From: Zhangjin Wu
Sent: 09 June 2023 05:43
Hi, Thomas, David, Willy
Hi David,
On 2023-06-08 14:35:49+0000, David Laight wrote:
From: Zhangjin Wu
Sent: 06 June 2023 09:10
most of the library routines share the same code model, let's add two helpers to simplify the coding and shrink the code lines too.
...
+/* Syscall return helper, set errno as -ret when ret < 0 */ +static inline __attribute__((always_inline)) long __sysret(long ret) +{
- if (ret < 0) {
SET_ERRNO(-ret);ret = -1;- }
- return ret;
+}
If that right? I thought that that only the first few (1024?) negative values got used as errno values.
Thanks David, this question did inspire me to think about the syscalls who returns pointers, we didn't touch them yet:
I'm also not sure whether lseek() is expected to return values that would be negative.
(I do remember having to patch out some checks (not Linux) in order to use: echo -n xxxx | dd of=/dev/kmem oseek=nnn in order to patch a live kernel!)
Technically read() and write() can do longer transfers, but Linux limits them to MAXINT. IIRC both BSD and SYSV allow drivers return all values (except -1) form ioctl().
The check for -4095UL is probably reasonable.
David
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