From 41040cf7c5f0f26c368bc5d3016fed3a9ca6dba4 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Wed, 12 Jun 2019 17:00:32 +0100 Subject: arm64/sve: Fix missing SVE/FPSIMD endianness conversions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The in-memory representation of SVE and FPSIMD registers is different: the FPSIMD V-registers are stored as single 128-bit host-endian values, whereas SVE registers are stored in an endianness-invariant byte order. This means that the two representations differ when running on a big-endian host. But we blindly copy data from one representation to another when converting between the two, resulting in the register contents being unintentionally byteswapped in certain situations. Currently this can be triggered by the first SVE instruction after a syscall, for example (though the potential trigger points may vary in future). So, fix the conversion functions fpsimd_to_sve(), sve_to_fpsimd() and sve_sync_from_fpsimd_zeropad() to swab where appropriate. There is no common swahl128() or swab128() that we could use here. Maybe it would be worth making this generic, but for now add a simple local hack. Since the byte order differences are exposed in ABI, also clarify the documentation. Cc: Alex Bennée Cc: Peter Maydell Cc: Alan Hayward Cc: Julien Grall Fixes: bc0ee4760364 ("arm64/sve: Core task context handling") Fixes: 8cd969d28fd2 ("arm64/sve: Signal handling support") Fixes: 43d4da2c45b2 ("arm64/sve: ptrace and ELF coredump support") Signed-off-by: Dave Martin [will: Fix typos in comments and docs spotted by Julien] Signed-off-by: Will Deacon --- arch/arm64/kernel/fpsimd.c | 42 +++++++++++++++++++++++++++++++++--------- 1 file changed, 33 insertions(+), 9 deletions(-) (limited to 'arch/arm64/kernel/fpsimd.c') 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 #include #include +#include #include #include @@ -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, -- cgit v1.2.3