On 30/08/24 08:46, Will Deacon wrote: > On Thu, Aug 29, 2024 at 08:17:14PM +0000, Adhemerval Zanella wrote: >> Hook up the generic vDSO implementation to the aarch64 vDSO data page. >> The _vdso_rng_data required data is placed within the _vdso_data vvar >> page, by using a offset larger than the vdso_data. >> >> The vDSO function requires a ChaCha20 implementation that does not >> write to the stack, and that can do an entire ChaCha20 permutation. >> The one provided is based on the current chacha-neon-core.S and uses NEON >> on the permute operation. The fallback for chips that do not support >> NEON issues the syscall. >> >> This also passes the vdso_test_chacha test along with >> vdso_test_getrandom. The vdso_test_getrandom bench-single result on >> Neoverse-N1 shows: >> >> vdso: 25000000 times in 0.746506464 seconds >> libc: 25000000 times in 8.849179444 seconds >> syscall: 25000000 times in 8.818726425 seconds >> >> Changes from v1: >> - Fixed style issues and typos. >> - Added fallback for systems without NEON support. >> - Avoid use of non-volatile vector registers in neon chacha20. >> - Use c-getrandom-y for vgetrandom.c. >> - Fixed TIMENS vdso_rnd_data access. >> >> Signed-off-by: Adhemerval Zanella <adhemerval.zanella@xxxxxxxxxx> >> --- >> arch/arm64/Kconfig | 1 + >> arch/arm64/include/asm/vdso.h | 6 + >> arch/arm64/include/asm/vdso/getrandom.h | 49 ++++++ >> arch/arm64/include/asm/vdso/vsyscall.h | 10 ++ >> arch/arm64/kernel/vdso.c | 6 - >> arch/arm64/kernel/vdso/Makefile | 11 +- >> arch/arm64/kernel/vdso/vdso | 1 + >> arch/arm64/kernel/vdso/vdso.lds.S | 4 + >> arch/arm64/kernel/vdso/vgetrandom-chacha.S | 168 +++++++++++++++++++++ >> arch/arm64/kernel/vdso/vgetrandom.c | 15 ++ >> lib/vdso/getrandom.c | 1 + >> tools/arch/arm64/vdso | 1 + >> tools/include/linux/compiler.h | 4 + >> tools/testing/selftests/vDSO/Makefile | 5 +- > > Please can you split the tools/ changes into a separate patch? Alright, it would require to be after the inclusion on vgetrandom-chacha.S otherwise vdso_test_chacha will not build on aarch64. > >> 14 files changed, 273 insertions(+), 9 deletions(-) >> create mode 100644 arch/arm64/include/asm/vdso/getrandom.h >> create mode 120000 arch/arm64/kernel/vdso/vdso >> create mode 100644 arch/arm64/kernel/vdso/vgetrandom-chacha.S >> create mode 100644 arch/arm64/kernel/vdso/vgetrandom.c >> create mode 120000 tools/arch/arm64/vdso >> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index a2f8ff354ca6..7f7424d1b3b8 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -262,6 +262,7 @@ config ARM64 >> select TRACE_IRQFLAGS_NMI_SUPPORT >> select HAVE_SOFTIRQ_ON_OWN_STACK >> select USER_STACKTRACE_SUPPORT >> + select VDSO_GETRANDOM >> help >> ARM 64-bit (AArch64) Linux support. >> >> diff --git a/arch/arm64/include/asm/vdso.h b/arch/arm64/include/asm/vdso.h >> index 4305995c8f82..18407b757c95 100644 >> --- a/arch/arm64/include/asm/vdso.h >> +++ b/arch/arm64/include/asm/vdso.h >> @@ -16,6 +16,12 @@ >> >> #ifndef __ASSEMBLY__ >> >> +enum vvar_pages { >> + VVAR_DATA_PAGE_OFFSET, >> + VVAR_TIMENS_PAGE_OFFSET, >> + VVAR_NR_PAGES, >> +}; >> + >> #include <generated/vdso-offsets.h> >> >> #define VDSO_SYMBOL(base, name) \ >> diff --git a/arch/arm64/include/asm/vdso/getrandom.h b/arch/arm64/include/asm/vdso/getrandom.h >> new file mode 100644 >> index 000000000000..fca66ba49d4c >> --- /dev/null >> +++ b/arch/arm64/include/asm/vdso/getrandom.h >> @@ -0,0 +1,49 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> + >> +#ifndef __ASM_VDSO_GETRANDOM_H >> +#define __ASM_VDSO_GETRANDOM_H >> + >> +#ifndef __ASSEMBLY__ >> + >> +#include <asm/vdso.h> >> +#include <asm/unistd.h> >> +#include <vdso/datapage.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) >> +{ >> + register void *buffer asm ("x0") = _buffer; >> + register size_t len asm ("x1") = _len; >> + register unsigned int flags asm ("x2") = _flags; >> + register long ret asm ("x0"); >> + register long nr asm ("x8") = __NR_getrandom; >> + >> + asm volatile( >> + " svc #0\n" >> + : "=r" (ret) >> + : "r" (buffer), "r" (len), "r" (flags), "r" (nr) >> + : "memory"); >> + >> + return ret; >> +} >> + >> +static __always_inline const struct vdso_rng_data *__arch_get_vdso_rng_data(void) >> +{ >> + /* >> + * If a task belongs to a time namespace then a namespace the real >> + * VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET. >> + */ > > This comment doesn't make sense. I reprased it from arch/arm64/kernel/vdso.c (vvar_fault). Did I confuse something? This is indeed required, otherwise the getrandom vDSO on a timens does not see the generation counter with correctly and fallback to syscall. > >> + 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/arm64/include/asm/vdso/vsyscall.h b/arch/arm64/include/asm/vdso/vsyscall.h >> index f94b1457c117..2a87f0e1b144 100644 >> --- a/arch/arm64/include/asm/vdso/vsyscall.h >> +++ b/arch/arm64/include/asm/vdso/vsyscall.h >> @@ -2,8 +2,11 @@ >> #ifndef __ASM_VDSO_VSYSCALL_H >> #define __ASM_VDSO_VSYSCALL_H >> >> +#define __VDSO_RND_DATA_OFFSET 480 > > Why 480? I used the x86 strategy to place the the vdso_rng_data and the vdso_data, but I could not make to fit the vdso_data generation with the linker script machinery required for vdso.lds.S (I think Jason faced a similar issue with x86). I will try to see if I can refactor in a subsequent patch the vdso_data definition to place the vdso_rng_data in a common struct. It does not help that it seems know that each architecture is placing the vdso_rng_data in a different place. > >> + >> #ifndef __ASSEMBLY__ >> >> +#include <asm/vdso.h> >> #include <linux/timekeeper_internal.h> >> #include <vdso/datapage.h> >> >> @@ -21,6 +24,13 @@ struct vdso_data *__arm64_get_k_vdso_data(void) >> } >> #define __arch_get_k_vdso_data __arm64_get_k_vdso_data >> >> +static __always_inline >> +struct vdso_rng_data *__arm64_get_k_vdso_rnd_data(void) >> +{ >> + return (void*)vdso_data + __VDSO_RND_DATA_OFFSET; >> +} >> +#define __arch_get_k_vdso_rng_data __arm64_get_k_vdso_rnd_data >> + >> static __always_inline >> void __arm64_update_vsyscall(struct vdso_data *vdata, struct timekeeper *tk) >> { >> diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c >> index 89b6e7840002..706c9c3a7a50 100644 >> --- a/arch/arm64/kernel/vdso.c >> +++ b/arch/arm64/kernel/vdso.c >> @@ -34,12 +34,6 @@ enum vdso_abi { >> VDSO_ABI_AA32, >> }; >> >> -enum vvar_pages { >> - VVAR_DATA_PAGE_OFFSET, >> - VVAR_TIMENS_PAGE_OFFSET, >> - VVAR_NR_PAGES, >> -}; >> - >> struct vdso_abi_info { >> const char *name; >> const char *vdso_code_start; >> diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile >> index d11da6461278..50246a38d6bd 100644 >> --- a/arch/arm64/kernel/vdso/Makefile >> +++ b/arch/arm64/kernel/vdso/Makefile >> @@ -9,7 +9,7 @@ >> # Include the generic Makefile to check the built vdso. >> include $(srctree)/lib/vdso/Makefile >> >> -obj-vdso := vgettimeofday.o note.o sigreturn.o >> +obj-vdso := vgettimeofday.o note.o sigreturn.o vgetrandom.o vgetrandom-chacha.o >> >> # Build rules >> targets := $(obj-vdso) vdso.so vdso.so.dbg >> @@ -40,13 +40,22 @@ CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) \ >> $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) \ >> $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) \ >> -Wmissing-prototypes -Wmissing-declarations >> +CFLAGS_REMOVE_vgetrandom.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) \ >> + $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) \ >> + $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) \ >> + -Wmissing-prototypes -Wmissing-declarations >> >> CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables >> +CFLAGS_vgetrandom.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables > > You're using identical CFLAGS_ and CFLAGS_REMOVE_ definitions for > vgettimeofdat.o and vgetrandom.o. Please refactor this so that they use > common definitions. Ack. > >> diff --git a/arch/arm64/kernel/vdso/vdso b/arch/arm64/kernel/vdso/vdso >> new file mode 120000 >> index 000000000000..233c7a26f6e5 >> --- /dev/null >> +++ b/arch/arm64/kernel/vdso/vdso >> @@ -0,0 +1 @@ >> +../../../arch/arm64/kernel/vdso >> \ No newline at end of file >> diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S >> index 45354f2ddf70..f204a9ddc833 100644 >> --- a/arch/arm64/kernel/vdso/vdso.lds.S >> +++ b/arch/arm64/kernel/vdso/vdso.lds.S >> @@ -11,7 +11,9 @@ >> #include <linux/const.h> >> #include <asm/page.h> >> #include <asm/vdso.h> >> +#include <asm/vdso/vsyscall.h> >> #include <asm-generic/vmlinux.lds.h> >> +#include <vdso/datapage.h> >> >> OUTPUT_FORMAT("elf64-littleaarch64", "elf64-bigaarch64", "elf64-littleaarch64") >> OUTPUT_ARCH(aarch64) >> @@ -19,6 +21,7 @@ OUTPUT_ARCH(aarch64) >> 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 >> @@ -102,6 +105,7 @@ VERSION >> __kernel_gettimeofday; >> __kernel_clock_gettime; >> __kernel_clock_getres; >> + __kernel_getrandom; >> local: *; >> }; >> } >> diff --git a/arch/arm64/kernel/vdso/vgetrandom-chacha.S b/arch/arm64/kernel/vdso/vgetrandom-chacha.S >> new file mode 100644 >> index 000000000000..9ebf12a09c65 >> --- /dev/null >> +++ b/arch/arm64/kernel/vdso/vgetrandom-chacha.S >> @@ -0,0 +1,168 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> + >> +#include <linux/linkage.h> >> +#include <asm/cache.h> >> +#include <asm/assembler.h> >> + >> + .text >> + >> +#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 copy3_d d7 >> +#define one_d d16 >> +#define one_q q16 >> +#define tmp v17 >> +#define rot8 v18 >> + >> +/* >> + * ARM64 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. Importantly 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) >> + * >> + * x0: output bytes >> + * x1: 32-byte key input >> + * x2: 8-byte counter input/output >> + * x3: number of 64-byte block to write to output >> + */ >> +SYM_FUNC_START(__arch_chacha20_blocks_nostack) > > Is there any way we can reuse the existing code in > crypto/chacha-neon-core.S for this? It looks to my untrained eye like > this is an arbitrarily different implementation to what we already have. > >> + /* copy0 = "expand 32-byte k" */ >> + adr_l x8, CTES >> + ld1 {copy0.4s}, [x8] >> + /* copy1,copy2 = key */ >> + ld1 { copy1.4s, copy2.4s }, [x1] >> + /* copy3 = counter || zero nonce */ >> + ldr copy3_d, [x2] >> + >> + adr_l x8, ONE >> + ldr one_q, [x8] >> + >> + adr_l x10, ROT8 >> + ld1 {rot8.4s}, [x10] >> +.Lblock: >> + /* copy state to auxiliary vectors for the final add after the permute. */ >> + mov state0.16b, copy0.16b >> + mov state1.16b, copy1.16b >> + mov state2.16b, copy2.16b >> + mov state3.16b, copy3.16b >> + >> + mov w4, 20 >> +.Lpermute: >> + /* >> + * Permute one 64-byte block where the state matrix is stored in the four NEON >> + * registers state0-state3. It performs matrix operations on four words in parallel, >> + * but requires shuffling to rearrange the words after each round. >> + */ >> + >> +.Ldoubleround: >> + /* state0 += state1, state3 = rotl32(state3 ^ state0, 16) */ >> + add state0.4s, state0.4s, state1.4s >> + eor state3.16b, state3.16b, state0.16b >> + rev32 state3.8h, state3.8h >> + >> + /* state2 += state3, state1 = rotl32(state1 ^ state2, 12) */ >> + add state2.4s, state2.4s, state3.4s >> + eor tmp.16b, state1.16b, state2.16b >> + shl state1.4s, tmp.4s, #12 >> + sri state1.4s, tmp.4s, #20 >> + >> + /* state0 += state1, state3 = rotl32(state3 ^ state0, 8) */ >> + add state0.4s, state0.4s, state1.4s >> + eor state3.16b, state3.16b, state0.16b >> + tbl state3.16b, {state3.16b}, rot8.16b >> + >> + /* state2 += state3, state1 = rotl32(state1 ^ state2, 7) */ >> + add state2.4s, state2.4s, state3.4s >> + eor tmp.16b, state1.16b, state2.16b >> + shl state1.4s, tmp.4s, #7 >> + sri state1.4s, tmp.4s, #25 >> + >> + /* state1[0,1,2,3] = state1[1,2,3,0] */ >> + ext state1.16b, state1.16b, state1.16b, #4 >> + /* state2[0,1,2,3] = state2[2,3,0,1] */ >> + ext state2.16b, state2.16b, state2.16b, #8 >> + /* state3[0,1,2,3] = state3[1,2,3,0] */ >> + ext state3.16b, state3.16b, state3.16b, #12 >> + >> + /* state0 += state1, state3 = rotl32(state3 ^ state0, 16) */ >> + add state0.4s, state0.4s, state1.4s >> + eor state3.16b, state3.16b, state0.16b >> + rev32 state3.8h, state3.8h >> + >> + /* state2 += state3, state1 = rotl32(state1 ^ state2, 12) */ >> + add state2.4s, state2.4s, state3.4s >> + eor tmp.16b, state1.16b, state2.16b >> + shl state1.4s, tmp.4s, #12 >> + sri state1.4s, tmp.4s, #20 >> + >> + /* state0 += state1, state3 = rotl32(state3 ^ state0, 8) */ >> + add state0.4s, state0.4s, state1.4s >> + eor state3.16b, state3.16b, state0.16b >> + tbl state3.16b, {state3.16b}, rot8.16b >> + >> + /* state2 += state3, state1 = rotl32(state1 ^ state2, 7) */ >> + add state2.4s, state2.4s, state3.4s >> + eor tmp.16b, state1.16b, state2.16b >> + shl state1.4s, tmp.4s, #7 >> + sri state1.4s, tmp.4s, #25 >> + >> + /* state1[0,1,2,3] = state1[3,0,1,2] */ >> + ext state1.16b, state1.16b, state1.16b, #12 >> + /* state2[0,1,2,3] = state2[2,3,0,1] */ >> + ext state2.16b, state2.16b, state2.16b, #8 >> + /* state3[0,1,2,3] = state3[1,2,3,0] */ >> + ext state3.16b, state3.16b, state3.16b, #4 >> + >> + subs w4, w4, #2 >> + b.ne .Ldoubleround >> + >> + /* output0 = state0 + state0 */ >> + add state0.4s, state0.4s, copy0.4s >> + /* output1 = state1 + state1 */ >> + add state1.4s, state1.4s, copy1.4s >> + /* output2 = state2 + state2 */ >> + add state2.4s, state2.4s, copy2.4s >> + /* output2 = state3 + state3 */ >> + add state3.4s, state3.4s, copy3.4s >> + st1 { state0.4s - state3.4s }, [x0] >> + >> + /* ++copy3.counter */ >> + add copy3_d, copy3_d, one_d >> + >> + /* output += 64, --nblocks */ >> + add x0, x0, 64 >> + subs x3, x3, #1 >> + b.ne .Lblock >> + >> + /* counter = copy3.counter */ >> + str copy3_d, [x2] >> + >> + /* Zero out the potentially sensitive regs, in case nothing uses these again. */ >> + eor state0.16b, state0.16b, state0.16b >> + eor state1.16b, state1.16b, state1.16b >> + eor state2.16b, state2.16b, state2.16b >> + eor state3.16b, state3.16b, state3.16b >> + eor copy1.16b, copy1.16b, copy1.16b >> + eor copy2.16b, copy2.16b, copy2.16b >> + ret >> +SYM_FUNC_END(__arch_chacha20_blocks_nostack) >> + >> + .section ".rodata", "a", %progbits >> + .align L1_CACHE_SHIFT >> + >> +CTES: .word 1634760805, 857760878, 2036477234, 1797285236 >> +ONE: .xword 1, 0 >> +ROT8: .word 0x02010003, 0x06050407, 0x0a09080b, 0x0e0d0c0f >> + >> +emit_aarch64_feature_1_and >> diff --git a/arch/arm64/kernel/vdso/vgetrandom.c b/arch/arm64/kernel/vdso/vgetrandom.c >> new file mode 100644 >> index 000000000000..0833d25f3121 >> --- /dev/null >> +++ b/arch/arm64/kernel/vdso/vgetrandom.c >> @@ -0,0 +1,15 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> + >> +typeof(__cvdso_getrandom) __kernel_getrandom; >> + >> +ssize_t __kernel_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len) >> +{ >> + asm goto ( >> + ALTERNATIVE("b %[fallback]", "nop", RM64_HAS_FPSIMD) : : : : fallback); > > "RM64_HAS_FPSIMD". Are you sure you've tested this? I am not sure why build has not failed (I double test and it does not generate a wrong relocation) or why vdso does seems to have the nop in the expected place. I have changed to ARM64_HAS_FPSIMD. > >> + return __cvdso_getrandom(buffer, len, flags, opaque_state, opaque_len); >> + >> +fallback: >> + if (unlikely(opaque_len == ~0UL && !buffer && !len && !flags)) >> + return -ENOSYS; >> + return getrandom_syscall(buffer, len, flags); >> +} >> diff --git a/lib/vdso/getrandom.c b/lib/vdso/getrandom.c >> index 938ca539aaa6..7c9711248d9b 100644 >> --- a/lib/vdso/getrandom.c >> +++ b/lib/vdso/getrandom.c >> @@ -5,6 +5,7 @@ >> >> #include <linux/array_size.h> >> #include <linux/minmax.h> >> +#include <linux/mm.h> >> #include <vdso/datapage.h> >> #include <vdso/getrandom.h> >> #include <vdso/unaligned.h> > > Looks like this should be a separate change? It is required so arm64 can use c-getrandom-y, otherwise vgetrandom.o build fails: CC arch/arm64/kernel/vdso/vgetrandom.o In file included from ./include/uapi/linux/mman.h:5, from /mnt/projects/linux/linux-git/lib/vdso/getrandom.c:13, from <command-line>: ./arch/arm64/include/asm/mman.h: In function ‘arch_calc_vm_prot_bits’: ./arch/arm64/include/asm/mman.h:14:13: error: implicit declaration of function ‘system_supports_bti’ [-Werror=implicit-function-declaration] 14 | if (system_supports_bti() && (prot & PROT_BTI)) | ^~~~~~~~~~~~~~~~~~~ ./arch/arm64/include/asm/mman.h:15:24: error: ‘VM_ARM64_BTI’ undeclared (first use in this function); did you mean ‘ARM64_BTI’? 15 | ret |= VM_ARM64_BTI; | ^~~~~~~~~~~~ | ARM64_BTI ./arch/arm64/include/asm/mman.h:15:24: note: each undeclared identifier is reported only once for each function it appears in ./arch/arm64/include/asm/mman.h:17:13: error: implicit declaration of function ‘system_supports_mte’ [-Werror=implicit-function-declaration] 17 | if (system_supports_mte() && (prot & PROT_MTE)) | ^~~~~~~~~~~~~~~~~~~ ./arch/arm64/include/asm/mman.h:18:24: error: ‘VM_MTE’ undeclared (first use in this function) 18 | ret |= VM_MTE; | ^~~~~~ ./arch/arm64/include/asm/mman.h: In function ‘arch_calc_vm_flag_bits’: ./arch/arm64/include/asm/mman.h:32:24: error: ‘VM_MTE_ALLOWED’ undeclared (first use in this function) 32 | return VM_MTE_ALLOWED; | ^~~~~~~~~~~~~~ ./arch/arm64/include/asm/mman.h: In function ‘arch_validate_flags’: ./arch/arm64/include/asm/mman.h:59:29: error: ‘VM_MTE’ undeclared (first use in this function) 59 | return !(vm_flags & VM_MTE) || (vm_flags & VM_MTE_ALLOWED); | ^~~~~~ ./arch/arm64/include/asm/mman.h:59:52: error: ‘VM_MTE_ALLOWED’ undeclared (first use in this function) 59 | return !(vm_flags & VM_MTE) || (vm_flags & VM_MTE_ALLOWED); | ^~~~~~~~~~~~~~ arch/arm64/kernel/vdso/vgetrandom.c: In function ‘__kernel_getrandom’: arch/arm64/kernel/vdso/vgetrandom.c:18:25: error: ‘ENOSYS’ undeclared (first use in this function); did you mean ‘ENOSPC’? 18 | return -ENOSYS; | ^~~~~~ | ENOSPC cc1: some warnings being treated as errors I can move to a different patch, but this is really tied to this patch.