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x86-64/setcontext: Pop the pointer into %rdx after syscall

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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.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

	* 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.
This commit is contained in:
H.J. Lu 2018-05-02 06:21:09 -07:00
parent d6cc1829aa
commit 8b8f32b280
2 changed files with 28 additions and 19 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2018-05-02 H.J. Lu <hongjiu.lu@intel.com>
* 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.
2018-05-02 H.J. Lu <hongjiu.lu@intel.com>
* nptl/pthread_create.c (START_THREAD_DEFN): Clear previous

41
sysdeps/unix/sysv/linux/x86_64/setcontext.S
View File

@ -44,21 +44,24 @@ ENTRY(__setcontext)
movl $_NSIG8,%r10d
movl $__NR_rt_sigprocmask, %eax
syscall
popq %rdi /* Reload %rdi, adjust stack. */
/* Pop the pointer into RDX. The choice is arbitrary, but
leaving RDI and RSI available for use later can avoid
shuffling values. */
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 +71,27 @@ 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