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hv: extend the AC bit of rflags operations for smap

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For apl_sdc_stable branch, we now have stac and clac to set and
clear AC bit of rflags. But it can't handle following sequence:
     stac
       stac
       clac
       user mode address access here will trigger page fault
     clac

This patch introduce two more functions:
     - stac_save: Save the rflags and set AC bit
     - ac_restore: Restore the AC bit saved to rflags

Now, only sbuf_put/get are using these new APIs.

Tracked-On: #2525
Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
This commit is contained in:
Wei Liu 2019-02-15 11:56:31 +08:00 committed by wenlingz
parent 9f9750051d
commit 0cdc13fa0e
2 changed files with 28 additions and 6 deletions
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14
hypervisor/debug/sbuf.c
View File

@ -29,10 +29,11 @@ uint32_t sbuf_get(struct shared_buf *sbuf, uint8_t *data)
{
const void *from;
uint32_t ele_size;
uint64_t rflags;
stac();
stac_save(&rflags);
if (sbuf_is_empty(sbuf)) {
clac();
ac_restore(&rflags);
/* no data available */
return 0;
}
@ -44,7 +45,7 @@ uint32_t sbuf_get(struct shared_buf *sbuf, uint8_t *data)
sbuf->head = sbuf_next_ptr(sbuf->head, sbuf->ele_size, sbuf->size);
ele_size = sbuf->ele_size;
clac();
ac_restore(&rflags);
return ele_size;
}
@ -72,9 +73,10 @@ uint32_t sbuf_put(struct shared_buf *sbuf, uint8_t *data)
void *to;
uint32_t next_tail;
uint32_t ele_size;
uint64_t rflags;
bool trigger_overwrite = false;
stac();
stac_save(&rflags);
next_tail = sbuf_next_ptr(sbuf->tail, sbuf->ele_size, sbuf->size);
/* if this write would trigger overrun */
if (next_tail == sbuf->head) {
@ -82,7 +84,7 @@ uint32_t sbuf_put(struct shared_buf *sbuf, uint8_t *data)
sbuf->overrun_cnt += sbuf->flags & OVERRUN_CNT_EN;
if ((sbuf->flags & OVERWRITE_EN) == 0U) {
/* if not enable over write, return here. */
clac();
ac_restore(&rflags);
return 0;
}
trigger_overwrite = true;
@ -99,7 +101,7 @@ uint32_t sbuf_put(struct shared_buf *sbuf, uint8_t *data)
sbuf->tail = next_tail;
ele_size = sbuf->ele_size;
clac();
ac_restore(&rflags);
return ele_size;
}

20
hypervisor/include/arch/x86/cpu.h
View File

@ -83,6 +83,9 @@
#define CR4_SMAP (1UL<<21U)
#define CR4_PKE (1UL<<22U) /* Protect-key-enable */
#define RFLAGS_C (1U<<0U)
#define RFLAGS_Z (1U<<6U)
#define RFLAGS_AC (1U<<18U)
/*
* Entries in the Interrupt Descriptor Table (IDT)
@ -542,6 +545,23 @@ static inline void clac(void)
asm volatile ("clac" : : : "memory");
}
/* Save rflags register and set AC bit */
static inline void stac_save(uint64_t *p_rflags)
{
CPU_RFLAGS_SAVE(p_rflags);
asm volatile ("stac" : : : "memory");
}
/* Restore AC bit saved in p_rflags */
static inline void ac_restore(uint64_t *p_rflags)
{
if (*p_rflags & RFLAGS_AC) {
stac();
} else {
clac();
}
}
#else /* ASSEMBLER defined */
#endif /* ASSEMBLER defined */