UefiPayloadPkg: Add support for logging to CBMEM console

Writes TianoCore debug logs into the CBMEM console ringbuffer, from
where the user can retrieve them with the `cbmem` userspace utility.

The intention is to aid in debugging non-fatal issues even in release
builds, or simply make TianoCore's logs available to those interested.
Consequently, MDEPKG_NDEBUG must be masked. As an in-memory debug
logging library, ASSERTs must be non-fatal to be seen, so they neither
dead-loop nor create a breakpoint. It is assumed that ASSERT() neither
enforces fatal conditions nor security integrity, as release builds do
not call DebugAssert() from the ASSERT macro.

More detailed debug logs are produced with the DEBUG_CODE macro, but
this guards other debug-related code throughout the codebase. To avoid
changing behaviour on release builds, this is only set for debug builds.

Tested on QEMU, dumping the appropriate memory region in the UEFI shell
shows the TianoCore log. An improved revision of the debug library used
in several coreboot-related EDK2 forks, including MrChromebox's.
Previous revisions also tested on an Acer Aspire VN7-572G laptop.

Cc: Guo Dong <guo.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Maurice Ma <maurice.ma@intel.com>
Cc: Benjamin You <benjamin.you@intel.com>
Cc: Sean Rhodes <sean@starlabs.systems>
Signed-off-by: Benjamin Doron <benjamin.doron00@gmail.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/UefiPayloadPkg/Include/Coreboot.h b/UefiPayloadPkg/Include/Coreboot.h
index a3e1109fe8..2d454f7c89 100644
--- a/UefiPayloadPkg/Include/Coreboot.h
+++ b/UefiPayloadPkg/Include/Coreboot.h
@@ -199,6 +199,13 @@ struct cb_forward {
   UINT64    forward;

 };

 

+struct cb_cbmem_ref {

+  UINT32    tag;

+  // Field contains size of this struct == 0x0010

+  UINT32    size;

+  UINT64    cbmem_addr;

+};

+

 #define CB_TAG_FRAMEBUFFER  0x0012

 struct cb_framebuffer {

   UINT32    tag;

@@ -229,7 +236,13 @@ struct cb_vdat {
 

 #define CB_TAG_TIMESTAMPS     0x0016

 #define CB_TAG_CBMEM_CONSOLE  0x0017

-#define CB_TAG_MRC_CACHE      0x0018

+struct cbmem_console {

+  UINT32    size;

+  UINT32    cursor;

+  UINT8     body[0];

+} __attribute__ ((packed));

+

+#define CB_TAG_MRC_CACHE  0x0018

 struct cb_cbmem_tab {

   UINT32    tag;

   UINT32    size;