Messages in this thread Patch in this message | | | Date | Wed, 22 Sep 2021 23:44:41 +0000 | From | Fenghua Yu <> | Subject | Re: [PATCH 7/8] tools/objtool: Check for use of the ENQCMD instruction in the kernel |
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Hi, Peter,
On Wed, Sep 22, 2021 at 11:03:43PM +0200, Peter Zijlstra wrote: > On Mon, Sep 20, 2021 at 07:23:48PM +0000, Fenghua Yu wrote: > > + ret = validate_enqcmd(file); > > + if (ret < 0) > > + goto out; > > + warnings += ret; > > + > > if (vmlinux && !validate_dup) { > > ret = validate_vmlinux_functions(file); > > if (ret < 0) > > Since you're making it a fatal error, before doing much of anything > else, you might at well fail decode and keep it all in the x86/decode.c > file, no need to spread this 'knowledge' any further. > > There's no actual state associated with it, you just want to avoid the > instruction being present. > > Much simpler patch too.
Is the following updated patch a right one?
Thanks.
-Fenghua
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index bc821056aba9..3e0f928e28a5 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -110,7 +110,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec, { struct insn insn; int x86_64, ret; - unsigned char op1, op2, + unsigned char op1, op2, op3, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0, rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0, sib = 0, /* sib_scale = 0, */ sib_index = 0, sib_base = 0; @@ -137,6 +137,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec, op1 = insn.opcode.bytes[0]; op2 = insn.opcode.bytes[1]; + op3 = insn.opcode.bytes[2]; if (insn.rex_prefix.nbytes) { rex = insn.rex_prefix.bytes[0]; @@ -489,6 +490,16 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec, /* nopl/nopw */ *type = INSN_NOP; + } else if (op2 == 0x38 && op3 == 0xf8) { + if (insn.prefixes.nbytes == 1 && + insn.prefixes.bytes[0] == 0xf2) { + /* ENQCMD cannot be used in the kernel. */ + WARN("ENQCMD instruction at %s:%lx", sec->name, + offset); + + return -1; + } + } else if (op2 == 0xa0 || op2 == 0xa8) { /* push fs/gs */
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