From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit d77cfe594ad50e0bf95d457e02ccd578791b2a15 upstream.
Use the return thunk in eBPF generated code, if needed.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
[bwh: Backported to 5.10: add the necessary cnt variable to emit_return()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/net/bpf_jit_comp.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -399,6 +399,22 @@ static void emit_indirect_jump(u8 **ppro
*pprog = prog;
}
+static void emit_return(u8 **pprog, u8 *ip)
+{
+ u8 *prog = *pprog;
+ int cnt = 0;
+
+ if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) {
+ emit_jump(&prog, &__x86_return_thunk, ip);
+ } else {
+ EMIT1(0xC3); /* ret */
+ if (IS_ENABLED(CONFIG_SLS))
+ EMIT1(0xCC); /* int3 */
+ }
+
+ *pprog = prog;
+}
+
/*
* Generate the following code:
*
@@ -1443,7 +1459,7 @@ emit_jmp:
ctx->cleanup_addr = proglen;
pop_callee_regs(&prog, callee_regs_used);
EMIT1(0xC9); /* leave */
- EMIT1(0xC3); /* ret */
+ emit_return(&prog, image + addrs[i - 1] + (prog - temp));
break;
default:
@@ -1884,7 +1900,7 @@ int arch_prepare_bpf_trampoline(struct b
if (flags & BPF_TRAMP_F_SKIP_FRAME)
/* skip our return address and return to parent */
EMIT4(0x48, 0x83, 0xC4, 8); /* add rsp, 8 */
- EMIT1(0xC3); /* ret */
+ emit_return(&prog, prog);
/* Make sure the trampoline generation logic doesn't overflow */
if (WARN_ON_ONCE(prog > (u8 *)image_end - BPF_INSN_SAFETY)) {
ret = -EFAULT;
