| Message ID | 20190910123111.33478-7-cristian.marussi@arm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add arm64/signal initial kselftest support | expand |
On Tue, Sep 10, 2019 at 01:31:06pm +0100, Cristian Marussi wrote: > 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 [...] > 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) */ If I've figured this out right, x0 as computed here actually looks like round_up(sigframe_size + misalign_bytes + 1, 16) - 1. (n + (m - 1)) & ~(m - 1) is the classic way to round up when m is a power of 2. That's why I originally suggested to add 15. Your code works, but I think it always allocates at least one byte more than needed (?) This is not a huge deal, and better than allocating one byte to few, but it would be good to understand whether this behaviour was intentional or not. > + 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/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. > + */ That's much clearer now, thanks for that. > +struct _aarch64_ctx *get_starting_head(struct _aarch64_ctx *shead, > + size_t need_sz, size_t resv_sz, > + size_t *offset) > +{ [...] Cheers ---Dave
On 17/09/2019 17:06, Dave Martin wrote: > On Tue, Sep 10, 2019 at 01:31:06pm +0100, Cristian Marussi wrote: >> 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 > > [...] > >> 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) */ > > If I've figured this out right, x0 as computed here actually looks > like round_up(sigframe_size + misalign_bytes + 1, 16) - 1. > > (n + (m - 1)) & ~(m - 1) is the classic way to round up when m is a > power of 2. > > That's why I originally suggested to add 15. Your code works, but I > think it always allocates at least one byte more than needed (?) > > This is not a huge deal, and better than allocating one byte to few, > but it would be good to understand whether this behaviour was > intentional or not. > Well the reason if that I was equally (but wrongly on my side) convinced to have to sum +16 before clearing the lower 0b1111. My bad. I'm fixing in v7. >> + 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/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. >> + */ > > That's much clearer now, thanks for that. > >> +struct _aarch64_ctx *get_starting_head(struct _aarch64_ctx *shead, >> + size_t need_sz, size_t resv_sz, >> + size_t *offset) >> +{ > > [...] > > Cheers > ---Dave > Cheers Cristian
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
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