[v5] bpf, arm64: use BPF prog pack allocator in BPF JIT

[PATCH bpf-next v5 2/3] arm64: patching: Add aarch64_insn_set()

Posted by Puranjay Mohan 2 years, 3 months ago

The BPF JIT needs to write invalid instructions to RX regions of memory
to invalidate removed BPF programs. This needs a function like memset()
that can work with RX memory.

Implement aarch64_insn_set() which is similar to text_poke_set() of x86.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
---
 arch/arm64/include/asm/patching.h |  1 +
 arch/arm64/kernel/patching.c      | 40 +++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/arch/arm64/include/asm/patching.h b/arch/arm64/include/asm/patching.h
index f78a0409cbdb..551933338739 100644
--- a/arch/arm64/include/asm/patching.h
+++ b/arch/arm64/include/asm/patching.h
@@ -8,6 +8,7 @@ int aarch64_insn_read(void *addr, u32 *insnp);
 int aarch64_insn_write(void *addr, u32 insn);
 
 int aarch64_insn_write_literal_u64(void *addr, u64 val);
+int aarch64_insn_set(void *dst, const u32 insn, size_t len);
 void *aarch64_insn_copy(void *dst, const void *src, size_t len);
 
 int aarch64_insn_patch_text_nosync(void *addr, u32 insn);
diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c
index 243d6ae8d2d8..63d9e0e77806 100644
--- a/arch/arm64/kernel/patching.c
+++ b/arch/arm64/kernel/patching.c
@@ -146,6 +146,46 @@ noinstr void *aarch64_insn_copy(void *dst, const void *src, size_t len)
 	return dst;
 }
 
+/**
+ * aarch64_insn_set - memset for RX memory regions.
+ * @dst: address to modify
+ * @c: value to set
+ * @len: length of memory region.
+ *
+ * Useful for JITs to fill regions of RX memory with illegal instructions.
+ */
+noinstr int aarch64_insn_set(void *dst, const u32 insn, size_t len)
+{
+	unsigned long flags;
+	size_t patched = 0;
+	size_t size;
+	void *waddr;
+	void *ptr;
+
+	/* A64 instructions must be word aligned */
+	if ((uintptr_t)dst & 0x3)
+		return -EINVAL;
+
+	raw_spin_lock_irqsave(&patch_lock, flags);
+
+	while (patched < len) {
+		ptr = dst + patched;
+		size = min_t(size_t, PAGE_SIZE - offset_in_page(ptr),
+			     len - patched);
+
+		waddr = patch_map(ptr, FIX_TEXT_POKE0);
+		memset32(waddr, insn, size / 4);
+		patch_unmap(FIX_TEXT_POKE0);
+
+		patched += size;
+	}
+	raw_spin_unlock_irqrestore(&patch_lock, flags);
+
+	caches_clean_inval_pou((uintptr_t)dst, (uintptr_t)dst + len);
+
+	return 0;
+}
+
 int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
 {
 	u32 *tp = addr;
-- 
2.40.1

Re: [PATCH bpf-next v5 2/3] arm64: patching: Add aarch64_insn_set()

Posted by Mark Rutland 2 years, 1 month ago

On Fri, Sep 08, 2023 at 02:43:19PM +0000, Puranjay Mohan wrote:
> The BPF JIT needs to write invalid instructions to RX regions of memory
> to invalidate removed BPF programs. This needs a function like memset()
> that can work with RX memory.
> 
> Implement aarch64_insn_set() which is similar to text_poke_set() of x86.
> 
> Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
> ---
>  arch/arm64/include/asm/patching.h |  1 +
>  arch/arm64/kernel/patching.c      | 40 +++++++++++++++++++++++++++++++
>  2 files changed, 41 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/patching.h b/arch/arm64/include/asm/patching.h
> index f78a0409cbdb..551933338739 100644
> --- a/arch/arm64/include/asm/patching.h
> +++ b/arch/arm64/include/asm/patching.h
> @@ -8,6 +8,7 @@ int aarch64_insn_read(void *addr, u32 *insnp);
>  int aarch64_insn_write(void *addr, u32 insn);
>  
>  int aarch64_insn_write_literal_u64(void *addr, u64 val);
> +int aarch64_insn_set(void *dst, const u32 insn, size_t len);
>  void *aarch64_insn_copy(void *dst, const void *src, size_t len);
>  
>  int aarch64_insn_patch_text_nosync(void *addr, u32 insn);
> diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c
> index 243d6ae8d2d8..63d9e0e77806 100644
> --- a/arch/arm64/kernel/patching.c
> +++ b/arch/arm64/kernel/patching.c
> @@ -146,6 +146,46 @@ noinstr void *aarch64_insn_copy(void *dst, const void *src, size_t len)
>  	return dst;
>  }
>  
> +/**
> + * aarch64_insn_set - memset for RX memory regions.
> + * @dst: address to modify
> + * @c: value to set
> + * @len: length of memory region.
> + *
> + * Useful for JITs to fill regions of RX memory with illegal instructions.
> + */
> +noinstr int aarch64_insn_set(void *dst, const u32 insn, size_t len)
> +{
> +	unsigned long flags;
> +	size_t patched = 0;
> +	size_t size;
> +	void *waddr;
> +	void *ptr;
> +
> +	/* A64 instructions must be word aligned */
> +	if ((uintptr_t)dst & 0x3)
> +		return -EINVAL;
> +
> +	raw_spin_lock_irqsave(&patch_lock, flags);
> +
> +	while (patched < len) {
> +		ptr = dst + patched;
> +		size = min_t(size_t, PAGE_SIZE - offset_in_page(ptr),
> +			     len - patched);
> +
> +		waddr = patch_map(ptr, FIX_TEXT_POKE0);
> +		memset32(waddr, insn, size / 4);

Do we need to use a specific instruction passed by the caller, or can we
hard-code a trapping instruction here?

If we don't care about the specific instruction, it'd be best to memset this to
0, as 0x00000000 is UDF #0 (which will trap), and that way memset can use DC
ZVA to zero the memory, which is faster than 4 bytes at a time.

If we did that, we can rename this to something like:

	aarch64_insn_clear(void *dst, size_t len)

> +		patch_unmap(FIX_TEXT_POKE0);
> +
> +		patched += size;
> +	}
> +	raw_spin_unlock_irqrestore(&patch_lock, flags);
> +
> +	caches_clean_inval_pou((uintptr_t)dst, (uintptr_t)dst + len);

Assuming the point of this is to trap if/when we accidentally execute the freed
instructions, we need an IPI here, and so this should use flush_icache_range()
or make it the caller's responsibility to do so.

Mark.

> +
> +	return 0;
> +}
> +
>  int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
>  {
>  	u32 *tp = addr;
> -- 
> 2.40.1
> 
>

Re: [PATCH bpf-next v5 2/3] arm64: patching: Add aarch64_insn_set()

Posted by Xu Kuohai 2 years, 3 months ago

On 9/8/2023 10:43 PM, Puranjay Mohan wrote:
> The BPF JIT needs to write invalid instructions to RX regions of memory
> to invalidate removed BPF programs. This needs a function like memset()
> that can work with RX memory.
> 
> Implement aarch64_insn_set() which is similar to text_poke_set() of x86.
> 
> Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
> ---
>   arch/arm64/include/asm/patching.h |  1 +
>   arch/arm64/kernel/patching.c      | 40 +++++++++++++++++++++++++++++++
>   2 files changed, 41 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/patching.h b/arch/arm64/include/asm/patching.h
> index f78a0409cbdb..551933338739 100644
> --- a/arch/arm64/include/asm/patching.h
> +++ b/arch/arm64/include/asm/patching.h
> @@ -8,6 +8,7 @@ int aarch64_insn_read(void *addr, u32 *insnp);
>   int aarch64_insn_write(void *addr, u32 insn);
>   
>   int aarch64_insn_write_literal_u64(void *addr, u64 val);
> +int aarch64_insn_set(void *dst, const u32 insn, size_t len);
>   void *aarch64_insn_copy(void *dst, const void *src, size_t len);
>   
>   int aarch64_insn_patch_text_nosync(void *addr, u32 insn);
> diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c
> index 243d6ae8d2d8..63d9e0e77806 100644
> --- a/arch/arm64/kernel/patching.c
> +++ b/arch/arm64/kernel/patching.c
> @@ -146,6 +146,46 @@ noinstr void *aarch64_insn_copy(void *dst, const void *src, size_t len)
>   	return dst;
>   }
>   
> +/**
> + * aarch64_insn_set - memset for RX memory regions.
> + * @dst: address to modify
> + * @c: value to set

insn

> + * @len: length of memory region.
> + *
> + * Useful for JITs to fill regions of RX memory with illegal instructions.
> + */
> +noinstr int aarch64_insn_set(void *dst, const u32 insn, size_t len)

const is unnecessary

> +{
> +	unsigned long flags;
> +	size_t patched = 0;
> +	size_t size;
> +	void *waddr;
> +	void *ptr;
> +
> +	/* A64 instructions must be word aligned */
> +	if ((uintptr_t)dst & 0x3)
> +		return -EINVAL;
> +
> +	raw_spin_lock_irqsave(&patch_lock, flags);
> +
> +	while (patched < len) {
> +		ptr = dst + patched;
> +		size = min_t(size_t, PAGE_SIZE - offset_in_page(ptr),
> +			     len - patched);
> +
> +		waddr = patch_map(ptr, FIX_TEXT_POKE0);
> +		memset32(waddr, insn, size / 4);
> +		patch_unmap(FIX_TEXT_POKE0);
> +
> +		patched += size;
> +	}
> +	raw_spin_unlock_irqrestore(&patch_lock, flags);
> +
> +	caches_clean_inval_pou((uintptr_t)dst, (uintptr_t)dst + len);
> +
> +	return 0;
> +}
> +

this function shares most of the code with aarch64_insn_copy(), how about
extracting the shared code to a separate function?

>   int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
>   {
>   	u32 *tp = addr;

Re: [PATCH bpf-next v5 2/3] arm64: patching: Add aarch64_insn_set()

Posted by Puranjay Mohan 2 years, 2 months ago

Xu Kuohai <xukuohai@huaweicloud.com> writes:

> On 9/8/2023 10:43 PM, Puranjay Mohan wrote:
>> The BPF JIT needs to write invalid instructions to RX regions of memory
>> to invalidate removed BPF programs. This needs a function like memset()
>> that can work with RX memory.
>> 
>> Implement aarch64_insn_set() which is similar to text_poke_set() of x86.
>> 
>> Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
>> ---
>>   arch/arm64/include/asm/patching.h |  1 +
>>   arch/arm64/kernel/patching.c      | 40 +++++++++++++++++++++++++++++++
>>   2 files changed, 41 insertions(+)
>> 
>> diff --git a/arch/arm64/include/asm/patching.h b/arch/arm64/include/asm/patching.h
>> index f78a0409cbdb..551933338739 100644
>> --- a/arch/arm64/include/asm/patching.h
>> +++ b/arch/arm64/include/asm/patching.h
>> @@ -8,6 +8,7 @@ int aarch64_insn_read(void *addr, u32 *insnp);
>>   int aarch64_insn_write(void *addr, u32 insn);
>>   
>>   int aarch64_insn_write_literal_u64(void *addr, u64 val);
>> +int aarch64_insn_set(void *dst, const u32 insn, size_t len);
>>   void *aarch64_insn_copy(void *dst, const void *src, size_t len);
>>   
>>   int aarch64_insn_patch_text_nosync(void *addr, u32 insn);
>> diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c
>> index 243d6ae8d2d8..63d9e0e77806 100644
>> --- a/arch/arm64/kernel/patching.c
>> +++ b/arch/arm64/kernel/patching.c
>> @@ -146,6 +146,46 @@ noinstr void *aarch64_insn_copy(void *dst, const void *src, size_t len)
>>   	return dst;
>>   }
>>   
>> +/**
>> + * aarch64_insn_set - memset for RX memory regions.
>> + * @dst: address to modify
>> + * @c: value to set
>
> insn

Thanks for catching.

>> + * @len: length of memory region.
>> + *
>> + * Useful for JITs to fill regions of RX memory with illegal instructions.
>> + */
>> +noinstr int aarch64_insn_set(void *dst, const u32 insn, size_t len)
>
> const is unnecessary
>

Will remove in next version.

>> +{
>> +	unsigned long flags;
>> +	size_t patched = 0;
>> +	size_t size;
>> +	void *waddr;
>> +	void *ptr;
>> +
>> +	/* A64 instructions must be word aligned */
>> +	if ((uintptr_t)dst & 0x3)
>> +		return -EINVAL;
>> +
>> +	raw_spin_lock_irqsave(&patch_lock, flags);
>> +
>> +	while (patched < len) {
>> +		ptr = dst + patched;
>> +		size = min_t(size_t, PAGE_SIZE - offset_in_page(ptr),
>> +			     len - patched);
>> +
>> +		waddr = patch_map(ptr, FIX_TEXT_POKE0);
>> +		memset32(waddr, insn, size / 4);
>> +		patch_unmap(FIX_TEXT_POKE0);
>> +
>> +		patched += size;
>> +	}
>> +	raw_spin_unlock_irqrestore(&patch_lock, flags);
>> +
>> +	caches_clean_inval_pou((uintptr_t)dst, (uintptr_t)dst + len);
>> +
>> +	return 0;
>> +}
>> +
>
> this function shares most of the code with aarch64_insn_copy(), how about
> extracting the shared code to a separate function?

I was thinking of writing it like the text_poke api of x86. Where you
can provide a function as an argument to work on a memory area.
Essentially, it will look like:

typedef int text_poke_f(void *dst, const void *src, size_t len);

static void *aarch64_insn_poke(text_poke_f func, void *addr, const void *src, size_t len)

We can call this function with a wrapper of `copy_to_kernel_nofault` for copy
and with a wrapper of memset32 for setting.

Do you think this is a good approach?

>
>>   int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
>>   {
>>   	u32 *tp = addr;

Thanks,
Puranjay

Re: [PATCH bpf-next v5 2/3] arm64: patching: Add aarch64_insn_set()

Posted by Xu Kuohai 2 years, 2 months ago

On 9/21/2023 10:50 PM, Puranjay Mohan wrote:
> Xu Kuohai <xukuohai@huaweicloud.com> writes:
> 
>> On 9/8/2023 10:43 PM, Puranjay Mohan wrote:
>>> The BPF JIT needs to write invalid instructions to RX regions of memory
>>> to invalidate removed BPF programs. This needs a function like memset()
>>> that can work with RX memory.
>>>
>>> Implement aarch64_insn_set() which is similar to text_poke_set() of x86.
>>>
>>> Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
>>> ---
>>>    arch/arm64/include/asm/patching.h |  1 +
>>>    arch/arm64/kernel/patching.c      | 40 +++++++++++++++++++++++++++++++
>>>    2 files changed, 41 insertions(+)
>>>
>>> diff --git a/arch/arm64/include/asm/patching.h b/arch/arm64/include/asm/patching.h
>>> index f78a0409cbdb..551933338739 100644
>>> --- a/arch/arm64/include/asm/patching.h
>>> +++ b/arch/arm64/include/asm/patching.h
>>> @@ -8,6 +8,7 @@ int aarch64_insn_read(void *addr, u32 *insnp);
>>>    int aarch64_insn_write(void *addr, u32 insn);
>>>    
>>>    int aarch64_insn_write_literal_u64(void *addr, u64 val);
>>> +int aarch64_insn_set(void *dst, const u32 insn, size_t len);
>>>    void *aarch64_insn_copy(void *dst, const void *src, size_t len);
>>>    
>>>    int aarch64_insn_patch_text_nosync(void *addr, u32 insn);
>>> diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c
>>> index 243d6ae8d2d8..63d9e0e77806 100644
>>> --- a/arch/arm64/kernel/patching.c
>>> +++ b/arch/arm64/kernel/patching.c
>>> @@ -146,6 +146,46 @@ noinstr void *aarch64_insn_copy(void *dst, const void *src, size_t len)
>>>    	return dst;
>>>    }
>>>    
>>> +/**
>>> + * aarch64_insn_set - memset for RX memory regions.
>>> + * @dst: address to modify
>>> + * @c: value to set
>>
>> insn
> 
> Thanks for catching.
> 
>>> + * @len: length of memory region.
>>> + *
>>> + * Useful for JITs to fill regions of RX memory with illegal instructions.
>>> + */
>>> +noinstr int aarch64_insn_set(void *dst, const u32 insn, size_t len)
>>
>> const is unnecessary
>>
> 
> Will remove in next version.
> 
>>> +{
>>> +	unsigned long flags;
>>> +	size_t patched = 0;
>>> +	size_t size;
>>> +	void *waddr;
>>> +	void *ptr;
>>> +
>>> +	/* A64 instructions must be word aligned */
>>> +	if ((uintptr_t)dst & 0x3)
>>> +		return -EINVAL;
>>> +
>>> +	raw_spin_lock_irqsave(&patch_lock, flags);
>>> +
>>> +	while (patched < len) {
>>> +		ptr = dst + patched;
>>> +		size = min_t(size_t, PAGE_SIZE - offset_in_page(ptr),
>>> +			     len - patched);
>>> +
>>> +		waddr = patch_map(ptr, FIX_TEXT_POKE0);
>>> +		memset32(waddr, insn, size / 4);
>>> +		patch_unmap(FIX_TEXT_POKE0);
>>> +
>>> +		patched += size;
>>> +	}
>>> +	raw_spin_unlock_irqrestore(&patch_lock, flags);
>>> +
>>> +	caches_clean_inval_pou((uintptr_t)dst, (uintptr_t)dst + len);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>
>> this function shares most of the code with aarch64_insn_copy(), how about
>> extracting the shared code to a separate function?
> 
> I was thinking of writing it like the text_poke api of x86. Where you
> can provide a function as an argument to work on a memory area.
> Essentially, it will look like:
> 
> typedef int text_poke_f(void *dst, const void *src, size_t len);
> 
> static void *aarch64_insn_poke(text_poke_f func, void *addr, const void *src, size_t len)
> 
> We can call this function with a wrapper of `copy_to_kernel_nofault` for copy
> and with a wrapper of memset32 for setting.
> 
> Do you think this is a good approach?
>
Sounds great, thanks.

>>
>>>    int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
>>>    {
>>>    	u32 *tp = addr;
> 
> Thanks,
> Puranjay