user/sven/linux.git/tools/objtool/check.c, branch v5.4.38

objtool: Fix CONFIG_UBSAN_TRAP unreachable warnings

2020-05-02T06:48:57Z

[ Upstream commit bd841d6154f5f41f8a32d3c1b0bc229e326e640a ] CONFIG_UBSAN_TRAP causes GCC to emit a UD2 whenever it encounters an unreachable code path. This includes __builtin_unreachable(). Because the BUG() macro uses __builtin_unreachable() after it emits its own UD2, this results in a double UD2. In this case objtool rightfully detects that the second UD2 is unreachable: init/main.o: warning: objtool: repair_env_string()+0x1c8: unreachable instruction We weren't able to figure out a way to get rid of the double UD2s, so just silence the warning. Reported-by: Randy Dunlap Signed-off-by: Josh Poimboeuf Signed-off-by: Borislav Petkov Reviewed-by: Kees Cook Reviewed-by: Miroslav Benes Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/6653ad73c6b59c049211bd7c11ed3809c20ee9f5.1585761021.git.jpoimboe@redhat.com Signed-off-by: Sasha Levin

objtool: Fix switch table detection in .text.unlikely

2020-04-23T08:36:16Z

commit b401efc120a399dfda1f4d2858a4de365c9b08ef upstream. If a switch jump table's indirect branch is in a ".cold" subfunction in .text.unlikely, objtool doesn't detect it, and instead prints a false warning: drivers/media/v4l2-core/v4l2-ioctl.o: warning: objtool: v4l_print_format.cold()+0xd6: sibling call from callable instruction with modified stack frame drivers/hwmon/max6650.o: warning: objtool: max6650_probe.cold()+0xa5: sibling call from callable instruction with modified stack frame drivers/media/dvb-frontends/drxk_hard.o: warning: objtool: init_drxk.cold()+0x16f: sibling call from callable instruction with modified stack frame Fix it by comparing the function, instead of the section and offset. Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions") Signed-off-by: Josh Poimboeuf Signed-off-by: Borislav Petkov Reviewed-by: Miroslav Benes Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/157c35d42ca9b6354bbb1604fe9ad7d1153ccb21.1585761021.git.jpoimboe@redhat.com Signed-off-by: Greg Kroah-Hartman

ubsan, x86: Annotate and allow __ubsan_handle_shift_out_of_bounds() in uaccess regions

2019-12-31T15:44:25Z

[ Upstream commit 9a50dcaf0416a43e1fe411dc61a99c8333c90119 ] The new check_zeroed_user() function uses variable shifts inside of a user_access_begin()/user_access_end() section and that results in GCC emitting __ubsan_handle_shift_out_of_bounds() calls, even though through value range analysis it would be able to see that the UB in question is impossible. Annotate and whitelist this UBSAN function; continued use of user_access_begin()/user_access_end() will undoubtedly result in further uses of function. Reported-by: Randy Dunlap Tested-by: Randy Dunlap Signed-off-by: Peter Zijlstra (Intel) Acked-by: Randy Dunlap Acked-by: Christian Brauner Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephen Rothwell Cc: Thomas Gleixner Cc: cyphar@cyphar.com Cc: keescook@chromium.org Cc: linux@rasmusvillemoes.dk Fixes: f5a1a536fa14 ("lib: introduce copy_struct_from_user() helper") Link: https://lkml.kernel.org/r/20191021131149.GA19358@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

KVM: x86: Check kvm_rebooting in kvm_spurious_fault()

2019-09-25T13:23:33Z

Explicitly check kvm_rebooting in kvm_spurious_fault() prior to invoking BUG(), as opposed to assuming the caller has already done so. Letting kvm_spurious_fault() be called "directly" will allow VMX to better optimize its low level assembly flows. As a happy side effect, kvm_spurious_fault() no longer needs to be marked as a dead end since it doesn't unconditionally BUG(). Acked-by: Paolo Bonzini Cc: Josh Poimboeuf Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini

objtool: Improve UACCESS coverage

2019-07-25T06:36:39Z

A clang build reported an (obvious) double CLAC while a GCC build did not; it turns out that objtool only re-visits instructions if the first visit was with AC=0. If OTOH the first visit was with AC=1, it completely ignores any subsequent visit, even when it has AC=0. Fix this by using a visited mask instead of a boolean, and (explicitly) mark the AC state. $ ./objtool check -b --no-fp --retpoline --uaccess drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x22: redundant UACCESS disable drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xea: (alt) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0xffffffffffffffff: (branch) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xd9: (alt) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xb2: (branch) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0x39: (branch) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0x0: <=== (func) Reported-by: Josh Poimboeuf Reported-by: Thomas Gleixner Reported-by: Sedat Dilek Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Tested-by: Nathan Chancellor Tested-by: Nick Desaulniers Tested-by: Sedat Dilek Link: https://github.com/ClangBuiltLinux/linux/issues/617 Link: https://lkml.kernel.org/r/5359166aad2d53f3145cd442d83d0e5115e0cd17.1564007838.git.jpoimboe@redhat.com

objtool: Support conditional retpolines

2019-07-18T19:01:10Z

A Clang-built kernel is showing the following warning: arch/x86/kernel/platform-quirks.o: warning: objtool: x86_early_init_platform_quirks()+0x84: unreachable instruction That corresponds to this code: 7e: 0f 85 00 00 00 00 jne 84 80: R_X86_64_PC32 __x86_indirect_thunk_r11-0x4 84: c3 retq This is a conditional retpoline sibling call, which is now possible thanks to retpolines. Objtool hasn't seen that before. It's incorrectly interpreting the conditional jump as an unconditional dynamic jump. Reported-by: Nick Desaulniers Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Tested-by: Nick Desaulniers Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/30d4c758b267ef487fb97e6ecb2f148ad007b554.1563413318.git.jpoimboe@redhat.com

objtool: Convert insn type to enum

2019-07-18T19:01:10Z

This makes it easier to add new instruction types. Also it's hopefully more robust since the compiler should warn about out-of-range enums. Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Tested-by: Nick Desaulniers Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/0740e96af0d40e54cfd6a07bf09db0fbd10793cd.1563413318.git.jpoimboe@redhat.com

objtool: Fix seg fault on bad switch table entry

2019-07-18T19:01:10Z

In one rare case, Clang generated the following code: 5ca: 83 e0 21 and $0x21,%eax 5cd: b9 04 00 00 00 mov $0x4,%ecx 5d2: ff 24 c5 00 00 00 00 jmpq *0x0(,%rax,8) 5d5: R_X86_64_32S .rodata+0x38 which uses the corresponding jump table relocations: 000000000038 000200000001 R_X86_64_64 0000000000000000 .text + 834 000000000040 000200000001 R_X86_64_64 0000000000000000 .text + 5d9 000000000048 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000050 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000058 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000060 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000068 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000070 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000078 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000080 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000088 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000090 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000098 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000a0 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000a8 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000b0 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000b8 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000c0 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000c8 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000d0 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000d8 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000e0 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000e8 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000f0 000200000001 R_X86_64_64 0000000000000000 .text + b96 0000000000f8 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000100 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000108 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000110 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000118 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000120 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000128 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000130 000200000001 R_X86_64_64 0000000000000000 .text + b96 000000000138 000200000001 R_X86_64_64 0000000000000000 .text + 82f 000000000140 000200000001 R_X86_64_64 0000000000000000 .text + 828 Since %eax was masked with 0x21, only the first two and the last two entries are possible. Objtool doesn't actually emulate all the code, so it isn't smart enough to know that all the middle entries aren't reachable. They point to the NOP padding area after the end of the function, so objtool seg faulted when it tried to dereference a NULL insn->func. After this fix, objtool still gives an "unreachable" error because it stops reading the jump table when it encounters the bad addresses: /home/jpoimboe/objtool-tests/adm1275.o: warning: objtool: adm1275_probe()+0x828: unreachable instruction While the above code is technically correct, it's very wasteful of memory -- it uses 34 jump table entries when only 4 are needed. It's also not possible for objtool to validate this type of switch table because the unused entries point outside the function and objtool has no way of determining if that's intentional. Hopefully the Clang folks can fix it. Reported-by: Arnd Bergmann Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Tested-by: Nick Desaulniers Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/a9db88eec4f1ca089e040989846961748238b6d8.1563413318.git.jpoimboe@redhat.com

objtool: Support repeated uses of the same C jump table

2019-07-18T19:01:09Z

This fixes objtool for both a GCC issue and a Clang issue: 1) GCC issue: kernel/bpf/core.o: warning: objtool: ___bpf_prog_run()+0x8d5: sibling call from callable instruction with modified stack frame With CONFIG_RETPOLINE=n, GCC is doing the following optimization in ___bpf_prog_run(). Before: select_insn: jmp *jumptable(,%rax,8) ... ALU64_ADD_X: ... jmp select_insn ALU_ADD_X: ... jmp select_insn After: select_insn: jmp *jumptable(, %rax, 8) ... ALU64_ADD_X: ... jmp *jumptable(, %rax, 8) ALU_ADD_X: ... jmp *jumptable(, %rax, 8) This confuses objtool. It has never seen multiple indirect jump sites which use the same jump table. For GCC switch tables, the only way of detecting the size of a table is by continuing to scan for more tables. The size of the previous table can only be determined after another switch table is found, or when the scan reaches the end of the function. That logic was reused for C jump tables, and was based on the assumption that each jump table only has a single jump site. The above optimization breaks that assumption. 2) Clang issue: drivers/usb/misc/sisusbvga/sisusb.o: warning: objtool: sisusb_write_mem_bulk()+0x588: can't find switch jump table With clang 9, code can be generated where a function contains two indirect jump instructions which use the same switch table. The fix is the same for both issues: split the jump table parsing into two passes. In the first pass, locate the heads of all switch tables for the function and mark their locations. In the second pass, parse the switch tables and add them. Fixes: e55a73251da3 ("bpf: Fix ORC unwinding in non-JIT BPF code") Reported-by: Randy Dunlap Reported-by: Arnd Bergmann Signed-off-by: Jann Horn Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Tested-by: Nick Desaulniers Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/e995befaada9d4d8b2cf788ff3f566ba900d2b4d.1563413318.git.jpoimboe@redhat.com Co-developed-by: Josh Poimboeuf

objtool: Refactor jump table code

2019-07-18T19:01:09Z

Now that C jump tables are supported, call them "jump tables" instead of "switch tables". Also rename some other variables, add comments, and simplify the code flow a bit. Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Tested-by: Nick Desaulniers Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/cf951b0c0641628e0b9b81f7ceccd9bcabcb4bd8.1563413318.git.jpoimboe@redhat.com