git: 185bd9fa3096 - main - linux(4): Simplify %r10 restoring on amd64

[Dmitry Chagin]

The branch main has been updated by dchagin:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=185bd9fa3096595350ebe7bcd7e0ddcf17773030

commit 185bd9fa3096595350ebe7bcd7e0ddcf17773030
Author:     Dmitry Chagin <dcha...@freebsd.org>
AuthorDate: 2023-05-28 14:06:23 +0000
Commit:     Dmitry Chagin <dcha...@freebsd.org>
CommitDate: 2023-05-28 14:06:23 +0000

    linux(4): Simplify %r10 restoring on amd64
    
    Restore %r10 at system call entry to avoid doing this multiply times.
    
    Differential Revision:  https://reviews.freebsd.org/D40154
    MFC after:              1 month
---
 sys/amd64/linux/linux_machdep.c | 6 ------
 sys/amd64/linux/linux_sysvec.c  | 6 +++---
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/sys/amd64/linux/linux_machdep.c b/sys/amd64/linux/linux_machdep.c
index 6ac0ab0cd3d7..155ea918cd0a 100644
--- a/sys/amd64/linux/linux_machdep.c
+++ b/sys/amd64/linux/linux_machdep.c
@@ -350,12 +350,6 @@ linux_ptrace_getregs_machdep(struct thread *td, pid_t pid,
                linux_msg(td, "PT_LWPINFO failed with error %d", error);
                return (error);
        }
-       if ((lwpinfo.pl_flags & PL_FLAG_SCE) != 0) {
-               /*
-                * 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)) != 0) {
                /*
                 * In Linux, the syscall number - passed to the syscall
diff --git a/sys/amd64/linux/linux_sysvec.c b/sys/amd64/linux/linux_sysvec.c
index 89d388dc6cf8..422cfbe7c5ba 100644
--- a/sys/amd64/linux/linux_sysvec.c
+++ b/sys/amd64/linux/linux_sysvec.c
@@ -167,6 +167,9 @@ linux_fetch_syscall_args(struct thread *td)
        else
                sa->callp = &p->p_sysent->sv_table[sa->code];
 
+       /* Restore r10 earlier to avoid doing this multiply times. */
+       frame->tf_r10 = frame->tf_rcx;
+
        td->td_retval[0] = 0;
        return (0);
 }
@@ -181,7 +184,6 @@ linux_set_syscall_retval(struct thread *td, int error)
        switch (error) {
        case 0:
                frame->tf_rax = td->td_retval[0];
-               frame->tf_r10 = frame->tf_rcx;
                break;
 
        case ERESTART:
@@ -192,7 +194,6 @@ linux_set_syscall_retval(struct thread *td, int error)
                 *
                 */
                frame->tf_rip -= frame->tf_err;
-               frame->tf_r10 = frame->tf_rcx;
                break;
 
        case EJUSTRETURN:
@@ -200,7 +201,6 @@ linux_set_syscall_retval(struct thread *td, int error)
 
        default:
                frame->tf_rax = bsd_to_linux_errno(error);
-               frame->tf_r10 = frame->tf_rcx;
                break;
        }