linux/arch/x86/um/stub_64.S
Johannes Berg 9f0b4807a4 um: rework userspace stubs to not hard-code stub location
The userspace stacks mostly have a stack (and in the case of the
syscall stub we can just set their stack pointer) that points to
the location of the stub data page already.

Rework the stubs to use the stack pointer to derive the start of
the data page, rather than requiring it to be hard-coded.

In the clone stub, also integrate the int3 into the stack remap,
since we really must not use the stack while we remap it.

This prepares for putting the stub at a variable location that's
not part of the normal address space of the userspace processes
running inside the UML machine.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
2021-02-12 21:35:02 +01:00

51 lines
779 B
ArmAsm

/* SPDX-License-Identifier: GPL-2.0 */
#include <as-layout.h>
.section .__syscall_stub, "ax"
.globl batch_syscall_stub
batch_syscall_stub:
/* %rsp has the pointer to first operation */
mov %rsp, %rbx
add $0x10, %rsp
again:
/* load length of additional data */
mov 0x0(%rsp), %rax
/* if(length == 0) : end of list */
/* write possible 0 to header */
mov %rax, 8(%rbx)
cmp $0, %rax
jz done
/* save current pointer */
mov %rsp, 8(%rbx)
/* skip additional data */
add %rax, %rsp
/* load syscall-# */
pop %rax
/* load syscall params */
pop %rdi
pop %rsi
pop %rdx
pop %r10
pop %r8
pop %r9
/* execute syscall */
syscall
/* check return value */
pop %rcx
cmp %rcx, %rax
je again
done:
/* save return value */
mov %rax, (%rbx)
/* stop */
int3