BPI/arm-trusted-firmware
5
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fix(fvp): support FEAT_RNG_TRAP without FEAT_RNG

Browse Source 
This is a perfectly valid architectural config, however we rely on
FEAT_RNG to come up with numbers and that might be unavailable. In case
FEAT_RNG is missing, mock some numbers so that lower EL SW works. The
FVP platform is a virtual platform mostly used for testing so the lack
of security is unimportant and simplicity of implementation is.

Change-Id: I302bf9b471e8e04a7a43321933e32f80d3b6c6ab
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
This commit is contained in:
Boyan Karatotev 2026-04-28 11:24:17 +01:00
parent fb6218df18
commit 3422b84eb0
1 changed files with 17 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
plat/arm/board/fvp/fvp_sync_traps.c
View File

@ -9,22 +9,33 @@
#include <stdbool.h>
#include <arch.h>
#include <arch_features.h>
#include <arch_helpers.h>
#include <bl31/sync_handle.h>
#include <context.h>
#define RANDOM_VALUE ((u_register_t) 3288484550995823360ULL)
/*
* This emulation code here is not very meaningful: enabling the RNG
* trap typically happens for a reason, so just calling the actual
* hardware instructions might not be useful or even possible.
* Emulation for testing purposes. If FEAT_RNG is available, just use that for
* simplicity. If not, quickly make up a number that can pass for being random.
* This is insecure, however, as a test platform, this is not relevant on FVP.
*/
#if ENABLE_FEAT_RNG_TRAP
int plat_handle_rng_trap(u_register_t *data, bool rndrrs)
{
if (rndrrs) {
*data = read_rndrrs();
if (is_feat_rng_supported()) {
/*
* Architecturally, these can return failure. In practice the
* model won't and even if does it doesn't matter.
*/
if (rndrrs) {
*data = read_rndrrs();
} else {
*data = read_rndr();
}
} else {
*data = read_rndr();
return RANDOM_VALUE ^ read_cntpct_el0();
}
return TRAP_RET_CONTINUE;