Mailing List Archive

commit 1e37e4d2c0e78108e06a6661ea82b785dc5a58fe
Author: Andrew Cooper <andrew.cooper3@citrix.com>
AuthorDate: Fri Oct 22 16:07:07 2021 +0100
Commit: Andrew Cooper <andrew.cooper3@citrix.com>
CommitDate: Tue Apr 9 17:16:32 2024 +0100

xen/wait: Remove indirect jump

There is no need for this to be an indirect jump at all. Execution always
returns to a specific location, so use a direct jump instead.

Use a named label for the jump. As both 1 and 2 have disappeared as labels,
rename 3 to skip to better describe its purpose.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit f03567bd7e8efc0f667a67905862e6047babdb7a)
---
xen/common/wait.c | 19 ++++++++-----------
1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/xen/common/wait.c b/xen/common/wait.c
index 24716e7676..9276d76464 100644
--- a/xen/common/wait.c
+++ b/xen/common/wait.c
@@ -144,18 +144,16 @@ static void __prepare_to_wait(struct waitqueue_vcpu *wqv)
"push %%r8; push %%r9; push %%r10; push %%r11;"
"push %%r12; push %%r13; push %%r14; push %%r15;"

- "call 1f;"
- "1: addq $2f-1b,(%%rsp);"
"sub %%esp,%%ecx;"
"cmp %3,%%ecx;"
- "ja 3f;"
+ "ja .L_skip;"
"mov %%rsp,%%rsi;"

/* check_wakeup_from_wait() longjmp()'s to this point. */
- "2: rep movsb;"
+ ".L_wq_resume: rep movsb;"
"mov %%rsp,%%rsi;"
- "3: pop %%rax;"

+ ".L_skip:"
"pop %%r15; pop %%r14; pop %%r13; pop %%r12;"
"pop %%r11; pop %%r10; pop %%r9; pop %%r8;"
"pop %%rbp; pop %%rdx; pop %%rbx; pop %%rax"
@@ -204,15 +202,14 @@ void check_wakeup_from_wait(void)
}

/*
- * Hand-rolled longjmp(). Returns to the pointer on the top of
- * wqv->stack, and lands on a `rep movs` instruction. All other GPRs are
- * restored from the stack, so are available for use here.
+ * Hand-rolled longjmp(). Returns to __prepare_to_wait(), and lands on a
+ * `rep movs` instruction. All other GPRs are restored from the stack, so
+ * are available for use here.
*/
asm volatile (
- "mov %1,%%"__OP"sp; INDIRECT_JMP %[ip]"
+ "mov %1,%%"__OP"sp; jmp .L_wq_resume;"
: : "S" (wqv->stack), "D" (wqv->esp),
- "c" ((char *)get_cpu_info() - (char *)wqv->esp),
- [ip] "r" (*(unsigned long *)wqv->stack)
+ "c" ((char *)get_cpu_info() - (char *)wqv->esp)
: "memory" );
unreachable();
}
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.15