kernel/arch/s390/include/asm/ftrace.h, branch linux-5.14.y

s390/ftrace: fix ftrace_update_ftrace_func implementation

2021-07-15T10:54:58Z

s390 enforces DYNAMIC_FTRACE if FUNCTION_TRACER is selected. At the same time implementation of ftrace_caller is not compliant with HAVE_DYNAMIC_FTRACE since it doesn't provide implementation of ftrace_update_ftrace_func() and calls ftrace_trace_function() directly. The subtle difference is that during ftrace code patching ftrace replaces function tracer via ftrace_update_ftrace_func() and activates it back afterwards. Unexpected direct calls to ftrace_trace_function() during ftrace code patching leads to nullptr-dereferences when tracing is activated for one of functions which are used during code patching. Those function currently are: copy_from_kernel_nofault() copy_from_kernel_nofault_allowed() preempt_count_sub() [with debug_defconfig] preempt_count_add() [with debug_defconfig] Corresponding KASAN report: BUG: KASAN: nullptr-dereference in function_trace_call+0x316/0x3b0 Read of size 4 at addr 0000000000001e08 by task migration/0/15 CPU: 0 PID: 15 Comm: migration/0 Tainted: G B 5.13.0-41423-g08316af3644d Hardware name: IBM 3906 M04 704 (LPAR) Stopper: multi_cpu_stop+0x0/0x3e0 <- stop_machine_cpuslocked+0x1e4/0x218 Call Trace: [<0000000001f77caa>] show_stack+0x16a/0x1d0 [<0000000001f8de42>] dump_stack+0x15a/0x1b0 [<0000000001f81d56>] print_address_description.constprop.0+0x66/0x2e0 [<000000000082b0ca>] kasan_report+0x152/0x1c0 [<00000000004cfd8e>] function_trace_call+0x316/0x3b0 [<0000000001fb7082>] ftrace_caller+0x7a/0x7e [<00000000006bb3e6>] copy_from_kernel_nofault_allowed+0x6/0x10 [<00000000006bb42e>] copy_from_kernel_nofault+0x3e/0xd0 [<000000000014605c>] ftrace_make_call+0xb4/0x1f8 [<000000000047a1b4>] ftrace_replace_code+0x134/0x1d8 [<000000000047a6e0>] ftrace_modify_all_code+0x120/0x1d0 [<000000000047a7ec>] __ftrace_modify_code+0x5c/0x78 [<000000000042395c>] multi_cpu_stop+0x224/0x3e0 [<0000000000423212>] cpu_stopper_thread+0x33a/0x5a0 [<0000000000243ff2>] smpboot_thread_fn+0x302/0x708 [<00000000002329ea>] kthread+0x342/0x408 [<00000000001066b2>] __ret_from_fork+0x92/0xf0 [<0000000001fb57fa>] ret_from_fork+0xa/0x30 The buggy address belongs to the page: page:(____ptrval____) refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1 flags: 0x1ffff00000001000(reserved|node=0|zone=0|lastcpupid=0x1ffff) raw: 1ffff00000001000 0000040000000048 0000040000000048 0000000000000000 raw: 0000000000000000 0000000000000000 ffffffff00000001 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: 0000000000001d00: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 0000000000001d80: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 >0000000000001e00: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 ^ 0000000000001e80: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 0000000000001f00: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 ================================================================== To fix that introduce ftrace_func callback to be called from ftrace_caller and update it in ftrace_update_ftrace_func(). Fixes: 4cc9bed034d1 ("[S390] cleanup ftrace backend functions") Cc: stable@vger.kernel.org Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Heiko Carstens

s390/ftrace: assume -mhotpatch or -mrecord-mcount always available

2020-11-20T18:19:11Z

Currently the kernel minimal compiler requirement is gcc 4.9 or clang 10.0.1. * gcc -mhotpatch option is supported since 4.8. * A combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags is supported since gcc 9 and since clang 10. Drop support for old -pg function prologues. Which leaves binary compatible -mhotpatch / -mnop-mcount -mfentry prologues in a form: brcl 0,0 Which are also do not require initial nop optimization / conversion and presence of _mcount symbol. Signed-off-by: Vasily Gorbik Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens

s390/ftrace: use HAVE_FUNCTION_GRAPH_RET_ADDR_PTR

2019-05-02T11:54:11Z

Make the call chain more reliable by tagging the ftrace stack entries with the stack pointer that is associated with the return address. Signed-off-by: Martin Schwidefsky

s390: avoid __builtin_return_address(n) on clang

2019-04-11T11:37:29Z

llvm on s390 has problems with __builtin_return_address(n), with n>0, this results in a somewhat cryptic error message: fatal error: error in backend: Unsupported stack frame traversal count To work around it, use the direct return address directly. This is probably not ideal here, but gets things to compile and should only lead to inferior reporting, not to misbehavior of the generated code. Link: https://bugs.llvm.org/show_bug.cgi?id=41424 Signed-off-by: Arnd Bergmann Signed-off-by: Martin Schwidefsky

s390: fix system call tracing

2019-01-23T11:38:07Z

When converting to autogenerated compat syscall wrappers all system call entry points got a different symbol name: they all got a __s390x_ prefix. This caused breakage with system call tracing, since an appropriate arch_syscall_match_sym_name() was not provided. Add this function, and while at it also add code to avoid compat system call tracing. s390 has different system call tables for native 64 bit system calls and compat system calls. This isn't really supported in the common code. However there are hardly any compat binaries left, therefore just ignore compat system calls, like x86 and arm64 also do for the same reason. Fixes: aa0d6e70d3b3 ("s390: autogenerate compat syscall wrappers") Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/ftrace: Add -mfentry and -mnop-mcount support

2018-08-16T02:39:53Z

Utilize -mfentry and -mnop-mcount gcc options together with -mrecord-mcount to get compiler generated calls to the profiling functions as nops which are compatible with current -mhotpatch=0,3 approach. At the same time -mrecord-mcount enables __mcount_loc section generation by the compiler which allows to avoid using scripts/recordmcount.pl script. Link: http://lkml.kernel.org/r/patch-4.thread-aa7b8d.git-aa7b8dbf236f.your-ad-here.call-01533557518-ext-9465@work.hours Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Steven Rostedt (VMware)

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55Z

Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

s390/dumpstack: get rid of return_address again

2016-10-17T12:44:33Z

With commit ef6000b4c670 ("Disable the __builtin_return_address() warning globally after all)" the kernel does not warn at all again if __builtin_return_address(n) is called with n > 0. Besides the fact that this was a false warning on s390 anyway, due to the always present backchain, we can now revert commit 5606330627ab ("s390/dumpstack: implement and use return_address()") again, to simplify the code again. After all I shouldn't have had return_address() implememted at all to workaround this issue. So get rid of this again. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/dumpstack: implement and use return_address()

2016-05-04T14:29:45Z

Implement return_address() and use it instead of __builtin_return_address(n). __builtin_return_address(n) is not guaranteed to work for n > 0, therefore implement a private return_address() function which walks the stack frames and returns the proper return address. This way we get also rid of a compile warning which gcc 6.1 emits and look like all other architectures. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/ftrace: hotpatch support for function tracing

2015-01-29T08:19:25Z

Make use of gcc's hotpatch support to generate better code for ftrace function tracing. The generated code now contains only a six byte nop in each function prologue instead of a 24 byte code block which will be runtime patched to support function tracing. With the new code generation the runtime overhead for supporting function tracing is close to zero, while the original code did show a significant performance impact. Acked-by: Steven Rostedt Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky