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KVM: arm64: Parametrize exception entry with a target EL 

We currently assume that an exception is delivered to EL1, always.
Once we emulate EL2, this no longer will be the case. To prepare
for this, add a target_mode parameter.

While we're at it, merge the computing of the target PC and PSTATE in
a single function that updates both PC and CPSR after saving their
previous values in the corresponding ELR/SPSR. This ensures that they
are updated in the correct order (a pretty common source of bugs...).

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2020-04-21 18:32:02 +01:00
parent 349c330ced
commit d9d7d84d99
2 changed files with 39 additions and 37 deletions
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1
arch/arm64/include/asm/ptrace.h
View File

@ -35,6 +35,7 @@
#define GIC_PRIO_PSR_I_SET (1 << 4)
/* Additional SPSR bits not exposed in the UABI */
#define PSR_MODE_THREAD_BIT (1 << 0)
#define PSR_IL_BIT (1 << 20)
/* AArch32-specific ptrace requests */

75
arch/arm64/kvm/inject_fault.c
View File

@ -26,28 +26,12 @@ enum exception_type {
except_type_serror = 0x180,
};
static u64 get_except_vector(struct kvm_vcpu *vcpu, enum exception_type type)
{
u64 exc_offset;
switch (*vcpu_cpsr(vcpu) & (PSR_MODE_MASK | PSR_MODE32_BIT)) {
case PSR_MODE_EL1t:
exc_offset = CURRENT_EL_SP_EL0_VECTOR;
break;
case PSR_MODE_EL1h:
exc_offset = CURRENT_EL_SP_ELx_VECTOR;
break;
case PSR_MODE_EL0t:
exc_offset = LOWER_EL_AArch64_VECTOR;
break;
default:
exc_offset = LOWER_EL_AArch32_VECTOR;
}
return vcpu_read_sys_reg(vcpu, VBAR_EL1) + exc_offset + type;
}
/*
* This performs the exception entry at a given EL (@target_mode), stashing PC
* and PSTATE into ELR and SPSR respectively, and compute the new PC/PSTATE.
* The EL passed to this function *must* be a non-secure, privileged mode with
* bit 0 being set (PSTATE.SP == 1).
*
* When an exception is taken, most PSTATE fields are left unchanged in the
* handler. However, some are explicitly overridden (e.g. M[4:0]). Luckily all
* of the inherited bits have the same position in the AArch64/AArch32 SPSR_ELx
@ -59,10 +43,35 @@ static u64 get_except_vector(struct kvm_vcpu *vcpu, enum exception_type type)
* Here we manipulate the fields in order of the AArch64 SPSR_ELx layout, from
* MSB to LSB.
*/
static unsigned long get_except64_pstate(struct kvm_vcpu *vcpu)
static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
enum exception_type type)
{
unsigned long sctlr = vcpu_read_sys_reg(vcpu, SCTLR_EL1);
unsigned long old, new;
unsigned long sctlr, vbar, old, new, mode;
u64 exc_offset;
mode = *vcpu_cpsr(vcpu) & (PSR_MODE_MASK | PSR_MODE32_BIT);
if (mode == target_mode)
exc_offset = CURRENT_EL_SP_ELx_VECTOR;
else if ((mode | PSR_MODE_THREAD_BIT) == target_mode)
exc_offset = CURRENT_EL_SP_EL0_VECTOR;
else if (!(mode & PSR_MODE32_BIT))
exc_offset = LOWER_EL_AArch64_VECTOR;
else
exc_offset = LOWER_EL_AArch32_VECTOR;
switch (target_mode) {
case PSR_MODE_EL1h:
vbar = vcpu_read_sys_reg(vcpu, VBAR_EL1);
sctlr = vcpu_read_sys_reg(vcpu, SCTLR_EL1);
vcpu_write_elr_el1(vcpu, *vcpu_pc(vcpu));
break;
default:
/* Don't do that */
BUG();
}
*vcpu_pc(vcpu) = vbar + exc_offset + type;
old = *vcpu_cpsr(vcpu);
new = 0;
@ -105,9 +114,10 @@ static unsigned long get_except64_pstate(struct kvm_vcpu *vcpu)
new |= PSR_I_BIT;
new |= PSR_F_BIT;
new |= PSR_MODE_EL1h;
new |= target_mode;
return new;
*vcpu_cpsr(vcpu) = new;
vcpu_write_spsr(vcpu, old);
}
static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr)
@ -116,11 +126,7 @@ static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr
bool is_aarch32 = vcpu_mode_is_32bit(vcpu);
u32 esr = 0;
vcpu_write_elr_el1(vcpu, *vcpu_pc(vcpu));
*vcpu_pc(vcpu) = get_except_vector(vcpu, except_type_sync);
*vcpu_cpsr(vcpu) = get_except64_pstate(vcpu);
vcpu_write_spsr(vcpu, cpsr);
enter_exception64(vcpu, PSR_MODE_EL1h, except_type_sync);
vcpu_write_sys_reg(vcpu, addr, FAR_EL1);
@ -148,14 +154,9 @@ static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr
static void inject_undef64(struct kvm_vcpu *vcpu)
{
unsigned long cpsr = *vcpu_cpsr(vcpu);
u32 esr = (ESR_ELx_EC_UNKNOWN << ESR_ELx_EC_SHIFT);
vcpu_write_elr_el1(vcpu, *vcpu_pc(vcpu));
*vcpu_pc(vcpu) = get_except_vector(vcpu, except_type_sync);
*vcpu_cpsr(vcpu) = get_except64_pstate(vcpu);
vcpu_write_spsr(vcpu, cpsr);
enter_exception64(vcpu, PSR_MODE_EL1h, except_type_sync);
/*
* Build an unknown exception, depending on the instruction