From: Brendan Shanks <bshanks@codeweavers.com>
To: linux-kernel@vger.kernel.org
Cc: ricardo.neri-calderon@linux.intel.com, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org,
ebiederm@xmission.com, andi@notmuch.email, Babu.Moger@amd.com,
Brendan Shanks <bshanks@codeweavers.com>
Subject: [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions
Date: Tue, 2 Jun 2020 11:42:12 -0700 [thread overview]
Message-ID: <20200602184212.10813-1-bshanks@codeweavers.com> (raw)
Add emulation/spoofing of SLDT and STR for both 32- and 64-bit
processes.
Wine users have found a small number of Windows apps using SLDT that
were crashing when run on UMIP-enabled systems.
Reported-by: Andreas Rammhold <andi@notmuch.email>
Originally-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Brendan Shanks <bshanks@codeweavers.com>
---
arch/x86/kernel/umip.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
index 8d5cbe1bbb3b..59dfceac5cc0 100644
--- a/arch/x86/kernel/umip.c
+++ b/arch/x86/kernel/umip.c
@@ -64,6 +64,8 @@
#define UMIP_DUMMY_GDT_BASE 0xfffffffffffe0000ULL
#define UMIP_DUMMY_IDT_BASE 0xffffffffffff0000ULL
+#define UMIP_DUMMY_TASK_REGISTER_SELECTOR 0x40
+
/*
* The SGDT and SIDT instructions store the contents of the global descriptor
* table and interrupt table registers, respectively. The destination is a
@@ -244,16 +246,24 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
*data_size += UMIP_GDT_IDT_LIMIT_SIZE;
memcpy(data, &dummy_limit, UMIP_GDT_IDT_LIMIT_SIZE);
- } else if (umip_inst == UMIP_INST_SMSW) {
- unsigned long dummy_value = CR0_STATE;
+ } else if (umip_inst == UMIP_INST_SMSW || umip_inst == UMIP_INST_SLDT ||
+ umip_inst == UMIP_INST_STR) {
+ unsigned long dummy_value;
+
+ if (umip_inst == UMIP_INST_SMSW)
+ dummy_value = CR0_STATE;
+ else if (umip_inst == UMIP_INST_STR)
+ dummy_value = UMIP_DUMMY_TASK_REGISTER_SELECTOR;
+ else
+ dummy_value = 0;
/*
- * Even though the CR0 register has 4 bytes, the number
+ * For these 3 instructions, the number
* of bytes to be copied in the result buffer is determined
* by whether the operand is a register or a memory location.
* If operand is a register, return as many bytes as the operand
* size. If operand is memory, return only the two least
- * siginificant bytes of CR0.
+ * siginificant bytes.
*/
if (X86_MODRM_MOD(insn->modrm.value) == 3)
*data_size = insn->opnd_bytes;
@@ -261,7 +271,6 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
*data_size = 2;
memcpy(data, &dummy_value, *data_size);
- /* STR and SLDT are not emulated */
} else {
return -EINVAL;
}
@@ -383,10 +392,6 @@ bool fixup_umip_exception(struct pt_regs *regs)
umip_pr_warn(regs, "%s instruction cannot be used by applications.\n",
umip_insns[umip_inst]);
- /* Do not emulate (spoof) SLDT or STR. */
- if (umip_inst == UMIP_INST_STR || umip_inst == UMIP_INST_SLDT)
- return false;
-
umip_pr_warn(regs, "For now, expensive software emulation returns the result.\n");
if (emulate_umip_insn(&insn, umip_inst, dummy_data, &dummy_data_size,
--
2.26.2
next reply other threads:[~2020-06-02 18:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-02 18:42 Brendan Shanks [this message]
2020-06-04 0:12 ` [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions Ricardo Neri
2020-06-04 4:39 ` Andy Lutomirski
[not found] ` <E32838F8-665E-488F-96E4-040DD7BDA284@codeweavers.com>
2020-06-05 22:42 ` Ricardo Neri
2020-06-08 18:13 ` Brendan Shanks
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