[PATCH 7/7] s390/vdso: Wire up getrandom() vdso implementation

Heiko Carstens
2024-09-13T13:05:52Z

Provide the s390 specific vdso getrandom() architecture backend.

_vdso_rng_data required data is placed within the _vdso_data vvar page, by
using a hardcoded offset larger than vdso_data.

As required the chacha20 implementation does not write to the stack.

The implementation follows more or less the arm64 implementations and
makes use of vector instructions. It has a fallback to the getrandom()
system call for machines where the vector facility is not
installed.
The check if the vector facility is installed, as well as an
optimization for machines with the vector-enhancements facility 2,
is implemented with alternatives, avoiding runtime checks.

Note that __kernel_getrandom() is implemented without the vdso user wrapper
which would setup a stack frame for odd cases (aka very old glibc variants)
where the caller has not done that. All callers of __kernel_getrandom() are
required to setup a stack frame, like the C ABI requires it.

The vdso testcases vdso_test_getrandom and vdso_test_chacha pass.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
arch/s390/Kconfig | 1 +
arch/s390/include/asm/fpu-insn-asm.h | 22 +++
arch/s390/include/asm/vdso/getrandom.h | 40 +++++
arch/s390/include/asm/vdso/vsyscall.h | 15 ++
arch/s390/kernel/vdso.c | 7 +-
arch/s390/kernel/vdso64/Makefile | 9 +-
arch/s390/kernel/vdso64/vdso.h | 1 +
arch/s390/kernel/vdso64/vdso64.lds.S | 3 +
arch/s390/kernel/vdso64/vgetrandom-chacha.S | 184 ++++++++++++++++++++
arch/s390/kernel/vdso64/vgetrandom.c | 14 ++
tools/arch/s390/vdso | 1 +
tools/testing/selftests/vDSO/Makefile | 2 +-
12 files changed, 290 insertions(+), 9 deletions(-)
create mode 100644 arch/s390/include/asm/vdso/getrandom.h
create mode 100644 arch/s390/kernel/vdso64/vgetrandom-chacha.S
create mode 100644 arch/s390/kernel/vdso64/vgetrandom.c
create mode 120000 tools/arch/s390/vdso

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index c60e699e99f5..b0d0b3a8d196 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -243,6 +243,7 @@ config S390
select TRACE_IRQFLAGS_SUPPORT
select TTY
select USER_STACKTRACE_SUPPORT
+ select VDSO_GETRANDOM
select VIRT_CPU_ACCOUNTING
select ZONE_DMA
# Note: keep the above list sorted alphabetically
diff --git a/arch/s390/include/asm/fpu-insn-asm.h b/arch/s390/include/asm/fpu-insn-asm.h
index 02ccfe46050a..d296322be4bc 100644
--- a/arch/s390/include/asm/fpu-insn-asm.h
+++ b/arch/s390/include/asm/fpu-insn-asm.h
@@ -407,6 +407,28 @@
MRXBOPC 0, 0x0E, v1
.endm

+/* VECTOR STORE BYTE REVERSED ELEMENTS */
+ .macro VSTBR vr1, disp, index="%r0", base, m
+ VX_NUM v1, \vr1
+ GR_NUM x2, \index
+ GR_NUM b2, \base
+ .word 0xE600 | ((v1&15) << 4) | (x2&15)
+ .word (b2 << 12) | (\disp)
+ MRXBOPC \m, 0x0E, v1
+.endm
+.macro VSTBRH vr1, disp, index="%r0", base
+ VSTBR \vr1, \disp, \index, \base, 1
+.endm
+.macro VSTBRF vr1, disp, index="%r0", base
+ VSTBR \vr1, \disp, \index, \base, 2
+.endm
+.macro VSTBRG vr1, disp, index="%r0", base
+ VSTBR \vr1, \disp, \index, \base, 3
+.endm
+.macro VSTBRQ vr1, disp, index="%r0", base
+ VSTBR \vr1, \disp, \index, \base, 4
+.endm
+
/* VECTOR STORE MULTIPLE */
.macro VSTM vfrom, vto, disp, base, hint=3
VX_NUM v1, \vfrom
diff --git a/arch/s390/include/asm/vdso/getrandom.h b/arch/s390/include/asm/vdso/getrandom.h
new file mode 100644
index 000000000000..36355af7160b
--- /dev/null
+++ b/arch/s390/include/asm/vdso/getrandom.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __ASM_VDSO_GETRANDOM_H
+#define __ASM_VDSO_GETRANDOM_H
+
+#ifndef __ASSEMBLY__
+
+#include <vdso/datapage.h>
+#include <asm/vdso/vsyscall.h>
+#include <asm/syscall.h>
+#include <asm/unistd.h>
+#include <asm/page.h>
+
+/**
+ * getrandom_syscall - Invoke the getrandom() syscall.
+ * @buffer: Destination buffer to fill with random bytes.
+ * @len: Size of @buffer in bytes.
+ * @flags: Zero or more GRND_* flags.
+ * Returns: The number of random bytes written to @buffer, or a negative value indicating an error.
+ */
+static __always_inline ssize_t getrandom_syscall(void *buffer, size_t len, unsigned int flags)
+{
+ return syscall3(__NR_getrandom, (long)buffer, (long)len, (long)flags);
+}
+
+static __always_inline const struct vdso_rng_data *__arch_get_vdso_rng_data(void)
+{
+ /*
+ * The RNG data is in the real VVAR data page, but if a task belongs to a time namespace
+ * then VVAR_DATA_PAGE_OFFSET points to the namespace-specific VVAR page and VVAR_TIMENS_
+ * PAGE_OFFSET points to the real VVAR page.
+ */
+ if (IS_ENABLED(CONFIG_TIME_NS) && _vdso_data->clock_mode == VDSO_CLOCKMODE_TIMENS)
+ return (void *)&_vdso_rng_data + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE;
+ return &_vdso_rng_data;
+}
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_GETRANDOM_H */
diff --git a/arch/s390/include/asm/vdso/vsyscall.h b/arch/s390/include/asm/vdso/vsyscall.h
index 6c67c08cefdd..3c5d5e47814e 100644
--- a/arch/s390/include/asm/vdso/vsyscall.h
+++ b/arch/s390/include/asm/vdso/vsyscall.h
@@ -2,12 +2,21 @@
#ifndef __ASM_VDSO_VSYSCALL_H
#define __ASM_VDSO_VSYSCALL_H

+#define __VDSO_RND_DATA_OFFSET 768
+
#ifndef __ASSEMBLY__

#include <linux/hrtimer.h>
#include <linux/timekeeper_internal.h>
#include <vdso/datapage.h>
#include <asm/vdso.h>
+
+enum vvar_pages {
+ VVAR_DATA_PAGE_OFFSET,
+ VVAR_TIMENS_PAGE_OFFSET,
+ VVAR_NR_PAGES
+};
+
/*
* Update the vDSO data page to keep in sync with kernel timekeeping.
*/
@@ -18,6 +27,12 @@ static __always_inline struct vdso_data *__s390_get_k_vdso_data(void)
}
#define __arch_get_k_vdso_data __s390_get_k_vdso_data

+static __always_inline struct vdso_rng_data *__s390_get_k_vdso_rnd_data(void)
+{
+ return (void *)vdso_data + __VDSO_RND_DATA_OFFSET;
+}
+#define __arch_get_k_vdso_rng_data __s390_get_k_vdso_rnd_data
+
/* The asm-generic header needs to be included after the definitions above */
#include <asm-generic/vdso/vsyscall.h>

diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index 8e4e6b316337..598b512cde01 100644
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -19,6 +19,7 @@
#include <linux/time_namespace.h>
#include <linux/random.h>
#include <vdso/datapage.h>
+#include <asm/vdso/vsyscall.h>
#include <asm/alternative.h>
#include <asm/vdso.h>

@@ -31,12 +32,6 @@ static union vdso_data_store vdso_data_store __page_aligned_data;

struct vdso_data *vdso_data = vdso_data_store.data;

-enum vvar_pages {
- VVAR_DATA_PAGE_OFFSET,
- VVAR_TIMENS_PAGE_OFFSET,
- VVAR_NR_PAGES,
-};
-
#ifdef CONFIG_TIME_NS
struct vdso_data *arch_get_vdso_data(void *vvar_page)
{
diff --git a/arch/s390/kernel/vdso64/Makefile b/arch/s390/kernel/vdso64/Makefile
index ba19c0ca7c87..37bb4b761229 100644
--- a/arch/s390/kernel/vdso64/Makefile
+++ b/arch/s390/kernel/vdso64/Makefile
@@ -3,12 +3,17 @@

# Include the generic Makefile to check the built vdso.
include $(srctree)/lib/vdso/Makefile
-obj-vdso64 = vdso_user_wrapper.o note.o
-obj-cvdso64 = vdso64_generic.o getcpu.o
+obj-vdso64 = vdso_user_wrapper.o note.o vgetrandom-chacha.o
+obj-cvdso64 = vdso64_generic.o getcpu.o vgetrandom.o
VDSO_CFLAGS_REMOVE := -pg $(CC_FLAGS_FTRACE) $(CC_FLAGS_EXPOLINE) $(CC_FLAGS_CHECK_STACK)
CFLAGS_REMOVE_getcpu.o = $(VDSO_CFLAGS_REMOVE)
+CFLAGS_REMOVE_vgetrandom.o = $(VDSO_CFLAGS_REMOVE)
CFLAGS_REMOVE_vdso64_generic.o = $(VDSO_CFLAGS_REMOVE)

+ifneq ($(c-getrandom-y),)
+ CFLAGS_vgetrandom.o += -include $(c-getrandom-y)
+endif
+
# Build rules

targets := $(obj-vdso64) $(obj-cvdso64) vdso64.so vdso64.so.dbg
diff --git a/arch/s390/kernel/vdso64/vdso.h b/arch/s390/kernel/vdso64/vdso.h
index 34c7a2312f9d..9e5397e7b590 100644
--- a/arch/s390/kernel/vdso64/vdso.h
+++ b/arch/s390/kernel/vdso64/vdso.h
@@ -10,5 +10,6 @@ int __s390_vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unuse
int __s390_vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz);
int __s390_vdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts);
int __s390_vdso_clock_getres(clockid_t clock, struct __kernel_timespec *ts);
+ssize_t __kernel_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len);

#endif /* __ARCH_S390_KERNEL_VDSO64_VDSO_H */
diff --git a/arch/s390/kernel/vdso64/vdso64.lds.S b/arch/s390/kernel/vdso64/vdso64.lds.S
index fa02c6ae3cac..753040a4b5ab 100644
--- a/arch/s390/kernel/vdso64/vdso64.lds.S
+++ b/arch/s390/kernel/vdso64/vdso64.lds.S
@@ -4,6 +4,7 @@
* library
*/

+#include <asm/vdso/vsyscall.h>
#include <asm/page.h>
#include <asm/vdso.h>

@@ -13,6 +14,7 @@ OUTPUT_ARCH(s390:64-bit)
SECTIONS
{
PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+ PROVIDE(_vdso_rng_data = _vdso_data + __VDSO_RND_DATA_OFFSET);
#ifdef CONFIG_TIME_NS
PROVIDE(_timens_data = _vdso_data + PAGE_SIZE);
#endif
@@ -144,6 +146,7 @@ VERSION
__kernel_restart_syscall;
__kernel_rt_sigreturn;
__kernel_sigreturn;
+ __kernel_getrandom;
local: *;
};
}
diff --git a/arch/s390/kernel/vdso64/vgetrandom-chacha.S b/arch/s390/kernel/vdso64/vgetrandom-chacha.S
new file mode 100644
index 000000000000..ecd44cf0eaba
--- /dev/null
+++ b/arch/s390/kernel/vdso64/vgetrandom-chacha.S
@@ -0,0 +1,184 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/linkage.h>
+#include <asm/alternative.h>
+#include <asm/fpu-insn.h>
+
+#define STATE0 %v0
+#define STATE1 %v1
+#define STATE2 %v2
+#define STATE3 %v3
+#define COPY0 %v4
+#define COPY1 %v5
+#define COPY2 %v6
+#define COPY3 %v7
+#define PERM4 %v16
+#define PERM8 %v17
+#define PERM12 %v18
+#define BEPERM %v19
+#define TMP0 %v20
+#define TMP1 %v21
+#define TMP2 %v22
+#define TMP3 %v23
+
+ .section .rodata
+
+ .balign 128
+.Lconstants:
+ .long 0x61707865,0x3320646e,0x79622d32,0x6b206574 # endian-neutral
+ .long 0x04050607,0x08090a0b,0x0c0d0e0f,0x00010203 # rotl 4 bytes
+ .long 0x08090a0b,0x0c0d0e0f,0x00010203,0x04050607 # rotl 8 bytes
+ .long 0x0c0d0e0f,0x00010203,0x04050607,0x08090a0b # rotl 12 bytes
+ .long 0x03020100,0x07060504,0x0b0a0908,0x0f0e0d0c # byte swap
+
+ .text
+/*
+ * s390 ChaCha20 implementation meant for vDSO. Produces a given positive
+ * number of blocks of output with nonce 0, taking an input key and 8-bytes
+ * counter. Does not spill to the stack.
+ *
+ * void __arch_chacha20_blocks_nostack(uint8_t *dst_bytes,
+ * const uint8_t *key,
+ * uint32_t *counter,
+ * size_t nblocks)
+ */
+SYM_FUNC_START(__arch_chacha20_blocks_nostack)
+ larl %r1,.Lconstants
+
+ /* COPY0 = "expand 32-byte k" */
+ VL COPY0,0,,%r1
+
+ /* PERM4-PERM12,BEPERM = byte selectors for VPERM */
+ VLM PERM4,BEPERM,16,%r1
+
+ /* COPY1,COPY2 = key */
+ VLM COPY1,COPY2,0,%r3
+
+ /* COPY3 = counter || zero nonce */
+ lg %r3,0(%r4)
+ VZERO COPY3
+ VLVGG COPY3,%r3,0
+
+ lghi %r1,0
+.Lblock:
+ VLR STATE0,COPY0
+ VLR STATE1,COPY1
+ VLR STATE2,COPY2
+ VLR STATE3,COPY3
+
+ lghi %r0,10
+.Ldoubleround:
+ /* STATE0 += STATE1, STATE3 = rotl32(STATE3 ^ STATE0, 16) */
+ VAF STATE0,STATE0,STATE1
+ VX STATE3,STATE3,STATE0
+ VERLLF STATE3,STATE3,16
+
+ /* STATE2 += STATE3, STATE1 = rotl32(STATE1 ^ STATE2, 12) */
+ VAF STATE2,STATE2,STATE3
+ VX STATE1,STATE1,STATE2
+ VERLLF STATE1,STATE1,12
+
+ /* STATE0 += STATE1, STATE3 = rotl32(STATE3 ^ STATE0, 8) */
+ VAF STATE0,STATE0,STATE1
+ VX STATE3,STATE3,STATE0
+ VERLLF STATE3,STATE3,8
+
+ /* STATE2 += STATE3, STATE1 = rotl32(STATE1 ^ STATE2, 7) */
+ VAF STATE2,STATE2,STATE3
+ VX STATE1,STATE1,STATE2
+ VERLLF STATE1,STATE1,7
+
+ /* STATE1[0,1,2,3] = STATE1[1,2,3,0] */
+ VPERM STATE1,STATE1,STATE1,PERM4
+ /* STATE2[0,1,2,3] = STATE2[2,3,0,1] */
+ VPERM STATE2,STATE2,STATE2,PERM8
+ /* STATE3[0,1,2,3] = STATE3[3,0,1,2] */
+ VPERM STATE3,STATE3,STATE3,PERM12
+
+ /* STATE0 += STATE1, STATE3 = rotl32(STATE3 ^ STATE0, 16) */
+ VAF STATE0,STATE0,STATE1
+ VX STATE3,STATE3,STATE0
+ VERLLF STATE3,STATE3,16
+
+ /* STATE2 += STATE3, STATE1 = rotl32(STATE1 ^ STATE2, 12) */
+ VAF STATE2,STATE2,STATE3
+ VX STATE1,STATE1,STATE2
+ VERLLF STATE1,STATE1,12
+
+ /* STATE0 += STATE1, STATE3 = rotl32(STATE3 ^ STATE0, 8) */
+ VAF STATE0,STATE0,STATE1
+ VX STATE3,STATE3,STATE0
+ VERLLF STATE3,STATE3,8
+
+ /* STATE2 += STATE3, STATE1 = rotl32(STATE1 ^ STATE2, 7) */
+ VAF STATE2,STATE2,STATE3
+ VX STATE1,STATE1,STATE2
+ VERLLF STATE1,STATE1,7
+
+ /* STATE1[0,1,2,3] = STATE1[3,0,1,2] */
+ VPERM STATE1,STATE1,STATE1,PERM12
+ /* STATE2[0,1,2,3] = STATE2[2,3,0,1] */
+ VPERM STATE2,STATE2,STATE2,PERM8
+ /* STATE3[0,1,2,3] = STATE3[1,2,3,0] */
+ VPERM STATE3,STATE3,STATE3,PERM4
+ brctg %r0,.Ldoubleround
+
+ /* OUTPUT0 = STATE0 + STATE0 */
+ VAF STATE0,STATE0,COPY0
+ /* OUTPUT1 = STATE1 + STATE1 */
+ VAF STATE1,STATE1,COPY1
+ /* OUTPUT2 = STATE2 + STATE2 */
+ VAF STATE2,STATE2,COPY2
+ /* OUTPUT2 = STATE3 + STATE3 */
+ VAF STATE3,STATE3,COPY3
+
+ /*
+ * 32 bit wise little endian store to OUTPUT. If the vector
+ * enhancement facility 2 is not installed use the slow path.
+ */
+ ALTERNATIVE "brc 0xf,.Lstoreslow", "nop", ALT_FACILITY(148)
+ VSTBRF STATE0,0,,%r2
+ VSTBRF STATE1,16,,%r2
+ VSTBRF STATE2,32,,%r2
+ VSTBRF STATE3,48,,%r2
+.Lstoredone:
+
+ /* ++COPY3.COUNTER */
+ alsih %r3,1
+ alcr %r3,%r1
+ VLVGG COPY3,%r3,0
+
+ /* OUTPUT += 64, --NBLOCKS */
+ aghi %r2,64
+ brctg %r5,.Lblock
+
+ /* COUNTER = COPY3.COUNTER */
+ stg %r3,0(%r4)
+
+ /* Zero out potentially sensitive regs */
+ VZERO STATE0
+ VZERO STATE1
+ VZERO STATE2
+ VZERO STATE3
+ VZERO COPY1
+ VZERO COPY2
+
+ /* Early exit if TMP0-TMP3 have not been used */
+ ALTERNATIVE "nopr", "br %r14", ALT_FACILITY(148)
+
+ VZERO TMP0
+ VZERO TMP1
+ VZERO TMP2
+ VZERO TMP3
+
+ br %r14
+
+.Lstoreslow:
+ /* Convert STATE to little endian format and store to OUTPUT */
+ VPERM TMP0,STATE0,STATE0,BEPERM
+ VPERM TMP1,STATE1,STATE1,BEPERM
+ VPERM TMP2,STATE2,STATE2,BEPERM
+ VPERM TMP3,STATE3,STATE3,BEPERM
+ VSTM TMP0,TMP3,0,%r2
+ j .Lstoredone
+SYM_FUNC_END(__arch_chacha20_blocks_nostack)
diff --git a/arch/s390/kernel/vdso64/vgetrandom.c b/arch/s390/kernel/vdso64/vgetrandom.c
new file mode 100644
index 000000000000..b5268b507fb5
--- /dev/null
+++ b/arch/s390/kernel/vdso64/vgetrandom.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <asm/facility.h>
+#include <uapi/asm-generic/errno.h>
+#include "vdso.h"
+
+ssize_t __kernel_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len)
+{
+ if (test_facility(129))
+ return __cvdso_getrandom(buffer, len, flags, opaque_state, opaque_len);
+ if (unlikely(opaque_len == ~0UL && !buffer && !len && !flags))
+ return -ENOSYS;
+ return getrandom_syscall(buffer, len, flags);
+}
diff --git a/tools/arch/s390/vdso b/tools/arch/s390/vdso
new file mode 120000
index 000000000000..6cf4c1cebdcd
--- /dev/null
+++ b/tools/arch/s390/vdso
@@ -0,0 +1 @@
+../../../arch/s390/kernel/vdso64
\ No newline at end of file
diff --git a/tools/testing/selftests/vDSO/Makefile b/tools/testing/selftests/vDSO/Makefile
index 86ebc4115eda..af9cedbf5357 100644
--- a/tools/testing/selftests/vDSO/Makefile
+++ b/tools/testing/selftests/vDSO/Makefile
@@ -9,7 +9,7 @@ ifeq ($(ARCH),$(filter $(ARCH),x86 x86_64))
TEST_GEN_PROGS += vdso_standalone_test_x86
endif
TEST_GEN_PROGS += vdso_test_correctness
-ifeq ($(ARCH)$(CONFIG_X86_32),$(filter $(ARCH)$(CONFIG_X86_32),x86 x86_64 loongarch arm64 powerpc))
+ifeq ($(ARCH)$(CONFIG_X86_32),$(filter $(ARCH)$(CONFIG_X86_32),x86 x86_64 loongarch arm64 powerpc s390))
TEST_GEN_PROGS += vdso_test_getrandom
TEST_GEN_PROGS += vdso_test_chacha
endif
--
2.43.0