diff options
| -rw-r--r-- | arch/riscv/Kconfig | 14 | ||||
| -rw-r--r-- | arch/riscv/Makefile | 2 | ||||
| -rw-r--r-- | arch/riscv/include/asm/asm-extable.h | 15 | ||||
| -rw-r--r-- | arch/riscv/include/asm/word-at-a-time.h | 27 | ||||
| -rw-r--r-- | arch/riscv/mm/extable.c | 31 |
5 files changed, 89 insertions, 0 deletions
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 19dfd521a52a..3db3d0fa046e 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -652,6 +652,20 @@ config RISCV_MISALIGNED load/store for both kernel and userspace. When disable, misaligned accesses will generate SIGBUS in userspace and panic in kernel. +config RISCV_EFFICIENT_UNALIGNED_ACCESS + bool "Assume the CPU supports fast unaligned memory accesses" + depends on NONPORTABLE + select DCACHE_WORD_ACCESS if MMU + select HAVE_EFFICIENT_UNALIGNED_ACCESS + help + Say Y here if you want the kernel to assume that the CPU supports + efficient unaligned memory accesses. When enabled, this option + improves the performance of the kernel on such CPUs. However, the + kernel will run much more slowly, or will not be able to run at all, + on CPUs that do not support efficient unaligned memory accesses. + + If unsure what to do here, say N. + endmenu # "Platform type" menu "Kernel features" diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index a74be78678eb..ebbe02628a27 100644 --- a/arch/riscv/Makefile +++ b/arch/riscv/Makefile @@ -108,7 +108,9 @@ KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax) # unaligned accesses. While unaligned accesses are explicitly allowed in the # RISC-V ISA, they're emulated by machine mode traps on all extant # architectures. It's faster to have GCC emit only aligned accesses. +ifneq ($(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS),y) KBUILD_CFLAGS += $(call cc-option,-mstrict-align) +endif ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) prepare: stack_protector_prepare diff --git a/arch/riscv/include/asm/asm-extable.h b/arch/riscv/include/asm/asm-extable.h index 00a96e7a9664..0c8bfd54fc4e 100644 --- a/arch/riscv/include/asm/asm-extable.h +++ b/arch/riscv/include/asm/asm-extable.h @@ -6,6 +6,7 @@ #define EX_TYPE_FIXUP 1 #define EX_TYPE_BPF 2 #define EX_TYPE_UACCESS_ERR_ZERO 3 +#define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4 #ifdef CONFIG_MMU @@ -47,6 +48,11 @@ #define EX_DATA_REG_ZERO_SHIFT 5 #define EX_DATA_REG_ZERO GENMASK(9, 5) +#define EX_DATA_REG_DATA_SHIFT 0 +#define EX_DATA_REG_DATA GENMASK(4, 0) +#define EX_DATA_REG_ADDR_SHIFT 5 +#define EX_DATA_REG_ADDR GENMASK(9, 5) + #define EX_DATA_REG(reg, gpr) \ "((.L__gpr_num_" #gpr ") << " __stringify(EX_DATA_REG_##reg##_SHIFT) ")" @@ -62,6 +68,15 @@ #define _ASM_EXTABLE_UACCESS_ERR(insn, fixup, err) \ _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, zero) +#define _ASM_EXTABLE_LOAD_UNALIGNED_ZEROPAD(insn, fixup, data, addr) \ + __DEFINE_ASM_GPR_NUMS \ + __ASM_EXTABLE_RAW(#insn, #fixup, \ + __stringify(EX_TYPE_LOAD_UNALIGNED_ZEROPAD), \ + "(" \ + EX_DATA_REG(DATA, data) " | " \ + EX_DATA_REG(ADDR, addr) \ + ")") + #endif /* __ASSEMBLY__ */ #else /* CONFIG_MMU */ diff --git a/arch/riscv/include/asm/word-at-a-time.h b/arch/riscv/include/asm/word-at-a-time.h index 7c086ac6ecd4..f3f031e34191 100644 --- a/arch/riscv/include/asm/word-at-a-time.h +++ b/arch/riscv/include/asm/word-at-a-time.h @@ -9,6 +9,7 @@ #define _ASM_RISCV_WORD_AT_A_TIME_H +#include <asm/asm-extable.h> #include <linux/kernel.h> struct word_at_a_time { @@ -45,4 +46,30 @@ static inline unsigned long find_zero(unsigned long mask) /* The mask we created is directly usable as a bytemask */ #define zero_bytemask(mask) (mask) +#ifdef CONFIG_DCACHE_WORD_ACCESS + +/* + * Load an unaligned word from kernel space. + * + * In the (very unlikely) case of the word being a page-crosser + * and the next page not being mapped, take the exception and + * return zeroes in the non-existing part. + */ +static inline unsigned long load_unaligned_zeropad(const void *addr) +{ + unsigned long ret; + + /* Load word from unaligned pointer addr */ + asm( + "1: " REG_L " %0, %2\n" + "2:\n" + _ASM_EXTABLE_LOAD_UNALIGNED_ZEROPAD(1b, 2b, %0, %1) + : "=&r" (ret) + : "r" (addr), "m" (*(unsigned long *)addr)); + + return ret; +} + +#endif /* CONFIG_DCACHE_WORD_ACCESS */ + #endif /* _ASM_RISCV_WORD_AT_A_TIME_H */ diff --git a/arch/riscv/mm/extable.c b/arch/riscv/mm/extable.c index 35484d830fd6..dd1530af3ef1 100644 --- a/arch/riscv/mm/extable.c +++ b/arch/riscv/mm/extable.c @@ -27,6 +27,14 @@ static bool ex_handler_fixup(const struct exception_table_entry *ex, return true; } +static inline unsigned long regs_get_gpr(struct pt_regs *regs, unsigned int offset) +{ + if (unlikely(!offset || offset > MAX_REG_OFFSET)) + return 0; + + return *(unsigned long *)((unsigned long)regs + offset); +} + static inline void regs_set_gpr(struct pt_regs *regs, unsigned int offset, unsigned long val) { @@ -50,6 +58,27 @@ static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex, return true; } +static bool +ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, + struct pt_regs *regs) +{ + int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->data); + int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data); + unsigned long data, addr, offset; + + addr = regs_get_gpr(regs, reg_addr * sizeof(unsigned long)); + + offset = addr & 0x7UL; + addr &= ~0x7UL; + + data = *(unsigned long *)addr >> (offset * 8); + + regs_set_gpr(regs, reg_data * sizeof(unsigned long), data); + + regs->epc = get_ex_fixup(ex); + return true; +} + bool fixup_exception(struct pt_regs *regs) { const struct exception_table_entry *ex; @@ -65,6 +94,8 @@ bool fixup_exception(struct pt_regs *regs) return ex_handler_bpf(ex, regs); case EX_TYPE_UACCESS_ERR_ZERO: return ex_handler_uaccess_err_zero(ex, regs); + case EX_TYPE_LOAD_UNALIGNED_ZEROPAD: + return ex_handler_load_unaligned_zeropad(ex, regs); } BUG(); |