nptl: Introduce <rseq-access.h> for RSEQ_* accessors

In preparation to move the rseq area to the 'extra TLS' block, we need
accessors based on the thread pointer and the rseq offset. The ONCE
variant of the accessors ensures single-copy atomicity for loads and
stores which is required for all fields once the registration is active.

A separate header is required to allow including <atomic.h> which
results in an include loop when added to <tcb-access.h>.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
This commit is contained in:
Michael Jeanson 2024-08-01 10:35:34 -04:00
parent be440f6c38
commit 494d65129e
4 changed files with 239 additions and 0 deletions

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@ -0,0 +1,98 @@
/* RSEQ_* accessors. i386 version.
Copyright (C) 2002-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#define __RSEQ_GETMEM(member) \
({ __typeof (RSEQ_SELF()->member) __value; \
if (sizeof (__value) == 1) \
asm volatile ("movb %%gs:%P2(%3),%b0" \
: "=q" (__value) \
: "0" (0), "i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
else if (sizeof (__value) == 4) \
asm volatile ("movl %%gs:%P1(%2),%0" \
: "=r" (__value) \
: "i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
else /* 8 */ \
{ \
asm volatile ("movl %%gs:%P1(%2),%%eax\n\t" \
"movl %%gs:4+%P1(%2),%%edx" \
: "=&A" (__value) \
: "i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
} \
__value; })
/* Read member of the RSEQ area directly. */
#define RSEQ_GETMEM(member) \
({ \
_Static_assert (sizeof (RSEQ_SELF()->member) == 1 \
|| sizeof (RSEQ_SELF()->member) == 4 \
|| sizeof (RSEQ_SELF()->member) == 8, \
"size of rseq data"); \
__RSEQ_GETMEM(member); })
/* Read member of the RSEQ area directly, with single-copy atomicity semantics.
Static assert for types >= 64 bits since they can't be loaded atomically on
x86-32. */
#define RSEQ_GETMEM_ONCE(member) \
({ \
_Static_assert (sizeof (RSEQ_SELF()->member) == 1 \
|| sizeof (RSEQ_SELF()->member) == 4, \
"size of rseq data"); \
__RSEQ_GETMEM(member); })
#define __RSEQ_SETMEM(member, value) \
({ \
if (sizeof (RSEQ_SELF()->member) == 1) \
asm volatile ("movb %b0,%%gs:%P1(%2)" : \
: "iq" (value), \
"i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
else if (sizeof (RSEQ_SELF()->member) == 4) \
asm volatile ("movl %0,%%gs:%P1(%2)" : \
: "ir" (value), \
"i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
else /* 8 */ \
{ \
asm volatile ("movl %%eax,%%gs:%P1(%2)\n\t" \
"movl %%edx,%%gs:4+%P1(%2)" : \
: "A" ((uint64_t) cast_to_integer (value)), \
"i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
}})
/* Set member of the RSEQ area directly. */
#define RSEQ_SETMEM(member, value) \
({ \
_Static_assert (sizeof (RSEQ_SELF()->member) == 1 \
|| sizeof (RSEQ_SELF()->member) == 4 \
|| sizeof (RSEQ_SELF()->member) == 8, \
"size of rseq data"); \
__RSEQ_SETMEM(member, value); })
/* Set member of the RSEQ area directly, with single-copy atomicity semantics.
Static assert for types >= 64 bits since they can't be stored atomically on
x86-32. */
#define RSEQ_SETMEM_ONCE(member, value) \
({ \
_Static_assert (sizeof (RSEQ_SELF()->member) == 1 \
|| sizeof (RSEQ_SELF()->member) == 4, \
"size of rseq data"); \
__RSEQ_SETMEM(member, value); })

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@ -0,0 +1,56 @@
/* RSEQ_* accessors. Generic version.
Copyright (C) 2002-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <atomic.h>
/* Read member of the RSEQ area directly. */
#define RSEQ_GETMEM(member) \
RSEQ_SELF()->member
/* Set member of the RSEQ area directly. */
#define RSEQ_SETMEM(member, value) \
RSEQ_SELF()->member = (value)
/* Static assert for types that can't be loaded/stored atomically on the
current architecture. */
#if __HAVE_64B_ATOMICS
#define __RSEQ_ASSERT_ATOMIC(member) \
_Static_assert (sizeof (RSEQ_SELF()->member) == 1 \
|| sizeof (RSEQ_SELF()->member) == 4 \
|| sizeof (RSEQ_SELF()->member) == 8, \
"size of rseq data")
#else
#define __RSEQ_ASSERT_ATOMIC(member) \
_Static_assert (sizeof (RSEQ_SELF()->member) == 1 \
|| sizeof (RSEQ_SELF()->member) == 4, \
"size of rseq data")
#endif
/* Read member of the RSEQ area directly, with single-copy atomicity semantics. */
#define RSEQ_GETMEM_ONCE(member) \
({ \
__RSEQ_ASSERT_ATOMIC(member); \
(*(volatile __typeof (RSEQ_SELF()->member) *)&RSEQ_SELF()->member); \
})
/* Set member of the RSEQ area directly, with single-copy atomicity semantics. */
#define RSEQ_SETMEM_ONCE(member, value) \
({ \
__RSEQ_ASSERT_ATOMIC(member); \
(*(volatile __typeof (RSEQ_SELF()->member) *)&RSEQ_SELF()->member = (value)); \
})

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@ -25,6 +25,7 @@
#include <stdio.h>
#include <sys/rseq.h>
#include <ldsodefs.h>
#include <thread_pointer.h>
/* Minimum size of the rseq area allocation required by the syscall. The
actually used rseq feature size may be less (20 bytes initially). */
@ -59,6 +60,13 @@ extern ptrdiff_t _rseq_offset attribute_hidden;
rtld_hidden_proto (__rseq_size)
rtld_hidden_proto (__rseq_offset)
/* Returns a pointer to the current thread rseq area. */
static inline struct rseq_area *
RSEQ_SELF (void)
{
return (struct rseq_area *) ((char *) __thread_pointer () + __rseq_offset);
}
#ifdef RSEQ_SIG
static inline bool
rseq_register_current_thread (struct pthread *self, bool do_rseq)

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@ -0,0 +1,77 @@
/* RSEQ_* accessors. x86_64 version.
Copyright (C) 2002-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/* Read member of the RSEQ area directly, with single-copy atomicity semantics. */
#define RSEQ_GETMEM_ONCE(member) \
({ __typeof (RSEQ_SELF()->member) __value; \
_Static_assert (sizeof (__value) == 1 \
|| sizeof (__value) == 4 \
|| sizeof (__value) == 8, \
"size of rseq data"); \
if (sizeof (__value) == 1) \
asm volatile ("movb %%fs:%P2(%q3),%b0" \
: "=q" (__value) \
: "0" (0), "i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
else if (sizeof (__value) == 4) \
asm volatile ("movl %%fs:%P1(%q2),%0" \
: "=r" (__value) \
: "i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
else /* 8 */ \
{ \
asm volatile ("movq %%fs:%P1(%q2),%q0" \
: "=r" (__value) \
: "i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
} \
__value; })
/* Read member of the RSEQ area directly. */
#define RSEQ_GETMEM(member) RSEQ_GETMEM_ONCE(member)
/* Set member of the RSEQ area directly, with single-copy atomicity semantics. */
#define RSEQ_SETMEM_ONCE(member, value) \
({ \
_Static_assert (sizeof (RSEQ_SELF()->member) == 1 \
|| sizeof (RSEQ_SELF()->member) == 4 \
|| sizeof (RSEQ_SELF()->member) == 8, \
"size of rseq data"); \
if (sizeof (RSEQ_SELF()->member) == 1) \
asm volatile ("movb %b0,%%fs:%P1(%q2)" : \
: "iq" (value), \
"i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
else if (sizeof (RSEQ_SELF()->member) == 4) \
asm volatile ("movl %0,%%fs:%P1(%q2)" : \
: IMM_MODE (value), \
"i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
else /* 8 */ \
{ \
/* Since movq takes a signed 32-bit immediate or a register source \
operand, use "er" constraint for 32-bit signed integer constant \
or register. */ \
asm volatile ("movq %q0,%%fs:%P1(%q2)" : \
: "er" ((uint64_t) cast_to_integer (value)), \
"i" (offsetof (struct rseq_area, member)), \
"r" (__rseq_offset)); \
}})
/* Set member of the RSEQ area directly. */
#define RSEQ_SETMEM(member, value) RSEQ_SETMEM_ONCE(member, value)