Use the ELF auxiliary vector AT_RSEQ_FEATURE_SIZE to detect the RSEQ features supported by the kernel. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> --- tools/testing/selftests/rseq/rseq-abi.h | 5 ++ tools/testing/selftests/rseq/rseq.c | 68 ++++++++++++++++++++++--- tools/testing/selftests/rseq/rseq.h | 18 +++++-- 3 files changed, 79 insertions(+), 12 deletions(-) diff --git a/tools/testing/selftests/rseq/rseq-abi.h b/tools/testing/selftests/rseq/rseq-abi.h index a8c44d9af71f..00ac846d85b0 100644 --- a/tools/testing/selftests/rseq/rseq-abi.h +++ b/tools/testing/selftests/rseq/rseq-abi.h @@ -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 */ diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c index 986b9458efb2..20ea536d1012 100644 --- a/tools/testing/selftests/rseq/rseq.c +++ b/tools/testing/selftests/rseq/rseq.c @@ -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" @@ -36,20 +38,38 @@ static const ptrdiff_t *libc_rseq_offset_p; static const unsigned int *libc_rseq_size_p; static const unsigned int *libc_rseq_flags_p; -/* Offset from the thread pointer to the rseq area. */ +/* 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 + +/* Orignal 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 +104,18 @@ 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(); + } + rseq_size = 0; + rseq_feature_size = 0; return -1; + } assert(rseq_current_cpu_raw() >= 0); + RSEQ_WRITE_ONCE(rseq_reg_success, 1); return 0; } @@ -99,12 +127,28 @@ 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) { @@ -116,14 +160,21 @@ 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; } if (!rseq_available()) return; rseq_ownership = 1; 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)) @@ -133,6 +184,7 @@ void rseq_exit(void) return; rseq_offset = 0; rseq_size = -1U; + rseq_feature_size = -1U; rseq_ownership = 0; } diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h index 6f7513384bf5..95adc1e1b0db 100644 --- a/tools/testing/selftests/rseq/rseq.h +++ b/tools/testing/selftests/rseq/rseq.h @@ -47,14 +47,24 @@ #include "rseq-thread-pointer.h" -/* Offset from the thread pointer to the rseq area. */ +/* 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. */ + +/* 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); -- 2.17.1