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Commit baf27f9b authored by Chris Wilson's avatar Chris Wilson Committed by Daniel Vetter
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drm/i915: Break up the large vsnprintf() in print_error_buffers() 



So it appears that I have encountered some bogosity when trying to call
i915_error_printf() with many arguments from print_error_buffers(). The
symptom is that the vsnprintf parser tries to interpret an integer arg
as a character string, the resulting OOPS indicating stack corruption.
Replacing the single call with its 13 format specifiers and arguments
with multiple calls to i915_error_printf() worked fine. This patch goes
one step further and introduced i915_error_puts() to pass the strings
simply.

It may not fix the root cause, but it does prevent my box from dying and
I think helps make print_error_buffers() more friendly.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=66077


Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent d26e3af8

drivers/gpu/drm/i915/i915_debugfs.c

+79 −30
Original line number Diff line number Diff line
@@ -647,41 +647,44 @@ static const char *purgeable_flag(int purgeable) 
	return purgeable ? " purgeable" : "";

}



static void i915_error_vprintf(struct drm_i915_error_state_buf *e,

			       const char *f, va_list args)

static bool __i915_error_ok(struct drm_i915_error_state_buf *e)

{

	unsigned len;



	if (!e->err && WARN(e->bytes > (e->size - 1), "overflow")) {

		e->err = -ENOSPC;

		return;

		return false;

	}



	if (e->bytes == e->size - 1 || e->err)

		return;

		return false;



	/* Seek the first printf which is hits start position */

	if (e->pos < e->start) {

		len = vsnprintf(NULL, 0, f, args);

	return true;

}



static bool __i915_error_seek(struct drm_i915_error_state_buf *e,

			      unsigned len)

{

	if (e->pos + len <= e->start) {

		e->pos += len;

			return;

		return false;

	}



		/* First vsnprintf needs to fit in full for memmove*/

	/* First vsnprintf needs to fit in its entirety for memmove */

	if (len >= e->size) {

		e->err = -EIO;

			return;

		}

		return false;

	}



	len = vsnprintf(e->buf + e->bytes, e->size - e->bytes, f, args);

	if (len >= e->size - e->bytes)

		len = e->size - e->bytes - 1;

	return true;

}



static void __i915_error_advance(struct drm_i915_error_state_buf *e,

				 unsigned len)

{

	/* If this is first printf in this window, adjust it so that

	 * start position matches start of the buffer

	 */



	if (e->pos < e->start) {

		const size_t off = e->start - e->pos;
@@ -701,6 +704,51 @@ static void i915_error_vprintf(struct drm_i915_error_state_buf *e, 
	e->pos += len;

}



static void i915_error_vprintf(struct drm_i915_error_state_buf *e,

			       const char *f, va_list args)

{

	unsigned len;



	if (!__i915_error_ok(e))

		return;



	/* Seek the first printf which is hits start position */

	if (e->pos < e->start) {

		len = vsnprintf(NULL, 0, f, args);

		if (!__i915_error_seek(e, len))

			return;

	}



	len = vsnprintf(e->buf + e->bytes, e->size - e->bytes, f, args);

	if (len >= e->size - e->bytes)

		len = e->size - e->bytes - 1;



	__i915_error_advance(e, len);

}



static void i915_error_puts(struct drm_i915_error_state_buf *e,

			    const char *str)

{

	unsigned len;



	if (!__i915_error_ok(e))

		return;



	len = strlen(str);



	/* Seek the first printf which is hits start position */

	if (e->pos < e->start) {

		if (!__i915_error_seek(e, len))

			return;

	}



	if (len >= e->size - e->bytes)

		len = e->size - e->bytes - 1;

	memcpy(e->buf + e->bytes, str, len);



	__i915_error_advance(e, len);

}



void i915_error_printf(struct drm_i915_error_state_buf *e, const char *f, ...)

{

	va_list args;
@@ -711,6 +759,7 @@ void i915_error_printf(struct drm_i915_error_state_buf *e, const char *f, ...) 
}



#define err_printf(e, ...) i915_error_printf(e, __VA_ARGS__)

#define err_puts(e, s) i915_error_puts(e, s)



static void print_error_buffers(struct drm_i915_error_state_buf *m,

				const char *name,
@@ -720,26 +769,26 @@ static void print_error_buffers(struct drm_i915_error_state_buf *m, 
	err_printf(m, "%s [%d]:\n", name, count);



	while (count--) {

		err_printf(m, "  %08x %8u %02x %02x %x %x%s%s%s%s%s%s%s",

		err_printf(m, "  %08x %8u %02x %02x %x %x",

			   err->gtt_offset,

			   err->size,

			   err->read_domains,

			   err->write_domain,

			   err->rseqno, err->wseqno,

			   pin_flag(err->pinned),

			   tiling_flag(err->tiling),

			   dirty_flag(err->dirty),

			   purgeable_flag(err->purgeable),

			   err->ring != -1 ? " " : "",

			   ring_str(err->ring),

			   cache_level_str(err->cache_level));

			   err->rseqno, err->wseqno);

		err_puts(m, pin_flag(err->pinned));

		err_puts(m, tiling_flag(err->tiling));

		err_puts(m, dirty_flag(err->dirty));

		err_puts(m, purgeable_flag(err->purgeable));

		err_puts(m, err->ring != -1 ? " " : "");

		err_puts(m, ring_str(err->ring));

		err_puts(m, cache_level_str(err->cache_level));



		if (err->name)

			err_printf(m, " (name: %d)", err->name);

		if (err->fence_reg != I915_FENCE_REG_NONE)

			err_printf(m, " (fence: %d)", err->fence_reg);



		err_printf(m, "\n");

		err_puts(m, "\n");

		err++;

	}

}