rseq: Introduce extensible rseq ABI
Introduce the extensible rseq ABI, where the feature size supported by the kernel and the required alignment are communicated to user-space through ELF auxiliary vectors. This allows user-space to call rseq registration with a rseq_len of either 32 bytes for the original struct rseq size (which includes padding), or larger. If rseq_len is larger than 32 bytes, then it must be large enough to contain the feature size communicated to user-space through ELF auxiliary vectors. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20221122203932.231377-4-mathieu.desnoyers@efficios.com
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@ -1302,6 +1302,7 @@ struct task_struct {
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#ifdef CONFIG_RSEQ
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struct rseq __user *rseq;
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u32 rseq_len;
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u32 rseq_sig;
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/*
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* RmW on rseq_event_mask must be performed atomically
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@ -2352,10 +2353,12 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags)
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{
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if (clone_flags & CLONE_VM) {
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t->rseq = NULL;
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t->rseq_len = 0;
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t->rseq_sig = 0;
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t->rseq_event_mask = 0;
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} else {
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t->rseq = current->rseq;
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t->rseq_len = current->rseq_len;
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t->rseq_sig = current->rseq_sig;
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t->rseq_event_mask = current->rseq_event_mask;
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}
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@ -2364,6 +2367,7 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags)
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static inline void rseq_execve(struct task_struct *t)
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{
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t->rseq = NULL;
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t->rseq_len = 0;
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t->rseq_sig = 0;
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t->rseq_event_mask = 0;
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}
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@ -813,7 +813,7 @@ static long ptrace_get_rseq_configuration(struct task_struct *task,
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{
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struct ptrace_rseq_configuration conf = {
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.rseq_abi_pointer = (u64)(uintptr_t)task->rseq,
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.rseq_abi_size = sizeof(*task->rseq),
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.rseq_abi_size = task->rseq_len,
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.signature = task->rseq_sig,
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.flags = 0,
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};
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@ -18,6 +18,9 @@
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#define CREATE_TRACE_POINTS
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#include <trace/events/rseq.h>
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/* The original rseq structure size (including padding) is 32 bytes. */
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#define ORIG_RSEQ_SIZE 32
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#define RSEQ_CS_NO_RESTART_FLAGS (RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT | \
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RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL | \
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RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE)
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@ -87,10 +90,15 @@ static int rseq_update_cpu_id(struct task_struct *t)
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u32 cpu_id = raw_smp_processor_id();
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struct rseq __user *rseq = t->rseq;
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if (!user_write_access_begin(rseq, sizeof(*rseq)))
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if (!user_write_access_begin(rseq, t->rseq_len))
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goto efault;
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unsafe_put_user(cpu_id, &rseq->cpu_id_start, efault_end);
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unsafe_put_user(cpu_id, &rseq->cpu_id, efault_end);
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/*
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* Additional feature fields added after ORIG_RSEQ_SIZE
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* need to be conditionally updated only if
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* t->rseq_len != ORIG_RSEQ_SIZE.
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*/
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user_write_access_end();
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trace_rseq_update(t);
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return 0;
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@ -117,6 +125,11 @@ static int rseq_reset_rseq_cpu_id(struct task_struct *t)
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*/
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if (put_user(cpu_id, &t->rseq->cpu_id))
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return -EFAULT;
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/*
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* Additional feature fields added after ORIG_RSEQ_SIZE
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* need to be conditionally reset only if
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* t->rseq_len != ORIG_RSEQ_SIZE.
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*/
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return 0;
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}
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@ -344,7 +357,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
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/* Unregister rseq for current thread. */
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if (current->rseq != rseq || !current->rseq)
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return -EINVAL;
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if (rseq_len != sizeof(*rseq))
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if (rseq_len != current->rseq_len)
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return -EINVAL;
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if (current->rseq_sig != sig)
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return -EPERM;
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@ -353,6 +366,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
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return ret;
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current->rseq = NULL;
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current->rseq_sig = 0;
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current->rseq_len = 0;
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return 0;
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}
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@ -365,7 +379,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
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* the provided address differs from the prior
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* one.
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*/
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if (current->rseq != rseq || rseq_len != sizeof(*rseq))
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if (current->rseq != rseq || rseq_len != current->rseq_len)
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return -EINVAL;
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if (current->rseq_sig != sig)
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return -EPERM;
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@ -374,15 +388,24 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
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}
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/*
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* If there was no rseq previously registered,
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* ensure the provided rseq is properly aligned and valid.
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* If there was no rseq previously registered, ensure the provided rseq
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* is properly aligned, as communcated to user-space through the ELF
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* auxiliary vector AT_RSEQ_ALIGN. If rseq_len is the original rseq
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* size, the required alignment is the original struct rseq alignment.
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*
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* In order to be valid, rseq_len is either the original rseq size, or
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* large enough to contain all supported fields, as communicated to
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* user-space through the ELF auxiliary vector AT_RSEQ_FEATURE_SIZE.
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*/
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if (!IS_ALIGNED((unsigned long)rseq, __alignof__(*rseq)) ||
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rseq_len != sizeof(*rseq))
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if (rseq_len < ORIG_RSEQ_SIZE ||
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(rseq_len == ORIG_RSEQ_SIZE && !IS_ALIGNED((unsigned long)rseq, ORIG_RSEQ_SIZE)) ||
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(rseq_len != ORIG_RSEQ_SIZE && (!IS_ALIGNED((unsigned long)rseq, __alignof__(*rseq)) ||
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rseq_len < offsetof(struct rseq, end))))
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return -EINVAL;
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if (!access_ok(rseq, rseq_len))
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return -EFAULT;
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current->rseq = rseq;
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current->rseq_len = rseq_len;
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current->rseq_sig = sig;
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/*
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* If rseq was previously inactive, and has just been
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