[Minios-devel] [UNIKRAFT PATCH v2 4/8] lib/ukdebug: key-value static storage for tracing

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

One more 'special' stripable section. Will contain strings in format
key = value. Currently, only the tracebuffer format version is stored
there.

Signed-off-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>
---
 lib/ukdebug/Makefile.uk |  2 +-
 lib/ukdebug/extra.ld    |  3 +++
 lib/ukdebug/trace.c     | 18 ++++++++++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/lib/ukdebug/Makefile.uk b/lib/ukdebug/Makefile.uk
index e2e6fd2a..663ac6de 100644
--- a/lib/ukdebug/Makefile.uk
+++ b/lib/ukdebug/Makefile.uk
@@ -11,4 +11,4 @@ LIBUKDEBUG_SRCS-y += $(LIBUKDEBUG_BASE)/hexdump.c
 LIBUKDEBUG_SRCS-$(CONFIG_LIBUKDEBUG_TRACEPOINTS) += $(LIBUKDEBUG_BASE)/trace.c
 
 EXTRA_LD_SCRIPT-$(CONFIG_LIBVFSCORE) += $(LIBUKDEBUG_BASE)/extra.ld
-STRIP_SECTIONS_FLAGS-$(CONFIG_LIBUKDEBUG_TRACEPOINTS) += -R 
.uk_tracepoints_list
+STRIP_SECTIONS_FLAGS-$(CONFIG_LIBUKDEBUG_TRACEPOINTS) += -R 
.uk_tracepoints_list -R .uk_trace_keyvals
diff --git a/lib/ukdebug/extra.ld b/lib/ukdebug/extra.ld
index 43154f9d..bb0b36b8 100644
--- a/lib/ukdebug/extra.ld
+++ b/lib/ukdebug/extra.ld
@@ -5,6 +5,9 @@ SECTIONS
                KEEP (*(.uk_tracepoints_list));
                uk_tracepoints_end = .;
        }
+       .uk_trace_keyvals : {
+               KEEP (*(.uk_trace_keyvals));
+       }
 }
 
 /* We do not want these section to be in the final image, they are
diff --git a/lib/ukdebug/trace.c b/lib/ukdebug/trace.c
index f3318557..91cc2387 100644
--- a/lib/ukdebug/trace.c
+++ b/lib/ukdebug/trace.c
@@ -43,3 +43,21 @@ char uk_trace_buffer[UK_TRACE_BUFFER_SIZE];
 
 size_t uk_trace_buffer_free = UK_TRACE_BUFFER_SIZE;
 char *uk_trace_buffer_writep = uk_trace_buffer;
+
+
+/* Store a string in format "key = value" in the section
+ * .uk_trace_keyvals. This can be anything what you want trace.py
+ * script to know about, and what you do not want to consume any space
+ * in runtime memory.
+ *
+ * This section will be stripped at the final states of building, but
+ * the key-value data can be easily extracted by:
+ *
+ *     $ readelf -p .uk_trace_keyvals <your_image.gdb>
+ */
+#define TRACE_DEFINE_KEY(key, val)                     \
+       __attribute((__section__(".uk_trace_keyvals"))) \
+       static const char key[] __used =                \
+               #key " = " #val
+
+TRACE_DEFINE_KEY(format_version, 1);
-- 
2.19.2


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