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Rework smc_unknown return code path in smc_handler 

The intention of this patch is to leverage the existing el3_exit() return
routine for smc_unknown return path rather than a custom set of instructions.
In order to leverage el3_exit(), the necessary counteraction (i.e., saving the
system registers apart from GP registers) must be performed. Hence a series of
instructions which save system registers( like SPSR_EL3, SCR_EL3 etc) to stack
are moved to the top of group of instructions which essentially decode the OEN
from the smc function identifier and obtain the specific service handler in
rt_svc_descs_array. This ensures that the control flow for both known and
unknown smc calls will be similar.

Change-Id: I67f94cfcba176bf8aee1a446fb58a4e383905a87
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
This commit is contained in:
Madhukar Pappireddy 2019-05-08 15:41:41 -05:00 committed by Sandrine Bailleux
parent af9ae7cfa1
commit cc485e27ac
1 changed files with 28 additions and 29 deletions
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57
bl31/aarch64/runtime_exceptions.S
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@ -352,28 +352,6 @@ smc_handler64:
mov x5, xzr
mov x6, sp
/* Get the unique owning entity number */
ubfx x16, x0, #FUNCID_OEN_SHIFT, #FUNCID_OEN_WIDTH
ubfx x15, x0, #FUNCID_TYPE_SHIFT, #FUNCID_TYPE_WIDTH
orr x16, x16, x15, lsl #FUNCID_OEN_WIDTH
/* Load descriptor index from array of indices */
adr x14, rt_svc_descs_indices
ldrb w15, [x14, x16]
/* Any index greater than 127 is invalid. Check bit 7. */
tbnz w15, 7, smc_unknown
/*
* Get the descriptor using the index
* x11 = (base + off), w15 = index
*
* handler = (base + off) + (index << log2(size))
*/
adr x11, (__RT_SVC_DESCS_START__ + RT_SVC_DESC_HANDLE)
lsl w10, w15, #RT_SVC_SIZE_LOG2
ldr x15, [x11, w10, uxtw]
/*
* Restore the saved C runtime stack value which will become the new
* SP_EL0 i.e. EL3 runtime stack. It was saved in the 'cpu_context'
@ -400,6 +378,28 @@ smc_handler64:
mov sp, x12
/* Get the unique owning entity number */
ubfx x16, x0, #FUNCID_OEN_SHIFT, #FUNCID_OEN_WIDTH
ubfx x15, x0, #FUNCID_TYPE_SHIFT, #FUNCID_TYPE_WIDTH
orr x16, x16, x15, lsl #FUNCID_OEN_WIDTH
/* Load descriptor index from array of indices */
adr x14, rt_svc_descs_indices
ldrb w15, [x14, x16]
/* Any index greater than 127 is invalid. Check bit 7. */
tbnz w15, 7, smc_unknown
/*
* Get the descriptor using the index
* x11 = (base + off), w15 = index
*
* handler = (base + off) + (index << log2(size))
*/
adr x11, (__RT_SVC_DESCS_START__ + RT_SVC_DESC_HANDLE)
lsl w10, w15, #RT_SVC_SIZE_LOG2
ldr x15, [x11, w10, uxtw]
/*
* Call the Secure Monitor Call handler and then drop directly into
* el3_exit() which will program any remaining architectural state
@ -414,15 +414,14 @@ smc_handler64:
smc_unknown:
/*
* Unknown SMC call. Populate return value with SMC_UNK, restore
* GP registers, and return to caller.
* Unknown SMC call. Populate return value with SMC_UNK and call
* el3_exit() which will restore the remaining architectural state
* i.e., SYS, GP and PAuth registers(if any) prior to issuing the ERET
* to the desired lower EL.
*/
mov x0, #SMC_UNK
str x0, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X0]
#if CTX_INCLUDE_PAUTH_REGS
bl pauth_context_restore
#endif
b restore_gp_registers_eret
str x0, [x6, #CTX_GPREGS_OFFSET + CTX_GPREG_X0]
b el3_exit
smc_prohibited:
ldr x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]