[coreboot-gerrit] Change in coreboot[master]: lib: Register exception handlers for ARMv8

[Asami Doi (Code Review)]

Asami Doi has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/34774 )

Change subject: lib: Register exception handlers for ARMv8
......................................................................

lib: Register exception handlers for ARMv8

Register exception handlers to avoid a Synchronous External Abort
that is raised when you try to access a non-memory address on ARMv8.
An exception handler can jump over the faulting instruction.

Signed-off-by: Asami Doi 
Change-Id: I09a306ca307ba4027d9758c3debc2e7c844c66b8
---
M src/lib/ramdetect.c
1 file changed, 54 insertions(+), 6 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/74/34774/1

diff --git a/src/lib/ramdetect.c b/src/lib/ramdetect.c
index 5416a58..7f53b57 100644
--- a/src/lib/ramdetect.c
+++ b/src/lib/ramdetect.c
@@ -15,24 +15,62 @@
 #include <symbols.h>
 #include <device/mmio.h>
 #include <ramdetect.h>
+#include <arch/exception.h>
 #include <console/console.h>

#define OVERLAP(a, b, s, e) ((b) > (s) && (a) < (e))

+static enum {
+	ABORT_CHECKER_NOT_REGISTERED,
+	ABORT_CHECKER_DEACTIVATED,
+	ABORT_CHECKER_NOT_TRIGGERED,
+	ABORT_CHECKER_TRIGGERED,
+} abort_state = ABORT_CHECKER_NOT_REGISTERED;
+
+static int abort_checker(struct exc_state *state, uint64_t vector_id)
+{
+	if (abort_state == ABORT_CHECKER_DEACTIVATED)
+		return EXC_RET_IGNORED;
+
+	if (raw_read_esr_el3() >> 26 != 0x25)
+		return EXC_RET_IGNORED; /* Not a data abort. */
+
+	abort_state = ABORT_CHECKER_TRIGGERED;
+	state->elx.elr += sizeof(uint32_t); /* Jump over faulting instruction. */
+	raw_write_elr_el3(state->elx.elr);
+	return EXC_RET_HANDLED;
+}
+
+static void register_checker(void)
+{
+	struct exception_handler sync_elx;
+	struct exception_handler sync_el0;
+
+	sync_elx.handler = &abort_checker;
+	sync_el0.handler = &abort_checker;
+
+	exception_handler_register(EXC_VID_CUR_SP_ELX_SYNC, &sync_elx);
+	exception_handler_register(EXC_VID_CUR_SP_EL0_SYNC, &sync_el0);
+
+	printk(BIOS_DEBUG, "ARM64: Abort checker handlers installed.\n");
+}
+
 static int probe_mb(const uintptr_t dram_start, const uintptr_t size)
 {
    uintptr_t addr = dram_start + (size * MiB) - sizeof(uint32_t);
-	static const uint32_t patterns[] = {
-		0x55aa55aa,
-		0x12345678
-	};
-	void *ptr = (void *) addr;
+	static const uint32_t patterns[] = {0x55aa55aa, 0x12345678};
+	void *ptr = (void *)addr;
    size_t i;

/* Don't accidentally clober oneself. */
-	if (OVERLAP(addr, addr + sizeof(uint32_t), (uintptr_t)_program, (uintptr_t) _eprogram))
+	if (OVERLAP(addr, addr + sizeof(uint32_t), (uintptr_t)_program, (uintptr_t)_eprogram))
    	return 1;

+	if (ENV_ARM64) {
+		read32((void *)addr);
+		return abort_state == ABORT_CHECKER_NOT_TRIGGERED;
+	}
+
    uint32_t old = read32(ptr);
    for (i = 0; i < ARRAY_SIZE(patterns); i++) {
    	write32(ptr, patterns[i]);
@@ -50,6 +88,12 @@
 /* Probe an area if it's read/writable. */
 size_t probe_ramsize(const uintptr_t dram_start, const size_t probe_size)
 {
+	if (ENV_ARM64) {
+		if (abort_state == ABORT_CHECKER_NOT_REGISTERED)
+			register_checker();
+		abort_state = ABORT_CHECKER_NOT_TRIGGERED;
+	}
+
    ssize_t i;
    size_t msb = 0;
    size_t discovered = 0;
@@ -74,5 +118,9 @@

saved_result = discovered;
    printk(BIOS_DEBUG, "RAMDETECT: Found %zu MiB RAM\n", discovered);
+
+	if (ENV_ARM64)
+		abort_state = ABORT_CHECKER_DEACTIVATED;
+
    return discovered;
 }