Hey Benjamin

The commit has been around for a while now and is perfectly functional. Why don't we upstream it and then `FindCbTag()` and `CopyMem()` can be a follow-up patch when/if time allows?

Cheers
Sean

Squashing that commit in:
[PATCH] UefiPayloadPkg: Add support for logging to CBMEM console

Tested on QEMU, dumping the appropriate memory region in UEFI shell
shows the TianoCore log. `find_cb_subtable` is sourced from STM/SeaBIOS.

Signed-off-by: Benjamin Doron <benjamin.doron00@gmail.com>
---
UefiPayloadPkg/Include/Coreboot.h             |  14 +
.../Library/CbSerialPortLib/CbSerialPortLib.c | 272 ++++++++++++++++++
.../CbSerialPortLib/CbSerialPortLib.inf       |  27 ++
UefiPayloadPkg/UefiPayloadPkg.dsc             |   5 +
UefiPayloadPkg/UefiPayloadPkg.fdf             |   6 +-
5 files changed, 323 insertions(+), 1 deletion(-)
create mode 100644 UefiPayloadPkg/Library/CbSerialPortLib/CbSerialPortLib.c
create mode 100644 UefiPayloadPkg/Library/CbSerialPortLib/CbSerialPortLib.inf

diff --git a/UefiPayloadPkg/Include/Coreboot.h b/UefiPayloadPkg/Include/Coreboot.h
index a3e1109fe8..f2f577a02e 100644
--- a/UefiPayloadPkg/Include/Coreboot.h
+++ b/UefiPayloadPkg/Include/Coreboot.h
@@ -199,7 +199,14 @@ struct cb_forward {
UINT64    forward;
};

+struct cb_cbmem_ref {
+  UINT32 tag;
+  UINT32 size;
+  UINT64 cbmem_addr;
+};
+
#define CB_TAG_FRAMEBUFFER  0x0012
+
struct cb_framebuffer {
UINT32    tag;
UINT32    size;
@@ -230,6 +237,13 @@ 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));
+
struct cb_cbmem_tab {
UINT32    tag;
UINT32    size;
diff --git a/UefiPayloadPkg/Library/CbSerialPortLib/CbSerialPortLib.c b/UefiPayloadPkg/Library/CbSerialPortLib/CbSerialPortLib.c
new file mode 100644
index 0000000000..7b26c08dd7
--- /dev/null
+++ b/UefiPayloadPkg/Library/CbSerialPortLib/CbSerialPortLib.c
@@ -0,0 +1,272 @@
+/** @file
+  CBMEM console SerialPortLib instance
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Base.h>
+#include <Coreboot.h>
+
+#include <Library/BaseLib.h>
+#include <Library/BlParseLib.h>
+#include <Library/SerialPortLib.h>
+
+//
+// We can't use DebugLib due to a constructor dependency cycle between DebugLib
+// and ourselves.
+//
+#define ASSERT(Expression)      \
+  do {                          \
+    if (!(Expression)) {        \
+      CpuDeadLoop ();           \
+    }                           \
+  } while (FALSE)
+
+#define CBMC_CURSOR_MASK ((1 << 28) - 1)
+#define CBMC_OVERFLOW (1 << 31)
+
+STATIC struct cbmem_console  *gCbConsole = NULL;
+STATIC UINT32 STM_cursor = 0;
+
+// Try to find the coreboot memory table in the given coreboot table.
+static void *
+find_cb_subtable(struct cb_header *cbh, UINT32 tag)
+{
+  char *tbl = (char *)cbh + sizeof(*cbh);
+  UINT32 count = cbh->table_entries;
+  int i;
+  for (i=0; i<count; i++) {
+    struct cb_memory *cbm = (void*)tbl;
+    tbl += cbm->size;
+    if (cbm->tag == tag)
+      return cbm;
+  }
+    return NULL;
+}
+
+/**
+  Initialize the serial device hardware.
+
+  If no initialization is required, then return RETURN_SUCCESS.
+  If the serial device was successfully initialized, then return RETURN_SUCCESS.
+  If the serial device could not be initialized, then return RETURN_DEVICE_ERROR.
+
+  @retval RETURN_SUCCESS        The serial device was initialized.
+  @retval RETURN_DEVICE_ERROR   The serial device could not be initialized.
+
+**/
+RETURN_STATUS
+EFIAPI
+SerialPortInitialize (
+  VOID
+  )
+{
+  /* `FindCbTag` doesn't work because we need direct access to the memory addresses? */
+  struct cb_header *cbh = GetParameterBase();
+  if (!cbh) {
+    return RETURN_DEVICE_ERROR;
+  }
+
+  struct cb_cbmem_ref *cbref = find_cb_subtable(cbh, CB_TAG_CBMEM_CONSOLE);
+  if (!cbref) {
+    return RETURN_DEVICE_ERROR;
+  }
+
+  gCbConsole = (void *)(UINTN)cbref->cbmem_addr; // Support PEI and DXE
+  if (gCbConsole == NULL) {
+    return RETURN_DEVICE_ERROR;
+  }
+
+  // set the cursor such that the STM console will not overwrite the
+  // coreboot console output
+  STM_cursor = gCbConsole->cursor & CBMC_CURSOR_MASK;
+
+  return RETURN_SUCCESS;
+}
+
+/**
+  Write data from buffer to serial device.
+
+  Writes NumberOfBytes data bytes from Buffer to the serial device.
+  The number of bytes actually written to the serial device is returned.
+  If the return value is less than NumberOfBytes, then the write operation failed.
+  If Buffer is NULL, then ASSERT().
+  If NumberOfBytes is zero, then return 0.
+
+  @param  Buffer           Pointer to the data buffer to be written.
+  @param  NumberOfBytes    Number of bytes to written to the serial device.
+
+  @retval 0                NumberOfBytes is 0.
+  @retval >0               The number of bytes written to the serial device.
+                           If this value is less than NumberOfBytes, then the write operation failed.
+
+**/
+UINTN
+EFIAPI
+SerialPortWrite (
+  IN UINT8     *Buffer,
+  IN UINTN     NumberOfBytes
+  )
+{
+  UINTN             Sent;
+  UINT32            cursor;
+  UINT32            flags;
+
+  ASSERT (Buffer != NULL);
+
+  if (NumberOfBytes == 0) {
+    return 0;
+  }
+
+  if (!gCbConsole) {
+    return 0;
+  }
+
+  Sent = 0;
+  do {
+    cursor = gCbConsole->cursor & CBMC_CURSOR_MASK;
+    flags = gCbConsole->cursor & ~CBMC_CURSOR_MASK;
+
+    if (cursor >= gCbConsole->size) {
+      return 0; // Old coreboot version with legacy overflow mechanism.
+    }
+
+    gCbConsole->body[cursor++] = Buffer[Sent++];
+
+    if (cursor >= gCbConsole->size) {
+      cursor = STM_cursor;
+      flags |= CBMC_OVERFLOW;
+    }
+
+    gCbConsole->cursor = flags | cursor;
+  } while (Sent < NumberOfBytes);
+
+  return Sent;
+}
+
+/**
+  Read data from serial device and save the datas in buffer.
+
+  Reads NumberOfBytes data bytes from a serial device into the buffer
+  specified by Buffer. The number of bytes actually read is returned.
+  If Buffer is NULL, then ASSERT().
+  If NumberOfBytes is zero, then return 0.
+
+  @param  Buffer           Pointer to the data buffer to store the data read from the serial device.
+  @param  NumberOfBytes    Number of bytes which will be read.
+
+  @retval 0                Read data failed, no data is to be read.
+  @retval >0               Actual number of bytes read from serial device.
+
+**/
+UINTN
+EFIAPI
+SerialPortRead (
+  OUT UINT8     *Buffer,
+  IN  UINTN     NumberOfBytes
+)
+{
+  return 0;
+}
+
+/**
+  Polls a serial device to see if there is any data waiting to be read.
+
+  @retval TRUE             Data is waiting to be read from the serial device.
+  @retval FALSE            There is no data waiting to be read from the serial device.
+
+**/
+BOOLEAN
+EFIAPI
+SerialPortPoll (
+  VOID
+  )
+{
+  return FALSE;
+}
+
+/**
+  Sets the control bits on a serial device.
+
+  @param Control                Sets the bits of Control that are settable.
+
+  @retval RETURN_SUCCESS        The new control bits were set on the serial device.
+  @retval RETURN_UNSUPPORTED    The serial device does not support this operation.
+  @retval RETURN_DEVICE_ERROR   The serial device is not functioning correctly.
+
+**/
+RETURN_STATUS
+EFIAPI
+SerialPortSetControl (
+  IN UINT32 Control
+  )
+{
+  return RETURN_UNSUPPORTED;
+}
+
+/**
+  Retrieve the status of the control bits on a serial device.
+
+  @param Control                A pointer to return the current control signals from the serial device.
+
+  @retval RETURN_SUCCESS        The control bits were read from the serial device.
+  @retval RETURN_UNSUPPORTED    The serial device does not support this operation.
+  @retval RETURN_DEVICE_ERROR   The serial device is not functioning correctly.
+
+**/
+RETURN_STATUS
+EFIAPI
+SerialPortGetControl (
+  OUT UINT32 *Control
+  )
+{
+  return RETURN_UNSUPPORTED;
+}
+
+/**
+  Sets the baud rate, receive FIFO depth, transmit/receive time out, parity,
+  data bits, and stop bits on a serial device.
+
+  @param BaudRate           The requested baud rate. A BaudRate value of 0 will use the
+                            device's default interface speed.
+                            On output, the value actually set.
+  @param ReceiveFifoDepth   The requested depth of the FIFO on the receive side of the
+                            serial interface. A ReceiveFifoDepth value of 0 will use
+                            the device's default FIFO depth.
+                            On output, the value actually set.
+  @param Timeout            The requested time out for a single character in microseconds.
+                            This timeout applies to both the transmit and receive side of the
+                            interface. A Timeout value of 0 will use the device's default time
+                            out value.
+                            On output, the value actually set.
+  @param Parity             The type of parity to use on this serial device. A Parity value of
+                            DefaultParity will use the device's default parity value.
+                            On output, the value actually set.
+  @param DataBits           The number of data bits to use on the serial device. A DataBits
+                            value of 0 will use the device's default data bit setting.
+                            On output, the value actually set.
+  @param StopBits           The number of stop bits to use on this serial device. A StopBits
+                            value of DefaultStopBits will use the device's default number of
+                            stop bits.
+                            On output, the value actually set.
+
+  @retval RETURN_SUCCESS            The new attributes were set on the serial device.
+  @retval RETURN_UNSUPPORTED        The serial device does not support this operation.
+  @retval RETURN_INVALID_PARAMETER  One or more of the attributes has an unsupported value.
+  @retval RETURN_DEVICE_ERROR       The serial device is not functioning correctly.
+
+**/
+RETURN_STATUS
+EFIAPI
+SerialPortSetAttributes (
+  IN OUT UINT64             *BaudRate,
+  IN OUT UINT32             *ReceiveFifoDepth,
+  IN OUT UINT32             *Timeout,
+  IN OUT EFI_PARITY_TYPE    *Parity,
+  IN OUT UINT8              *DataBits,
+  IN OUT EFI_STOP_BITS_TYPE *StopBits
+  )
+{
+  return RETURN_UNSUPPORTED;
+}
diff --git a/UefiPayloadPkg/Library/CbSerialPortLib/CbSerialPortLib.inf b/UefiPayloadPkg/Library/CbSerialPortLib/CbSerialPortLib.inf
new file mode 100644
index 0000000000..37b33c24ad
--- /dev/null
+++ b/UefiPayloadPkg/Library/CbSerialPortLib/CbSerialPortLib.inf
@@ -0,0 +1,27 @@
+## @file
+#  Component description file for CbSerialPortLib module.
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = CbSerialPortLib
+  FILE_GUID                      = 0DB3EF12-1426-4086-B012-113184C4CE11
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 0.5
+  LIBRARY_CLASS                  = SerialPortLib
+  CONSTRUCTOR                    = SerialPortInitialize
+
+[Sources]
+  CbSerialPortLib.c
+
+[Packages]
+  MdeModulePkg/MdeModulePkg.dec
+  MdePkg/MdePkg.dec
+  UefiPayloadPkg/UefiPayloadPkg.dec
+
+[LibraryClasses]
+  BaseLib
+  BlParseLib
diff --git a/UefiPayloadPkg/UefiPayloadPkg.dsc b/UefiPayloadPkg/UefiPayloadPkg.dsc
index 3d08edfe31..b3770b9be6 100644
--- a/UefiPayloadPkg/UefiPayloadPkg.dsc
+++ b/UefiPayloadPkg/UefiPayloadPkg.dsc
@@ -33,6 +33,7 @@
DEFINE UNIVERSAL_PAYLOAD            = FALSE
DEFINE SECURITY_STUB_ENABLE         = TRUE
DEFINE SMM_SUPPORT                  = FALSE
+  DEFINE USE_CBMEM_FOR_CONSOLE        = FALSE
#
# SBL:      UEFI payload for Slim Bootloader
# COREBOOT: UEFI payload for coreboot
@@ -223,7 +224,11 @@
TimerLib|UefiPayloadPkg/Library/AcpiTimerLib/AcpiTimerLib.inf
!endif
ResetSystemLib|UefiPayloadPkg/Library/ResetSystemLib/ResetSystemLib.inf
+!if $(USE_CBMEM_FOR_CONSOLE) == TRUE
+  SerialPortLib|UefiPayloadPkg/Library/CbSerialPortLib/CbSerialPortLib.inf
+!else
SerialPortLib|MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.inf
+!endif
PlatformHookLib|UefiPayloadPkg/Library/PlatformHookLib/PlatformHookLib.inf
PlatformBootManagerLib|UefiPayloadPkg/Library/PlatformBootManagerLib/PlatformBootManagerLib.inf
IoApicLib|PcAtChipsetPkg/Library/BaseIoApicLib/BaseIoApicLib.inf
diff --git a/UefiPayloadPkg/UefiPayloadPkg.fdf b/UefiPayloadPkg/UefiPayloadPkg.fdf
index f619a23139..0df8342252 100644
--- a/UefiPayloadPkg/UefiPayloadPkg.fdf
+++ b/UefiPayloadPkg/UefiPayloadPkg.fdf
@@ -15,8 +15,12 @@ DEFINE FD_BLOCK_SIZE = 0x00001000
!if $(TARGET) == "NOOPT"
DEFINE FD_SIZE     = 0x00850000
DEFINE NUM_BLOCKS  = 0x850
-!else

+!elseif $(USE_CBMEM_FOR_CONSOLE) == TRUE
+DEFINE FD_SIZE     = 0x00600000
+DEFINE NUM_BLOCKS  = 0x600
+
+!else
DEFINE FD_SIZE     = 0x00590000
DEFINE NUM_BLOCKS  = 0x590
!endif
--
2.32.0