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@xxxxxxx>
---
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
--
2.17.1
