Commit 03f5c027 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Peter Zijlstra
Browse files

selftests/rseq: Use ELF auxiliary vector for extensible rseq 



Use the ELF auxiliary vector AT_RSEQ_FEATURE_SIZE to detect the RSEQ
features supported by the kernel.

Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221122203932.231377-6-mathieu.desnoyers@efficios.com
parent cbae6bac

tools/testing/selftests/rseq/rseq-abi.h

+5 −0
Original line number Diff line number Diff line
@@ -146,6 +146,11 @@ struct rseq_abi { 
	 *     this thread.

	 */

	__u32 flags;



	/*

	 * Flexible array member at end of structure, after last feature field.

	 */

	char end[];

} __attribute__((aligned(4 * sizeof(__u64))));



#endif /* _RSEQ_ABI_H */

tools/testing/selftests/rseq/rseq.c

+59 −8
Original line number Diff line number Diff line
@@ -28,6 +28,8 @@ 
#include <limits.h>

#include <dlfcn.h>

#include <stddef.h>

#include <sys/auxv.h>

#include <linux/auxvec.h>



#include "../kselftest.h"

#include "rseq.h"
@@ -39,17 +41,35 @@ static const unsigned int *libc_rseq_flags_p; 
/* Offset from the thread pointer to the rseq area. */

ptrdiff_t rseq_offset;



/* Size of the registered rseq area.  0 if the registration was

   unsuccessful.  */

/*

 * Size of the registered rseq area. 0 if the registration was

 * unsuccessful.

 */

unsigned int rseq_size = -1U;



/* Flags used during rseq registration.  */

unsigned int rseq_flags;



/*

 * rseq feature size supported by the kernel. 0 if the registration was

 * unsuccessful.

 */

unsigned int rseq_feature_size = -1U;



static int rseq_ownership;

static int rseq_reg_success;	/* At least one rseq registration has succeded. */



/* Allocate a large area for the TLS. */

#define RSEQ_THREAD_AREA_ALLOC_SIZE	1024



/* Original struct rseq feature size is 20 bytes. */

#define ORIG_RSEQ_FEATURE_SIZE		20



/* Original struct rseq allocation size is 32 bytes. */

#define ORIG_RSEQ_ALLOC_SIZE		32



static

__thread struct rseq_abi __rseq_abi __attribute__((tls_model("initial-exec"))) = {

__thread struct rseq_abi __rseq_abi __attribute__((tls_model("initial-exec"), aligned(RSEQ_THREAD_AREA_ALLOC_SIZE))) = {

	.cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED,

};
@@ -84,10 +104,16 @@ int rseq_register_current_thread(void) 
		/* Treat libc's ownership as a successful registration. */

		return 0;

	}

	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), 0, RSEQ_SIG);

	if (rc)

	rc = sys_rseq(&__rseq_abi, rseq_size, 0, RSEQ_SIG);

	if (rc) {

		if (RSEQ_READ_ONCE(rseq_reg_success)) {

			/* Incoherent success/failure within process. */

			abort();

		}

		return -1;

	}

	assert(rseq_current_cpu_raw() >= 0);

	RSEQ_WRITE_ONCE(rseq_reg_success, 1);

	return 0;

}
@@ -99,12 +125,28 @@ int rseq_unregister_current_thread(void) 
		/* Treat libc's ownership as a successful unregistration. */

		return 0;

	}

	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);

	rc = sys_rseq(&__rseq_abi, rseq_size, RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);

	if (rc)

		return -1;

	return 0;

}



static

unsigned int get_rseq_feature_size(void)

{

	unsigned long auxv_rseq_feature_size, auxv_rseq_align;



	auxv_rseq_align = getauxval(AT_RSEQ_ALIGN);

	assert(!auxv_rseq_align || auxv_rseq_align <= RSEQ_THREAD_AREA_ALLOC_SIZE);



	auxv_rseq_feature_size = getauxval(AT_RSEQ_FEATURE_SIZE);

	assert(!auxv_rseq_feature_size || auxv_rseq_feature_size <= RSEQ_THREAD_AREA_ALLOC_SIZE);

	if (auxv_rseq_feature_size)

		return auxv_rseq_feature_size;

	else

		return ORIG_RSEQ_FEATURE_SIZE;

}



static __attribute__((constructor))

void rseq_init(void)

{
@@ -117,16 +159,24 @@ void rseq_init(void) 
		rseq_offset = *libc_rseq_offset_p;

		rseq_size = *libc_rseq_size_p;

		rseq_flags = *libc_rseq_flags_p;

		rseq_feature_size = get_rseq_feature_size();

		if (rseq_feature_size > rseq_size)

			rseq_feature_size = rseq_size;

		return;

	}

	rseq_ownership = 1;

	if (!rseq_available()) {

		rseq_size = 0;

		rseq_feature_size = 0;

		return;

	}

	rseq_offset = (void *)&__rseq_abi - rseq_thread_pointer();

	rseq_size = sizeof(struct rseq_abi);

	rseq_flags = 0;

	rseq_feature_size = get_rseq_feature_size();

	if (rseq_feature_size == ORIG_RSEQ_FEATURE_SIZE)

		rseq_size = ORIG_RSEQ_ALLOC_SIZE;

	else

		rseq_size = RSEQ_THREAD_AREA_ALLOC_SIZE;

}



static __attribute__((destructor))
@@ -136,6 +186,7 @@ void rseq_exit(void) 
		return;

	rseq_offset = 0;

	rseq_size = -1U;

	rseq_feature_size = -1U;

	rseq_ownership = 0;

}

tools/testing/selftests/rseq/rseq.h

+14 −4
Original line number Diff line number Diff line
@@ -49,12 +49,22 @@ 


/* Offset from the thread pointer to the rseq area. */

extern ptrdiff_t rseq_offset;

/* Size of the registered rseq area.  0 if the registration was

   unsuccessful.  */



/*

 * Size of the registered rseq area. 0 if the registration was

 * unsuccessful.

 */

extern unsigned int rseq_size;



/* Flags used during rseq registration. */

extern unsigned int rseq_flags;



/*

 * rseq feature size supported by the kernel. 0 if the registration was

 * unsuccessful.

 */

extern unsigned int rseq_feature_size;



static inline struct rseq_abi *rseq_get_abi(void)

{

	return (struct rseq_abi *) ((uintptr_t) rseq_thread_pointer() + rseq_offset);