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在optee中 arm_va2pa_helper實現了virtual addr轉換phys addr，具體實現如下

/*virt transform to phys, regardless of the virt is ddr addr or register addr*/arm_va2pa_helper((void *)buf_in, &phy_in);arm_va2pa_helper((void *)buf_out, &phy_out); #include <linux/module.h>#define BIT32(nr) ((1 & 0xffffffff) << (nr)) #define BIT64(nr) ((1 & 0xffffffffffffffff) << (nr))#define PAR_F BIT32(0) #define PAR_PA_SHIFT 12 #define PAR_PA_MASK (BIT64(36) - 1)#define DEFINE_REG_READ_FUNC_(reg, type, asmreg) \ static inline type read_##reg(void) \ { \type val; \\asm volatile("mrs %0, " #asmreg : "=r" (val)); \return val; \ }#define DEFINE_U64_REG_READ_FUNC(reg) \DEFINE_REG_READ_FUNC_(reg, uint64_t, reg)DEFINE_U64_REG_READ_FUNC(par_el1)static inline void write_at_s1e1r(uint64_t va) {asm volatile ("at S1E1R, %0" : : "r" (va)); }bool arm_va2pa_helper(void *va, uint64_t *pa) {uint64_t par;uint64_t par_pa_mask;bool ret = false;local_irq_disable();write_at_s1e1r((uint64_t)va);isb();par = read_par_el1();par_pa_mask = PAR_PA_MASK;if (par & PAR_F)goto out;*pa = (par & (par_pa_mask << PAR_PA_SHIFT)) |((uint64_t)va & ((1 << PAR_PA_SHIFT) - 1));ret = true; out:local_irq_enable();;return ret; } EXPORT_SYMBOL(arm_va2pa_helper);

總結一下arm_va2pa_helper，其實就是將虛擬地址寫入MMU寄存器，然后再讀取另外一個寄存器獲取物理地址

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