From: Nicholas Piggin <npiggin@gmail.com>
To: Thomas Huth <thuth@redhat.com>
Cc: Laurent Vivier <lvivier@redhat.com>,
kvm@vger.kernel.org, Nicholas Piggin <npiggin@gmail.com>,
Andrew Jones <andrew.jones@linux.dev>,
Paolo Bonzini <pbonzini@redhat.com>,
linuxppc-dev@lists.ozlabs.org
Subject: [kvm-unit-tests PATCH v7 09/35] powerpc: Fix stack backtrace termination
Date: Tue, 19 Mar 2024 17:59:00 +1000 [thread overview]
Message-ID: <20240319075926.2422707-10-npiggin@gmail.com> (raw)
In-Reply-To: <20240319075926.2422707-1-npiggin@gmail.com>
The backtrace handler terminates when it sees a NULL caller address,
but the powerpc stack setup does not keep such a NULL caller frame
at the start of the stack.
This happens to work on pseries because the memory at 0 is mapped and
it contains 0 at the location of the return address pointer if it
were a stack frame. But this is fragile, and does not work with powernv
where address 0 contains firmware instructions.
Use the existing dummy frame on stack as the NULL caller, and create a
new frame on stack for the entry code.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
powerpc/cstart64.S | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
index e18ae9a22..80baabe8f 100644
--- a/powerpc/cstart64.S
+++ b/powerpc/cstart64.S
@@ -46,6 +46,21 @@ start:
add r1, r1, r31
add r2, r2, r31
+ /* Zero backpointers in initial stack frame so backtrace() stops */
+ li r0,0
+ std r0,0(r1)
+ std r0,16(r1)
+
+ /*
+ * Create entry frame of 64-bytes, same as the initial frame. A callee
+ * may use the caller frame to store LR, and backtrace() termination
+ * looks for return address == NULL, so the initial stack frame can't
+ * be used to call C or else it could overwrite the zeroed LR save slot
+ * and break backtrace termination. This frame would be unnecessary if
+ * backtrace looked for a zeroed frame address.
+ */
+ stdu r1,-64(r1)
+
/* save DTB pointer */
std r3, 56(r1)
--
2.42.0
next prev parent reply other threads:[~2024-03-19 8:06 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-19 7:58 [kvm-unit-tests PATCH v7 00/35] migration, powerpc improvements Nicholas Piggin
2024-03-19 7:58 ` [kvm-unit-tests PATCH v7 01/35] arch-run: Add functions to help handle migration directives from test Nicholas Piggin
2024-03-25 15:54 ` Thomas Huth
2024-03-19 7:58 ` [kvm-unit-tests PATCH v7 02/35] arch-run: Keep infifo open Nicholas Piggin
2024-03-19 7:58 ` [kvm-unit-tests PATCH v7 03/35] migration: Add a migrate_skip command Nicholas Piggin
2024-03-19 7:58 ` [kvm-unit-tests PATCH v7 04/35] (arm|s390): Use migrate_skip in test cases Nicholas Piggin
2024-03-19 7:58 ` [kvm-unit-tests PATCH v7 05/35] arch-run: Add a "continuous" migration option for tests Nicholas Piggin
2024-03-19 7:58 ` [kvm-unit-tests PATCH v7 06/35] gitlab-ci: Run migration selftest on s390x and powerpc Nicholas Piggin
2024-03-25 16:08 ` Thomas Huth
2024-03-28 8:16 ` Nicholas Piggin
2024-03-19 7:58 ` [kvm-unit-tests PATCH v7 07/35] common: add memory dirtying vs migration test Nicholas Piggin
2024-03-28 17:37 ` Thomas Huth
2024-04-05 4:54 ` Nicholas Piggin
2024-03-19 7:58 ` [kvm-unit-tests PATCH v7 08/35] powerpc: Fix KVM caps on POWER9 hosts Nicholas Piggin
2024-03-19 7:59 ` Nicholas Piggin [this message]
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 10/35] powerpc: interrupt stack backtracing Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 11/35] powerpc/sprs: Specify SPRs with data rather than code Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 12/35] powerpc/sprs: Avoid taking PMU interrupts caused by register fuzzing Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 13/35] doc: start documentation directory with unittests.cfg doc Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 14/35] scripts: allow machine option to be specified in unittests.cfg Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 15/35] scripts: Accommodate powerpc powernv machine differences Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 16/35] powerpc: Support powernv machine with QEMU TCG Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 17/35] powerpc: Fix emulator illegal instruction test for powernv Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 18/35] powerpc/sprs: Test hypervisor registers on powernv machine Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 19/35] powerpc: general interrupt tests Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 20/35] powerpc: Add rtas stop-self support Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 21/35] powerpc: Remove broken SMP exception stack setup Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 22/35] powerpc: add SMP and IPI support Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 23/35] powerpc: Permit ACCEL=tcg,thread=single Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 24/35] powerpc: Avoid using larx/stcx. in spinlocks when only one CPU is running Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 25/35] powerpc: Add atomics tests Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 26/35] powerpc: Add timebase tests Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 27/35] powerpc: Add MMU support Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 28/35] common/sieve: Use vmalloc.h for setup_mmu definition Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 29/35] common/sieve: Support machines without MMU Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 30/35] powerpc: Add sieve.c common test Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 31/35] powerpc: add usermode support Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 32/35] powerpc: add pmu tests Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 33/35] configure: Make arch_libdir a first-class entity Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 34/35] powerpc: Remove remnants of ppc64 directory and build structure Nicholas Piggin
2024-03-19 7:59 ` [kvm-unit-tests PATCH v7 35/35] powerpc: gitlab CI update Nicholas Piggin
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