/*******************************************************************************
* Run a loaded image from the given entry point. This could result in either
* dropping into a lower exception level or jumping to a higher exception level.
* The only way of doing the latter is through an SMC. In either case, setup the
* parameters for the EL change request correctly.
******************************************************************************/
void __dead2 run_image(unsigned long entrypoint,
unsigned long spsr,
unsigned long target_security_state,
void *first_arg,
void *second_arg)
{
el_change_info run_image_info;
unsigned long current_el = read_current_el();
/* Tell next EL what we want done */
run_image_info.args.arg0 = RUN_IMAGE;
run_image_info.entrypoint = entrypoint;
run_image_info.spsr = spsr;
run_image_info.security_state = target_security_state;
/*
* If we are EL3 then only an eret can take us to the desired
* exception level. Else for the time being assume that we have
* to jump to a higher EL and issue an SMC. Contents of argY
* will go into the general purpose register xY e.g. arg0->x0
*/
if (GET_EL(current_el) == MODE_EL3) {
run_image_info.args.arg1 = (unsigned long) first_arg;
run_image_info.args.arg2 = (unsigned long) second_arg;
} else {
run_image_info.args.arg1 = entrypoint;
run_image_info.args.arg2 = spsr;
run_image_info.args.arg3 = (unsigned long) first_arg;
run_image_info.args.arg4 = (unsigned long) second_arg;
}
change_el(&run_image_info);
}
/*
* TODO: If we are not EL3 then currently we only issue an SMC.
* Add support for dropping into EL0 etc. Consider adding support
* for switching from S-EL1 to S-EL0/1 etc.
*/
void __dead2 change_el(el_change_info *info)
{
unsigned long current_el = read_current_el();
if (GET_EL(current_el) == MODE_EL3) {
/*
* We can go anywhere from EL3. So find where.
* TODO: Lots to do if we are going non-secure.
* Flip the NS bit. Restore NS registers etc.
* Just doing the bare minimal for now.
*/
if (info->security_state == NON_SECURE)
change_security_state(info->security_state);
drop_el(&info->args, info->spsr, info->entrypoint);
} else
raise_el(&info->args);
}
/*
* Handle SMC from a lower exception level to switch its execution state
* (either from AArch64 to AArch32, or vice versa).
*
* smc_fid:
* SMC function ID - either ARM_SIP_SVC_STATE_SWITCH_64 or
* ARM_SIP_SVC_STATE_SWITCH_32.
* pc_hi, pc_lo:
* PC upon re-entry to the calling exception level; width dependent on the
* calling exception level.
* cookie_hi, cookie_lo:
* Opaque pointer pairs received from the caller to pass it back, upon
* re-entry.
* handle:
* Handle to saved context.
*/
int arm_execution_state_switch(unsigned int smc_fid,
uint32_t pc_hi,
uint32_t pc_lo,
uint32_t cookie_hi,
uint32_t cookie_lo,
void *handle)
{
/* Execution state can be switched only if EL3 is AArch64 */
#ifdef AARCH64
int caller_64, from_el2, el, endianness, thumb = 0;
u_register_t spsr, pc, scr, sctlr;
entry_point_info_t ep;
cpu_context_t *ctx = (cpu_context_t *) handle;
el3_state_t *el3_ctx = get_el3state_ctx(ctx);
/* That the SMC originated from NS is already validated by the caller */
/*
* Disallow state switch if any of the secondaries have been brought up.
*/
if (psci_secondaries_brought_up())
goto exec_denied;
spsr = read_ctx_reg(el3_ctx, CTX_SPSR_EL3);
caller_64 = (GET_RW(spsr) == MODE_RW_64);
if (caller_64) {
/*
* If the call originated from AArch64, expect 32-bit pointers when
* switching to AArch32.
*/
if ((pc_hi != 0) || (cookie_hi != 0))
goto invalid_param;
pc = pc_lo;
/* Instruction state when entering AArch32 */
thumb = pc & 1;
} else {
/* Construct AArch64 PC */
pc = (((u_register_t) pc_hi) << 32) | pc_lo;
}
/* Make sure PC is 4-byte aligned, except for Thumb */
if ((pc & 0x3) && !thumb)
goto invalid_param;
/*
* EL3 controls register width of the immediate lower EL only. Expect
* this request from EL2/Hyp unless:
*
* - EL2 is not implemented;
* - EL2 is implemented, but was disabled. This can be inferred from
* SCR_EL3.HCE.
*/
from_el2 = caller_64 ? (GET_EL(spsr) == MODE_EL2) :
(GET_M32(spsr) == MODE32_hyp);
scr = read_ctx_reg(el3_ctx, CTX_SCR_EL3);
if (!from_el2) {
/* The call is from NS privilege level other than HYP */
/*
* Disallow switching state if there's a Hypervisor in place;
* this request must be taken up with the Hypervisor instead.
*/
if (scr & SCR_HCE_BIT)
goto exec_denied;
}
/*
* Return to the caller using the same endianness. Extract
* endianness bit from the respective system control register
* directly.
*/
sctlr = from_el2 ? read_sctlr_el2() : read_sctlr_el1();
endianness = !!(sctlr & SCTLR_EE_BIT);
/* Construct SPSR for the exception state we're about to switch to */
if (caller_64) {
int impl;
/*
* Switching from AArch64 to AArch32. Ensure this CPU implements
* the target EL in AArch32.
*/
impl = from_el2 ? EL_IMPLEMENTED(2) : EL_IMPLEMENTED(1);
if (impl != EL_IMPL_A64_A32)
goto exec_denied;
/* Return to the equivalent AArch32 privilege level */
el = from_el2 ? MODE32_hyp : MODE32_svc;
spsr = SPSR_MODE32(el, thumb ? SPSR_T_THUMB : SPSR_T_ARM,
endianness, DISABLE_ALL_EXCEPTIONS);
} else {
/*
* Switching from AArch32 to AArch64. Since it's not possible to
* implement an EL as AArch32-only (from which this call was
* raised), it's safe to assume AArch64 is also implemented.
*/
el = from_el2 ? MODE_EL2 : MODE_EL1;
spsr = SPSR_64(el, MODE_SP_ELX, DISABLE_ALL_EXCEPTIONS);
}
/*
* Use the context management library to re-initialize the existing
* context with the execution state flipped. Since the library takes
* entry_point_info_t pointer as the argument, construct a dummy one
* with PC, state width, endianness, security etc. appropriately set.
* Other entries in the entry point structure are irrelevant for
* purpose.
*/
zeromem(&ep, sizeof(ep));
ep.pc = pc;
ep.spsr = spsr;
SET_PARAM_HEAD(&ep, PARAM_EP, VERSION_1,
((endianness ? EP_EE_BIG : EP_EE_LITTLE) | NON_SECURE |
EP_ST_DISABLE));
/*
* Re-initialize the system register context, and exit EL3 as if for the
* first time. State switch is effectively a soft reset of the
* calling EL.
*/
cm_init_my_context(&ep);
cm_prepare_el3_exit(NON_SECURE);
/*
* State switch success. The caller of SMC wouldn't see the SMC
* returning. Instead, execution starts at the supplied entry point,
* with context pointers populated in registers 0 and 1.
*/
SMC_RET2(handle, cookie_hi, cookie_lo);
invalid_param:
SMC_RET1(handle, STATE_SW_E_PARAM);
exec_denied:
#endif
/* State switch denied */
SMC_RET1(handle, STATE_SW_E_DENIED);
}
