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qemu-riscv32: Syscall LSEEK returns -14 (EFAULT)
Description of problem:
The lseek() system call returns -14 (EFAULT) if the file descriptor is correct,
which it should never do (According to the lseek(2) man page).
Here is some demonstrative code:
```
/* System Call numbers, according to https://github.com/riscv-software-src/riscv-pk/blob/master/pk/syscall.h */
.set SYS_OPENAT, 0x38
.set SYS_CLOSE, 0x39
.set SYS_LSEEK, 0x3e
.set SYS_READ, 0x3f
.set SYS_WRITE, 0x40
.set SYS_EXIT, 0x5d
.set SEEK_CUR, 1
/* According to https://elixir.bootlin.com/linux/v5.16.2/C/ident/AT_FDCWD */
.set AT_FDCWD, (-100)
.section .text
.global _start
_start:
/* Open the file with SYS_OPENAT, because SYS_OPEN does not exist on riscv32 for some reason.
Effectively:
s0 = open(argv[1], 0, 0644); */
li a7, SYS_OPENAT
li a0, AT_FDCWD
lw a1, 8(sp)
li a2, 0
li a3, 0644
ecall
/* Error checking. This succeeds. */
blt a0, zero, unrelated_error
mv s0, a0
/* The broken lseek() call.
Same also happens no matter the position in the file.
Effectively:
lseek(s0, 0, SEEK_CUR); */
li a7, SYS_LSEEK
mv a0, s0
li a1, 0
li a2, SEEK_CUR
ecall
/* XXX: lseek() returns -14 */
blt a0, zero, lseek_error
/* Close the file. */
li a7, SYS_CLOSE
mv a0, s0
ecall
/* Error checking. This also succeeds. */
blt a0, zero, unrelated_error
/* exit(0); */
li a7, SYS_EXIT
li a0, 0
ecall
/* exit(-return_value); */
lseek_error:
li a7, SYS_EXIT
sub a0, zero, a0
ecall
unrelated_error:
li a7, SYS_EXIT
li a0, 128
ecall
```
Steps to reproduce:
1. riscv32-unknown-linux-gnu-as test.s -o test.o
2. riscv32-unknown-linux-gnu-ld test.o
3. qemu-riscv32 ./a.out test
4. echo $? # This returns 14
Additional information:
Complete test setup:
[test.tgz](/uploads/af68c9a5236628a9c6f31f2ce94e2f04/test.tgz)
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