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arm-trusted-firmware/bl31/bl31_traps.c

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feat(el3-runtime): introduce system register trap handler At the moment we only handle SMC traps from lower ELs, but ignore any other synchronous traps and just panic. To cope with system register traps, which we might need to emulate, introduce a C function to handle those traps, and wire that up in the exception handler to be called. We provide a dispatcher function (in C), that will call platform specific implementation for certain (classes of) system registers. For now this is empty. Signed-off-by: Andre Przywara <andre.przywara@arm.com> Change-Id: If147bcb49472eb02791498700300926afbcf75ff
2 years ago
/*
* Copyright (c) 2022, ARM Limited. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*
* Dispatch synchronous system register traps from lower ELs.
*/
#include <bl31/sync_handle.h>
#include <context.h>
int handle_sysreg_trap(uint64_t esr_el3, cpu_context_t *ctx)
{
switch (esr_el3 & ISS_SYSREG_OPCODE_MASK) {
feat(fvp): emulate trapped RNDR When a platform decides to use FEAT_RNG_TRAP, every RNDR or RNDRSS read will trap into EL3. The platform can then emulate those instructions, by either executing the real CPU instructions, potentially conditioning the results, or use rate-limiting or filtering to protect the hardware entropy pool. Another possiblitiy would be to use some platform specific TRNG device to get entropy and returning this. To demonstrate platform specific usage, add a demo implementation for the FVP: It will execute the actual CPU instruction and just return the result. This should serve as reference code to implement platform specific policies. We change the definition of read_rndr() and read_rndrrs() to use the alternative sysreg encoding, so that all assemblers can handle that. Add documentation about the new platform specific RNG handler function. Signed-off-by: Andre Przywara &lt;andre.przywara@arm.com&gt; Change-Id: Ibce817b3b06ad20129d15531b81402e3cc3e9a9e
2 years ago
#if ENABLE_FEAT_RNG_TRAP
case ISS_SYSREG_OPCODE_RNDR:
case ISS_SYSREG_OPCODE_RNDRRS:
return plat_handle_rng_trap(esr_el3, ctx);
#endif
feat(el3-runtime): introduce system register trap handler At the moment we only handle SMC traps from lower ELs, but ignore any other synchronous traps and just panic. To cope with system register traps, which we might need to emulate, introduce a C function to handle those traps, and wire that up in the exception handler to be called. We provide a dispatcher function (in C), that will call platform specific implementation for certain (classes of) system registers. For now this is empty. Signed-off-by: Andre Przywara &lt;andre.przywara@arm.com&gt; Change-Id: If147bcb49472eb02791498700300926afbcf75ff
2 years ago
default:
return TRAP_RET_UNHANDLED;
}
}