tools/testing/selftests/rseq/rseq.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-)
Adding the aligned(1024) attribute to the definition of __rseq_abi did
not increase its size to 1024, for this attribute to impact the size of
__rseq_abi it would need to be added to the declaration of 'struct
rseq_abi'. We only want to increase the size of the TLS allocation to
ensure registration will succeed with future extended ABI. Use a union
with a dummy member to ensure we allocate 1024 bytes.
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
tools/testing/selftests/rseq/rseq.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
index f6156790c3b4..aa9ae866bc1a 100644
--- a/tools/testing/selftests/rseq/rseq.c
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -71,9 +71,20 @@ static int rseq_ownership;
/* Original struct rseq allocation size is 32 bytes. */
#define ORIG_RSEQ_ALLOC_SIZE 32
+/*
+ * Use a union to ensure we allocate a TLS area of 1024 bytes to accomodate an
+ * rseq registration that is larger than the current rseq ABI.
+ */
+union rseq {
+ struct rseq_abi abi;
+ char dummy[RSEQ_THREAD_AREA_ALLOC_SIZE];
+};
+
static
-__thread struct rseq_abi __rseq_abi __attribute__((tls_model("initial-exec"), aligned(RSEQ_THREAD_AREA_ALLOC_SIZE))) = {
- .cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED,
+__thread union rseq __rseq __attribute__((tls_model("initial-exec"))) = {
+ .abi = {
+ .cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED,
+ },
};
static int sys_rseq(struct rseq_abi *rseq_abi, uint32_t rseq_len,
@@ -149,7 +160,7 @@ int rseq_register_current_thread(void)
/* Treat libc's ownership as a successful registration. */
return 0;
}
- rc = sys_rseq(&__rseq_abi, get_rseq_min_alloc_size(), 0, RSEQ_SIG);
+ rc = sys_rseq(&__rseq.abi, get_rseq_min_alloc_size(), 0, RSEQ_SIG);
if (rc) {
/*
* After at least one thread has registered successfully
@@ -183,7 +194,7 @@ int rseq_unregister_current_thread(void)
/* Treat libc's ownership as a successful unregistration. */
return 0;
}
- rc = sys_rseq(&__rseq_abi, get_rseq_min_alloc_size(), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
+ rc = sys_rseq(&__rseq.abi, get_rseq_min_alloc_size(), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
if (rc)
return -1;
return 0;
@@ -249,7 +260,7 @@ void rseq_init(void)
rseq_ownership = 1;
/* Calculate the offset of the rseq area from the thread pointer. */
- rseq_offset = (void *)&__rseq_abi - rseq_thread_pointer();
+ rseq_offset = (void *)&__rseq.abi - rseq_thread_pointer();
/* rseq flags are deprecated, always set to 0. */
rseq_flags = 0;
--
2.43.0On Tue, Mar 11, 2025 at 03:21:45PM -0400, Michael Jeanson wrote:
> Adding the aligned(1024) attribute to the definition of __rseq_abi did
> not increase its size to 1024, for this attribute to impact the size of
> __rseq_abi it would need to be added to the declaration of 'struct
> rseq_abi'. We only want to increase the size of the TLS allocation to
> ensure registration will succeed with future extended ABI. Use a union
> with a dummy member to ensure we allocate 1024 bytes.
This is in today's -next and breaks the build of the KVM selftests:
In file included from rseq_test.c:24:
/home/broonie/git/bisect/usr/include/linux/rseq.h:62:1: error: use of 'rseq' with tag type that does not match previous declaration
62 | struct rseq {
| ^
./../rseq/rseq.c:78:7: note: previous use is here
78 | union rseq {
| ^
In file included from rseq_test.c:24:
/home/broonie/git/bisect/usr/include/linux/rseq.h:62:8: error: redefinition of 'rseq'
62 | struct rseq {
| ^
./../rseq/rseq.c:78:7: note: previous definition is here
78 | union rseq {
| ^
since unlike the rseq tests the KVM rseq test includes the UAPI header
for rseq which the padded union conflicts with.
On 2025-03-18 10:01, Mark Brown wrote:
> On Tue, Mar 11, 2025 at 03:21:45PM -0400, Michael Jeanson wrote:
>
>> Adding the aligned(1024) attribute to the definition of __rseq_abi did
>> not increase its size to 1024, for this attribute to impact the size of
>> __rseq_abi it would need to be added to the declaration of 'struct
>> rseq_abi'. We only want to increase the size of the TLS allocation to
>> ensure registration will succeed with future extended ABI. Use a union
>> with a dummy member to ensure we allocate 1024 bytes.
>
> This is in today's -next and breaks the build of the KVM selftests:
>
> In file included from rseq_test.c:24:
> /home/broonie/git/bisect/usr/include/linux/rseq.h:62:1: error: use of 'rseq' with tag type that does not match previous declaration
> 62 | struct rseq {
> | ^
> ./../rseq/rseq.c:78:7: note: previous use is here
> 78 | union rseq {
> | ^
> In file included from rseq_test.c:24:
> /home/broonie/git/bisect/usr/include/linux/rseq.h:62:8: error: redefinition of 'rseq'
> 62 | struct rseq {
> | ^
> ./../rseq/rseq.c:78:7: note: previous definition is here
> 78 | union rseq {
> | ^
>
> since unlike the rseq tests the KVM rseq test includes the UAPI header
> for rseq which the padded union conflicts with.
Oh, I missed that, we need a more unique name for the union.
I'm unfamiliar with the workflow of linux-next, should I send a V2 of
the current patch, or a new one that applies on top?
Thanks,
Michael
On Tue, Mar 18, 2025 at 10:50:58AM -0400, Michael Jeanson wrote: > On 2025-03-18 10:01, Mark Brown wrote: > > On Tue, Mar 11, 2025 at 03:21:45PM -0400, Michael Jeanson wrote: > > > > > Adding the aligned(1024) attribute to the definition of __rseq_abi did > > > not increase its size to 1024, for this attribute to impact the size of > > > __rseq_abi it would need to be added to the declaration of 'struct > > > rseq_abi'. We only want to increase the size of the TLS allocation to > > > ensure registration will succeed with future extended ABI. Use a union > > > with a dummy member to ensure we allocate 1024 bytes. > > This is in today's -next and breaks the build of the KVM selftests: ... > > since unlike the rseq tests the KVM rseq test includes the UAPI header > > for rseq which the padded union conflicts with. > Oh, I missed that, we need a more unique name for the union. > I'm unfamiliar with the workflow of linux-next, should I send a V2 of the > current patch, or a new one that applies on top? It depends on the tree that the patch was applied to - -next merges the current stat of the maintainer trees daily rather than applying anything itself. In this case that's -tip, I think incremental is good for them but ICBW?
The following commit has been merged into the sched/core branch of tip:
Commit-ID: e6644c967d3c076969336bd8a9b85ffb45f677f7
Gitweb: https://git.kernel.org/tip/e6644c967d3c076969336bd8a9b85ffb45f677f7
Author: Michael Jeanson <mjeanson@efficios.com>
AuthorDate: Tue, 11 Mar 2025 15:21:45 -04:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 12 Mar 2025 13:19:47 +01:00
rseq/selftests: Ensure the rseq ABI TLS is actually 1024 bytes
Adding the aligned(1024) attribute to the definition of __rseq_abi did
not increase its size to 1024, for this attribute to impact the size of
__rseq_abi it would need to be added to the declaration of 'struct
rseq_abi'. We only want to increase the size of the TLS allocation to
ensure registration will succeed with future extended ABI. Use a union
with a dummy member to ensure we allocate 1024 bytes.
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/r/20250311192222.323453-1-mjeanson@efficios.com
---
tools/testing/selftests/rseq/rseq.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
index 1e29db9..6d8997d 100644
--- a/tools/testing/selftests/rseq/rseq.c
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -71,9 +71,20 @@ static int rseq_ownership;
/* Original struct rseq allocation size is 32 bytes. */
#define ORIG_RSEQ_ALLOC_SIZE 32
+/*
+ * Use a union to ensure we allocate a TLS area of 1024 bytes to accomodate an
+ * rseq registration that is larger than the current rseq ABI.
+ */
+union rseq {
+ struct rseq_abi abi;
+ char dummy[RSEQ_THREAD_AREA_ALLOC_SIZE];
+};
+
static
-__thread struct rseq_abi __rseq_abi __attribute__((tls_model("initial-exec"), aligned(RSEQ_THREAD_AREA_ALLOC_SIZE))) = {
- .cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED,
+__thread union rseq __rseq __attribute__((tls_model("initial-exec"))) = {
+ .abi = {
+ .cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED,
+ },
};
static int sys_rseq(struct rseq_abi *rseq_abi, uint32_t rseq_len,
@@ -149,7 +160,7 @@ int rseq_register_current_thread(void)
/* Treat libc's ownership as a successful registration. */
return 0;
}
- rc = sys_rseq(&__rseq_abi, get_rseq_min_alloc_size(), 0, RSEQ_SIG);
+ rc = sys_rseq(&__rseq.abi, get_rseq_min_alloc_size(), 0, RSEQ_SIG);
if (rc) {
/*
* After at least one thread has registered successfully
@@ -183,7 +194,7 @@ int rseq_unregister_current_thread(void)
/* Treat libc's ownership as a successful unregistration. */
return 0;
}
- rc = sys_rseq(&__rseq_abi, get_rseq_min_alloc_size(), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
+ rc = sys_rseq(&__rseq.abi, get_rseq_min_alloc_size(), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
if (rc)
return -1;
return 0;
@@ -249,7 +260,7 @@ void rseq_init(void)
rseq_ownership = 1;
/* Calculate the offset of the rseq area from the thread pointer. */
- rseq_offset = (void *)&__rseq_abi - rseq_thread_pointer();
+ rseq_offset = (void *)&__rseq.abi - rseq_thread_pointer();
/* rseq flags are deprecated, always set to 0. */
rseq_flags = 0;© 2016 - 2025 Red Hat, Inc.