lwn.git/arch/powerpc/kernel/kprobes.c, branch docs-6.9

Merge tag 'powerpc-6.2-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

2022-12-19T13:13:33+00:00

Pull powerpc updates from Michael Ellerman: - Add powerpc qspinlock implementation optimised for large system scalability and paravirt. See the merge message for more details - Enable objtool to be built on powerpc to generate mcount locations - Use a temporary mm for code patching with the Radix MMU, so the writable mapping is restricted to the patching CPU - Add an option to build the 64-bit big-endian kernel with the ELFv2 ABI - Sanitise user registers on interrupt entry on 64-bit Book3S - Many other small features and fixes Thanks to Aboorva Devarajan, Angel Iglesias, Benjamin Gray, Bjorn Helgaas, Bo Liu, Chen Lifu, Christoph Hellwig, Christophe JAILLET, Christophe Leroy, Christopher M. Riedl, Colin Ian King, Deming Wang, Disha Goel, Dmitry Torokhov, Finn Thain, Geert Uytterhoeven, Gustavo A. R. Silva, Haowen Bai, Joel Stanley, Jordan Niethe, Julia Lawall, Kajol Jain, Laurent Dufour, Li zeming, Miaoqian Lin, Michael Jeanson, Nathan Lynch, Naveen N. Rao, Nayna Jain, Nicholas Miehlbradt, Nicholas Piggin, Pali Rohár, Randy Dunlap, Rohan McLure, Russell Currey, Sathvika Vasireddy, Shaomin Deng, Stephen Kitt, Stephen Rothwell, Thomas Weißschuh, Tiezhu Yang, Uwe Kleine-König, Xie Shaowen, Xiu Jianfeng, XueBing Chen, Yang Yingliang, Zhang Jiaming, ruanjinjie, Jessica Yu, and Wolfram Sang. * tag 'powerpc-6.2-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (181 commits) powerpc/code-patching: Fix oops with DEBUG_VM enabled powerpc/qspinlock: Fix 32-bit build powerpc/prom: Fix 32-bit build powerpc/rtas: mandate RTAS syscall filtering powerpc/rtas: define pr_fmt and convert printk call sites powerpc/rtas: clean up includes powerpc/rtas: clean up rtas_error_log_max initialization powerpc/pseries/eeh: use correct API for error log size powerpc/rtas: avoid scheduling in rtas_os_term() powerpc/rtas: avoid device tree lookups in rtas_os_term() powerpc/rtasd: use correct OF API for event scan rate powerpc/rtas: document rtas_call() powerpc/pseries: unregister VPA when hot unplugging a CPU powerpc/pseries: reset the RCU watchdogs after a LPM powerpc: Take in account addition CPU node when building kexec FDT powerpc: export the CPU node count powerpc/cpuidle: Set CPUIDLE_FLAG_POLLING for snooze state powerpc/dts/fsl: Fix pca954x i2c-mux node names cxl: Remove unnecessary cxl_pci_window_alignment() selftests/powerpc: Fix resource leaks ...

mm: Introduce set_memory_rox()

2022-12-15T18:37:26+00:00

Because endlessly repeating: set_memory_ro() set_memory_x() is getting tedious. Suggested-by: Linus Torvalds Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/Y1jek64pXOsougmz@hirez.programming.kicks-ass.net

powerpc/kprobes: Use preempt_enable() rather than the no_resched variant

2022-11-24T12:31:49+00:00

preempt_enable_no_resched() is just the same as preempt_enable() when we are in a irqs disabled context. kprobe_handler() and the post/fault handlers are all called with irqs disabled. As such, convert those to just use preempt_enable(). Reported-by: Nicholas Piggin Signed-off-by: Naveen N. Rao Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/72639f75fe66f931ec8c2165276ffbfb0fe1006f.1666262278.git.naveen.n.rao@linux.vnet.ibm.com

powerpc/kprobes: Remove preempt disable around call to get_kprobe() in arch_prepare_kprobe()

2022-11-24T12:31:49+00:00

arch_prepare_kprobe() is called from register_kprobe() via prepare_kprobe(), or through register_aggr_kprobe(), both with the kprobe_mutex held. Per the comment for get_kprobe(): /* * This routine is called either: * - under the 'kprobe_mutex' - during kprobe_[un]register(). * OR * - with preemption disabled - from architecture specific code. */ As such, there is no need to disable preemption around the call to get_kprobe(). Drop the same. Reported-by: Nicholas Piggin Signed-off-by: Naveen N. Rao Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/1043d06a0affed83a4a46dd29466e72820ee215d.1666262278.git.naveen.n.rao@linux.vnet.ibm.com

powerpc/kprobes: Fix null pointer reference in arch_prepare_kprobe()

2022-09-28T12:19:52+00:00

I found a null pointer reference in arch_prepare_kprobe(): # echo 'p cmdline_proc_show' > kprobe_events # echo 'p cmdline_proc_show+16' >> kprobe_events Kernel attempted to read user page (0) - exploit attempt? (uid: 0) BUG: Kernel NULL pointer dereference on read at 0x00000000 Faulting instruction address: 0xc000000000050bfc Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA PowerNV Modules linked in: CPU: 0 PID: 122 Comm: sh Not tainted 6.0.0-rc3-00007-gdcf8e5633e2e #10 NIP: c000000000050bfc LR: c000000000050bec CTR: 0000000000005bdc REGS: c0000000348475b0 TRAP: 0300 Not tainted (6.0.0-rc3-00007-gdcf8e5633e2e) MSR: 9000000000009033 CR: 88002444 XER: 20040006 CFAR: c00000000022d100 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0 ... NIP arch_prepare_kprobe+0x10c/0x2d0 LR arch_prepare_kprobe+0xfc/0x2d0 Call Trace: 0xc0000000012f77a0 (unreliable) register_kprobe+0x3c0/0x7a0 __register_trace_kprobe+0x140/0x1a0 __trace_kprobe_create+0x794/0x1040 trace_probe_create+0xc4/0xe0 create_or_delete_trace_kprobe+0x2c/0x80 trace_parse_run_command+0xf0/0x210 probes_write+0x20/0x40 vfs_write+0xfc/0x450 ksys_write+0x84/0x140 system_call_exception+0x17c/0x3a0 system_call_vectored_common+0xe8/0x278 --- interrupt: 3000 at 0x7fffa5682de0 NIP: 00007fffa5682de0 LR: 0000000000000000 CTR: 0000000000000000 REGS: c000000034847e80 TRAP: 3000 Not tainted (6.0.0-rc3-00007-gdcf8e5633e2e) MSR: 900000000280f033 CR: 44002408 XER: 00000000 The address being probed has some special: cmdline_proc_show: Probe based on ftrace cmdline_proc_show+16: Probe for the next instruction at the ftrace location The ftrace-based kprobe does not generate kprobe::ainsn::insn, it gets set to NULL. In arch_prepare_kprobe() it will check for: ... prev = get_kprobe(p->addr - 1); preempt_enable_no_resched(); if (prev && ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) { ... If prev is based on ftrace, 'ppc_inst_read(prev->ainsn.insn)' will occur with a null pointer reference. At this point prev->addr will not be a prefixed instruction, so the check can be skipped. Check if prev is ftrace-based kprobe before reading 'prev->ainsn.insn' to fix this problem. Fixes: b4657f7650ba ("powerpc/kprobes: Don't allow breakpoints on suffixes") Signed-off-by: Li Huafei [mpe: Trim oops] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220923093253.177298-1-lihuafei1@huawei.com

powerpc/64: Drop ppc_inst_as_str()

2022-06-29T09:37:07+00:00

The ppc_inst_as_str() macro tries to make printing variable length, aka "prefixed", instructions convenient. It mostly succeeds, but it does hide an on-stack buffer, which triggers stack protector. More problematically it doesn't compile at all with GCC 12, with -Wdangling-pointer, due to the fact that it returns the char buffer declared inside the macro: arch/powerpc/kernel/trace/ftrace.c: In function '__ftrace_modify_call': ./include/linux/printk.h:475:44: error: using a dangling pointer to '__str' [-Werror=dangling-pointer=] 475 | #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__) ... arch/powerpc/kernel/trace/ftrace.c:567:17: note: in expansion of macro 'pr_err' 567 | pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op)); | ^~~~~~ ./arch/powerpc/include/asm/inst.h:156:14: note: '__str' declared here 156 | char __str[PPC_INST_STR_LEN]; \ | ^~~~~ This could be fixed by having the caller declare the buffer, but in some places there'd need to be two buffers. In all cases where ppc_inst_as_str() is used the output is not really meant for user consumption, it's almost always indicative of a kernel bug. A simpler solution is to just print the value as an unsigned long. For normal instructions the output is identical. For prefixed instructions the value is printed as a single 64-bit quantity, whereas previously the low half was printed first. But that is good enough for debug output, especially as prefixed instructions will be rare in kernel code in practice. Old: c000000000111170 60420000 ori r2,r2,0 c000000000111174 04100001 e580fb00 .long 0xe580fb0004100001 New: c00000000010f90c 60420000 ori r2,r2,0 c00000000010f910 e580fb0004100001 .long 0xe580fb0004100001 Reported-by: Bagas Sanjaya Reported-by: Petr Mladek Signed-off-by: Michael Ellerman Tested-by: Bagas Sanjaya Link: https://lore.kernel.org/r/20220531065936.3674348-1-mpe@ellerman.id.au

powerpc: Replace PPC64_ELF_ABI_v{1/2} by CONFIG_PPC64_ELF_ABI_V{1/2}

2022-05-19T13:11:29+00:00

Replace all uses of PPC64_ELF_ABI_v1 and PPC64_ELF_ABI_v2 by resp CONFIG_PPC64_ELF_ABI_V1 and CONFIG_PPC64_ELF_ABI_V2. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/ba13d59e8c50bc9aa6328f1c7f0c0d0278e0a3a7.1652074503.git.christophe.leroy@csgroup.eu

powerpc: Reject probes on instructions that can't be single stepped

2022-05-05T14:00:20+00:00

Per the ISA, a Trace interrupt is not generated for: - [h|u]rfi[d] - rfscv - sc, scv, and Trap instructions that trap - Power-Saving Mode instructions - other instructions that cause interrupts (other than Trace interrupts) - the first instructions of any interrupt handler (applies to Branch and Single Step tracing; CIABR matches may still occur) - instructions that are emulated by software Add a helper to check for instructions belonging to the first four categories above and to reject kprobes, uprobes and xmon breakpoints on such instructions. We reject probing on instructions belonging to these categories across all ISA versions and across both BookS and BookE. For trap instructions, we can't know in advance if they can cause a trap, and there is no good reason to allow probing on those. Also, uprobes already refuses to probe trap instructions and kprobes does not allow probes on trap instructions used for kernel warnings and bugs. As such, stop allowing any type of probes/breakpoints on trap instruction across uprobes, kprobes and xmon. For some of the fp/altivec instructions that can generate an interrupt and which we emulate in the kernel (altivec assist, for example), we check and turn off single stepping in emulate_single_step(). Instructions generating a DSI are restarted and single stepping normally completes once the instruction is completed. In uprobes, if a single stepped instruction results in a non-fatal signal to be delivered to the task, such signals are "delayed" until after the instruction completes. For fatal signals, single stepping is cancelled and the instruction restarted in-place so that core dump captures proper addresses. In kprobes, we do not allow probes on instructions having an extable entry and we also do not allow probing interrupt vectors. Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/f56ee979d50b8711fae350fc97870f3ca34acd75.1648648712.git.naveen.n.rao@linux.vnet.ibm.com

x86/ibt,kprobes: Cure sym+0 equals fentry woes

2022-03-15T09:32:38+00:00

In order to allow kprobes to skip the ENDBR instructions at sym+0 for X86_KERNEL_IBT builds, change _kprobe_addr() to take an architecture callback to inspect the function at hand and modify the offset if needed. This streamlines the existing interface to cover more cases and require less hooks. Once PowerPC gets fully converted there will only be the one arch hook. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Masami Hiramatsu Acked-by: Josh Poimboeuf Link: https://lore.kernel.org/r/20220308154318.405947704@infradead.org

powerpc/inst: Define ppc_inst_t

2021-12-09T11:41:21+00:00

In order to stop using 'struct ppc_inst' on PPC32, define a ppc_inst_t typedef. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/fe5baa2c66fea9db05a8b300b3e8d2880a42596c.1638208156.git.christophe.leroy@csgroup.eu