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| author | Peter Zijlstra <peterz@infradead.org> | 2022-06-14 23:15:41 +0200 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2022-06-27 10:33:58 +0200 |
| commit | d77cfe594ad50e0bf95d457e02ccd578791b2a15 (patch) | |
| tree | 34e7f66c81cfaca9280a4a3156c4efddb19fc8ee /arch/x86/net | |
| parent | 1f001e9da6bbf482311e45e48f53c2bd2179e59c (diff) | |
| download | linux-d77cfe594ad50e0bf95d457e02ccd578791b2a15.tar.bz2 | |
x86/bpf: Use alternative RET encoding
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>
Diffstat (limited to 'arch/x86/net')
| -rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 79d26908c143..b808c9a80d1b 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -425,6 +425,21 @@ static void emit_indirect_jump(u8 **pprog, int reg, u8 *ip) *pprog = prog; } +static void emit_return(u8 **pprog, u8 *ip) +{ + u8 *prog = *pprog; + + 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: * @@ -1685,7 +1700,7 @@ 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: @@ -2188,7 +2203,7 @@ 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; |