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| author | Johannes Berg <johannes.berg@intel.com> | 2021-01-13 22:09:43 +0100 |
|---|---|---|
| committer | Richard Weinberger <richard@nod.at> | 2021-02-12 21:35:02 +0100 |
| commit | 9f0b4807a44ff81cf59421c8a86641efec586610 (patch) | |
| tree | 2fa591a8256cc5a56423323f40b0c87edf9199de /arch/x86/um/stub_32.S | |
| parent | 84b2789d61156db0224724806b20110c0d34b07c (diff) | |
| download | linux-stable-9f0b4807a44ff81cf59421c8a86641efec586610.tar.gz linux-stable-9f0b4807a44ff81cf59421c8a86641efec586610.tar.bz2 linux-stable-9f0b4807a44ff81cf59421c8a86641efec586610.zip | |
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>
Diffstat (limited to 'arch/x86/um/stub_32.S')
| -rw-r--r-- | arch/x86/um/stub_32.S | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/arch/x86/um/stub_32.S b/arch/x86/um/stub_32.S index a193e88536a9..8291899e6aaf 100644 --- a/arch/x86/um/stub_32.S +++ b/arch/x86/um/stub_32.S @@ -5,21 +5,22 @@ .globl batch_syscall_stub batch_syscall_stub: - /* load pointer to first operation */ - mov $(STUB_DATA+8), %esp - + /* %esp comes in as "top of page" */ + mov %esp, %ecx + /* %esp has pointer to first operation */ + add $8, %esp again: /* load length of additional data */ mov 0x0(%esp), %eax /* if(length == 0) : end of list */ /* write possible 0 to header */ - mov %eax, STUB_DATA+4 + mov %eax, 0x4(%ecx) cmpl $0, %eax jz done /* save current pointer */ - mov %esp, STUB_DATA+4 + mov %esp, 0x4(%ecx) /* skip additional data */ add %eax, %esp @@ -38,6 +39,10 @@ again: /* execute syscall */ int $0x80 + /* restore top of page pointer in %ecx */ + mov %esp, %ecx + andl $(~UM_KERN_PAGE_SIZE) + 1, %ecx + /* check return value */ pop %ebx cmp %ebx, %eax @@ -45,7 +50,7 @@ again: done: /* save return value */ - mov %eax, STUB_DATA + mov %eax, (%ecx) /* stop */ int3 |