forked from Minki/linux
9f416319f4
do_task_stat() calls get_wchan(), which further does unwind_frame().
unwind_frame() restores frame->pc to original value in case function
graph tracer has modified a return address (LR) in a stack frame to hook
a function return. However, if function graph tracer has hit a filtered
function, then we can't unwind it as ftrace_push_return_trace() has
biased the index(frame->graph) with a 'huge negative'
offset(-FTRACE_NOTRACE_DEPTH).
Moreover, arm64 stack walker defines index(frame->graph) as unsigned
int, which can not compare a -ve number.
Similar problem we can have with calling of walk_stackframe() from
save_stack_trace_tsk() or dump_backtrace().
This patch fixes unwind_frame() to test the index for -ve value and
restore index accordingly before we can restore frame->pc.
Reproducer:
cd /sys/kernel/debug/tracing/
echo schedule > set_graph_notrace
echo 1 > options/display-graph
echo wakeup > current_tracer
ps -ef | grep -i agent
Above commands result in:
Unable to handle kernel paging request at virtual address ffff801bd3d1e000
pgd = ffff8003cbe97c00
[ffff801bd3d1e000] *pgd=0000000000000000, *pud=0000000000000000
Internal error: Oops: 96000006 [#1] SMP
[...]
CPU: 5 PID: 11696 Comm: ps Not tainted 4.11.0+ #33
[...]
task: ffff8003c21ba000 task.stack: ffff8003cc6c0000
PC is at unwind_frame+0x12c/0x180
LR is at get_wchan+0xd4/0x134
pc : [<ffff00000808892c>] lr : [<ffff0000080860b8>] pstate: 60000145
sp : ffff8003cc6c3ab0
x29: ffff8003cc6c3ab0 x28: 0000000000000001
x27: 0000000000000026 x26: 0000000000000026
x25: 00000000000012d8 x24: 0000000000000000
x23: ffff8003c1c04000 x22: ffff000008c83000
x21: ffff8003c1c00000 x20: 000000000000000f
x19: ffff8003c1bc0000 x18: 0000fffffc593690
x17: 0000000000000000 x16: 0000000000000001
x15: 0000b855670e2b60 x14: 0003e97f22cf1d0f
x13: 0000000000000001 x12: 0000000000000000
x11: 00000000e8f4883e x10: 0000000154f47ec8
x9 : 0000000070f367c0 x8 : 0000000000000000
x7 : 00008003f7290000 x6 : 0000000000000018
x5 : 0000000000000000 x4 : ffff8003c1c03cb0
x3 : ffff8003c1c03ca0 x2 : 00000017ffe80000
x1 : ffff8003cc6c3af8 x0 : ffff8003d3e9e000
Process ps (pid: 11696, stack limit = 0xffff8003cc6c0000)
Stack: (0xffff8003cc6c3ab0 to 0xffff8003cc6c4000)
[...]
[<ffff00000808892c>] unwind_frame+0x12c/0x180
[<ffff000008305008>] do_task_stat+0x864/0x870
[<ffff000008305c44>] proc_tgid_stat+0x3c/0x48
[<ffff0000082fde0c>] proc_single_show+0x5c/0xb8
[<ffff0000082b27e0>] seq_read+0x160/0x414
[<ffff000008289e6c>] __vfs_read+0x58/0x164
[<ffff00000828b164>] vfs_read+0x88/0x144
[<ffff00000828c2e8>] SyS_read+0x60/0xc0
[<ffff0000080834a0>] __sys_trace_return+0x0/0x4
Fixes:
|
||
|---|---|---|
| .. | ||
| probes | ||
| vdso | ||
| .gitignore | ||
| acpi_numa.c | ||
| acpi_parking_protocol.c | ||
| acpi.c | ||
| alternative.c | ||
| arm64ksyms.c | ||
| armv8_deprecated.c | ||
| asm-offsets.c | ||
| bpi.S | ||
| cacheinfo.c | ||
| cpu_errata.c | ||
| cpu_ops.c | ||
| cpu-reset.h | ||
| cpu-reset.S | ||
| cpufeature.c | ||
| cpuidle.c | ||
| cpuinfo.c | ||
| crash_dump.c | ||
| debug-monitors.c | ||
| efi-entry.S | ||
| efi-header.S | ||
| efi.c | ||
| entry32.S | ||
| entry-fpsimd.S | ||
| entry-ftrace.S | ||
| entry.S | ||
| fpsimd.c | ||
| ftrace.c | ||
| head.S | ||
| hibernate-asm.S | ||
| hibernate.c | ||
| hw_breakpoint.c | ||
| hyp-stub.S | ||
| image.h | ||
| insn.c | ||
| io.c | ||
| irq.c | ||
| jump_label.c | ||
| kaslr.c | ||
| kgdb.c | ||
| kuser32.S | ||
| machine_kexec.c | ||
| Makefile | ||
| module-plts.c | ||
| module.c | ||
| module.lds | ||
| paravirt.c | ||
| pci.c | ||
| perf_callchain.c | ||
| perf_event.c | ||
| perf_regs.c | ||
| process.c | ||
| psci.c | ||
| ptrace.c | ||
| reloc_test_core.c | ||
| reloc_test_syms.S | ||
| relocate_kernel.S | ||
| return_address.c | ||
| sdei.c | ||
| setup.c | ||
| signal32.c | ||
| signal.c | ||
| sleep.S | ||
| smccc-call.S | ||
| smp_spin_table.c | ||
| smp.c | ||
| stacktrace.c | ||
| suspend.c | ||
| sys32.c | ||
| sys_compat.c | ||
| sys.c | ||
| time.c | ||
| topology.c | ||
| trace-events-emulation.h | ||
| traps.c | ||
| vdso.c | ||
| vmlinux.lds.S | ||