[PATCH v2] arch/x86: port I/O tracing on x86

[PATCH v2] arch/x86: port I/O tracing on x86

[Dan Raymond]

Add support for port I/O tracing on x86.  Memory mapped I/O tracing is
available on x86 via CONFIG_MMIOTRACE but that relies on page faults
so it doesn't work with port I/O.  This feature uses tracepoints in a
similar manner as CONFIG_TRACE_MMIO_ACCESS.

Signed-off-by: Dan Raymond <raymod2@gmail.com>
---
V1 -> V2:
  - create header file for prototypes to silence new compiler warning
  - reduce CPU overhead to 2 instructions (no branching) when tracing is disabled
  - fix imprecise IP logging by retrieving the IP off the stack instead of using
    compile time labels

 arch/x86/include/asm/shared/io.h | 25 ++++++++++++++++
 arch/x86/lib/Makefile            |  1 +
 arch/x86/lib/trace_portio.c      | 21 ++++++++++++++
 include/linux/trace_portio.h     |  6 ++++
 include/trace/events/portio.h    | 49 ++++++++++++++++++++++++++++++++
 5 files changed, 102 insertions(+)
 create mode 100644 arch/x86/lib/trace_portio.c
 create mode 100644 include/linux/trace_portio.h
 create mode 100644 include/trace/events/portio.h

diff --git a/arch/x86/include/asm/shared/io.h b/arch/x86/include/asm/shared/io.h
index c0ef921c0586..9e5dce1cb62d 100644
--- a/arch/x86/include/asm/shared/io.h
+++ b/arch/x86/include/asm/shared/io.h
@@ -2,13 +2,36 @@
 #ifndef _ASM_X86_SHARED_IO_H
 #define _ASM_X86_SHARED_IO_H
 
+#include <linux/trace_portio.h>
 #include <linux/types.h>
 
+/*
+ * We don't want the tracing logic included in the early boot modules (under
+ * arch/x86/boot) so we check for their include guards here.  If we don't do
+ * this we will get compiler errors.  These checks are not present in
+ * arch/x86/include/asm/msr.h which contains similar tracing logic.  That is
+ * possible only because none of the msr inline functions are instantiated in
+ * the early boot modules.  If that changes this issue will need to be addressed
+ * there as well.  Therefore it might be better to handle this centrally in
+ * tracepoint-defs.h.
+ */
+
+#if defined(CONFIG_TRACEPOINTS) && !defined(BOOT_COMPRESSED_MISC_H) && !defined(BOOT_BOOT_H)
+#include <linux/tracepoint-defs.h>
+DECLARE_TRACEPOINT(portio_write);
+DECLARE_TRACEPOINT(portio_read);
+#define _tracepoint_enabled(tracepoint) tracepoint_enabled(tracepoint)
+#else
+#define _tracepoint_enabled(tracepoint) false
+#endif
+
 #define BUILDIO(bwl, bw, type)						\
 static inline void __out##bwl(type value, u16 port)			\
 {									\
 	asm volatile("out" #bwl " %" #bw "0, %w1"			\
 		     : : "a"(value), "Nd"(port));			\
+	if (_tracepoint_enabled(portio_write))				\
+		do_trace_portio_write(value, port, #bwl[0]);		\
 }									\
 									\
 static inline type __in##bwl(u16 port)					\
@@ -16,6 +39,8 @@ static inline type __in##bwl(u16 port)					\
 	type value;							\
 	asm volatile("in" #bwl " %w1, %" #bw "0"			\
 		     : "=a"(value) : "Nd"(port));			\
+	if (_tracepoint_enabled(portio_read))				\
+		do_trace_portio_read(value, port, #bwl[0]);		\
 	return value;							\
 }
 
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index f76747862bd2..254f223c025d 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -40,6 +40,7 @@ $(obj)/inat.o: $(obj)/inat-tables.c
 clean-files := inat-tables.c
 
 obj-$(CONFIG_SMP) += msr-smp.o cache-smp.o
+obj-$(CONFIG_TRACEPOINTS) += trace_portio.o
 
 lib-y := delay.o misc.o cmdline.o cpu.o
 lib-y += usercopy_$(BITS).o usercopy.o getuser.o putuser.o
diff --git a/arch/x86/lib/trace_portio.c b/arch/x86/lib/trace_portio.c
new file mode 100644
index 000000000000..4b340c97b97e
--- /dev/null
+++ b/arch/x86/lib/trace_portio.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/instruction_pointer.h>
+#include <linux/trace_portio.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/portio.h>
+
+void do_trace_portio_read(u32 value, u16 port, char width)
+{
+	trace_portio_read(value, port, width, _RET_IP_);
+}
+EXPORT_SYMBOL_GPL(do_trace_portio_read);
+EXPORT_TRACEPOINT_SYMBOL_GPL(portio_read);
+
+void do_trace_portio_write(u32 value, u16 port, char width)
+{
+	trace_portio_write(value, port, width, _RET_IP_);
+}
+EXPORT_SYMBOL_GPL(do_trace_portio_write);
+EXPORT_TRACEPOINT_SYMBOL_GPL(portio_write)
diff --git a/include/linux/trace_portio.h b/include/linux/trace_portio.h
new file mode 100644
index 000000000000..013418d3d2ae
--- /dev/null
+++ b/include/linux/trace_portio.h
@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#include <linux/types.h>
+
+extern void do_trace_portio_read(u32 value, u16 port, char width);
+extern void do_trace_portio_write(u32 value, u16 port, char width);
diff --git a/include/trace/events/portio.h b/include/trace/events/portio.h
new file mode 100644
index 000000000000..3591a75a475e
--- /dev/null
+++ b/include/trace/events/portio.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM portio
+
+#if !defined(_TRACE_PORTIO_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_PORTIO_H
+
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(portio_class,
+	TP_PROTO(u32 value, u16 port, char width, long ip_addr),
+
+	TP_ARGS(value, port, width, ip_addr),
+
+	TP_STRUCT__entry(
+		__field(u32, value)
+		__field(u16, port)
+		__field(char, width)
+		__field(long, ip_addr)
+	),
+
+	TP_fast_assign(
+		__entry->value = value;
+		__entry->port = port;
+		__entry->width = width;
+		__entry->ip_addr = ip_addr;
+	),
+
+	TP_printk("port=0x%04x value=0x%0*x %pS",
+		__entry->port,
+		__entry->width == 'b' ? 2 :
+		__entry->width == 'w' ? 4 : 8,
+		__entry->value, (void *)__entry->ip_addr)
+);
+
+DEFINE_EVENT(portio_class, portio_read,
+	TP_PROTO(u32 value, u16 port, char width, long ip_addr),
+	TP_ARGS(value, port, width, ip_addr)
+);
+
+DEFINE_EVENT(portio_class, portio_write,
+	TP_PROTO(u32 value, u16 port, char width, long ip_addr),
+	TP_ARGS(value, port, width, ip_addr)
+);
+
+#endif /* _TRACE_PORTIO_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

base-commit: be8b93b5cc7d533eb8c9b0590cdac055ecafe13a
-- 
2.25.1

Re: [PATCH v2] arch/x86: port I/O tracing on x86

[Peter Zijlstra]

On Wed, Sep 27, 2023 at 09:52:11AM -0600, Dan Raymond wrote:

>  #define BUILDIO(bwl, bw, type)						\
>  static inline void __out##bwl(type value, u16 port)			\
>  {									\
>  	asm volatile("out" #bwl " %" #bw "0, %w1"			\
>  		     : : "a"(value), "Nd"(port));			\
> +	if (_tracepoint_enabled(portio_write))				\
> +		do_trace_portio_write(value, port, #bwl[0]);		\
>  }									\
>  									\
>  static inline type __in##bwl(u16 port)					\
> @@ -16,6 +39,8 @@ static inline type __in##bwl(u16 port)					\
>  	type value;							\
>  	asm volatile("in" #bwl " %w1, %" #bw "0"			\
>  		     : "=a"(value) : "Nd"(port));			\
> +	if (_tracepoint_enabled(portio_read))				\
> +		do_trace_portio_read(value, port, #bwl[0]);		\
>  	return value;							\
>  }

NACK