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rseq/selftests: Ensure the rseq ABI TLS is actually 1024 bytes

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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
This commit is contained in:
Michael Jeanson 2025-03-11 15:21:45 -04:00 committed by Ingo Molnar
parent fd881d0a08
commit e6644c967d
1 changed files with 16 additions and 5 deletions
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21
tools/testing/selftests/rseq/rseq.c
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@ -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;