transition.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <arch/cache.h>
#include <arch/lib_helpers.h>
#include <arch/mmu.h>
#include <arch/transition.h>
#include <assert.h>
 
void __weak exc_dispatch(struct exc_state *exc_state, uint64_t id)
{
        /* Default weak implementation does nothing. */
}
 
void exc_entry(struct exc_state *exc_state, uint64_t id)
{
        struct elx_state *elx = &exc_state->elx;
        struct regs *regs = &exc_state->regs;
        uint8_t elx_mode;
 
        elx->spsr = raw_read_spsr_el3();
        elx_mode = get_mode_from_spsr(elx->spsr);
 
        if (elx_mode == SPSR_USE_H)
                regs->sp = (uint64_t)&exc_state[1];
        else
                regs->sp = raw_read_sp_el0();
 
        elx->elr = raw_read_elr_el3();
 
        exc_dispatch(exc_state, id);
}
 
void transition_to_el2(void *entry, void *arg, uint64_t spsr)
{
        struct exc_state exc_state;
        struct elx_state *elx = &exc_state.elx;
        struct regs *regs = &exc_state.regs;
 
        regs->x[X0_INDEX] = (uint64_t)arg;
        elx->elr = (uint64_t)entry;
        elx->spsr = spsr;
 
        /*
         * Policies enforced:
         * 1. We support only transitions to EL2
         * 2. We support transitions to Aarch64 mode only
         *
         * If any of the above conditions holds false, then we need a proper way
         * to update SCR/HCR before removing the checks below
         */
        assert(get_el_from_spsr(spsr) == EL2 && !(spsr & SPSR_ERET_32));
 
        /* Initialize SCR with defaults for running without secure monitor
           (disable all traps, enable all instructions, run NS at AArch64). */
        raw_write_scr_el3(SCR_FIEN | SCR_API | SCR_APK | SCR_ST | SCR_RW |
                          SCR_HCE | SCR_SMD | SCR_RES1 | SCR_NS);
 
        /* Initialize CPTR to not trap anything to EL3. */
        raw_write_cptr_el3(CPTR_EL3_TCPAC_DISABLE | CPTR_EL3_TTA_DISABLE |
                           CPTR_EL3_TFP_DISABLE);
 
        /* ELR/SPSR: Write entry point and processor state of program */
        raw_write_elr_el3(elx->elr);
        raw_write_spsr_el3(elx->spsr);
 
        /* SCTLR: Initialize EL with everything disabled */
        raw_write_sctlr_el2(SCTLR_RES1);
 
        /* SP_ELx: Initialize stack pointer */
        raw_write_sp_el2(elx->sp_elx);
 
        /* Payloads expect to be entered with MMU disabled. Includes an ISB. */
        mmu_disable();
 
        /* Eret to the entry point */
        trans_switch(regs);
}