Commit e6644c96 authored by Michael Jeanson's avatar Michael Jeanson Committed by Ingo Molnar
Browse files

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: default avatarMichael Jeanson <mjeanson@efficios.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/r/20250311192222.323453-1-mjeanson@efficios.com
parent fd881d0a

tools/testing/selftests/rseq/rseq.c

+16 −5
Original line number Diff line number Diff line
@@ -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))) = {

__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;