update NestedInterruptTplLib patches

This commit is contained in:
Gerd Hoffmann 2023-05-11 07:30:24 +02:00
parent 82b6b6aa9f
commit 9839d74e46
4 changed files with 143 additions and 41 deletions

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@ -0,0 +1,66 @@
From 51846ff74e3352151f99cfcfbe091c09f3ec8097 Mon Sep 17 00:00:00 2001
From: Michael Brown <mcb30@ipxe.org>
Date: Tue, 9 May 2023 12:09:30 +0000
Subject: [PATCH 16/18] OvmfPkg: Clarify invariants for NestedInterruptTplLib
NestedInterruptTplLib relies on CPU interrupts being disabled to
guarantee exclusive (and hence atomic) access to the shared state in
IsrState. Nothing in the calling interrupt handler should have
re-enabled interrupts before calling NestedInterruptRestoreTPL(), and
the loop in NestedInterruptRestoreTPL() itself maintains the invariant
that interrupts are disabled at the start of each iteration.
Add assertions to clarify this invariant, and expand the comments
around the calls to RestoreTPL() and DisableInterrupts() to clarify
the expectations around enabling and disabling interrupts.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Acked-by: Laszlo Ersek <lersek@redhat.com>
(cherry picked from commit ae0be176a83efebe9a8c13d2124151f7dd13443a)
---
OvmfPkg/Library/NestedInterruptTplLib/Tpl.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c b/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c
index e19d98878eb7..e921a09c5599 100644
--- a/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c
+++ b/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c
@@ -104,6 +104,7 @@ NestedInterruptRestoreTPL (
// defer our call to RestoreTPL() to the in-progress outer instance
// of the same interrupt handler.
//
+ ASSERT (GetInterruptState () == FALSE);
if (InterruptedTPL == IsrState->InProgressRestoreTPL) {
//
// Trigger outer instance of this interrupt handler to perform the
@@ -153,6 +154,7 @@ NestedInterruptRestoreTPL (
//
// Check shared state loop invariants.
//
+ ASSERT (GetInterruptState () == FALSE);
ASSERT (IsrState->InProgressRestoreTPL < InterruptedTPL);
ASSERT (IsrState->DeferredRestoreTPL == FALSE);
@@ -167,13 +169,17 @@ NestedInterruptRestoreTPL (
//
// Call RestoreTPL() to allow event notifications to be
- // dispatched. This will implicitly re-enable interrupts.
+ // dispatched. This will implicitly re-enable interrupts (if
+ // InterruptedTPL is below TPL_HIGH_LEVEL), even though we are
+ // still inside the interrupt handler.
//
gBS->RestoreTPL (InterruptedTPL);
//
// Re-disable interrupts after the call to RestoreTPL() to ensure
- // that we have exclusive access to the shared state.
+ // that we have exclusive access to the shared state. Interrupts
+ // will be re-enabled by the IRET or equivalent instruction when
+ // we subsequently return from the interrupt handler.
//
DisableInterrupts ();
--
2.40.1

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@ -1,40 +0,0 @@
From 7c65395d2b45e388c6c106cb619ab93c2359f5e4 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Thu, 27 Apr 2023 12:14:16 +0200
Subject: [PATCH 16/17] OvmfPkg/NestedInterruptTplLib: replace ASSERT() with a
warning logged.
OVMF can't guarantee that the ASSERT() doesn't happen. Misbehaving
EFI applications can trigger this. So log a warning instead and try
to continue.
Reproducer: Fetch windows 11 22H2 iso image, boot it in qemu with OVMF.
Traced to BootServices->Stall() being called with IPL=TPL_HIGH_LEVEL
and Interrupts /enabled/ while windows is booting.
Cc: Michael Brown <mcb30@ipxe.org>
Cc: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
OvmfPkg/Library/NestedInterruptTplLib/Tpl.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c b/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c
index e19d98878eb7..fdd7d15c4ba8 100644
--- a/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c
+++ b/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c
@@ -39,7 +39,9 @@ NestedInterruptRaiseTPL (
//
ASSERT (GetInterruptState () == FALSE);
InterruptedTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);
- ASSERT (InterruptedTPL < TPL_HIGH_LEVEL);
+ if (InterruptedTPL >= TPL_HIGH_LEVEL) {
+ DEBUG ((DEBUG_WARN, "%a: Called at IPL %d\n", __func__, InterruptedTPL));
+ }
return InterruptedTPL;
}
--
2.40.1

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@ -0,0 +1,75 @@
From 7272c2fbe66941f0785be7ec437ed79ab9e35b80 Mon Sep 17 00:00:00 2001
From: Michael Brown <mcb30@ipxe.org>
Date: Tue, 9 May 2023 12:09:33 +0000
Subject: [PATCH 17/18] OvmfPkg: Relax assertion that interrupts do not occur
at TPL_HIGH_LEVEL
At TPL_HIGH_LEVEL, CPU interrupts are disabled (as per the UEFI
specification) and so we should never encounter a situation in which
an interrupt occurs at TPL_HIGH_LEVEL. The specification also
restricts usage of TPL_HIGH_LEVEL to the firmware itself.
However, nothing actually prevents a UEFI application from calling
gBS->RaiseTPL(TPL_HIGH_LEVEL) and then violating the invariant by
enabling interrupts via the STI or equivalent instruction. Some
versions of the Microsoft Windows bootloader are known to do this.
NestedInterruptTplLib maintains the invariant that interrupts are
disabled at TPL_HIGH_LEVEL (even when performing the dark art of
deliberately manipulating the stack so that IRET will return with
interrupts still disabled), but does not itself rely on external code
maintaining this invariant.
Relax the assertion that the interrupted TPL is below TPL_HIGH_LEVEL
to an error message, to allow UEFI applications such as these versions
of the Microsoft Windows bootloader to continue to function.
Debugged-by: Gerd Hoffmann <kraxel@redhat.com>
Debugged-by: Laszlo Ersek <lersek@redhat.com>
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=2189136
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit bee67e0c142af6599a85aa7640094816b8a24c4f)
---
OvmfPkg/Library/NestedInterruptTplLib/Tpl.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c b/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c
index e921a09c5599..d56c12a44529 100644
--- a/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c
+++ b/OvmfPkg/Library/NestedInterruptTplLib/Tpl.c
@@ -34,12 +34,27 @@ NestedInterruptRaiseTPL (
//
// Raise TPL and assert that we were called from within an interrupt
- // handler (i.e. with TPL below TPL_HIGH_LEVEL but with interrupts
- // disabled).
+ // handler (i.e. with interrupts already disabled before raising the
+ // TPL).
//
ASSERT (GetInterruptState () == FALSE);
InterruptedTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);
- ASSERT (InterruptedTPL < TPL_HIGH_LEVEL);
+
+ //
+ // At TPL_HIGH_LEVEL, CPU interrupts are disabled (as per the UEFI
+ // specification) and so we should never encounter a situation in
+ // which InterruptedTPL==TPL_HIGH_LEVEL. The specification also
+ // restricts usage of TPL_HIGH_LEVEL to the firmware itself.
+ //
+ // However, nothing actually prevents a UEFI application from
+ // invalidly calling gBS->RaiseTPL(TPL_HIGH_LEVEL) and then
+ // violating the invariant by enabling interrupts via the STI or
+ // equivalent instruction. Some versions of the Microsoft Windows
+ // bootloader are known to do this.
+ //
+ if (InterruptedTPL >= TPL_HIGH_LEVEL) {
+ DEBUG ((DEBUG_ERROR, "ERROR: Interrupts enabled at TPL_HIGH_LEVEL!\n"));
+ }
return InterruptedTPL;
}
--
2.40.1

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@ -98,7 +98,8 @@ Patch0012: 0012-OvmfPkg-QemuKernelLoaderFsDxe-suppress-error-on-no-k.patch
Patch0013: 0013-SecurityPkg-Tcg2Dxe-suppress-error-on-no-swtpm-in-si.patch
Patch0014: 0014-SecurityPkg-add-TIS-sanity-check-tpm2.patch
Patch0015: 0015-SecurityPkg-add-TIS-sanity-check-tpm12.patch
Patch0016: 0016-OvmfPkg-NestedInterruptTplLib-replace-ASSERT-with-a-.patch
Patch0016: 0016-OvmfPkg-Clarify-invariants-for-NestedInterruptTplLib.patch
Patch0017: 0017-OvmfPkg-Relax-assertion-that-interrupts-do-not-occur.patch
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