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tools/objtool: Check for use of the ENQCMD instruction in the kernel

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The ENQCMD instruction implicitly accesses the PASID_MSR to fill in the
pasid field of the descriptor being submitted to an accelerator. But
there is no precise (and stable across kernel changes) point at which
the PASID_MSR is updated from the value for one task to the next.

Kernel code that uses accelerators must always use the ENQCMDS instruction
which does not access the PASID_MSR.

Check for use of the ENQCMD instruction in the kernel and warn on its
usage.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220207230254.3342514-11-fenghua.yu@intel.com
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
This commit is contained in:
Fenghua Yu 2022-02-07 15:02:53 -08:00 committed by Peter Zijlstra
parent 09688c0166
commit 227a06553f
1 changed files with 10 additions and 1 deletions
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11
tools/objtool/arch/x86/decode.c
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@ -112,7 +112,7 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
const struct elf *elf = file->elf;
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;
@ -139,6 +139,7 @@ int arch_decode_instruction(struct objtool_file *file, 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];
@ -491,6 +492,14 @@ int arch_decode_instruction(struct objtool_file *file, 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);
}
} else if (op2 == 0xa0 || op2 == 0xa8) {
/* push fs/gs */