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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 |
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| .. | ||
| arch | ||
| Documentation | ||
| include/objtool | ||
| .gitignore | ||
| Build | ||
| builtin-check.c | ||
| check.c | ||
| elf.c | ||
| Makefile | ||
| noreturns.h | ||
| objtool.c | ||
| orc_dump.c | ||
| orc_gen.c | ||
| special.c | ||
| sync-check.sh | ||
| weak.c | ||