Add a simple fake_sigreturn testcase which builds a ucontext_t with a bad magic header and place it onto the stack. Expects a SIGSEGV on test PASS.
Introduce a common utility assembly trampoline function to invoke a sigreturn while placing the provided sigframe at wanted alignment and also an helper to make space when needed inside the sigframe reserved area.
Signed-off-by: Cristian Marussi cristian.marussi@arm.com --- v5 --> v6 - fake_sigreturn: cleaned up, avoiding excessive SP misalignments - fake_sigreturn: better formatting and prologue - get_starting_header: cleand up and commented - avoid timeout on failure v3 --> v4 - fix commit - fix signal.S, handle misalign requests too - remove unneeded comments - add signal.h include - added get_starting_head() helper - added test description --- tools/testing/selftests/arm64/signal/Makefile | 2 +- .../testing/selftests/arm64/signal/signals.S | 64 +++++++++++++++++++ .../arm64/signal/test_signals_utils.h | 2 + .../testcases/fake_sigreturn_bad_magic.c | 52 +++++++++++++++ .../arm64/signal/testcases/testcases.c | 46 +++++++++++++ .../arm64/signal/testcases/testcases.h | 4 ++ 6 files changed, 169 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/arm64/signal/signals.S create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_magic.c
diff --git a/tools/testing/selftests/arm64/signal/Makefile b/tools/testing/selftests/arm64/signal/Makefile index f78f5190e3d4..b497cfea4643 100644 --- a/tools/testing/selftests/arm64/signal/Makefile +++ b/tools/testing/selftests/arm64/signal/Makefile @@ -28,5 +28,5 @@ clean: # Common test-unit targets to build common-layout test-cases executables # Needs secondary expansion to properly include the testcase c-file in pre-reqs .SECONDEXPANSION: -$(PROGS): test_signals.c test_signals_utils.c testcases/testcases.c $$@.c test_signals.h test_signals_utils.h testcases/testcases.h +$(PROGS): test_signals.c test_signals_utils.c testcases/testcases.c signals.S $$@.c test_signals.h test_signals_utils.h testcases/testcases.h $(CC) $(CFLAGS) $^ -o $@ diff --git a/tools/testing/selftests/arm64/signal/signals.S b/tools/testing/selftests/arm64/signal/signals.S new file mode 100644 index 000000000000..e670f8f2c8de --- /dev/null +++ b/tools/testing/selftests/arm64/signal/signals.S @@ -0,0 +1,64 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (C) 2019 ARM Limited */ + +#include <asm/unistd.h> + +.section .rodata, "a" +call_fmt: + .asciz "Calling sigreturn with fake sigframe sized:%zd at SP @%08lX\n" + +.text + +.globl fake_sigreturn + +/* fake_sigreturn x0:&sigframe, x1:sigframe_size, x2:misalign_bytes */ +fake_sigreturn: + stp x29, x30, [sp, #-16]! + mov x29, sp + + mov x20, x0 + mov x21, x1 + mov x22, x2 + + /* create space on the stack for fake sigframe 16 bytes-aligned */ + add x0, x21, x22 + add x0, x0, #16 + bic x0, x0, #15 /* round_up(sigframe_size + misalign_bytes, 16) */ + sub sp, sp, x0 + add x23, sp, x22 /* new sigframe base with misaligment if any */ + + ldr x0, =call_fmt + mov x1, x21 + mov x2, x23 + bl printf + + /* memcpy the provided content, while still keeping SP aligned */ + mov x0, x23 + mov x1, x20 + mov x2, x21 + bl memcpy + + /* + * Here saving a last minute SP to current->token acts as a marker: + * if we got here, we are successfully faking a sigreturn; in other + * words we are sure no bad fatal signal has been raised till now + * for unrelated reasons, so we should consider the possibly observed + * fatal signal like SEGV coming from Kernel restore_sigframe() and + * triggered as expected from our test-case. + * For simplicity this assumes that current field 'token' is laid out + * as first in struct tdescr + */ + ldr x0, current + str x23, [x0] + /* finally move SP to misaligned address...if any requested */ + mov sp, x23 + + mov x8, #__NR_rt_sigreturn + svc #0 + + /* + * Above sigreturn should not return...looping here leads to a timeout + * and ensure proper and clean test failure, instead of jumping around + * on a potentially corrupted stack. + */ + b . diff --git a/tools/testing/selftests/arm64/signal/test_signals_utils.h b/tools/testing/selftests/arm64/signal/test_signals_utils.h index 3ad062af1fa7..3320a69fb2a7 100644 --- a/tools/testing/selftests/arm64/signal/test_signals_utils.h +++ b/tools/testing/selftests/arm64/signal/test_signals_utils.h @@ -115,4 +115,6 @@ static __always_inline bool get_current_context(struct tdescr *td,
return td->live_uc_valid; } + +int fake_sigreturn(void *sigframe, size_t sz, int misalign_bytes); #endif diff --git a/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_magic.c b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_magic.c new file mode 100644 index 000000000000..8dc600a7d4fd --- /dev/null +++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_magic.c @@ -0,0 +1,52 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2019 ARM Limited + * + * Place a fake sigframe on the stack including a BAD Unknown magic + * record: on sigreturn Kernel must spot this attempt and the test + * case is expected to be terminated via SEGV. + */ + +#include <signal.h> +#include <ucontext.h> + +#include "test_signals_utils.h" +#include "testcases.h" + +struct fake_sigframe sf; + +static int fake_sigreturn_bad_magic_run(struct tdescr *td, + siginfo_t *si, ucontext_t *uc) +{ + struct _aarch64_ctx *shead = GET_SF_RESV_HEAD(sf), *head; + + /* just to fill the ucontext_t with something real */ + if (!get_current_context(td, &sf.uc)) + return 1; + + /* need at least 2*HDR_SZ space: KSFT_BAD_MAGIC + terminator. */ + head = get_starting_head(shead, HDR_SZ * 2, GET_SF_RESV_SIZE(sf), NULL); + if (!head) + return 0; + + /* + * use a well known NON existent bad magic...something + * we should pretty sure won't be ever defined in Kernel + */ + head->magic = KSFT_BAD_MAGIC; + head->size = HDR_SZ; + write_terminator_record(GET_RESV_NEXT_HEAD(head)); + + ASSERT_BAD_CONTEXT(&sf.uc); + fake_sigreturn(&sf, sizeof(sf), 0); + + return 1; +} + +struct tdescr tde = { + .name = "FAKE_SIGRETURN_BAD_MAGIC", + .descr = "Trigger a sigreturn with a sigframe with a bad magic", + .sig_ok = SIGSEGV, + .timeout = 3, + .run = fake_sigreturn_bad_magic_run, +}; diff --git a/tools/testing/selftests/arm64/signal/testcases/testcases.c b/tools/testing/selftests/arm64/signal/testcases/testcases.c index 1914a01222a1..e3521949b800 100644 --- a/tools/testing/selftests/arm64/signal/testcases/testcases.c +++ b/tools/testing/selftests/arm64/signal/testcases/testcases.c @@ -148,3 +148,49 @@ bool validate_reserved(ucontext_t *uc, size_t resv_sz, char **err)
return true; } + +/* + * This function walks through the records inside the provided reserved area + * trying to find enough space to fit @need_sz bytes: if not enough space is + * available and an extra_context record is present, it throws away the + * extra_context record. + * + * It returns a pointer to a new header where it is possible to start storing + * our need_sz bytes. + * + * @shead: points to the start of reserved area + * @need_sz: needed bytes + * @resv_sz: reserved area size in bytes + * @offset: if not null, this will be filled with the offset of the return + * head pointer from @shead + * + * @return: pointer to a new head where to start storing need_sz bytes, or + * NULL if space could not be made available. + */ +struct _aarch64_ctx *get_starting_head(struct _aarch64_ctx *shead, + size_t need_sz, size_t resv_sz, + size_t *offset) +{ + size_t offs = 0; + struct _aarch64_ctx *head; + + head = get_terminator(shead, resv_sz, &offs); + /* not found a terminator...no need to update offset if any */ + if (!head) + return head; + if (resv_sz - offs < need_sz) { + fprintf(stderr, "Low on space:%zd. Discarding extra_context.\n", + resv_sz - offs); + head = get_header(shead, EXTRA_MAGIC, resv_sz, &offs); + if (!head || resv_sz - offs < need_sz) { + fprintf(stderr, + "Failed to reclaim space on sigframe.\n"); + return NULL; + } + } + + fprintf(stderr, "Available space:%zd\n", resv_sz - offs); + if (offset) + *offset = offs; + return head; +} diff --git a/tools/testing/selftests/arm64/signal/testcases/testcases.h b/tools/testing/selftests/arm64/signal/testcases/testcases.h index 04987f7870bc..ad884c135314 100644 --- a/tools/testing/selftests/arm64/signal/testcases/testcases.h +++ b/tools/testing/selftests/arm64/signal/testcases/testcases.h @@ -97,4 +97,8 @@ static inline void write_terminator_record(struct _aarch64_ctx *tail) tail->size = 0; } } + +struct _aarch64_ctx *get_starting_head(struct _aarch64_ctx *shead, + size_t need_sz, size_t resv_sz, + size_t *offset); #endif