arm64: Treat ESR_ELx as a 64-bit register

In the initial release of the ARM Architecture Reference Manual for
ARMv8-A, the ESR_ELx registers were defined as 32-bit registers. This
changed in 2018 with version D.a (ARM DDI 0487D.a) of the architecture,
when they became 64-bit registers, with bits [63:32] defined as RES0. In
version G.a, a new field was added to ESR_ELx, ISS2, which covers bits
[36:32].  This field is used when the Armv8.7 extension FEAT_LS64 is
implemented.

As a result of the evolution of the register width, Linux stores it as
both a 64-bit value and a 32-bit value, which hasn't affected correctness
so far as Linux only uses the lower 32 bits of the register.

Make the register type consistent and always treat it as 64-bit wide. The
register is redefined as an "unsigned long", which is an unsigned
double-word (64-bit quantity) for the LP64 machine (aapcs64 [1], Table 1,
page 14). The type was chosen because "unsigned int" is the most frequent
type for ESR_ELx and because FAR_ELx, which is used together with ESR_ELx
in exception handling, is also declared as "unsigned long". The 64-bit type
also makes adding support for architectural features that use fields above
bit 31 easier in the future.

The KVM hypervisor will receive a similar update in a subsequent patch.

[1] https://github.com/ARM-software/abi-aa/releases/download/2021Q3/aapcs64.pdf

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220425114444.368693-4-alexandru.elisei@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 878c65aa7206..6ba10edfb49c 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -282,13 +282,13 @@ extern void (*handle_arch_irq)(struct pt_regs *);
 extern void (*handle_arch_fiq)(struct pt_regs *);
 
 static void noinstr __panic_unhandled(struct pt_regs *regs, const char *vector,
-				      unsigned int esr)
+				      unsigned long esr)
 {
 	arm64_enter_nmi(regs);
 
 	console_verbose();
 
-	pr_crit("Unhandled %s exception on CPU%d, ESR 0x%08x -- %s\n",
+	pr_crit("Unhandled %s exception on CPU%d, ESR 0x%016lx -- %s\n",
 		vector, smp_processor_id(), esr,
 		esr_get_class_string(esr));
 
@@ -818,7 +818,7 @@ UNHANDLED(el0t, 32, error)
 #ifdef CONFIG_VMAP_STACK
 asmlinkage void noinstr handle_bad_stack(struct pt_regs *regs)
 {
-	unsigned int esr = read_sysreg(esr_el1);
+	unsigned long esr = read_sysreg(esr_el1);
 	unsigned long far = read_sysreg(far_el1);
 
 	arm64_enter_nmi(regs);