B
Branch causes an unconditional branch to a label at a PC-relative offset, with a hint that this is not a subroutine call or return.
在PC相对偏移处对标签进行无条件分支，并提示这不是子程序调用或返回。
操作码 助记符 标志 含义
0x2 0010 CS/HS C = 1 无符号数大于或等于
402c88: f9401fe2 ldr x2, sp, #56 // x2="%s/%d/task/%d/stat"
402c8c: 2a1c03e5 mov w5, w28 // w5=w28=tid
402c90: f94047e1 ldr x1, sp, #136 // x1=len
402c94: 2a1303e4 mov w4, w19 // w4=w19=pid
402c98: aa1a03e3 mov x3, x26 // x3=x26="/proc"
402c9c: 97fffb91 bl 401ae0 <snprintf@plt>
int nbytes = snprintf(path, len, "%s/%d/task/%d/stat", "/proc", pid, tid);
402ca0: b94013e1 ldr w1, sp, #16 // w1 = len
402ca4: 6b01001f cmp w0, w1 // w0 = nbytes
402ca8: 54000a02 b.cs 402de8 <ferror@plt+0xf08> // b.hs, b.nlast
if (nbytes < 0 || nbytes >= len)
perror("get_threadname: snprintf");