Gabe Black has uploaded this change for review. (
https://gem5-review.googlesource.com/c/public/gem5/+/55448 )
Change subject: arch-x86: Implement IRET for real mode.
......................................................................
arch-x86: Implement IRET for real mode.
The IRET instruction is comparitively very simple in real mode. It just
pops a few values off the stack into CS, RIP, and RFLAGS, and sets the
CS base.
Change-Id: I2bc6015209f1beca31253e288dad7c8de5cd22fc
---
M
src/arch/x86/isa/insts/general_purpose/control_transfer/interrupts_and_exceptions.py
1 file changed, 44 insertions(+), 1 deletion(-)
diff --git
a/src/arch/x86/isa/insts/general_purpose/control_transfer/interrupts_and_exceptions.py
b/src/arch/x86/isa/insts/general_purpose/control_transfer/interrupts_and_exceptions.py
index 0460fd3..81babf3 100644
---
a/src/arch/x86/isa/insts/general_purpose/control_transfer/interrupts_and_exceptions.py
+++
b/src/arch/x86/isa/insts/general_purpose/control_transfer/interrupts_and_exceptions.py
@@ -36,7 +36,37 @@
microcode = '''
def macroop IRET_REAL {
.serialize_after
- panic "Real mode iret isn't implemented!"
+
+ # temp_RIP
+ ld t1, ss, [1, t0, rsp], "0 * env.dataSize", addressSize=ssz
+ # temp_CS
+ ld t2, ss, [1, t0, rsp], "1 * env.dataSize", addressSize=ssz
+ # temp_RFLAGS
+ ld t3, ss, [1, t0, rsp], "2 * env.dataSize", addressSize=ssz
+
+ # Update RSP now that all memory accesses have succeeded.
+ addi rsp, rsp, "3 * env.dataSize", dataSize=ssz
+
+ # Update CS.
+ wrsel cs, t2
+ # Make sure there isn't any junk in the upper bits of the base.
+ mov t4, t0, t2
+ slli t4, t4, 4, dataSize=8
+ wrbase cs, t4, dataSize=8
+
+ # Update RFLAGS
+ # Get the current RFLAGS
+ rflags t4
+ # Flip flag bits if they should change.
+ xor t5, t4, t3
+ # Don't change VIF, VIP, or VM
+ limm t6, "~(VIFBit | VIPBit | VMBit)", dataSize=8
+ and t5, t5, t6, dataSize=8
+ # Write back RFLAGS with flipped bits.
+ wrflags t4, t5, dataSize=8
+
+ # Update RIP
+ wrip t1, t0
};
def macroop IRET_PROT {
--
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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: I2bc6015209f1beca31253e288dad7c8de5cd22fc
Gerrit-Change-Number: 55448
Gerrit-PatchSet: 1
Gerrit-Owner: Gabe Black <[email protected]>
Gerrit-MessageType: newchange
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