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linux(4): fix ptrace(2) to properly handle orig_rax

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This fixes strace(1) erroneously reporting return values
as "Function not implemented", combined with reporting the binary
ABI as X32.

Very similar code in linux_ptrace_getregs() is left as it is - it's
probably wrong too, but I don't have a way to test it.

Sponsored By:	EPSRC
Differential Revision:	https://reviews.freebsd.org/D29927
This commit is contained in:
Edward Tomasz Napierala 2021-05-04 14:11:01 +01:00
parent b59851e99c
commit 023bff7990
1 changed files with 9 additions and 9 deletions
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18
sys/amd64/linux/linux_ptrace.c
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@ -505,21 +505,21 @@ linux_ptrace_getregset_prstatus(struct thread *td, pid_t pid, l_ulong data)
return (error);
}
if (lwpinfo.pl_flags & PL_FLAG_SCE) {
/*
* The strace(1) utility depends on RAX being set to -ENOSYS
* on syscall entry; otherwise it loops printing those:
*
* [ Process PID=928 runs in 64 bit mode. ]
* [ Process PID=928 runs in x32 mode. ]
*/
l_regset.rax = -38; /* -ENOSYS */
/*
* Undo the mangling done in exception.S:fast_syscall_common().
*/
l_regset.r10 = l_regset.rcx;
}
if (lwpinfo.pl_flags & (PL_FLAG_SCE | PL_FLAG_SCX)) {
/*
* In Linux, the syscall number - passed to the syscall
* as rax - is preserved in orig_rax; rax gets overwritten
* with syscall return value.
*/
l_regset.orig_rax = lwpinfo.pl_syscall_code;
}
len = MIN(iov.iov_len, sizeof(l_regset));
error = copyout(&l_regset, (void *)iov.iov_base, len);
if (error != 0) {