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Diffstat (limited to 'tools/testing/selftests/rseq/rseq-arm.h')
| -rw-r--r-- | tools/testing/selftests/rseq/rseq-arm.h | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/tools/testing/selftests/rseq/rseq-arm.h b/tools/testing/selftests/rseq/rseq-arm.h new file mode 100644 index 0000000000..d887b3bbe2 --- /dev/null +++ b/tools/testing/selftests/rseq/rseq-arm.h @@ -0,0 +1,176 @@ +/* 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 |