb *tcp)
 			return rc;
 	}
 
+	tcp->true_scno = tcp->scno;
 	tcp->scno = shuffle_scno(tcp->scno);
 
 	if (scno_is_valid(tcp->scno)) {
diff --git a/tests/options-syntax.test b/tests/options-syntax.test
index 6788e63a6..e9aaf30ec 100755
--- a/tests/options-syntax.test
+++ b/tests/options-syntax.test
@@ -268,18 +268,19 @@ if [ "$uid" -ge 0 ]; then
 
 	check_e "$umsg" -u :nosuchuser: true
 
-	for c in i/--instruction-pointer r/--relative-timestamps t/--absolute-timestamps T/--syscall-times y/--decode-fds; do
+	for c in i/--instruction-pointer n/--syscall-number r/--relative-timestamps t/--absolute-timestamps T/--syscall-times y/--decode-fds; do
 		check_e "-$c has no effect with -c/--summary-only
 $STRACE_EXE: $umsg" -u :nosuchuser: -c -${c%%/*} true
 	done
 
 	check_e "-i/--instruction-pointer has no effect with -c/--summary-only
+$STRACE_EXE: -n/--syscall-number has no effect with -c/--summary-only
 $STRACE_EXE: -r/--relative-timestamps has no effect with -c/--summary-only
 $STRACE_EXE: -t/--absolute-timestamps has no effect with -c/--summary-only
 $STRACE_EXE: -T/--syscall-times has no effect with -c/--summary-only
 $STRACE_EXE: -y/--decode-fds has no effect with -c/--summary-only
 $STRACE_EXE: Only the last of -z/--successful-only/-Z/--failed-only options will take effect. See status qualifier for more complex filters.
-$STRACE_EXE: $umsg" -u :nosuchuser: -cirtTyzZ true
+$STRACE_EXE: $umsg" -u :nosuchuser: -cinrtTyzZ true
 
 	for c in --output-separately -A/--output-append-mode; do
 		check_e "$c has no effect without -o/--output
@@ -303,6 +304,9 @@ $STRACE_EXE: $umsg" -u :nosuchuser: --successful-only -Z true
 	check_e "Only the last of -z/--successful-only/-Z/--failed-only options will take effect. See status qualifier for more complex filters.
 $STRACE_EXE: $umsg" -u :nosuchuser: --successful-only --failed-only true
 
+	check_e "-n/--syscall-number has no effect with -c/--summary-only
+$STRACE_EXE: $umsg" --user=:nosuchuser: --syscall-number --summary-only true
+
 	check_e "-i/--instruction-pointer has no effect with -c/--summary-only
 $STRACE_EXE: $umsg" --user=:nosuchuser: --instruction-pointer --summary-only true
 fi