diff options
| -rw-r--r-- | Documentation/arm64/sve.txt | 16 | ||||
| -rw-r--r-- | arch/arm64/include/uapi/asm/kvm.h | 7 | ||||
| -rw-r--r-- | arch/arm64/include/uapi/asm/ptrace.h | 4 | ||||
| -rw-r--r-- | arch/arm64/include/uapi/asm/sigcontext.h | 14 | ||||
| -rw-r--r-- | arch/arm64/kernel/fpsimd.c | 42 |
5 files changed, 74 insertions, 9 deletions
diff --git a/Documentation/arm64/sve.txt b/Documentation/arm64/sve.txt index 9940e924a47e..5689fc9a976a 100644 --- a/Documentation/arm64/sve.txt +++ b/Documentation/arm64/sve.txt @@ -56,6 +56,18 @@ model features for SVE is included in Appendix A. is to connect to a target process first and then attempt a ptrace(PTRACE_GETREGSET, pid, NT_ARM_SVE, &iov). +* Whenever SVE scalable register values (Zn, Pn, FFR) are exchanged in memory + between userspace and the kernel, the register value is encoded in memory in + an endianness-invariant layout, with bits [(8 * i + 7) : (8 * i)] encoded at + byte offset i from the start of the memory representation. This affects for + example the signal frame (struct sve_context) and ptrace interface + (struct user_sve_header) and associated data. + + Beware that on big-endian systems this results in a different byte order than + for the FPSIMD V-registers, which are stored as single host-endian 128-bit + values, with bits [(127 - 8 * i) : (120 - 8 * i)] of the register encoded at + byte offset i. (struct fpsimd_context, struct user_fpsimd_state). + 2. Vector length terminology ----------------------------- @@ -124,6 +136,10 @@ the SVE instruction set architecture. size and layout. Macros SVE_SIG_* are defined [1] to facilitate access to the members. +* Each scalable register (Zn, Pn, FFR) is stored in an endianness-invariant + layout, with bits [(8 * i + 7) : (8 * i)] stored at byte offset i from the + start of the register's representation in memory. + * If the SVE context is too big to fit in sigcontext.__reserved[], then extra space is allocated on the stack, an extra_context record is written in __reserved[] referencing this space. sve_context is then written in the diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h index 7b7ac0f6cec9..d819a3e8b552 100644 --- a/arch/arm64/include/uapi/asm/kvm.h +++ b/arch/arm64/include/uapi/asm/kvm.h @@ -260,6 +260,13 @@ struct kvm_vcpu_events { KVM_REG_SIZE_U256 | \ ((i) & (KVM_ARM64_SVE_MAX_SLICES - 1))) +/* + * Register values for KVM_REG_ARM64_SVE_ZREG(), KVM_REG_ARM64_SVE_PREG() and + * KVM_REG_ARM64_SVE_FFR() are represented in memory in an endianness- + * invariant layout which differs from the layout used for the FPSIMD + * V-registers on big-endian systems: see sigcontext.h for more explanation. + */ + #define KVM_ARM64_SVE_VQ_MIN __SVE_VQ_MIN #define KVM_ARM64_SVE_VQ_MAX __SVE_VQ_MAX diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h index d78623acb649..97c53203150b 100644 --- a/arch/arm64/include/uapi/asm/ptrace.h +++ b/arch/arm64/include/uapi/asm/ptrace.h @@ -176,6 +176,10 @@ struct user_sve_header { * FPCR uint32_t FPCR * * Additional data might be appended in the future. + * + * The Z-, P- and FFR registers are represented in memory in an endianness- + * invariant layout which differs from the layout used for the FPSIMD + * V-registers on big-endian systems: see sigcontext.h for more explanation. */ #define SVE_PT_SVE_ZREG_SIZE(vq) __SVE_ZREG_SIZE(vq) diff --git a/arch/arm64/include/uapi/asm/sigcontext.h b/arch/arm64/include/uapi/asm/sigcontext.h index 5f3c0cec5af9..3d448a0bb225 100644 --- a/arch/arm64/include/uapi/asm/sigcontext.h +++ b/arch/arm64/include/uapi/asm/sigcontext.h @@ -77,6 +77,15 @@ struct fpsimd_context { __uint128_t vregs[32]; }; +/* + * Note: similarly to all other integer fields, each V-register is stored in an + * endianness-dependent format, with the byte at offset i from the start of the + * in-memory representation of the register value containing + * + * bits [(7 + 8 * i) : (8 * i)] of the register on little-endian hosts; or + * bits [(127 - 8 * i) : (120 - 8 * i)] on big-endian hosts. + */ + /* ESR_EL1 context */ #define ESR_MAGIC 0x45535201 @@ -204,6 +213,11 @@ struct sve_context { * FFR uint16_t[vq] first-fault status register * * Additional data might be appended in the future. + * + * Unlike vregs[] in fpsimd_context, each SVE scalable register (Z-, P- or FFR) + * is encoded in memory in an endianness-invariant format, with the byte at + * offset i from the start of the in-memory representation containing bits + * [(7 + 8 * i) : (8 * i)] of the register value. */ #define SVE_SIG_ZREG_SIZE(vq) __SVE_ZREG_SIZE(vq) diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index a38bf74bcca8..bb42cd04baec 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -39,6 +39,7 @@ #include <linux/slab.h> #include <linux/stddef.h> #include <linux/sysctl.h> +#include <linux/swab.h> #include <asm/esr.h> #include <asm/fpsimd.h> @@ -352,6 +353,23 @@ static int __init sve_sysctl_init(void) { return 0; } #define ZREG(sve_state, vq, n) ((char *)(sve_state) + \ (SVE_SIG_ZREG_OFFSET(vq, n) - SVE_SIG_REGS_OFFSET)) +#ifdef CONFIG_CPU_BIG_ENDIAN +static __uint128_t arm64_cpu_to_le128(__uint128_t x) +{ + u64 a = swab64(x); + u64 b = swab64(x >> 64); + + return ((__uint128_t)a << 64) | b; +} +#else +static __uint128_t arm64_cpu_to_le128(__uint128_t x) +{ + return x; +} +#endif + +#define arm64_le128_to_cpu(x) arm64_cpu_to_le128(x) + /* * Transfer the FPSIMD state in task->thread.uw.fpsimd_state to * task->thread.sve_state. @@ -369,14 +387,16 @@ static void fpsimd_to_sve(struct task_struct *task) void *sst = task->thread.sve_state; struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state; unsigned int i; + __uint128_t *p; if (!system_supports_sve()) return; vq = sve_vq_from_vl(task->thread.sve_vl); - for (i = 0; i < 32; ++i) - memcpy(ZREG(sst, vq, i), &fst->vregs[i], - sizeof(fst->vregs[i])); + for (i = 0; i < 32; ++i) { + p = (__uint128_t *)ZREG(sst, vq, i); + *p = arm64_cpu_to_le128(fst->vregs[i]); + } } /* @@ -395,14 +415,16 @@ static void sve_to_fpsimd(struct task_struct *task) void const *sst = task->thread.sve_state; struct user_fpsimd_state *fst = &task->thread.uw.fpsimd_state; unsigned int i; + __uint128_t const *p; if (!system_supports_sve()) return; vq = sve_vq_from_vl(task->thread.sve_vl); - for (i = 0; i < 32; ++i) - memcpy(&fst->vregs[i], ZREG(sst, vq, i), - sizeof(fst->vregs[i])); + for (i = 0; i < 32; ++i) { + p = (__uint128_t const *)ZREG(sst, vq, i); + fst->vregs[i] = arm64_le128_to_cpu(*p); + } } #ifdef CONFIG_ARM64_SVE @@ -491,6 +513,7 @@ void sve_sync_from_fpsimd_zeropad(struct task_struct *task) void *sst = task->thread.sve_state; struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state; unsigned int i; + __uint128_t *p; if (!test_tsk_thread_flag(task, TIF_SVE)) return; @@ -499,9 +522,10 @@ void sve_sync_from_fpsimd_zeropad(struct task_struct *task) memset(sst, 0, SVE_SIG_REGS_SIZE(vq)); - for (i = 0; i < 32; ++i) - memcpy(ZREG(sst, vq, i), &fst->vregs[i], - sizeof(fst->vregs[i])); + for (i = 0; i < 32; ++i) { + p = (__uint128_t *)ZREG(sst, vq, i); + *p = arm64_cpu_to_le128(fst->vregs[i]); + } } int sve_set_vector_length(struct task_struct *task, |