diff options
author | Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | 2019-04-29 18:27:55 +0300 |
---|---|---|
committer | Shuah Khan <skhan@linuxfoundation.org> | 2019-05-08 00:31:46 +0300 |
commit | 5b0c308a0565a94d2e1070cbf287197b676faaaf (patch) | |
tree | ea40e240db1dd0b3f0d3761ceffbe9a47dd76769 /tools/testing/selftests/rseq/rseq.c | |
parent | a3e3131f94aa1daeb978ed66d0b4e61156ef2c2a (diff) | |
download | linux-5b0c308a0565a94d2e1070cbf287197b676faaaf.tar.xz |
rseq/selftests: Use __rseq_handled symbol to coexist with glibc
In order to integrate rseq into user-space applications, expose a
__rseq_handled symbol so many rseq users can be linked into the same
application (e.g. librseq and glibc).
The __rseq_refcount TLS variable is static to the librseq library. It
ensures that rseq syscall registration/unregistration happens only for
the most early/late caller to rseq_{,un}register_current_thread for each
thread, thus ensuring that rseq is registered across the lifetime of all
rseq users for a given thread.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Shuah Khan <shuah@kernel.org>
CC: Carlos O'Donell <carlos@redhat.com>
CC: Florian Weimer <fweimer@redhat.com>
CC: Joseph Myers <joseph@codesourcery.com>
CC: Szabolcs Nagy <szabolcs.nagy@arm.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ben Maurer <bmaurer@fb.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Dave Watson <davejwatson@fb.com>
CC: Paul Turner <pjt@google.com>
CC: linux-api@vger.kernel.org
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Diffstat (limited to 'tools/testing/selftests/rseq/rseq.c')
-rw-r--r-- | tools/testing/selftests/rseq/rseq.c | 55 |
1 files changed, 47 insertions, 8 deletions
diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c index 4847e97ed049..7159eb777fd3 100644 --- a/tools/testing/selftests/rseq/rseq.c +++ b/tools/testing/selftests/rseq/rseq.c @@ -25,18 +25,27 @@ #include <syscall.h> #include <assert.h> #include <signal.h> +#include <limits.h> #include "rseq.h" #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0])) -__attribute__((tls_model("initial-exec"))) __thread -volatile struct rseq __rseq_abi = { +__thread volatile struct rseq __rseq_abi = { .cpu_id = RSEQ_CPU_ID_UNINITIALIZED, }; -static __attribute__((tls_model("initial-exec"))) __thread -volatile int refcount; +/* + * Shared with other libraries. This library may take rseq ownership if it is + * still 0 when executing the library constructor. Set to 1 by library + * constructor when handling rseq. Set to 0 in destructor if handling rseq. + */ +int __rseq_handled; + +/* Whether this library have ownership of rseq registration. */ +static int rseq_ownership; + +static __thread volatile uint32_t __rseq_refcount; static void signal_off_save(sigset_t *oldset) { @@ -69,8 +78,14 @@ int rseq_register_current_thread(void) int rc, ret = 0; sigset_t oldset; + if (!rseq_ownership) + return 0; signal_off_save(&oldset); - if (refcount++) + if (__rseq_refcount == UINT_MAX) { + ret = -1; + goto end; + } + if (__rseq_refcount++) goto end; rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG); if (!rc) { @@ -78,9 +93,9 @@ int rseq_register_current_thread(void) goto end; } if (errno != EBUSY) - __rseq_abi.cpu_id = -2; + __rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED; ret = -1; - refcount--; + __rseq_refcount--; end: signal_restore(oldset); return ret; @@ -91,13 +106,20 @@ int rseq_unregister_current_thread(void) int rc, ret = 0; sigset_t oldset; + if (!rseq_ownership) + return 0; signal_off_save(&oldset); - if (--refcount) + if (!__rseq_refcount) { + ret = -1; + goto end; + } + if (--__rseq_refcount) goto end; rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), RSEQ_FLAG_UNREGISTER, RSEQ_SIG); if (!rc) goto end; + __rseq_refcount = 1; ret = -1; end: signal_restore(oldset); @@ -115,3 +137,20 @@ int32_t rseq_fallback_current_cpu(void) } return cpu; } + +void __attribute__((constructor)) rseq_init(void) +{ + /* Check whether rseq is handled by another library. */ + if (__rseq_handled) + return; + __rseq_handled = 1; + rseq_ownership = 1; +} + +void __attribute__((destructor)) rseq_fini(void) +{ + if (!rseq_ownership) + return; + __rseq_handled = 0; + rseq_ownership = 0; +} |