Added 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. This commit also introduces a common utility assembly function to invoke a sigreturn using a fake provided sigframe.
Signed-off-by: Cristian Marussi cristian.marussi@arm.com --- tools/testing/selftests/arm64/signal/Makefile | 2 +- .../testing/selftests/arm64/signal/signals.S | 64 +++++++++++++++++++ .../arm64/signal/test_signals_utils.h | 1 + .../arm64/signal/testcases/.gitignore | 1 + .../testcases/fake_sigreturn_bad_magic.c | 63 ++++++++++++++++++ 5 files changed, 130 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 8c8d08be4b0d..b3dcf315b5a4 100644 --- a/tools/testing/selftests/arm64/signal/Makefile +++ b/tools/testing/selftests/arm64/signal/Makefile @@ -80,7 +80,7 @@ endif # 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 @if [ ! -d $(khdr_dir) ]; then \ echo -n "\n!!! WARNING: $(khdr_dir) NOT FOUND."; \ echo "===> Are you sure Kernel Headers have been installed properly ?\n"; \ diff --git a/tools/testing/selftests/arm64/signal/signals.S b/tools/testing/selftests/arm64/signal/signals.S new file mode 100644 index 000000000000..6262b877400b --- /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 calculated SP @%08lX\n" + +.text + +.globl fake_sigreturn + +/* fake_sigreturn x0:&sigframe, x1:sigframe_size, x2:alignment_SP */ +fake_sigreturn: + mov x20, x0 + mov x21, x1 + mov x22, x2 + mov x23, sp + + /* create space on the stack for fake sigframe..."x22"-aligned */ + mov x0, #0 + add x0, x21, x22 + sub x22, x22, #1 + bic x0, x0, x22 + sub x23, x23, x0 + + ldr x0, =call_fmt + mov x1, x21 + mov x2, x23 + bl printf + + mov sp, x23 + + /* now fill it with the provided content... */ + mov x0, sp + 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 possibl 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] + /* SP is already pointing back to the just built fake sigframe here */ + 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 ce35be8ebc8e..2a71da7e6695 100644 --- a/tools/testing/selftests/arm64/signal/test_signals_utils.h +++ b/tools/testing/selftests/arm64/signal/test_signals_utils.h @@ -12,4 +12,5 @@ int test_run(struct tdescr *td); void test_result(struct tdescr *td);
bool get_current_context(struct tdescr *td, ucontext_t *dest_uc); +int fake_sigreturn(void *sigframe, size_t sz, int alignment); #endif diff --git a/tools/testing/selftests/arm64/signal/testcases/.gitignore b/tools/testing/selftests/arm64/signal/testcases/.gitignore index a48a118b1a1a..0ea6fdc3765c 100644 --- a/tools/testing/selftests/arm64/signal/testcases/.gitignore +++ b/tools/testing/selftests/arm64/signal/testcases/.gitignore @@ -4,3 +4,4 @@ mangle_pstate_invalid_mode_el1 mangle_pstate_invalid_mode_el2 mangle_pstate_invalid_mode_el3 mangle_pstate_ssbs_regs +fake_sigreturn_bad_magic 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..b4c063e02a7a --- /dev/null +++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_magic.c @@ -0,0 +1,63 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (C) 2019 ARM Limited */ + +#include <stdio.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) +{ + size_t resv_sz, offset; + 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; + + resv_sz = GET_SF_RESV_SIZE(sf); + /* + * find the terminator, preserving existing headers + * and verify amount of spare room in __reserved area. + */ + head = get_terminator(shead, resv_sz, &offset); + /* + * try stripping extra_context header when low on space: + * we need at least 2*HDR_SZ space ... one for the KSFT_BAD_MAGIC + * and the other for the usual terminator. + */ + if (head && resv_sz - offset < HDR_SZ * 2) { + fprintf(stderr, "Low on space:%zd. Discarding extra_context.\n", + resv_sz - offset); + head = get_header(shead, EXTRA_MAGIC, resv_sz, &offset); + } + /* just give up and timeout if still not enough space */ + if (head && resv_sz - offset >= HDR_SZ) { + fprintf(stderr, "Mangling template header. Spare space:%zd\n", + resv_sz - offset); + /* + * 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), 16); + } + + return 1; +} + +struct tdescr tde = { + .name = "FAKE_SIGRETURN_BAD_MAGIC", + .descr = "Triggers a fake sigreturn with a sigframe including a bad non-existent magic", + .sig_ok = SIGSEGV, + .timeout = 3, + .run = fake_sigreturn_bad_magic_run, +};