Hi, When we write syscall wrappers with inline assembly, we often need to assign one register for both an input variable and an output variable. Per https://gcc.gnu.org/onlinedocs/gcc/Local-Register-Variables.html, such an inline assembly can be written register int *p1 asm ("r0") = …; register int *p2 asm ("r1") = …; register int *result asm ("r0"); asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2)); Note the use of constraint "0" for p1 which shares the same register as result. But currently in the Linux kernel vDSO, they are actually written like asm ("sysint" : "=r" (result) : "r" (p1), "r" (p2)); So the question here: is using "r" for p1 valid or not? Do we need to "fix" this everywhere for the vDSO? -- Xi Ruoyao <xry111@xxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University
