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x86/bpf: Use alternative RET encoding

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commit d77cfe594ad50e0bf95d457e02ccd578791b2a15 upstream.

Use the return thunk in eBPF generated code, if needed.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
[bwh: Backported to 5.10: add the necessary cnt variable to emit_return()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Zijlstra 2022-06-14 23:15:41 +02:00 committed by Greg Kroah-Hartman
parent 00b136bb62
commit e0e06a9227
1 changed files with 18 additions and 2 deletions
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20
arch/x86/net/bpf_jit_comp.c
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@ -399,6 +399,22 @@ static void emit_indirect_jump(u8 **pprog, int reg, u8 *ip)
*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 @@ xadd: if (is_imm8(insn->off))
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 bpf_tramp_image *im, void *image, void *i
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;