&xdp_buff and &xdp_frame are bound in a way that
xdp_buff->data_hard_start == xdp_frame
It's always the case and e.g. xdp_convert_buff_to_frame() relies on
this.
IOW, the following:
for (u32 i = 0; i < 0xdead; i++) {
xdpf = xdp_convert_buff_to_frame(&xdp);
xdp_convert_frame_to_buff(xdpf, &xdp);
}
shouldn't ever modify @xdpf's contents or the pointer itself.
However, "live packet" code wrongly treats &xdp_frame as part of its
context placed *before* the data_hard_start. With such flow,
data_hard_start is sizeof(*xdpf) off to the right and no longer points
to the XDP frame.
Instead of replacing `sizeof(ctx)` with `offsetof(ctx, xdpf)` in several
places and praying that there are no more miscalcs left somewhere in the
code, unionize ::frm with ::data in a flex array, so that both starts
pointing to the actual data_hard_start and the XDP frame actually starts
being a part of it, i.e. a part of the headroom, not the context.
A nice side effect is that the maximum frame size for this mode gets
increased by 40 bytes, as xdp_buff::frame_sz includes everything from
data_hard_start (-> includes xdpf already) to the end of XDP/skb shared
info.
Minor: align `&head->data` with how `head->frm` is assigned for
consistency.
Minor #2: rename 'frm' to 'frame' in &xdp_page_head while at it for
clarity.
(was found while testing XDP traffic generator on ice, which calls
xdp_convert_frame_to_buff() for each XDP frame)
Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in BPF_PROG_RUN")
Signed-off-by: Alexander Lobakin <[email protected]>
---
From v1[0]:
- align `&head->data` with how `head->frm` is assigned for consistency
(Toke);
- rename 'frm' to 'frame' in &xdp_page_head (Jakub);
- no functional changes.
[0] https://lore.kernel.org/bpf/[email protected]
---
net/bpf/test_run.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 2723623429ac..522869ccc007 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -97,8 +97,11 @@ static bool bpf_test_timer_continue(struct bpf_test_timer *t, int iterations,
struct xdp_page_head {
struct xdp_buff orig_ctx;
struct xdp_buff ctx;
- struct xdp_frame frm;
- u8 data[];
+ union {
+ /* ::data_hard_start starts here */
+ DECLARE_FLEX_ARRAY(struct xdp_frame, frame);
+ DECLARE_FLEX_ARRAY(u8, data);
+ };
};
struct xdp_test_data {
@@ -132,8 +135,8 @@ static void xdp_test_run_init_page(struct page *page, void *arg)
headroom -= meta_len;
new_ctx = &head->ctx;
- frm = &head->frm;
- data = &head->data;
+ frm = head->frame;
+ data = head->data;
memcpy(data + headroom, orig_ctx->data_meta, frm_len);
xdp_init_buff(new_ctx, TEST_XDP_FRAME_SIZE, &xdp->rxq);
@@ -223,7 +226,7 @@ static void reset_ctx(struct xdp_page_head *head)
head->ctx.data = head->orig_ctx.data;
head->ctx.data_meta = head->orig_ctx.data_meta;
head->ctx.data_end = head->orig_ctx.data_end;
- xdp_update_frame_from_buff(&head->ctx, &head->frm);
+ xdp_update_frame_from_buff(&head->ctx, head->frame);
}
static int xdp_recv_frames(struct xdp_frame **frames, int nframes,
@@ -285,7 +288,7 @@ static int xdp_test_run_batch(struct xdp_test_data *xdp, struct bpf_prog *prog,
head = phys_to_virt(page_to_phys(page));
reset_ctx(head);
ctx = &head->ctx;
- frm = &head->frm;
+ frm = head->frame;
xdp->frame_cnt++;
act = bpf_prog_run_xdp(prog, ctx);
--
2.39.1
Alexander Lobakin <[email protected]> writes:
> &xdp_buff and &xdp_frame are bound in a way that
>
> xdp_buff->data_hard_start == xdp_frame
>
> It's always the case and e.g. xdp_convert_buff_to_frame() relies on
> this.
> IOW, the following:
>
> for (u32 i = 0; i < 0xdead; i++) {
> xdpf = xdp_convert_buff_to_frame(&xdp);
> xdp_convert_frame_to_buff(xdpf, &xdp);
> }
>
> shouldn't ever modify @xdpf's contents or the pointer itself.
> However, "live packet" code wrongly treats &xdp_frame as part of its
> context placed *before* the data_hard_start. With such flow,
> data_hard_start is sizeof(*xdpf) off to the right and no longer points
> to the XDP frame.
>
> Instead of replacing `sizeof(ctx)` with `offsetof(ctx, xdpf)` in several
> places and praying that there are no more miscalcs left somewhere in the
> code, unionize ::frm with ::data in a flex array, so that both starts
> pointing to the actual data_hard_start and the XDP frame actually starts
> being a part of it, i.e. a part of the headroom, not the context.
> A nice side effect is that the maximum frame size for this mode gets
> increased by 40 bytes, as xdp_buff::frame_sz includes everything from
> data_hard_start (-> includes xdpf already) to the end of XDP/skb shared
> info.
>
> Minor: align `&head->data` with how `head->frm` is assigned for
> consistency.
> Minor #2: rename 'frm' to 'frame' in &xdp_page_head while at it for
> clarity.
>
> (was found while testing XDP traffic generator on ice, which calls
> xdp_convert_frame_to_buff() for each XDP frame)
>
> Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in BPF_PROG_RUN")
> Signed-off-by: Alexander Lobakin <[email protected]>
> ---
> From v1[0]:
> - align `&head->data` with how `head->frm` is assigned for consistency
> (Toke);
> - rename 'frm' to 'frame' in &xdp_page_head (Jakub);
> - no functional changes.
>
> [0]
> https://lore.kernel.org/bpf/[email protected]
Acked-by: Toke Høiland-Jørgensen <[email protected]>
On 2/13/23 3:27 PM, Alexander Lobakin wrote:
> &xdp_buff and &xdp_frame are bound in a way that
>
> xdp_buff->data_hard_start == xdp_frame
>
> It's always the case and e.g. xdp_convert_buff_to_frame() relies on
> this.
> IOW, the following:
>
> for (u32 i = 0; i < 0xdead; i++) {
> xdpf = xdp_convert_buff_to_frame(&xdp);
> xdp_convert_frame_to_buff(xdpf, &xdp);
> }
>
> shouldn't ever modify @xdpf's contents or the pointer itself.
> However, "live packet" code wrongly treats &xdp_frame as part of its
> context placed *before* the data_hard_start. With such flow,
> data_hard_start is sizeof(*xdpf) off to the right and no longer points
> to the XDP frame.
>
> Instead of replacing `sizeof(ctx)` with `offsetof(ctx, xdpf)` in several
> places and praying that there are no more miscalcs left somewhere in the
> code, unionize ::frm with ::data in a flex array, so that both starts
> pointing to the actual data_hard_start and the XDP frame actually starts
> being a part of it, i.e. a part of the headroom, not the context.
> A nice side effect is that the maximum frame size for this mode gets
> increased by 40 bytes, as xdp_buff::frame_sz includes everything from
> data_hard_start (-> includes xdpf already) to the end of XDP/skb shared
> info.
>
> Minor: align `&head->data` with how `head->frm` is assigned for
> consistency.
> Minor #2: rename 'frm' to 'frame' in &xdp_page_head while at it for
> clarity.
>
> (was found while testing XDP traffic generator on ice, which calls
> xdp_convert_frame_to_buff() for each XDP frame)
>
> Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in BPF_PROG_RUN")
> Signed-off-by: Alexander Lobakin <[email protected]>
Could you double check BPF CI? Looks like a number of XDP related tests
are failing on your patch which I'm not seeing on other patches where runs
are green, for example test_progs on several archs report the below:
https://github.com/kernel-patches/bpf/actions/runs/4164593416/jobs/7207290499
[...]
test_xdp_do_redirect:PASS:prog_run 0 nsec
test_xdp_do_redirect:PASS:pkt_count_xdp 0 nsec
test_xdp_do_redirect:PASS:pkt_count_zero 0 nsec
test_xdp_do_redirect:PASS:pkt_count_tc 0 nsec
test_max_pkt_size:PASS:prog_run_max_size 0 nsec
test_max_pkt_size:FAIL:prog_run_too_big unexpected prog_run_too_big: actual -28 != expected -22
close_netns:PASS:setns 0 nsec
#275 xdp_do_redirect:FAIL
Summary: 273/1581 PASSED, 21 SKIPPED, 2 FAILED
From: Daniel Borkmann <[email protected]>
Date: Tue, 14 Feb 2023 16:24:10 +0100
> On 2/13/23 3:27 PM, Alexander Lobakin wrote:
>> &xdp_buff and &xdp_frame are bound in a way that
>>
>> xdp_buff->data_hard_start == xdp_frame
>>
>> It's always the case and e.g. xdp_convert_buff_to_frame() relies on
>> this.
>> IOW, the following:
>>
>> for (u32 i = 0; i < 0xdead; i++) {
>> xdpf = xdp_convert_buff_to_frame(&xdp);
>> xdp_convert_frame_to_buff(xdpf, &xdp);
>> }
>>
>> shouldn't ever modify @xdpf's contents or the pointer itself.
>> However, "live packet" code wrongly treats &xdp_frame as part of its
>> context placed *before* the data_hard_start. With such flow,
>> data_hard_start is sizeof(*xdpf) off to the right and no longer points
>> to the XDP frame.
>>
>> Instead of replacing `sizeof(ctx)` with `offsetof(ctx, xdpf)` in several
>> places and praying that there are no more miscalcs left somewhere in the
>> code, unionize ::frm with ::data in a flex array, so that both starts
>> pointing to the actual data_hard_start and the XDP frame actually starts
>> being a part of it, i.e. a part of the headroom, not the context.
>> A nice side effect is that the maximum frame size for this mode gets
>> increased by 40 bytes, as xdp_buff::frame_sz includes everything from
>> data_hard_start (-> includes xdpf already) to the end of XDP/skb shared
>> info.
>>
>> Minor: align `&head->data` with how `head->frm` is assigned for
>> consistency.
>> Minor #2: rename 'frm' to 'frame' in &xdp_page_head while at it for
>> clarity.
>>
>> (was found while testing XDP traffic generator on ice, which calls
>> xdp_convert_frame_to_buff() for each XDP frame)
>>
>> Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in
>> BPF_PROG_RUN")
>> Signed-off-by: Alexander Lobakin <[email protected]>
>
> Could you double check BPF CI? Looks like a number of XDP related tests
> are failing on your patch which I'm not seeing on other patches where runs
> are green, for example test_progs on several archs report the below:
>
> https://github.com/kernel-patches/bpf/actions/runs/4164593416/jobs/7207290499
>
> [...]
> test_xdp_do_redirect:PASS:prog_run 0 nsec
> test_xdp_do_redirect:PASS:pkt_count_xdp 0 nsec
> test_xdp_do_redirect:PASS:pkt_count_zero 0 nsec
> test_xdp_do_redirect:PASS:pkt_count_tc 0 nsec
> test_max_pkt_size:PASS:prog_run_max_size 0 nsec
> test_max_pkt_size:FAIL:prog_run_too_big unexpected prog_run_too_big:
> actual -28 != expected -22
> close_netns:PASS:setns 0 nsec
> #275 xdp_do_redirect:FAIL
> Summary: 273/1581 PASSED, 21 SKIPPED, 2 FAILED
Ah I see. xdp_do_redirect.c test defines:
/* The maximum permissible size is: PAGE_SIZE -
* sizeof(struct xdp_page_head) - sizeof(struct skb_shared_info) -
* XDP_PACKET_HEADROOM = 3368 bytes
*/
#define MAX_PKT_SIZE 3368
This needs to be updated as it now became bigger. The test checks that
this size passes and size + 1 fails, but now it doesn't.
Will send v3 in a couple minutes.
Thanks,
Olek
From: Alexander Lobakin <[email protected]>
Date: Tue, 14 Feb 2023 16:39:25 +0100
> From: Daniel Borkmann <[email protected]>
> Date: Tue, 14 Feb 2023 16:24:10 +0100
>
>> On 2/13/23 3:27 PM, Alexander Lobakin wrote:
[...]
>>> Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in
>>> BPF_PROG_RUN")
>>> Signed-off-by: Alexander Lobakin <[email protected]>
>>
>> Could you double check BPF CI? Looks like a number of XDP related tests
>> are failing on your patch which I'm not seeing on other patches where runs
>> are green, for example test_progs on several archs report the below:
>>
>> https://github.com/kernel-patches/bpf/actions/runs/4164593416/jobs/7207290499
>>
>> [...]
>> test_xdp_do_redirect:PASS:prog_run 0 nsec
>> test_xdp_do_redirect:PASS:pkt_count_xdp 0 nsec
>> test_xdp_do_redirect:PASS:pkt_count_zero 0 nsec
>> test_xdp_do_redirect:PASS:pkt_count_tc 0 nsec
>> test_max_pkt_size:PASS:prog_run_max_size 0 nsec
>> test_max_pkt_size:FAIL:prog_run_too_big unexpected prog_run_too_big:
>> actual -28 != expected -22
>> close_netns:PASS:setns 0 nsec
>> #275 xdp_do_redirect:FAIL
>> Summary: 273/1581 PASSED, 21 SKIPPED, 2 FAILED
> Ah I see. xdp_do_redirect.c test defines:
>
> /* The maximum permissible size is: PAGE_SIZE -
> * sizeof(struct xdp_page_head) - sizeof(struct skb_shared_info) -
> * XDP_PACKET_HEADROOM = 3368 bytes
> */
> #define MAX_PKT_SIZE 3368
>
> This needs to be updated as it now became bigger. The test checks that
> this size passes and size + 1 fails, but now it doesn't.
> Will send v3 in a couple minutes.
Problem :s
This 3368/3408 assumes %L1_CACHE_BYTES is 64 and we're running on a
64-bit arch. For 32 bits the value will be bigger, also for cachelines
bigger than 64 it will be smaller (skb_shared_info has to be aligned).
Given that selftests are generic / arch-independent, how to approach
this? I added a static_assert() to test_run.c to make sure this value
is in sync to not run into the same problem in future, but then realized
it will fail on a number of architectures.
My first thought was to hardcode the worst-case value (64 bit, cacheline
is 128) in test_run.c for every architecture, but there might be more
elegant ways.
>
> Thanks,
> Olek
Thanks,
Olek
Alexander Lobakin <[email protected]> writes:
> From: Alexander Lobakin <[email protected]>
> Date: Tue, 14 Feb 2023 16:39:25 +0100
>
>> From: Daniel Borkmann <[email protected]>
>> Date: Tue, 14 Feb 2023 16:24:10 +0100
>>
>>> On 2/13/23 3:27 PM, Alexander Lobakin wrote:
>
> [...]
>
>>>> Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in
>>>> BPF_PROG_RUN")
>>>> Signed-off-by: Alexander Lobakin <[email protected]>
>>>
>>> Could you double check BPF CI? Looks like a number of XDP related tests
>>> are failing on your patch which I'm not seeing on other patches where runs
>>> are green, for example test_progs on several archs report the below:
>>>
>>> https://github.com/kernel-patches/bpf/actions/runs/4164593416/jobs/7207290499
>>>
>>> [...]
>>> test_xdp_do_redirect:PASS:prog_run 0 nsec
>>> test_xdp_do_redirect:PASS:pkt_count_xdp 0 nsec
>>> test_xdp_do_redirect:PASS:pkt_count_zero 0 nsec
>>> test_xdp_do_redirect:PASS:pkt_count_tc 0 nsec
>>> test_max_pkt_size:PASS:prog_run_max_size 0 nsec
>>> test_max_pkt_size:FAIL:prog_run_too_big unexpected prog_run_too_big:
>>> actual -28 != expected -22
>>> close_netns:PASS:setns 0 nsec
>>> #275 xdp_do_redirect:FAIL
>>> Summary: 273/1581 PASSED, 21 SKIPPED, 2 FAILED
>> Ah I see. xdp_do_redirect.c test defines:
>>
>> /* The maximum permissible size is: PAGE_SIZE -
>> * sizeof(struct xdp_page_head) - sizeof(struct skb_shared_info) -
>> * XDP_PACKET_HEADROOM = 3368 bytes
>> */
>> #define MAX_PKT_SIZE 3368
>>
>> This needs to be updated as it now became bigger. The test checks that
>> this size passes and size + 1 fails, but now it doesn't.
>> Will send v3 in a couple minutes.
>
> Problem :s
>
> This 3368/3408 assumes %L1_CACHE_BYTES is 64 and we're running on a
> 64-bit arch. For 32 bits the value will be bigger, also for cachelines
> bigger than 64 it will be smaller (skb_shared_info has to be aligned).
> Given that selftests are generic / arch-independent, how to approach
> this? I added a static_assert() to test_run.c to make sure this value
> is in sync to not run into the same problem in future, but then realized
> it will fail on a number of architectures.
>
> My first thought was to hardcode the worst-case value (64 bit, cacheline
> is 128) in test_run.c for every architecture, but there might be more
> elegant ways.
The 32/64 bit split should be straight-forward to handle for the head;
an xdp_buff is 6*sizeof(void)+8 bytes long, and xdp_page_head is just
two of those after this patch. The skb_shared_info size is a bit harder;
do we have the alignment / size macros available to userspace somewhere?
Hmm, the selftests generate a vmlinux.h file which would have the
structure definitions; maybe something could be generated from that? Not
straight-forward to include it in a userspace application, though.
Otherwise, does anyone run the selftests on architectures that don't
have a 64-byte cache-line size? Or even on 32-bit arches? We don't
handle larger page sizes either...
-Toke
From: Toke Høiland-Jørgensen <[email protected]>
Date: Tue, 14 Feb 2023 22:05:26 +0100
> Alexander Lobakin <[email protected]> writes:
>
>> From: Alexander Lobakin <[email protected]>
>> Date: Tue, 14 Feb 2023 16:39:25 +0100
>>
>>> From: Daniel Borkmann <[email protected]>
>>> Date: Tue, 14 Feb 2023 16:24:10 +0100
>>>
>>>> On 2/13/23 3:27 PM, Alexander Lobakin wrote:
>>
>> [...]
>>
>>>>> Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in
>>>>> BPF_PROG_RUN")
>>>>> Signed-off-by: Alexander Lobakin <[email protected]>
>>>>
>>>> Could you double check BPF CI? Looks like a number of XDP related tests
>>>> are failing on your patch which I'm not seeing on other patches where runs
>>>> are green, for example test_progs on several archs report the below:
>>>>
>>>> https://github.com/kernel-patches/bpf/actions/runs/4164593416/jobs/7207290499
>>>>
>>>> [...]
>>>> test_xdp_do_redirect:PASS:prog_run 0 nsec
>>>> test_xdp_do_redirect:PASS:pkt_count_xdp 0 nsec
>>>> test_xdp_do_redirect:PASS:pkt_count_zero 0 nsec
>>>> test_xdp_do_redirect:PASS:pkt_count_tc 0 nsec
>>>> test_max_pkt_size:PASS:prog_run_max_size 0 nsec
>>>> test_max_pkt_size:FAIL:prog_run_too_big unexpected prog_run_too_big:
>>>> actual -28 != expected -22
>>>> close_netns:PASS:setns 0 nsec
>>>> #275 xdp_do_redirect:FAIL
>>>> Summary: 273/1581 PASSED, 21 SKIPPED, 2 FAILED
>>> Ah I see. xdp_do_redirect.c test defines:
>>>
>>> /* The maximum permissible size is: PAGE_SIZE -
>>> * sizeof(struct xdp_page_head) - sizeof(struct skb_shared_info) -
>>> * XDP_PACKET_HEADROOM = 3368 bytes
>>> */
>>> #define MAX_PKT_SIZE 3368
>>>
>>> This needs to be updated as it now became bigger. The test checks that
>>> this size passes and size + 1 fails, but now it doesn't.
>>> Will send v3 in a couple minutes.
>>
>> Problem :s
>>
>> This 3368/3408 assumes %L1_CACHE_BYTES is 64 and we're running on a
>> 64-bit arch. For 32 bits the value will be bigger, also for cachelines
>> bigger than 64 it will be smaller (skb_shared_info has to be aligned).
>> Given that selftests are generic / arch-independent, how to approach
>> this? I added a static_assert() to test_run.c to make sure this value
>> is in sync to not run into the same problem in future, but then realized
>> it will fail on a number of architectures.
>>
>> My first thought was to hardcode the worst-case value (64 bit, cacheline
>> is 128) in test_run.c for every architecture, but there might be more
>> elegant ways.
>
> The 32/64 bit split should be straight-forward to handle for the head;
> an xdp_buff is 6*sizeof(void)+8 bytes long, and xdp_page_head is just
> two of those after this patch. The skb_shared_info size is a bit harder;
> do we have the alignment / size macros available to userspace somewhere?
>
> Hmm, the selftests generate a vmlinux.h file which would have the
> structure definitions; maybe something could be generated from that? Not
> straight-forward to include it in a userspace application, though.
>
> Otherwise, does anyone run the selftests on architectures that don't
> have a 64-byte cache-line size? Or even on 32-bit arches? We don't
> handle larger page sizes either...
I believe nobody does that :D Everyone just use x86_64 and ARM64 with 4k
pages.
I think for this particular patch we can just change 3368 to 3408
without trying to assert it in the kernel code. And later I'll
brainstorm this :D
>
> -Toke
>
Thanks,
Olek