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Date:   Mon, 18 Jan 2021 10:44:27 +0000
From:   David Brazdil <dbrazdil@google.com>
To:     Elena Petrova <lenaptr@google.com>
Cc:     kvmarm@lists.cs.columbia.edu,
        George-Aurelian Popescu <georgepope@google.com>,
        Marc Zyngier <maz@kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        George Popescu <george.apopescu97@gmail.com>
Subject: Re: [PATCH v3 9/9] KVM: arm64: Add UBSan tests for PKVM.
Message-ID: <20210118104427.lgjt4ndhnntz4bld@google.com>
References: <20210115171830.3602110-1-lenaptr@google.com>
 <20210115171830.3602110-10-lenaptr@google.com>
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On Fri, Jan 15, 2021 at 05:18:30PM +0000, Elena Petrova wrote:
> From: George-Aurelian Popescu <georgepope@google.com>
> 
> Test the UBsan functionality inside hyp/nVHE.
> Because modules are not supported inside of hyp/nVHE code, the default
> testing module for UBSan can not be used.
> New functions have to be defined inside of hyp/nVHE.
> They are called in kvm_get_mdcr_el2, to test UBSAN whenever a VM starts.
> 
> Signed-off-by: Elena Petrova <lenaptr@google.com>
> ---
>  arch/arm64/include/asm/assembler.h          |  17 ++-
>  arch/arm64/include/asm/kvm_debug_buffer.h   |  10 +-
>  arch/arm64/include/asm/kvm_ubsan.h          |   2 +-
>  arch/arm64/kvm/hyp/include/hyp/test_ubsan.h | 112 ++++++++++++++++++++
>  arch/arm64/kvm/hyp/nvhe/hyp-main.c          |   3 +
>  arch/arm64/kvm/kvm_ubsan_buffer.c           |   1 -
>  6 files changed, 128 insertions(+), 17 deletions(-)
>  create mode 100644 arch/arm64/kvm/hyp/include/hyp/test_ubsan.h
> 
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index ebc18a8a0e1f..8422b0d925e8 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -259,16 +259,15 @@ alternative_endif
>  	.endm
>  
>  	/*
> -         * @sym: The name of the per-cpu variable
> -         * @reg: value to store
> -         * @tmp1: scratch register
> -         * @tmp2: scratch register
> -         */
> -        .macro str_this_cpu sym, reg, tmp1, tmp2
> -        adr_this_cpu \tmp1, \sym, \tmp2
> +	 * @sym: The name of the per-cpu variable
> +	 * @reg: value to store
> +	 * @tmp1: scratch register
> +	 * @tmp2: scratch register
> +	 */
> +	.macro str_this_cpu sym, reg, tmp1, tmp2
> +	adr_this_cpu \tmp1, \sym, \tmp2
>          str \reg, [\tmp1]
> -        .endm
> -
> +	.endm
>  /*
>   * vma_vm_mm - get mm pointer from vma pointer (vma->vm_mm)
>   */
> diff --git a/arch/arm64/include/asm/kvm_debug_buffer.h b/arch/arm64/include/asm/kvm_debug_buffer.h
> index e5375c2cff1a..361b473bb004 100644
> --- a/arch/arm64/include/asm/kvm_debug_buffer.h
> +++ b/arch/arm64/include/asm/kvm_debug_buffer.h
> @@ -3,10 +3,8 @@
>   * Copyright 2020 Google LLC
>   * Author: George Popescu <georgepope@google.com>
>   */
> -
>  #include <linux/percpu-defs.h>
>  
> -
>  #define KVM_DEBUG_BUFFER_SIZE 1000
>  
>  #ifdef __KVM_NVHE_HYPERVISOR__
> @@ -20,17 +18,17 @@
>  #else
>  #define DECLARE_KVM_DEBUG_BUFFER(type_name, buffer_name, write_ind, size)\
>  	DECLARE_KVM_NVHE_PER_CPU(type_name, buffer_name)[size]; 	\
> -        DECLARE_KVM_NVHE_PER_CPU(unsigned long, write_ind);
> +	DECLARE_KVM_NVHE_PER_CPU(unsigned long, write_ind);
>  #endif //__KVM_NVHE_HYPERVISOR__
>  
>  #ifdef __ASSEMBLY__
>  #include <asm/assembler.h>
>  
>  .macro clear_buffer tmp1, tmp2, tmp3
> -        mov \tmp1, 0
> +	mov \tmp1, 0
>  #ifdef CONFIG_UBSAN
> -        str_this_cpu kvm_ubsan_buff_wr_ind, \tmp1, \tmp2, \tmp3
> +	str_this_cpu kvm_ubsan_buff_wr_ind, \tmp1, \tmp2, \tmp3
>  #endif //CONFIG_UBSAN
>  .endm
Are these fixing formatting? If so, move it to the patch that introduced this.

>  
> -#endif
> \ No newline at end of file
> +#endif
> diff --git a/arch/arm64/include/asm/kvm_ubsan.h b/arch/arm64/include/asm/kvm_ubsan.h
> index da4a3b4e28e0..0b8bed08d48e 100644
> --- a/arch/arm64/include/asm/kvm_ubsan.h
> +++ b/arch/arm64/include/asm/kvm_ubsan.h
> @@ -9,7 +9,6 @@
>  #define UBSAN_MAX_TYPE 6
>  #define KVM_UBSAN_BUFFER_SIZE 1000
>  
> -
ditto

>  struct ubsan_values {
>  	void *lval;
>  	void *rval;
> @@ -18,6 +17,7 @@ struct ubsan_values {
>  
>  struct kvm_ubsan_info {
>  	enum {
> +		UBSAN_NONE,

This also looks like it should have been in a previous patch. The code assumes
that 'type == 0' means 'empty slot'. So presumably this is fixing a bug?

>  		UBSAN_OUT_OF_BOUNDS,
>  		UBSAN_UNREACHABLE_DATA,
>  		UBSAN_SHIFT_OUT_OF_BOUNDS,
> diff --git a/arch/arm64/kvm/hyp/include/hyp/test_ubsan.h b/arch/arm64/kvm/hyp/include/hyp/test_ubsan.h
> new file mode 100644
> index 000000000000..07759c0d1e0e
> --- /dev/null
> +++ b/arch/arm64/kvm/hyp/include/hyp/test_ubsan.h
> @@ -0,0 +1,112 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#include <linux/ctype.h>
> +
> +typedef void(*test_ubsan_fp)(void);
> +
> +static void test_ubsan_add_overflow(void)
> +{
> +	volatile int val = INT_MAX;
> +
> +	val += 2;
> +}
> +
> +static void test_ubsan_sub_overflow(void)
> +{
> +	volatile int val = INT_MIN;
> +	volatile int val2 = 2;
> +
> +	val -= val2;
> +}
> +
> +static void test_ubsan_mul_overflow(void)
> +{
> +	volatile int val = INT_MAX / 2;
> +
> +	val *= 3;
> +}
> +
> +static void test_ubsan_negate_overflow(void)
> +{
> +	volatile int val = INT_MIN;
> +
> +	val = -val;
> +}
> +
> +static void test_ubsan_divrem_overflow(void)
> +{
> +	volatile int val = 16;
> +	volatile int val2 = 0;
> +
> +	val /= val2;
> +}
> +
> +static void test_ubsan_shift_out_of_bounds(void)
> +{
> +	volatile int val = -1;
> +	int val2 = 10;
> +
> +	val2 <<= val;
> +}
> +
> +static void test_ubsan_out_of_bounds(void)
> +{
> +	volatile int i = 4, j = 5;
> +	volatile int arr[4];
> +	
> +	arr[j] = i;
> +}
> +
> +static void test_ubsan_load_invalid_value(void)
> +{
> +	volatile char *dst, *src;
> +	bool val, val2, *ptr;
> +	char c = 4;
> +
> +	dst = (char *)&val;
> +	src = &c;
> +	*dst = *src;
> +
> +	ptr = &val2;
> +	val2 = val;
> +}
> +
> +static void test_ubsan_misaligned_access(void)
> +{
> +	volatile char arr[5] __aligned(4) = {1, 2, 3, 4, 5};
> +	volatile int *ptr, val = 6;
> +
> +	ptr = (int *)(arr + 1);
> +	*ptr = val;
> +}
> +
> +static void test_ubsan_object_size_mismatch(void)
> +{
> +	/* "((aligned(8)))" helps this not into be misaligned for ptr-access. */
> +	volatile int val __aligned(8) = 4;
> +	volatile long long *ptr, val2;
> +
> +	ptr = (long long *)&val;
> +	val2 = *ptr;
> +}
> +
> +static const test_ubsan_fp test_ubsan_array[] = {
> +	test_ubsan_out_of_bounds,
> +	test_ubsan_add_overflow,
> +	test_ubsan_sub_overflow,
> +	test_ubsan_mul_overflow,
> +	test_ubsan_negate_overflow,
> +	test_ubsan_divrem_overflow,
> +	test_ubsan_shift_out_of_bounds,
> +	test_ubsan_load_invalid_value,
> +	test_ubsan_misaligned_access,
> +	test_ubsan_object_size_mismatch,
> +};
> +
> +static void test_ubsan(void)
> +{
> +	unsigned int i;
> +	
> +	for (i = 0; i < ARRAY_SIZE(test_ubsan_array); i++)
> +		test_ubsan_array[i]();
> +}
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index a906f9e2ff34..939600e9fdd6 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -13,6 +13,7 @@
>  #include <asm/kvm_mmu.h>
>  
>  #include <nvhe/trap_handler.h>
> +#include <hyp/test_ubsan.h>
>  
>  DEFINE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
>  
> @@ -90,6 +91,8 @@ static void handle___vgic_v3_init_lrs(struct kvm_cpu_context *host_ctxt)
>  static void handle___kvm_get_mdcr_el2(struct kvm_cpu_context *host_ctxt)
>  {
>  	cpu_reg(host_ctxt, 1) = __kvm_get_mdcr_el2();
> +	if (IS_ENABLED(CONFIG_TEST_UBSAN))
> +		test_ubsan();
>  }

We cannot keep this in here. It's useful to exercise your code in development
but not something you should upstream. I would either remove this completely or
implement it as a separate hypercall.

>  
>  static void handle___vgic_v3_save_aprs(struct kvm_cpu_context *host_ctxt)
> diff --git a/arch/arm64/kvm/kvm_ubsan_buffer.c b/arch/arm64/kvm/kvm_ubsan_buffer.c
> index 2c7060cbb48b..49bedc9de139 100644
> --- a/arch/arm64/kvm/kvm_ubsan_buffer.c
> +++ b/arch/arm64/kvm/kvm_ubsan_buffer.c
> @@ -11,7 +11,6 @@
>  #include <asm/kvm_asm.h>
>  #include <kvm/arm_pmu.h>
>  
> -#include <ubsan.h>
ditto

>  #include <asm/kvm_ubsan.h>
>  
>  DECLARE_KVM_DEBUG_BUFFER(struct kvm_ubsan_info, kvm_ubsan_buffer,
> -- 
> 2.30.0.296.g2bfb1c46d8-goog
> 
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