diff options
| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2025-04-08 00:02:16 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-04-08 09:14:12 +0200 |
| commit | 2dbbca9be4e5ed68d0972a2bcf4561d9cb85b7b7 (patch) | |
| tree | dfbe503ba0737da4dcdd8bc0c6cf261ce4669e32 /arch | |
| parent | 9f9cc012c2cbac4833746a0182e06a8eec940d19 (diff) | |
objtool, xen: Fix INSN_SYSCALL / INSN_SYSRET semantics
Objtool uses an arbitrary rule for INSN_SYSCALL and INSN_SYSRET that
almost works by accident: if it's in a function, control flow continues
after the instruction, otherwise it terminates.
That behavior should instead be based on the semantics of the underlying
instruction. Change INSN_SYSCALL to always preserve control flow and
INSN_SYSRET to always terminate it.
The changed semantic for INSN_SYSCALL requires a tweak to the
!CONFIG_IA32_EMULATION version of xen_entry_SYSCALL_compat(). In Xen,
SYSCALL is a hypercall which usually returns. But in this case it's a
hypercall to IRET which doesn't return. Add UD2 to tell objtool to
terminate control flow, and to prevent undefined behavior at runtime.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com> # for the Xen part
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/19453dfe9a0431b7f016e9dc16d031cad3812a50.1744095216.git.jpoimboe@kernel.org
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/xen/xen-asm.S | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S index 109af12f7647..461bb1526502 100644 --- a/arch/x86/xen/xen-asm.S +++ b/arch/x86/xen/xen-asm.S @@ -226,9 +226,7 @@ SYM_CODE_END(xen_early_idt_handler_array) push %rax mov $__HYPERVISOR_iret, %eax syscall /* Do the IRET. */ -#ifdef CONFIG_MITIGATION_SLS - int3 -#endif + ud2 /* The SYSCALL should never return. */ .endm SYM_CODE_START(xen_iret) |