2013-07-20 01:24:27

by Ren Qiaowei

Subject: [PATCH] x86, tboot: iomem fixes

Current code doesn't use specific interface to access I/O space.
So some potential bugs can be caused. We can fix this by using
specific API.

Signed-off-by: Qiaowei Ren <[email protected]>
---
arch/x86/kernel/tboot.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index 3ff42d2..c902237 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -466,9 +466,12 @@ struct sinit_mle_data {
u32 vtd_dmars_off;
} __packed;

+#define SINIT_MLE_DATA_VTD_DMAR_OFF 140
+
struct acpi_table_header *tboot_get_dmar_table(struct acpi_table_header *dmar_tbl)
{
- void *heap_base, *heap_ptr, *config;
+ void __iomem *heap_base, *heap_ptr, *config;
+ u32 dmar_tbl_off;

if (!tboot_enabled())
return dmar_tbl;
@@ -485,25 +488,25 @@ struct acpi_table_header *tboot_get_dmar_table(struct acpi_table_header *dmar_tb
return NULL;

/* now map TXT heap */
- heap_base = ioremap(*(u64 *)(config + TXTCR_HEAP_BASE),
- *(u64 *)(config + TXTCR_HEAP_SIZE));
+ heap_base = ioremap(readl(config + TXTCR_HEAP_BASE),
+ readl(config + TXTCR_HEAP_SIZE));
iounmap(config);
if (!heap_base)
return NULL;

/* walk heap to SinitMleData */
/* skip BiosData */
- heap_ptr = heap_base + *(u64 *)heap_base;
+ heap_ptr = heap_base + readq(heap_base);
/* skip OsMleData */
- heap_ptr += *(u64 *)heap_ptr;
+ heap_ptr += readq(heap_ptr);
/* skip OsSinitData */
- heap_ptr += *(u64 *)heap_ptr;
+ heap_ptr += readq(heap_ptr);
/* now points to SinitMleDataSize; set to SinitMleData */
heap_ptr += sizeof(u64);
/* get addr of DMAR table */
+ dmar_tbl_off = readl(heap_ptr + SINIT_MLE_DATA_VTD_DMAR_OFF);
dmar_tbl = (struct acpi_table_header *)(heap_ptr +
- ((struct sinit_mle_data *)heap_ptr)->vtd_dmars_off -
- sizeof(u64));
+ dmar_tbl_off - sizeof(u64));

/* don't unmap heap because dmar.c needs access to this */

--
1.7.9.5

2013-07-20 07:35:05

by Ingo Molnar

Subject: Re: [PATCH] x86, tboot: iomem fixes

* Qiaowei Ren <[email protected]> wrote:

> +#define SINIT_MLE_DATA_VTD_DMAR_OFF 140

> /* get addr of DMAR table */
> + dmar_tbl_off = readl(heap_ptr + SINIT_MLE_DATA_VTD_DMAR_OFF);
> dmar_tbl = (struct acpi_table_header *)(heap_ptr +
> - ((struct sinit_mle_data *)heap_ptr)->vtd_dmars_off -
> - sizeof(u64));
> + dmar_tbl_off - sizeof(u64));

So the offset of ->vtd_dmars_off within struct sinit_mle_data is 140?

The new code is less readable: what's wrong with getting the offset
automatically via C, instead of hardcoding it manually? You can use
offsetof() primitive for increased readability.

Thanks,

Ingo

2013-07-20 16:16:48

by Ren Qiaowei

Subject: RE: [PATCH] x86, tboot: iomem fixes

On 2013-07-20, Ingo Molnar wrote:
>
> * Qiaowei Ren <[email protected]> wrote:
>
>> +#define SINIT_MLE_DATA_VTD_DMAR_OFF 140
>
>> /* get addr of DMAR table */ + dmar_tbl_off = readl(heap_ptr +
>> SINIT_MLE_DATA_VTD_DMAR_OFF); dmar_tbl = (struct acpi_table_header
>> *)(heap_ptr +
>> - ((struct sinit_mle_data *)heap_ptr)->vtd_dmars_off -
>> - sizeof(u64));
>> + dmar_tbl_off - sizeof(u64));
>
> So the offset of ->vtd_dmars_off within struct sinit_mle_data is 140?
>
> The new code is less readable: what's wrong with getting the offset
> automatically via C, instead of hardcoding it manually? You can use
> offsetof() primitive for increased readability.
>
Ok. Thanks for your suggestion. I will try to use offsetof() to increase readability.

Thanks,
Qiaowei