From: "H.J. Lu" <hongjiu.lu@intel.com>
To: GNU C Library <libc-alpha@sourceware.org>
Subject: [PATCH 1/2] x86-64/setcontext: Pop the pointer into %rdx after syscall
Date: Thu, 26 Apr 2018 12:17:00 -0000 [thread overview]
Message-ID: <20180426121700.GA30766@intel.com> (raw)
To prepare for shadow stack support, pop the pointer into %rdx after
syscall and use %rdx, instead of %rsi, to restore context. There is
no functional change.
Any comments?
H.J.
----
* sysdeps/unix/sysv/linux/x86_64/setcontext.S (__setcontext):
Pop the pointer into %rdx after syscall and use %rdx, instead
of %rsi, to restore context.
---
sysdeps/unix/sysv/linux/x86_64/setcontext.S | 39 +++++++++++++++--------------
1 file changed, 20 insertions(+), 19 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/x86_64/setcontext.S b/sysdeps/unix/sysv/linux/x86_64/setcontext.S
index 4a9b662074..5a1bdd8de6 100644
--- a/sysdeps/unix/sysv/linux/x86_64/setcontext.S
+++ b/sysdeps/unix/sysv/linux/x86_64/setcontext.S
@@ -44,21 +44,22 @@ ENTRY(__setcontext)
movl $_NSIG8,%r10d
movl $__NR_rt_sigprocmask, %eax
syscall
- popq %rdi /* Reload %rdi, adjust stack. */
+ /* Pop the pointer into RDX which is preserved by the syscall. */
+ popq %rdx
cfi_adjust_cfa_offset(-8)
cmpq $-4095, %rax /* Check %rax for error. */
jae SYSCALL_ERROR_LABEL /* Jump to error handler if error. */
/* Restore the floating-point context. Not the registers, only the
rest. */
- movq oFPREGS(%rdi), %rcx
+ movq oFPREGS(%rdx), %rcx
fldenv (%rcx)
- ldmxcsr oMXCSR(%rdi)
+ ldmxcsr oMXCSR(%rdx)
/* Load the new stack pointer, the preserved registers and
registers used for passing args. */
- cfi_def_cfa(%rdi, 0)
+ cfi_def_cfa(%rdx, 0)
cfi_offset(%rbx,oRBX)
cfi_offset(%rbp,oRBP)
cfi_offset(%r12,oR12)
@@ -68,27 +69,27 @@ ENTRY(__setcontext)
cfi_offset(%rsp,oRSP)
cfi_offset(%rip,oRIP)
- movq oRSP(%rdi), %rsp
- movq oRBX(%rdi), %rbx
- movq oRBP(%rdi), %rbp
- movq oR12(%rdi), %r12
- movq oR13(%rdi), %r13
- movq oR14(%rdi), %r14
- movq oR15(%rdi), %r15
+ movq oRSP(%rdx), %rsp
+ movq oRBX(%rdx), %rbx
+ movq oRBP(%rdx), %rbp
+ movq oR12(%rdx), %r12
+ movq oR13(%rdx), %r13
+ movq oR14(%rdx), %r14
+ movq oR15(%rdx), %r15
/* The following ret should return to the address set with
getcontext. Therefore push the address on the stack. */
- movq oRIP(%rdi), %rcx
+ movq oRIP(%rdx), %rcx
pushq %rcx
- movq oRSI(%rdi), %rsi
- movq oRDX(%rdi), %rdx
- movq oRCX(%rdi), %rcx
- movq oR8(%rdi), %r8
- movq oR9(%rdi), %r9
+ movq oRSI(%rdx), %rsi
+ movq oRDI(%rdx), %rdi
+ movq oRCX(%rdx), %rcx
+ movq oR8(%rdx), %r8
+ movq oR9(%rdx), %r9
- /* Setup finally %rdi. */
- movq oRDI(%rdi), %rdi
+ /* Setup finally %rdx. */
+ movq oRDX(%rdx), %rdx
/* End FDE here, we fall into another context. */
cfi_endproc
--
2.14.3
next reply other threads:[~2018-04-26 12:17 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-26 12:17 H.J. Lu [this message]
2018-04-29 21:03 ` Florian Weimer
2018-04-29 22:07 ` H.J. Lu
2018-05-02 5:03 ` Carlos O'Donell
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