diff options
| author | H.J. Lu <hjl.tools@gmail.com> | 2018-05-02 06:21:09 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2018-05-02 06:21:24 -0700 |
| commit | 8b8f32b2800a132b4d95053fad7c9b44309f1d6e (patch) | |
| tree | af54b6e0201e547f58dbeb460b9aa2a48b782e38 /sysdeps/unix/sysv/linux | |
| parent | d6cc1829aa31b6fb060f24dffd28aa6705cdd33a (diff) | |
x86-64/setcontext: Pop the pointer into %rdx after syscall
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.
Diffstat (limited to 'sysdeps/unix/sysv/linux')
| -rw-r--r-- | sysdeps/unix/sysv/linux/x86_64/setcontext.S | 41 |
1 files changed, 22 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..b42af8e291 100644 --- a/sysdeps/unix/sysv/linux/x86_64/setcontext.S +++ b/sysdeps/unix/sysv/linux/x86_64/setcontext.S @@ -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 |