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2022-01-11Merge tag 'kcsan.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcuLinus Torvalds2-7/+36
Pull KCSAN updates from Paul McKenney: "This provides KCSAN fixes and also the ability to take memory barriers into account for weakly-ordered systems. This last can increase the probability of detecting certain types of data races" * tag 'kcsan.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (29 commits) kcsan: Only test clear_bit_unlock_is_negative_byte if arch defines it kcsan: Avoid nested contexts reading inconsistent reorder_access kcsan: Turn barrier instrumentation into macros kcsan: Make barrier tests compatible with lockdep kcsan: Support WEAK_MEMORY with Clang where no objtool support exists compiler_attributes.h: Add __disable_sanitizer_instrumentation objtool, kcsan: Remove memory barrier instrumentation from noinstr objtool, kcsan: Add memory barrier instrumentation to whitelist sched, kcsan: Enable memory barrier instrumentation mm, kcsan: Enable barrier instrumentation x86/qspinlock, kcsan: Instrument barrier of pv_queued_spin_unlock() x86/barriers, kcsan: Use generic instrumentation for non-smp barriers asm-generic/bitops, kcsan: Add instrumentation for barriers locking/atomics, kcsan: Add instrumentation for barriers locking/barriers, kcsan: Support generic instrumentation locking/barriers, kcsan: Add instrumentation for barriers kcsan: selftest: Add test case to check memory barrier instrumentation kcsan: Ignore GCC 11+ warnings about TSan runtime support kcsan: test: Add test cases for memory barrier instrumentation kcsan: test: Match reordered or normal accesses ...
2021-12-09objtool, kcsan: Remove memory barrier instrumentation from noinstrMarco Elver2-7/+32
Teach objtool to turn instrumentation required for memory barrier modeling into nops in noinstr text. The __tsan_func_entry/exit calls are still emitted by compilers even with the __no_sanitize_thread attribute. The memory barrier instrumentation will be inserted explicitly (without compiler help), and thus needs to also explicitly be removed. Signed-off-by: Marco Elver <elver@google.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-12-09objtool, kcsan: Add memory barrier instrumentation to whitelistMarco Elver1-0/+4
Adds KCSAN's memory barrier instrumentation to objtool's uaccess whitelist. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-12-03objtool: Fix pv_ops noinstr validationPeter Zijlstra2-0/+5
Boris reported that in one of his randconfig builds, objtool got infinitely stuck. Turns out there's trivial list corruption in the pv_ops tracking when a function is both in a static table and in a code assignment. Avoid re-adding function to the pv_ops[] lists when they're already on it. Fixes: db2b0c5d7b6f ("objtool: Support pv_opsindirect calls for noinstr") Reported-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Borislav Petkov <bp@alien8.de> Link: https://lkml.kernel.org/r/20211202204534.GA16608@worktop.programming.kicks-ass.net
2021-11-11static_call,x86: Robustify trampoline patchingPeter Zijlstra1-0/+3
Add a few signature bytes after the static call trampoline and verify those bytes match before patching the trampoline. This avoids patching random other JMPs (such as CFI jump-table entries) instead. These bytes decode as: d: 53 push %rbx e: 43 54 rex.XB push %r12 And happen to spell "SCT". Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20211030074758.GT174703@worktop.programming.kicks-ass.net
2021-11-01Merge tag 'trace-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-traceLinus Torvalds1-1/+1
Pull tracing updates from Steven Rostedt: - kprobes: Restructured stack unwinder to show properly on x86 when a stack dump happens from a kretprobe callback. - Fix to bootconfig parsing - Have tracefs allow owner and group permissions by default (only denying others). There's been pressure to allow non root to tracefs in a controlled fashion, and using groups is probably the safest. - Bootconfig memory managament updates. - Bootconfig clean up to have the tools directory be less dependent on changes in the kernel tree. - Allow perf to be traced by function tracer. - Rewrite of function graph tracer to be a callback from the function tracer instead of having its own trampoline (this change will happen on an arch by arch basis, and currently only x86_64 implements it). - Allow multiple direct trampolines (bpf hooks to functions) be batched together in one synchronization. - Allow histogram triggers to add variables that can perform calculations against the event's fields. - Use the linker to determine architecture callbacks from the ftrace trampoline to allow for proper parameter prototypes and prevent warnings from the compiler. - Extend histogram triggers to key off of variables. - Have trace recursion use bit magic to determine preempt context over if branches. - Have trace recursion disable preemption as all use cases do anyway. - Added testing for verification of tracing utilities. - Various small clean ups and fixes. * tag 'trace-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (101 commits) tracing/histogram: Fix semicolon.cocci warnings tracing/histogram: Fix documentation inline emphasis warning tracing: Increase PERF_MAX_TRACE_SIZE to handle Sentinel1 and docker together tracing: Show size of requested perf buffer bootconfig: Initialize ret in xbc_parse_tree() ftrace: do CPU checking after preemption disabled ftrace: disable preemption when recursion locked tracing/histogram: Document expression arithmetic and constants tracing/histogram: Optimize division by a power of 2 tracing/histogram: Covert expr to const if both operands are constants tracing/histogram: Simplify handling of .sym-offset in expressions tracing: Fix operator precedence for hist triggers expression tracing: Add division and multiplication support for hist triggers tracing: Add support for creating hist trigger variables from literal selftests/ftrace: Stop tracing while reading the trace file by default MAINTAINERS: Update KPROBES and TRACING entries test_kprobes: Move it from kernel/ to lib/ docs, kprobes: Remove invalid URL and add new reference samples/kretprobes: Fix return value if register_kretprobe() failed lib/bootconfig: Fix the xbc_get_info kerneldoc ...
2021-11-01Merge tag 'objtool-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tipLinus Torvalds11-379/+604
Pull objtool updates from Thomas Gleixner: - Improve retpoline code patching by separating it from alternatives which reduces memory footprint and allows to do better optimizations in the actual runtime patching. - Add proper retpoline support for x86/BPF - Address noinstr warnings in x86/kvm, lockdep and paravirtualization code - Add support to handle pv_opsindirect calls in the noinstr analysis - Classify symbols upfront and cache the result to avoid redundant str*cmp() invocations. - Add a CFI hash to reduce memory consumption which also reduces runtime on a allyesconfig by ~50% - Adjust XEN code to make objtool handling more robust and as a side effect to prevent text fragmentation due to placement of the hypercall page. * tag 'objtool-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (41 commits) bpf,x86: Respect X86_FEATURE_RETPOLINE* bpf,x86: Simplify computing label offsets x86,bugs: Unconditionally allow spectre_v2=retpoline,amd x86/alternative: Add debug prints to apply_retpolines() x86/alternative: Try inline spectre_v2=retpoline,amd x86/alternative: Handle Jcc __x86_indirect_thunk_\reg x86/alternative: Implement .retpoline_sites support x86/retpoline: Create a retpoline thunk array x86/retpoline: Move the retpoline thunk declarations to nospec-branch.h x86/asm: Fixup odd GEN-for-each-reg.h usage x86/asm: Fix register order x86/retpoline: Remove unused replacement symbols objtool,x86: Replace alternatives with .retpoline_sites objtool: Shrink struct instruction objtool: Explicitly avoid self modifying code in .altinstr_replacement objtool: Classify symbols objtool: Support pv_opsindirect calls for noinstr x86/xen: Rework the xen_{cpu,irq,mmu}_opsarrays x86/xen: Mark xen_force_evtchn_callback() noinstr x86/xen: Make irq_disable() noinstr ...
2021-10-28objtool,x86: Replace alternatives with .retpoline_sitesPeter Zijlstra5-252/+93
Instead of writing complete alternatives, simply provide a list of all the retpoline thunk calls. Then the kernel is free to do with them as it pleases. Simpler code all-round. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Tested-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/r/20211026120309.850007165@infradead.org
2021-10-28objtool: Shrink struct instructionPeter Zijlstra2-4/+3
Any one instruction can only ever call a single function, therefore insn->mcount_loc_node is superfluous and can use insn->call_node. This shrinks struct instruction, which is by far the most numerous structure objtool creates. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Tested-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/r/20211026120309.785456706@infradead.org
2021-10-28objtool: Explicitly avoid self modifying code in .altinstr_replacementPeter Zijlstra1-11/+31
Assume ALTERNATIVE()s know what they're doing and do not change, or cause to change, instructions in .altinstr_replacement sections. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Tested-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/r/20211026120309.722511775@infradead.org
2021-10-28objtool: Classify symbolsPeter Zijlstra2-14/+27
In order to avoid calling str*cmp() on symbol names, over and over, do them all once upfront and store the result. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Tested-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/r/20211026120309.658539311@infradead.org
2021-10-06objtool: Update section header before relocationsMichael Forney1-29/+17
The libelf implementation from elftoolchain has a safety check in gelf_update_rel[a] to check that the data corresponds to a section that has type SHT_REL[A] [0]. If the relocation is updated before the section header is updated with the proper type, this check fails. To fix this, update the section header first, before the relocations. Previously, the section size was calculated in elf_rebuild_reloc_section by counting the number of entries in the reloc_list. However, we now need the size during elf_write so instead keep a running total and add to it for every new relocation. [0] https://sourceforge.net/p/elftoolchain/mailman/elftoolchain-developers/thread/CAGw6cBtkZro-8wZMD2ULkwJ39J+tHtTtAWXufMjnd3cQ7XG54g@mail.gmail.com/ Signed-off-by: Michael Forney <mforney@mforney.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lore.kernel.org/r/20210509000103.11008-2-mforney@mforney.org
2021-10-06objtool: Check for gelf_update_rel[a] failuresMichael Forney1-2/+8
Otherwise, if these fail we end up with garbage data in the .rela.orc_unwind_ip section, leading to errors like ld: fs/squashfs/namei.o: bad reloc symbol index (0x7f16 >= 0x12) for offset 0x7f16d5c82cc8 in section `.orc_unwind_ip' Signed-off-by: Michael Forney <mforney@mforney.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lore.kernel.org/r/20210509000103.11008-1-mforney@mforney.org
2021-10-07Merge branch 'objtool/urgent'Peter Zijlstra6-30/+27
Fixup conflicts. # Conflicts: # tools/objtool/check.c
2021-10-05objtool: Remove redundant 'len' field from struct sectionJoe Lawrence5-20/+17
The section structure already contains sh_size, so just remove the extra 'len' member that requires extra mirroring and potential confusion. Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lore.kernel.org/r/20210822225037.54620-3-joe.lawrence@redhat.com Cc: Andy Lavr <andy.lavr@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org
2021-10-05objtool: Make .altinstructions section entry size consistentJoe Lawrence1-1/+1
Commit e31694e0a7a7 ("objtool: Don't make .altinstructions writable") aligned objtool-created and kernel-created .altinstructions section flags, but there remains a minor discrepency in their use of a section entry size: objtool sets one while the kernel build does not. While sh_entsize of sizeof(struct alt_instr) seems intuitive, this small deviation can cause failures with external tooling (kpatch-build). Fix this by creating new .altinstructions sections with sh_entsize of 0 and then later updating sec->sh_size as alternatives are added to the section. An added benefit is avoiding the data descriptor and buffer created by elf_create_section(), but previously unused by elf_add_alternative(). Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lore.kernel.org/r/20210822225037.54620-2-joe.lawrence@redhat.com Cc: Andy Lavr <andy.lavr@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org
2021-10-05objtool: Remove reloc symbol type checks in get_alt_entry()Josh Poimboeuf1-29/+7
Converting a special section's relocation reference to a symbol is straightforward. No need for objtool to complain that it doesn't know how to handle it. Just handle it. This fixes the following warning: arch/x86/kvm/emulate.o: warning: objtool: __ex_table+0x4: don't know how to handle reloc symbol type: kvm_fastop_exception Fixes: 24ff65257375 ("objtool: Teach get_alt_entry() about more relocation types") Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lore.kernel.org/r/feadbc3dfb3440d973580fad8d3db873cbfe1694.1633367242.git.jpoimboe@redhat.com Cc: Peter Zijlstra <peterz@infradead.org> Cc: x86@kernel.org Cc: Miroslav Benes <mbenes@suse.cz> Cc: linux-kernel@vger.kernel.org
2021-10-03objtool: print out the symbol type when complaining about itLinus Torvalds1-4/+8
The objtool warning that the kvm instruction emulation code triggered wasn't very useful: arch/x86/kvm/emulate.o: warning: objtool: __ex_table+0x4: don't know how to handle reloc symbol type: kvm_fastop_exception in that it helpfully tells you which symbol name it had trouble figuring out the relocation for, but it doesn't actually say what the unknown symbol type was that triggered it all. In this case it was because of missing type information (type 0, aka STT_NOTYPE), but on the whole it really should just have printed that out as part of the message. Because if this warning triggers, that's very much the first thing you want to know - why did reloc2sec_off() return failure for that symbol? So rather than just saying you can't handle some type of symbol without saying what the type _was_, just print out the type number too. Fixes: 24ff65257375 ("objtool: Teach get_alt_entry() about more relocation types") Link: https://lore.kernel.org/lkml/CAHk-=wiZwq-0LknKhXN4M+T8jbxn_2i9mcKpO+OaBSSq_Eh7tg@mail.gmail.com/ Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-10-01objtool: Teach get_alt_entry() about more relocation typesPeter Zijlstra1-7/+25
Occasionally objtool encounters symbol (as opposed to section) relocations in .altinstructions. Typically they are the alternatives written by elf_add_alternative() as encountered on a noinstr validation run on vmlinux after having already ran objtool on the individual .o files. Basically this is the counterpart of commit 44f6a7c0755d ("objtool: Fix seg fault with Clang non-section symbols"), because when these new assemblers (binutils now also does this) strip the section symbols, elf_add_reloc_to_insn() is forced to emit symbol based relocations. As such, teach get_alt_entry() about different relocation types. Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Reported-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Tested-by: Nathan Chancellor <nathan@kernel.org> Link: https://lore.kernel.org/r/YVWUvknIEVNkPvnP@hirez.programming.kicks-ass.net
2021-09-30objtool: Ignore unwind hints for ignored functionsJosh Poimboeuf1-1/+1
If a function is ignored, also ignore its hints. This is useful for the case where the function ignore is conditional on frame pointers, e.g. STACK_FRAME_NON_STANDARD_FP(). Link: https://lkml.kernel.org/r/163163048317.489837.10988954983369863209.stgit@devnote2 Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Tested-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2021-09-17objtool: Support pv_opsindirect calls for noinstrPeter Zijlstra6-12/+207
Normally objtool will now follow indirect calls; there is no need. However, this becomes a problem with noinstr validation; if there's an indirect call from noinstr code, we very much need to know it is to another noinstr function. Luckily there aren't many indirect calls in entry code with the obvious exception of paravirt. As such, noinstr validation didn't work with paravirt kernels. In order to track pv_ops[] call targets, objtool reads the static pv_ops[] tables as well as direct assignments to the pv_ops[] array, provided the compiler makes them a single instruction like: bf87: 48 c7 05 00 00 00 00 00 00 00 00 movq $0x0,0x0(%rip) bf92 <xen_init_spinlocks+0x5f> bf8a: R_X86_64_PC32 pv_ops+0x268 There are, as of yet, no warnings for when this goes wrong :/ Using the functions found with the above means, all pv_ops[] calls are now subject to noinstr validation. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20210624095149.118815755@infradead.org
2021-09-15objtool: Handle __sanitize_cov*() tail callsPeter Zijlstra3-74/+105
Turns out the compilers also generate tail calls to __sanitize_cov*(), make sure to also patch those out in noinstr code. Fixes: 0f1441b44e82 ("objtool: Fix noinstr vs KCOV") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Marco Elver <elver@google.com> Link: https://lore.kernel.org/r/20210624095147.818783799@infradead.org
2021-09-15objtool: Introduce CFI hashPeter Zijlstra6-35/+160
Andi reported that objtool on vmlinux.o consumes more memory than his system has, leading to horrific performance. This is in part because we keep a struct instruction for every instruction in the file in-memory. Shrink struct instruction by removing the CFI state (which includes full register state) from it and demand allocating it. Given most instructions don't actually change CFI state, there's lots of repetition there, so add a hash table to find previous CFI instances. Reduces memory consumption (and runtime) for processing an x86_64-allyesconfig: pre: 4:40.84 real, 143.99 user, 44.18 sys, 30624988 mem post: 2:14.61 real, 108.58 user, 25.04 sys, 16396184 mem Suggested-by: Andi Kleen <andi@firstfloor.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20210624095147.756759107@infradead.org
2021-09-15x86/xen: Mark cpu_bringup_and_idle() as dead_end_functionPeter Zijlstra1-0/+1
The asm_cpu_bringup_and_idle() function is required to push the return value on the stack in order to make ORC happy, but the only reason objtool doesn't complain is because of a happy accident. The thing is that asm_cpu_bringup_and_idle() doesn't return, so validate_branch() never terminates and falls through to the next function, which in the normal case is the hypercall_page. And that, as it happens, is 4095 NOPs and a RET. Make asm_cpu_bringup_and_idle() terminate on it's own, by making the function it calls as a dead-end. This way we no longer rely on what code happens to come after. Fixes: c3881eb58d56 ("x86/xen: Make the secondary CPU idle tasks reliable") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Juergen Gross <jgross@suse.com> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lore.kernel.org/r/20210624095147.693801717@infradead.org
2021-06-28Merge tags 'objtool-urgent-2021-06-28' and 'objtool-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tipLinus Torvalds8-51/+136
Pull objtool fix and updates from Ingo Molnar: "An ELF format fix for a section flags mismatch bug that breaks kernel tooling such as kpatch-build. The biggest change in this cycle is the new code to handle and rewrite variable sized jump labels - which results in slightly tighter code generation in hot paths, through the use of short(er) NOPs. Also a number of cleanups and fixes, and a change to the generic include/linux/compiler.h to handle a s390 GCC quirk" * tag 'objtool-urgent-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: objtool: Don't make .altinstructions writable * tag 'objtool-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: objtool: Improve reloc hash size guestimate instrumentation.h: Avoid using inline asm operand modifiers compiler.h: Avoid using inline asm operand modifiers kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n' objtool: Reflow handle_jump_alt() jump_label/x86: Remove unused JUMP_LABEL_NOP_SIZE jump_label, x86: Allow short NOPs objtool: Provide stats for jump_labels objtool: Rewrite jump_label instructions objtool: Decode jump_entry::key addend jump_label, x86: Emit short JMP jump_label: Free jump_entry::key bit1 for build use jump_label, x86: Add variable length patching support jump_label, x86: Introduce jump_entry_size() jump_label, x86: Improve error when we fail expected text jump_label, x86: Factor out the __jump_table generation jump_label, x86: Strip ASM jump_label support x86, objtool: Dont exclude arch/x86/realmode/ objtool: Rewrite hashtable sizing
2021-06-24objtool: Don't make .altinstructions writableJosh Poimboeuf1-1/+1
When objtool creates the .altinstructions section, it sets the SHF_WRITE flag to make the section writable -- unless the section had already been previously created by the kernel. The mismatch between kernel-created and objtool-created section flags can cause failures with external tooling (kpatch-build). And the section doesn't need to be writable anyway. Make the section flags consistent with the kernel's. Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Reported-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/6c284ae89717889ea136f9f0064d914cd8329d31.1624462939.git.jpoimboe@redhat.com
2021-06-14objtool: Improve reloc hash size guestimatePeter Zijlstra2-7/+5
Nathan reported that LLVM ThinLTO builds have a performance regression with commit 25cf0d8aa2a3 ("objtool: Rewrite hashtable sizing"). Sami was quick to note that this is due to their use of -ffunction-sections. As a result the .text section is small and basing the number of relocs off of that no longer works. Instead have read_sections() compute the sum of all SHF_EXECINSTR sections and use that. Fixes: 25cf0d8aa2a3 ("objtool: Rewrite hashtable sizing") Reported-by: Nathan Chancellor <nathan@kernel.org> Debugged-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Link: https://lkml.kernel.org/r/YMJpGLuGNsGtA5JJ@hirez.programming.kicks-ass.net
2021-06-11objtool: Only rewrite unconditional retpoline thunk callsPeter Zijlstra1-0/+4
It turns out that the compilers generate conditional branches to the retpoline thunks like: 5d5: 0f 85 00 00 00 00 jne 5db <cpuidle_reflect+0x22> 5d7: R_X86_64_PLT32 __x86_indirect_thunk_r11-0x4 while the rewrite can only handle JMP/CALL to the thunks. The result is the alternative wrecking the code. Make sure to skip writing the alternatives for conditional branches. Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Reported-by: Lukasz Majczak <lma@semihalf.com> Reported-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Nathan Chancellor <nathan@kernel.org>
2021-06-10objtool: Fix .symtab_shndx handling for elf_create_undef_symbol()Peter Zijlstra1-1/+24
When an ELF object uses extended symbol section indexes (IOW it has a .symtab_shndx section), these must be kept in sync with the regular symbol table (.symtab). So for every new symbol we emit, make sure to also emit a .symtab_shndx value to keep the arrays of equal size. Note: since we're writing an UNDEF symbol, most GElf_Sym fields will be 0 and we can repurpose one (st_size) to host the 0 for the xshndx value. Fixes: 2f2f7e47f052 ("objtool: Add elf_create_undef_symbol()") Reported-by: Nick Desaulniers <ndesaulniers@google.com> Suggested-by: Fangrui Song <maskray@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Link: https://lkml.kernel.org/r/YL3q1qFO9QIRL/BA@hirez.programming.kicks-ass.net
2021-05-14objtool: Reflow handle_jump_alt()Peter Zijlstra1-11/+11
Miroslav figured the code flow in handle_jump_alt() was sub-optimal with that goto. Reflow the code to make it clearer. Reported-by: Miroslav Benes <mbenes@suse.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/YJ00lgslY+IpA/rL@hirez.programming.kicks-ass.net
2021-05-12objtool/x86: Fix elf_add_alternative() endiannessVasily Gorbik1-1/+2
Currently x86 kernel cross-compiled on big endian system fails at boot with: kernel BUG at arch/x86/kernel/alternative.c:258! Corresponding bug condition look like the following: BUG_ON(feature >= (NCAPINTS + NBUGINTS) * 32); Fix that by converting alternative feature/cpuid to target endianness. Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Signed-off-by: Vasily Gorbik <gor@linux.ibm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: https://lore.kernel.org/r/patch-2.thread-6c9df9.git-6c9df9a8098d.your-ad-here.call-01620841104-ext-2554@work.hours
2021-05-12objtool: Fix elf_create_undef_symbol() endiannessVasily Gorbik1-0/+1
Currently x86 cross-compilation fails on big endian system with: x86_64-cross-ld: init/main.o: invalid string offset 488112128 >= 6229 for section `.strtab' Mark new ELF data in elf_create_undef_symbol() as symbol, so that libelf does endianness handling correctly. Fixes: 2f2f7e47f052 ("objtool: Add elf_create_undef_symbol()") Signed-off-by: Vasily Gorbik <gor@linux.ibm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: https://lore.kernel.org/r/patch-1.thread-6c9df9.git-d39264656387.your-ad-here.call-01620841104-ext-2554@work.hours
2021-05-12objtool: Provide stats for jump_labelsPeter Zijlstra2-2/+23
Add objtool --stats to count the jump_label sites it encounters. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20210506194158.153101906@infradead.org
2021-05-12objtool: Rewrite jump_label instructionsPeter Zijlstra1-0/+14
When a jump_entry::key has bit1 set, rewrite the instruction to be a NOP. This allows the compiler/assembler to emit JMP (and thus decide on which encoding to use). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20210506194158.091028792@infradead.org
2021-05-12objtool: Decode jump_entry::key addendPeter Zijlstra3-0/+16
Teach objtool about the the low bits in the struct static_key pointer. That is, the low two bits of @key in: struct jump_entry { s32 code; s32 target; long key; } as found in the __jump_table section. Since @key has a relocation to the variable (to be resolved by the linker), the low two bits will be reflected in the relocation's addend. As such, find the reloc and store the addend, such that we can access these bits. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20210506194158.028024143@infradead.org
2021-05-12objtool: Rewrite hashtable sizingPeter Zijlstra2-47/+83
Currently objtool has 5 hashtables and sizes them 16 or 20 bits depending on the --vmlinux argument. However, a single side doesn't really work well for the 5 tables, which among them, cover 3 different uses. Also, while vmlinux is larger, there is still a very wide difference between a defconfig and allyesconfig build, which again isn't optimally covered by a single size. Another aspect is the cost of elf_hash_init(), which for large tables dominates the runtime for small input files. It turns out that all it does it assign NULL, something that is required when using malloc(). However, when we allocate memory using mmap(), we're guaranteed to get zero filled pages. Therefore, rewrite the whole thing to: 1) use more dynamic sized tables, depending on the input file, 2) avoid the need for elf_hash_init() entirely by using mmap(). This speeds up a regular kernel build (100s to 98s for x86_64-defconfig), and potentially dramatically speeds up vmlinux processing. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20210506194157.452881700@infradead.org
2021-04-28Merge tag 'objtool-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tipLinus Torvalds8-166/+299
Pull objtool updates from Ingo Molnar: - Standardize the crypto asm code so that it looks like compiler- generated code to objtool - so that it can understand it. This enables unwinding from crypto asm code - and also fixes the last known remaining objtool warnings for LTO and more. - x86 decoder fixes: clean up and fix the decoder, and also extend it a bit - Misc fixes and cleanups * tag 'objtool-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits) x86/crypto: Enable objtool in crypto code x86/crypto/sha512-ssse3: Standardize stack alignment prologue x86/crypto/sha512-avx2: Standardize stack alignment prologue x86/crypto/sha512-avx: Standardize stack alignment prologue x86/crypto/sha256-avx2: Standardize stack alignment prologue x86/crypto/sha1_avx2: Standardize stack alignment prologue x86/crypto/sha_ni: Standardize stack alignment prologue x86/crypto/crc32c-pcl-intel: Standardize jump table x86/crypto/camellia-aesni-avx2: Unconditionally allocate stack buffer x86/crypto/aesni-intel_avx: Standardize stack alignment prologue x86/crypto/aesni-intel_avx: Fix register usage comments x86/crypto/aesni-intel_avx: Remove unused macros objtool: Support asm jump tables objtool: Parse options from OBJTOOL_ARGS objtool: Collate parse_options() users objtool: Add --backup objtool,x86: More ModRM sugar objtool,x86: Rewrite ADD/SUB/AND objtool,x86: Support %riz encodings objtool,x86: Simplify register decode ...
2021-04-19objtool: Support asm jump tablesJosh Poimboeuf1-1/+13
Objtool detection of asm jump tables would normally just work, except for the fact that asm retpolines use alternatives. Objtool thinks the alternative code path (a jump to the retpoline) is a sibling call. Don't treat alternative indirect branches as sibling calls when the original instruction has a jump table. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Tested-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Ard Biesheuvel <ardb@kernel.org> Tested-by: Sami Tolvanen <samitolvanen@google.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Link: https://lore.kernel.org/r/460cf4dc675d64e1124146562cabd2c05aa322e8.1614182415.git.jpoimboe@redhat.com
2021-04-02objtool/x86: Rewrite retpoline thunk callsPeter Zijlstra1-0/+117
When the compiler emits: "CALL __x86_indirect_thunk_\reg" for an indirect call, have objtool rewrite it to: ALTERNATIVE "call __x86_indirect_thunk_\reg", "call *%reg", ALT_NOT(X86_FEATURE_RETPOLINE) Additionally, in order to not emit endless identical .altinst_replacement chunks, use a global symbol for them, see __x86_indirect_alt_*. This also avoids objtool from having to do code generation. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151300.320177914@infradead.org
2021-04-02objtool: Skip magical retpoline .altinstr_replacementPeter Zijlstra1-1/+11
When the .altinstr_replacement is a retpoline, skip the alternative. We already special case retpolines anyway. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151300.259429287@infradead.org
2021-04-02objtool: Cache instruction relocsPeter Zijlstra2-6/+23
Track the reloc of instructions in the new instruction->reloc field to avoid having to look them up again later. ( Technically x86 instructions can have two relocations, but not jumps and calls, for which we're using this. ) Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151300.195441549@infradead.org
2021-04-02objtool: Keep track of retpoline call sitesPeter Zijlstra5-6/+34
Provide infrastructure for architectures to rewrite/augment compiler generated retpoline calls. Similar to what we do for static_call()s, keep track of the instructions that are retpoline calls. Use the same list_head, since a retpoline call cannot also be a static_call. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151300.130805730@infradead.org
2021-04-02objtool: Add elf_create_undef_symbol()Peter Zijlstra2-0/+61
Allow objtool to create undefined symbols; this allows creating relocations to symbols not currently in the symbol table. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151300.064743095@infradead.org
2021-04-02objtool: Extract elf_symbol_add()Peter Zijlstra1-25/+31
Create a common helper to add symbols. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151300.003468981@infradead.org
2021-04-02objtool: Extract elf_strtab_concat()Peter Zijlstra1-22/+38
Create a common helper to append strings to a strtab. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151259.941474004@infradead.org
2021-04-02objtool: Create reloc sections implicitlyPeter Zijlstra4-10/+8
Have elf_add_reloc() create the relocation section implicitly. Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151259.880174448@infradead.org
2021-04-02objtool: Add elf_create_reloc() helperPeter Zijlstra4-119/+85
We have 4 instances of adding a relocation. Create a common helper to avoid growing even more. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151259.817438847@infradead.org
2021-04-02objtool: Rework the elf_rebuild_reloc_section() logicPeter Zijlstra4-16/+14
Instead of manually calling elf_rebuild_reloc_section() on sections we've called elf_add_reloc() on, have elf_write() DTRT. This makes it easier to add random relocations in places without carefully tracking when we're done and need to flush what section. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151259.754213408@infradead.org
2021-04-02objtool: Fix static_call list generationPeter Zijlstra1-5/+12
Currently, objtool generates tail call entries in add_jump_destination() but waits until validate_branch() to generate the regular call entries. Move these to add_call_destination() for consistency. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151259.691529901@infradead.org
2021-04-02objtool: Handle per arch retpoline namingPeter Zijlstra3-2/+14
The __x86_indirect_ naming is obviously not generic. Shorten to allow matching some additional magic names later. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Link: https://lkml.kernel.org/r/20210326151259.630296706@infradead.org
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