[RFC] Allow empty Trigger Error Action Table

[Niklas Söderlund]

When troubleshooting some BIOS code I encounter strange errors about firmware bugs. On closer inspection I found that the Trigger table returned from the firmware was empty but the header looked OK:

header_size = 16
table_size = 16
entry_count = 0

When looking at einj.c I found that this header would result in the error I was receiving. I took a quick look at the docs and from what I can tell this is a valid header, yes?

I don't know much about ACPI so I might be way off but the attached patch fix the error message for me (however I still can't detect the injected error but that might depend on my detection code or buggy firmware...)

Thanks
// Niklas

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[Niklas Söderlund]

According to the ACPI spec [1] section 18.6.4 the TRIGGER_ERROR action
table can consists of zero elements.

[1] Advanced Configuration and Power Interface Specification
Revision 5.0, December 6, 2011
http://www.acpi.info/DOWNLOADS/ACPIspec50.pdf

Signed-off-by: Niklas Söderlund <niklas.s...@ericsson.com>
---
drivers/acpi/apei/einj.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
index 589b96c..94c05ff 100644
--- a/drivers/acpi/apei/einj.c
+++ b/drivers/acpi/apei/einj.c
@@ -184,7 +184,7 @@ static int einj_check_trigger_header(struct acpi_einj_trigger *trigger_tab)
if (trigger_tab->header_size != sizeof(struct acpi_einj_trigger))
return -EINVAL;
if (trigger_tab->table_size > PAGE_SIZE ||
- trigger_tab->table_size <= trigger_tab->header_size)
+ trigger_tab->table_size < trigger_tab->header_size)
return -EINVAL;
if (trigger_tab->entry_count !=
(trigger_tab->table_size - trigger_tab->header_size) /
@@ -225,6 +225,11 @@ static int __einj_error_trigger(u64 trigger_paddr)
"The trigger error action table is invalid\n");
goto out_rel_header;
}
+
+ /* No action structures in the TRIGGER_ERROR table, nothing to do */
+ if (!trigger_tab->entry_count)
+ goto out_rel_header;
+
rc = -EIO;
table_size = trigger_tab->table_size;
r = request_mem_region(trigger_paddr + sizeof(*trigger_tab),
--
1.7.8.3

[Huang Ying]

On Mon, 2012-01-09 at 16:49 +0100, Niklas Söderlund wrote:
> According to the ACPI spec [1] section 18.6.4 the TRIGGER_ERROR action
> table can consists of zero elements.
>
> [1] Advanced Configuration and Power Interface Specification
> Revision 5.0, December 6, 2011
> http://www.acpi.info/DOWNLOADS/ACPIspec50.pdf
>
> Signed-off-by: Niklas Söderlund <niklas.s...@ericsson.com>

Acked-by: Huang Ying <ying....@intel.com>

Best Regards,
Huang Ying