From 59d2aeb3b18d94f3397d7097e34bc61790e37b0d Mon Sep 17 00:00:00 2001 From: He Zhe Date: Mon, 17 Oct 2022 18:01:01 +0800 Subject: lttng-modules: Fix crash on powerpc64 Backport a patch to fix the following on powerpc64 ABIv2. root@qemuppc64:~# lttng create trace_session --live -U net://127.0.0.1 Spawning a session daemon lttng_kretprobes: loading out-of-tree module taints kernel. BUG: Unable to handle kernel data access on read at 0xfffffffffffffff8 Faulting instruction address: 0xc0000000001f6fd0 Oops: Kernel access of bad area, sig: 11 [#1] (From OE-Core rev: 4781fee6aea9512b7cb390b76e6f9f0a86a5bd11) Signed-off-by: He Zhe Signed-off-by: Steve Sakoman Signed-off-by: Richard Purdie --- ...erpc64-fix-kernel-crash-caused-by-do_get_.patch | 94 ++++++++++++++++++++++ meta/recipes-kernel/lttng/lttng-modules_2.13.4.bb | 1 + 2 files changed, 95 insertions(+) create mode 100644 meta/recipes-kernel/lttng/lttng-modules/0001-wrapper-powerpc64-fix-kernel-crash-caused-by-do_get_.patch (limited to 'meta/recipes-kernel') diff --git a/meta/recipes-kernel/lttng/lttng-modules/0001-wrapper-powerpc64-fix-kernel-crash-caused-by-do_get_.patch b/meta/recipes-kernel/lttng/lttng-modules/0001-wrapper-powerpc64-fix-kernel-crash-caused-by-do_get_.patch new file mode 100644 index 0000000000..b3b191c7ac --- /dev/null +++ b/meta/recipes-kernel/lttng/lttng-modules/0001-wrapper-powerpc64-fix-kernel-crash-caused-by-do_get_.patch @@ -0,0 +1,94 @@ +From 480cce4315ce5bf59a509e8a53a52545f393de68 Mon Sep 17 00:00:00 2001 +From: He Zhe +Date: Tue, 27 Sep 2022 15:59:42 +0800 +Subject: [PATCH] wrapper: powerpc64: fix kernel crash caused by + do_get_kallsyms + +Kernel crashes on powerpc64 ABIv2 as follow when lttng_tracer initializes, +since do_get_kallsyms in lttng_wrapper fails to return a proper address of +kallsyms_lookup_name. + +root@qemuppc64:~# lttng create trace_session --live -U net://127.0.0.1 +Spawning a session daemon +lttng_kretprobes: loading out-of-tree module taints kernel. +BUG: Unable to handle kernel data access on read at 0xfffffffffffffff8 +Faulting instruction address: 0xc0000000001f6fd0 +Oops: Kernel access of bad area, sig: 11 [#1] + +NIP [c0000000001f6fd0] module_kallsyms_lookup_name+0xf0/0x180 +LR [c0000000001f6f28] module_kallsyms_lookup_name+0x48/0x180 +Call Trace: +module_kallsyms_lookup_name+0x34/0x180 (unreliable) +kallsyms_lookup_name+0x258/0x2b0 +wrapper_kallsyms_lookup_name+0x4c/0xd0 [lttng_wrapper] +wrapper_get_pfnblock_flags_mask_init+0x28/0x60 [lttng_wrapper] +lttng_events_init+0x40/0x344 [lttng_tracer] +do_one_initcall+0x78/0x340 +do_init_module+0x6c/0x2f0 +__do_sys_finit_module+0xd0/0x120 +system_call_exception+0x194/0x2f0 +system_call_vectored_common+0xe8/0x278 + + +do_get_kallsyms makes use of kprobe_register and in turn kprobe_lookup_name +to get the address of the kernel function kallsyms_lookup_name. In case of +PPC64_ELF_ABI_v2, when kprobes are placed at function entry, +kprobe_lookup_name adjusts the global entry point of the function returned +by kallsyms_lookup_name to the local entry point(at some fixed offset of +global one). This adjustment is all for kprobes to be able to work properly. +Global and local entry point are defined in powerpc64 ABIv2. + +When the local entry point is given, some instructions at the beginning of +the function are skipped and thus causes the above kernel crash. We just +want to make a simple function call which needs global entry point. + +This patch adds 4 bytes which is the length of one instruction to +kallsyms_lookup_name so that it will not trigger the global to local +adjustment, and then substracts 4 bytes from the returned address. See the +following kernel change for more details. + +https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=290e3070762ac80e5fc4087d8c4de7e3f1d90aca + +Upstream-Status: Backport + +Signed-off-by: He Zhe +Signed-off-by: Mathieu Desnoyers +Change-Id: I34e68e886b97e3976d0b5e25be295a8bb866c1a4 +--- + src/wrapper/kallsyms.c | 16 ++++++++++++++++ + 1 file changed, 16 insertions(+) + +diff --git a/src/wrapper/kallsyms.c b/src/wrapper/kallsyms.c +index d2848764..93017adc 100644 +--- a/src/wrapper/kallsyms.c ++++ b/src/wrapper/kallsyms.c +@@ -39,10 +39,26 @@ unsigned long do_get_kallsyms(void) + memset(&probe, 0, sizeof(probe)); + probe.pre_handler = dummy_kprobe_handler; + probe.symbol_name = "kallsyms_lookup_name"; ++#ifdef PPC64_ELF_ABI_v2 ++ /* ++ * With powerpc64 ABIv2, we need the global entry point of ++ * kallsyms_lookup_name to call it later, while kprobe_register would ++ * automatically adjust the global entry point to the local entry point, ++ * when a kprobe was registered at a function entry. So we add 4 bytes ++ * which is the length of one instruction to kallsyms_lookup_name to ++ * avoid the adjustment. ++ */ ++ probe.offset = 4; ++#endif + ret = register_kprobe(&probe); + if (ret) + return 0; ++#ifdef PPC64_ELF_ABI_v2 ++ /* Substract 4 bytes to get what we originally want */ ++ addr = (unsigned long)(((char *)probe.addr) - 4); ++#else + addr = (unsigned long)probe.addr; ++#endif + #ifdef CONFIG_ARM + #ifdef CONFIG_THUMB2_KERNEL + if (addr) +-- +2.17.1 + diff --git a/meta/recipes-kernel/lttng/lttng-modules_2.13.4.bb b/meta/recipes-kernel/lttng/lttng-modules_2.13.4.bb index 80b9ceec3f..ad4063bed3 100644 --- a/meta/recipes-kernel/lttng/lttng-modules_2.13.4.bb +++ b/meta/recipes-kernel/lttng/lttng-modules_2.13.4.bb @@ -17,6 +17,7 @@ SRC_URI = "https://lttng.org/files/${BPN}/${BPN}-${PV}.tar.bz2 \ file://0001-fix-net-skb-introduce-kfree_skb_reason-v5.15.58.v5.1.patch \ file://0001-fix-compaction.patch \ file://0001-fix-adjust-range-v5.10.137-in-block-probe.patch \ + file://0001-wrapper-powerpc64-fix-kernel-crash-caused-by-do_get_.patch \ " # Use :append here so that the patch is applied also when using devupstream -- cgit v1.2.3-54-g00ecf