From: Zhangjin Wu
Sent: 14 August 2023 11:42
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Sure it's not pretty, and I'd rather just go back to SET_ERRNO() to be honest, because we're there just because of the temptation to remove lines that were not causing any difficulties :-/
I think we can do something in-between and deal only with signed returns, and explicitly place the test for MAX_ERRNO on the two unsigned ones (brk and mmap). It should look approximately like this:
#define __sysret(arg) \ ({ \ __typeof__(arg) __sysret_arg = (arg); \ (__sysret_arg < 0) ? ({ /* error ? */ \ SET_ERRNO(-__sysret_arg); /* yes: errno != -ret */ \ ((__typeof__(arg)) -1); /* return -1 */ \
I'm pretty sure you don't need the explicit cast. (It would be needed for a pointer type.) Can you use __arg < ? SET_ERRNO(-__arg), -1 : __arg
Thinking, maybe it should be:
#define __sysret(syscall_fn_args) ({ __typeof__(syscall_fn_args) __rval = syscall_fn_args; __rval >= 0 ? __rval : SET_ERRNO(-__rval), -1; })
Since, IIRC, the usage is return __sysret(sycall_fn(args));
I'm not sure how public SET_ERRO() is. But it could include the negate have the value of -1 cast to its argument type? I think: error = -(int)(long)(arg + 0u); will avoid any sign extension - the (int) might not even be needed.
David
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