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/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
* rseq-arm.h
*
* (C) Copyright 2016-2022 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*/
/*
* - ARM little endian
*
* RSEQ_SIG uses the udf A32 instruction with an uncommon immediate operand
* value 0x5de3. This traps if user-space reaches this instruction by mistake,
* and the uncommon operand ensures the kernel does not move the instruction
* pointer to attacker-controlled code on rseq abort.
*
* The instruction pattern in the A32 instruction set is:
*
* e7f5def3 udf #24035 ; 0x5de3
*
* This translates to the following instruction pattern in the T16 instruction
* set:
*
* little endian:
* def3 udf #243 ; 0xf3
* e7f5 b.n <7f5>
*
* - ARMv6+ big endian (BE8):
*
* ARMv6+ -mbig-endian generates mixed endianness code vs data: little-endian
* code and big-endian data. The data value of the signature needs to have its
* byte order reversed to generate the trap instruction:
*
* Data: 0xf3def5e7
*
* Translates to this A32 instruction pattern:
*
* e7f5def3 udf #24035 ; 0x5de3
*
* Translates to this T16 instruction pattern:
*
* def3 udf #243 ; 0xf3
* e7f5 b.n <7f5>
*
* - Prior to ARMv6 big endian (BE32):
*
* Prior to ARMv6, -mbig-endian generates big-endian code and data
* (which match), so the endianness of the data representation of the
* signature should not be reversed. However, the choice between BE32
* and BE8 is done by the linker, so we cannot know whether code and
* data endianness will be mixed before the linker is invoked. So rather
* than try to play tricks with the linker, the rseq signature is simply
* data (not a trap instruction) prior to ARMv6 on big endian. This is
* why the signature is expressed as data (.word) rather than as
* instruction (.inst) in assembler.
*/
#ifdef __ARMEB__
#define RSEQ_SIG 0xf3def5e7 /* udf #24035 ; 0x5de3 (ARMv6+) */
#else
#define RSEQ_SIG 0xe7f5def3 /* udf #24035 ; 0x5de3 */
#endif
#define rseq_smp_mb() __asm__ __volatile__ ("dmb" ::: "memory", "cc")
#define rseq_smp_rmb() __asm__ __volatile__ ("dmb" ::: "memory", "cc")
#define rseq_smp_wmb() __asm__ __volatile__ ("dmb" ::: "memory", "cc")
#define rseq_smp_load_acquire(p) \
__extension__ ({ \
rseq_unqual_scalar_typeof(*(p)) ____p1 = RSEQ_READ_ONCE(*(p)); \
rseq_smp_mb(); \
____p1; \
})
#define rseq_smp_acquire__after_ctrl_dep() rseq_smp_rmb()
#define rseq_smp_store_release(p, v) \
do { \
rseq_smp_mb(); \
RSEQ_WRITE_ONCE(*(p), v); \
} while (0)
#define __RSEQ_ASM_DEFINE_TABLE(label, version, flags, start_ip, \
post_commit_offset, abort_ip) \
".pushsection __rseq_cs, \"aw\"\n\t" \
".balign 32\n\t" \
__rseq_str(label) ":\n\t" \
".word " __rseq_str(version) ", " __rseq_str(flags) "\n\t" \
".word " __rseq_str(start_ip) ", 0x0, " __rseq_str(post_commit_offset) ", 0x0, " __rseq_str(abort_ip) ", 0x0\n\t" \
".popsection\n\t" \
".pushsection __rseq_cs_ptr_array, \"aw\"\n\t" \
".word " __rseq_str(label) "b, 0x0\n\t" \
".popsection\n\t"
#define RSEQ_ASM_DEFINE_TABLE(label, start_ip, post_commit_ip, abort_ip) \
__RSEQ_ASM_DEFINE_TABLE(label, 0x0, 0x0, start_ip, \
(post_commit_ip - start_ip), abort_ip)
/*
* Exit points of a rseq critical section consist of all instructions outside
* of the critical section where a critical section can either branch to or
* reach through the normal course of its execution. The abort IP and the
* post-commit IP are already part of the __rseq_cs section and should not be
* explicitly defined as additional exit points. Knowing all exit points is
* useful to assist debuggers stepping over the critical section.
*/
#define RSEQ_ASM_DEFINE_EXIT_POINT(start_ip, exit_ip) \
".pushsection __rseq_exit_point_array, \"aw\"\n\t" \
".word " __rseq_str(start_ip) ", 0x0, " __rseq_str(exit_ip) ", 0x0\n\t" \
".popsection\n\t"
#define RSEQ_ASM_STORE_RSEQ_CS(label, cs_label, rseq_cs) \
RSEQ_INJECT_ASM(1) \
"adr r0, " __rseq_str(cs_label) "\n\t" \
"str r0, %[" __rseq_str(rseq_cs) "]\n\t" \
__rseq_str(label) ":\n\t"
#define RSEQ_ASM_CMP_CPU_ID(cpu_id, current_cpu_id, label) \
RSEQ_INJECT_ASM(2) \
"ldr r0, %[" __rseq_str(current_cpu_id) "]\n\t" \
"cmp %[" __rseq_str(cpu_id) "], r0\n\t" \
"bne " __rseq_str(label) "\n\t"
#define __RSEQ_ASM_DEFINE_ABORT(table_label, label, teardown, \
abort_label, version, flags, \
start_ip, post_commit_offset, abort_ip) \
".balign 32\n\t" \
__rseq_str(table_label) ":\n\t" \
".word " __rseq_str(version) ", " __rseq_str(flags) "\n\t" \
".word " __rseq_str(start_ip) ", 0x0, " __rseq_str(post_commit_offset) ", 0x0, " __rseq_str(abort_ip) ", 0x0\n\t" \
".word " __rseq_str(RSEQ_SIG) "\n\t" \
__rseq_str(label) ":\n\t" \
teardown \
"b %l[" __rseq_str(abort_label) "]\n\t"
#define RSEQ_ASM_DEFINE_ABORT(table_label, label, teardown, abort_label, \
start_ip, post_commit_ip, abort_ip) \
__RSEQ_ASM_DEFINE_ABORT(table_label, label, teardown, \
abort_label, 0x0, 0x0, start_ip, \
(post_commit_ip - start_ip), abort_ip)
#define RSEQ_ASM_DEFINE_CMPFAIL(label, teardown, cmpfail_label) \
__rseq_str(label) ":\n\t" \
teardown \
"b %l[" __rseq_str(cmpfail_label) "]\n\t"
/* Per-cpu-id indexing. */
#define RSEQ_TEMPLATE_CPU_ID
#define RSEQ_TEMPLATE_MO_RELAXED
#include "rseq-arm-bits.h"
#undef RSEQ_TEMPLATE_MO_RELAXED
#define RSEQ_TEMPLATE_MO_RELEASE
#include "rseq-arm-bits.h"
#undef RSEQ_TEMPLATE_MO_RELEASE
#undef RSEQ_TEMPLATE_CPU_ID
/* Per-mm-cid indexing. */
#define RSEQ_TEMPLATE_MM_CID
#define RSEQ_TEMPLATE_MO_RELAXED
#include "rseq-arm-bits.h"
#undef RSEQ_TEMPLATE_MO_RELAXED
#define RSEQ_TEMPLATE_MO_RELEASE
#include "rseq-arm-bits.h"
#undef RSEQ_TEMPLATE_MO_RELEASE
#undef RSEQ_TEMPLATE_MM_CID
/* APIs which are not based on cpu ids. */
#define RSEQ_TEMPLATE_CPU_ID_NONE
#define RSEQ_TEMPLATE_MO_RELAXED
#include "rseq-arm-bits.h"
#undef RSEQ_TEMPLATE_MO_RELAXED
#undef RSEQ_TEMPLATE_CPU_ID_NONE
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