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Diffstat (limited to 'results/classifier/105/assembly/1877136')
| -rw-r--r-- | results/classifier/105/assembly/1877136 | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/results/classifier/105/assembly/1877136 b/results/classifier/105/assembly/1877136 new file mode 100644 index 00000000..462edfe5 --- /dev/null +++ b/results/classifier/105/assembly/1877136 @@ -0,0 +1,77 @@ +assembly: 0.260 +vnc: 0.236 +device: 0.233 +KVM: 0.232 +semantic: 0.213 +boot: 0.190 +instruction: 0.184 +other: 0.183 +network: 0.178 +mistranslation: 0.172 +graphic: 0.156 +socket: 0.150 + +Qemu GDB Arm core registers XML description not valid for M-profile + +When trying to debug an armv7-m binary running on Qemu, GDB makes some mistakes due to mistakenly believing the target is not M-profile. + +One observable is that backtraces over signal handlers are not handled correctly -- since the special M-profile EXC_RETURN value is not recognised. That happens because GDB doesn't think the target is M-profile. + +This happens because GDB sees a reported feature set from the Qemu remote connection that includes the feature `org.gnu.gdb.arm.core`. + +As described in the GDB online docs, for "M-profile targets (e.g. Cortex-M3), the ‘org.gnu.gdb.arm.core’ feature is replaced by ‘org.gnu.gdb.arm.m-profile’" +https://sourceware.org/gdb/current/onlinedocs/gdb/ARM-Features.html + +From a scan of the Qemu source code on commit ea1329bb3a8d5cd25b70e3dbf73e7ded4d5ad756 it seems that when emulating an arm core it uses `arm-core.xml` unconditionally for `CPUClass->gdb_core_xml_file`, and that means the only feature provided is `org.gnu.gdb.arm.core`. + +Note that even though there is a command to set the architecture in GDB, setting the target architecture to an M-profile core is still not a valid workaround. +This is because the target description overrides everything in setting the `is_m` attribute within GDB. + +Reproduction of the observable: +Using the examples here https://git.linaro.org/people/peter.maydell/m-profile-tests.git/tree/ . +Build the examples, and run +``` +qemu-system-arm -s -S -no-reboot -M lm3s6965evb -m 16 -serial stdio -display none -net nic -net user,restrict=on -d guest_errors,unimp -kernel test3-kern.bin +``` + +Then in a GDB session +``` +vshcmd: > arm-none-eabi-gdb -q +(gdb) +vshcmd: > file test3-kern.elf +Reading symbols from test3-kern.elf... +(gdb) +vshcmd: > target remote localhost:1234 +Remote debugging using localhost:1234 +_start () at init-m.S:53 +53 mov r0, #0 +(gdb) +vshcmd: > show architecture +The target architecture is set automatically (currently armv7) +(gdb) +vshcmd: > break svc +Breakpoint 1 at 0x6fc: svc. (2 locations) +(gdb) +vshcmd: > cont +Continuing. + +Breakpoint 1, svc () at test3.c:16 +16 int test = SEQ(); +(gdb) +vshcmd: > bt +#0 svc () at test3.c:16 +#1 0xfffffff8 in ?? () +Backtrace stopped: previous frame identical to this frame (corrupt stack?) +(gdb) +vshcmd: > print/x $lr +$1 = 0xfffffff9 +(gdb) +``` + +Patch submitted: https://<email address hidden>/ + + +Fix now in master, will be in QEMU 5.1. + +https://git.qemu.org/?p=qemu.git;a=commitdiff;h=c888f7e0fdcc09c8600 + |