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 /tools | |
| 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 'tools')
| -rw-r--r-- | tools/objtool/check.c | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 2dd89b0f4d5e..69f94bc47499 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -3685,14 +3685,19 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, break; case INSN_SYSCALL: + if (func && (!next_insn || !next_insn->hint)) { + WARN_INSN(insn, "unsupported instruction in callable function"); + return 1; + } + + break; + case INSN_SYSRET: - if (func) { - if (!next_insn || !next_insn->hint) { - WARN_INSN(insn, "unsupported instruction in callable function"); - return 1; - } - break; + if (func && (!next_insn || !next_insn->hint)) { + WARN_INSN(insn, "unsupported instruction in callable function"); + return 1; } + return 0; case INSN_STAC: @@ -3888,9 +3893,9 @@ static int validate_unret(struct objtool_file *file, struct instruction *insn) return 1; case INSN_SYSCALL: + break; + case INSN_SYSRET: - if (insn_func(insn)) - break; return 0; case INSN_NOP: |