| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20141129162115.GF23653@cbox>
Date: Sat, 29 Nov 2014 17:21:15 +0100
From: Christoffer Dall <christoffer.dall@...aro.org>
To: Alex Bennée <alex.bennee@...aro.org>
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.cs.columbia.edu, marc.zyngier@....com,
peter.maydell@...aro.org, agraf@...e.de, jan.kiszka@...mens.com,
dahi@...ux.vnet.ibm.com, r65777@...escale.com, bp@...e.de,
pbonzini@...hat.com, Gleb Natapov <gleb@...nel.org>,
Jonathan Corbet <corbet@....net>,
Russell King <linux@....linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/7] KVM: arm64: guest debug, add SW break point support
On Tue, Nov 25, 2014 at 04:10:02PM +0000, Alex Bennée wrote:
> This adds support for SW breakpoints inserted by userspace.
>
> First we need to trap all BKPT exceptions in the hypervisor (ELS). This
> in controlled through the MDCR_EL2 register. I've added a new field to
this is ?
> the vcpu structure to hold this value. There should be scope to
> rationlise this with the VCPU_DEBUG_FLAGS/KVM_ARM64_DEBUG_DIRTY_SHIFT
> manipulation in later patches.
I don't understand what you mean with rationalising something in later
patches.
>
> Once the exception arrives we triggers an exit from the main hypervisor
> loop to the hypervisor controller. The kvm_debug_exit_arch carries the
hypervisor controller is userspace?
> address of the exception. If the controller doesn't know of breakpoint
the breakint ?
> then we have a guest inserted breakpoint and the hypervisor needs to
> start again and deliver the exception to guest.
to the guest
>
> Signed-off-by: Alex Bennée <alex.bennee@...aro.org>
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 2c6386e..9383359 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2592,7 +2592,7 @@ when running. Common control bits are:
> The top 16 bits of the control field are architecture specific control
> flags which can include the following:
>
> - - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86]
> + - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64]
> - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390]
> - KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
> - KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index a0ff410..48d26bb 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -303,6 +303,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
> struct kvm_guest_debug *dbg)
> {
> + /* Route debug traps to el2? */
> + bool route_el2 = false;
> +
> /* If it's not enabled clear all flags */
> if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
> vcpu->guest_debug = 0;
> @@ -320,8 +323,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>
> /* Software Break Points */
> if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
> - kvm_info("SW BP support requested, not yet implemented\n");
> - return -EINVAL;
> + kvm_info("SW BP support requested\n");
> + route_el2 = true;
> }
>
> /* Hardware assisted Break and Watch points */
> @@ -330,6 +333,20 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
> return -EINVAL;
> }
>
> + /* If we are going to handle any debug exceptions we need to
wings on the comments
> + * set MDCE_EL2.TDE to ensure they are routed to the
> + * hypervisor. If userspace determines the exception was
> + * actually internal to the guest it needs to handle
> + * re-injecting the exception.
> + */
> + if (route_el2) {
> + kvm_info("routing debug exceptions");
> + vcpu->arch.mdcr_el2 = MDCR_EL2_TDE;
> + } else {
> + kvm_info("not routing debug exceptions");
> + vcpu->arch.mdcr_el2 = 0;
> + }
> +
> return 0;
> }
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 2012c4b..38b0f07 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -98,6 +98,7 @@ struct kvm_vcpu_arch {
>
> /* HYP configuration */
> u64 hcr_el2;
> + u32 mdcr_el2;
>
> /* Exception Information */
> struct kvm_vcpu_fault_info fault;
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 9a9fce0..8da1043 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -122,6 +122,7 @@ int main(void)
> DEFINE(VCPU_HPFAR_EL2, offsetof(struct kvm_vcpu, arch.fault.hpfar_el2));
> DEFINE(VCPU_DEBUG_FLAGS, offsetof(struct kvm_vcpu, arch.debug_flags));
> DEFINE(VCPU_HCR_EL2, offsetof(struct kvm_vcpu, arch.hcr_el2));
> + DEFINE(VCPU_MDCR_EL2, offsetof(struct kvm_vcpu, arch.mdcr_el2));
> DEFINE(VCPU_IRQ_LINES, offsetof(struct kvm_vcpu, arch.irq_lines));
> DEFINE(VCPU_HOST_CONTEXT, offsetof(struct kvm_vcpu, arch.host_cpu_context));
> DEFINE(VCPU_TIMER_CNTV_CTL, offsetof(struct kvm_vcpu, arch.timer_cpu.cntv_ctl));
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 34b8bd0..28dc92b 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -71,6 +71,26 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
> return 1;
> }
>
> +/**
> + * kvm_handle_bkpt - handle a break-point instruction
> + *
> + * @vcpu: the vcpu pointer
> + *
> + * By definition if we arrive here it's because we are routing
> + * all SW breakpoints to the hyper-visor as some may be a result of
s/hyper-visor/hypervisor/
this sentence is weird. I think what you want is a full stop after
hypervisor and then a new sentence: Userspace may decide that this
particular breakpoint should be routed to the guest (if the breakpoint
does not come form userspace but by someone debugging a process inside
the guest), and in that case inject a software breakpoint instruction by
<insert the method here>.
> + * guest debugging. If user-space decides this particular break-point
> + * isn't for the host to handle it can re-feed the exception to the
> + * guest.
> + */
> +static int kvm_handle_bkpt(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +{
> + run->exit_reason = KVM_EXIT_DEBUG;
> + run->debug.arch.exit_type = KVM_DEBUG_EXIT_SW_BKPT;
> + run->debug.arch.address = *vcpu_pc(vcpu);
> + kvm_info("exiting from %llx\n", run->debug.arch.address);
> + return 0;
> +}
> +
> static exit_handle_fn arm_exit_handlers[] = {
> [ESR_EL2_EC_WFI] = kvm_handle_wfx,
> [ESR_EL2_EC_CP15_32] = kvm_handle_cp15_32,
> @@ -85,6 +105,8 @@ static exit_handle_fn arm_exit_handlers[] = {
> [ESR_EL2_EC_SYS64] = kvm_handle_sys_reg,
> [ESR_EL2_EC_IABT] = kvm_handle_guest_abort,
> [ESR_EL2_EC_DABT] = kvm_handle_guest_abort,
> + [ESR_EL2_EC_BKPT32] = kvm_handle_bkpt,
> + [ESR_EL2_EC_BRK64] = kvm_handle_bkpt,
> };
>
> static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
> index b72aa9f..3c733ea 100644
> --- a/arch/arm64/kvm/hyp.S
> +++ b/arch/arm64/kvm/hyp.S
> @@ -772,6 +772,10 @@
> orr x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
> orr x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA)
>
> + // Any other bits (currently TDE)
> + ldr x3, [x0, #VCPU_MDCR_EL2]
> + orr x2, x2, x3
> +
> // Check for KVM_ARM64_DEBUG_DIRTY, and set debug to trap
> // if not dirty.
> ldr x3, [x0, #VCPU_DEBUG_FLAGS]
> --
> 2.1.3
>
It may be simpler to just load/restore the MDCR_EL2 and do all
bit-manipulations for a specific VCPU in C-code instead of this.
-Christoffer
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists