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