Commit ec1455ce authored by John Harrison's avatar John Harrison
Browse files

drm/xe/devcoredump: Add ASCII85 dump helper function 



There is a need to include the GuC log and other large binary objects
in core dumps and via dmesg. So add a helper for dumping to a printer
function via conversion to ASCII85 encoding.

Another issue with dumping such a large buffer is that it can be slow,
especially if dumping to dmesg over a serial port. So add a yield to
prevent the 'task has been stuck for 120s' kernel hang check feature
from firing.

v2: Add a prefix to the output string. Fix memory allocation bug.
v3: Correct a string size calculation and clean up a define (review
feedback from Julia F).

Signed-off-by: default avatarJohn Harrison <John.C.Harrison@Intel.com>
Reviewed-by: default avatarJulia Filipchuk <julia.filipchuk@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241003004611.2323493-5-John.C.Harrison@Intel.com
parent c28fd6c3

drivers/gpu/drm/xe/xe_devcoredump.c

+87 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include "xe_devcoredump.h"

#include "xe_devcoredump_types.h"



#include <linux/ascii85.h>

#include <linux/devcoredump.h>

#include <generated/utsrelease.h>
@@ -315,3 +316,89 @@ int xe_devcoredump_init(struct xe_device *xe) 
}



#endif



/**

 * xe_print_blob_ascii85 - print a BLOB to some useful location in ASCII85

 *

 * The output is split to multiple lines because some print targets, e.g. dmesg

 * cannot handle arbitrarily long lines. Note also that printing to dmesg in

 * piece-meal fashion is not possible, each separate call to drm_puts() has a

 * line-feed automatically added! Therefore, the entire output line must be

 * constructed in a local buffer first, then printed in one atomic output call.

 *

 * There is also a scheduler yield call to prevent the 'task has been stuck for

 * 120s' kernel hang check feature from firing when printing to a slow target

 * such as dmesg over a serial port.

 *

 * TODO: Add compression prior to the ASCII85 encoding to shrink huge buffers down.

 *

 * @p: the printer object to output to

 * @prefix: optional prefix to add to output string

 * @blob: the Binary Large OBject to dump out

 * @offset: offset in bytes to skip from the front of the BLOB, must be a multiple of sizeof(u32)

 * @size: the size in bytes of the BLOB, must be a multiple of sizeof(u32)

 */

void xe_print_blob_ascii85(struct drm_printer *p, const char *prefix,

			   const void *blob, size_t offset, size_t size)

{

	const u32 *blob32 = (const u32 *)blob;

	char buff[ASCII85_BUFSZ], *line_buff;

	size_t line_pos = 0;



#define DMESG_MAX_LINE_LEN	800

#define MIN_SPACE		(ASCII85_BUFSZ + 2)		/* 85 + "\n\0" */



	if (size & 3)

		drm_printf(p, "Size not word aligned: %zu", size);

	if (offset & 3)

		drm_printf(p, "Offset not word aligned: %zu", size);



	line_buff = kzalloc(DMESG_MAX_LINE_LEN, GFP_KERNEL);

	if (IS_ERR_OR_NULL(line_buff)) {

		drm_printf(p, "Failed to allocate line buffer: %pe", line_buff);

		return;

	}



	blob32 += offset / sizeof(*blob32);

	size /= sizeof(*blob32);



	if (prefix) {

		strscpy(line_buff, prefix, DMESG_MAX_LINE_LEN - MIN_SPACE - 2);

		line_pos = strlen(line_buff);



		line_buff[line_pos++] = ':';

		line_buff[line_pos++] = ' ';

	}



	while (size--) {

		u32 val = *(blob32++);



		strscpy(line_buff + line_pos, ascii85_encode(val, buff),

			DMESG_MAX_LINE_LEN - line_pos);

		line_pos += strlen(line_buff + line_pos);



		if ((line_pos + MIN_SPACE) >= DMESG_MAX_LINE_LEN) {

			line_buff[line_pos++] = '\n';

			line_buff[line_pos++] = 0;



			drm_puts(p, line_buff);



			line_pos = 0;



			/* Prevent 'stuck thread' time out errors */

			cond_resched();

		}

	}



	if (line_pos) {

		line_buff[line_pos++] = '\n';

		line_buff[line_pos++] = 0;



		drm_puts(p, line_buff);

	}



	kfree(line_buff);



#undef MIN_SPACE

#undef DMESG_MAX_LINE_LEN

}

drivers/gpu/drm/xe/xe_devcoredump.h

+6 −0
Original line number Diff line number Diff line
@@ -6,6 +6,9 @@ 
#ifndef _XE_DEVCOREDUMP_H_

#define _XE_DEVCOREDUMP_H_



#include <linux/types.h>



struct drm_printer;

struct xe_device;

struct xe_sched_job;
@@ -23,4 +26,7 @@ static inline int xe_devcoredump_init(struct xe_device *xe) 
}

#endif



void xe_print_blob_ascii85(struct drm_printer *p, const char *prefix,

			   const void *blob, size_t offset, size_t size);



#endif