The ENQCMD 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.
Checking the invalid instruction is a relatively new use of objtool and
I'm open to feedback about the approach.
Signed-off-by: Fenghua Yu <fenghua...@intel.com>
Reviewed-by: Tony Luck <tony.l...@intel.com>
---
tools/objtool/arch/x86/decode.c | 10 +++++++++-
tools/objtool/check.c | 20 ++++++++++++++++++++
tools/objtool/include/objtool/arch.h | 1 +
3 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index bc821056aba9..e63b44ba3bd4 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 +490,13 @@ 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 */
+ *type = INSN_ENQCMD;
+ }
+
} else if (op2 == 0xa0 || op2 == 0xa8) {
/* push fs/gs */
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index e5947fbb9e7a..91d13521d9d6 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3133,6 +3133,21 @@ static int validate_reachable_instructions(struct
objtool_file *file)
return 0;
}
+static int validate_enqcmd(struct objtool_file *file)
+{
+ struct instruction *insn;
+
+ for_each_insn(file, insn) {
+ if (insn->type == INSN_ENQCMD) {
+ WARN_FUNC("enqcmd instruction", insn->sec,
+ insn->offset);
+ return 1;
+ }
+ }
+
+ return 0;
+}
+
int check(struct objtool_file *file)
{
int ret, warnings = 0;
@@ -3147,6 +3162,11 @@ int check(struct objtool_file *file)
if (list_empty(&file->insn_list))
goto out;
+ ret = validate_enqcmd(file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
+
if (vmlinux && !validate_dup) {
ret = validate_vmlinux_functions(file);
if (ret < 0)
diff --git a/tools/objtool/include/objtool/arch.h
b/tools/objtool/include/objtool/arch.h
index 062bb6e9b865..5147c0762b49 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -26,6 +26,7 @@ enum insn_type {
INSN_CLAC,
INSN_STD,
INSN_CLD,
+ INSN_ENQCMD,
INSN_OTHER,
};
--
2.33.0
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