Re: [PATCH v2 00/20] objtool: vmlinux.o and CLANG LTO support
On Fri, Jan 22, 2021 at 6:26 PM Josh Poimboeuf wrote: > > On Fri, Jan 22, 2021 at 05:32:43PM -0800, Nick Desaulniers wrote: > > > In this specific case, find_func_by_offset returns NULL for > > > .text..L.cfi.jumptable.43 at addend 0x8, because Clang doesn't emit > > > jump table symbols for static functions: > > > > > > <__typeid__ZTSFjmiE_global_addr>: > > >0: e9 00 00 00 00 jmpq 5 > > > <__typeid__ZTSFjmiE_global_addr+0x5> > > > 1: R_X86_64_PLT32 io_serial_in-0x4 > > >5: cc int3 > > >6: cc int3 > > >7: cc int3 > > >8: e9 00 00 00 00 jmpq d > > > <__typeid__ZTSFjmiE_global_addr+0xd> > > > 9: R_X86_64_PLT32 mem32_serial_in-0x4 > > >d: cc int3 > > >e: cc int3 > > >f: cc int3 > > > > > > Nick, do you remember if there were plans to change this? > > > > Do you have a link to any previous discussion to help jog my mind; I > > don't really remember this one. > > > > Is it that `__typeid__ZTSFjmiE_global_addr` is the synthesized jump > > table, and yet there is no `__typeid__ZTSFjmiE_global_addr` entry in > > the symbol table? > > I think he means there's not a 'mem32_serial_in.cfi_jt' symbol at > '__typeid__ZTSFjmiE_global_addr+8'. Probably more aggressive symbol > pruning from the assembler. Correct, the compiler is not emitting mem32_serial_in.cfi_jt here. I seem to recall that the missing jump table symbols also made stack traces harder to follow (__typeid__ZTSFjmiE_global_addr+8 is not very readable), so ideally they shouldn't be pruned. > It's fine though. I just need to rewrite the CFI support a bit. > > But that can come later. For now I'll just drop the two CFI-related > patches from this set so I can merge the others next week. Sure, sounds good. Sami
Re: [PATCH v2 00/20] objtool: vmlinux.o and CLANG LTO support
On Sat, Jan 23, 2021 at 3:46 AM Josh Poimboeuf wrote: > > On Sat, Jan 23, 2021 at 03:31:20AM +0100, Sedat Dilek wrote: > > On Sat, Jan 23, 2021 at 3:26 AM Josh Poimboeuf wrote: > > > > > > On Fri, Jan 22, 2021 at 05:32:43PM -0800, Nick Desaulniers wrote: > > > > > In this specific case, find_func_by_offset returns NULL for > > > > > .text..L.cfi.jumptable.43 at addend 0x8, because Clang doesn't emit > > > > > jump table symbols for static functions: > > > > > > > > > > <__typeid__ZTSFjmiE_global_addr>: > > > > >0: e9 00 00 00 00 jmpq 5 > > > > > <__typeid__ZTSFjmiE_global_addr+0x5> > > > > > 1: R_X86_64_PLT32 io_serial_in-0x4 > > > > >5: cc int3 > > > > >6: cc int3 > > > > >7: cc int3 > > > > >8: e9 00 00 00 00 jmpq d > > > > > <__typeid__ZTSFjmiE_global_addr+0xd> > > > > > 9: R_X86_64_PLT32 mem32_serial_in-0x4 > > > > >d: cc int3 > > > > >e: cc int3 > > > > >f: cc int3 > > > > > > > > > > Nick, do you remember if there were plans to change this? > > > > > > > > Do you have a link to any previous discussion to help jog my mind; I > > > > don't really remember this one. > > > > > > > > Is it that `__typeid__ZTSFjmiE_global_addr` is the synthesized jump > > > > table, and yet there is no `__typeid__ZTSFjmiE_global_addr` entry in > > > > the symbol table? > > > > > > I think he means there's not a 'mem32_serial_in.cfi_jt' symbol at > > > '__typeid__ZTSFjmiE_global_addr+8'. Probably more aggressive symbol > > > pruning from the assembler. > > > > > > It's fine though. I just need to rewrite the CFI support a bit. > > > > > > But that can come later. For now I'll just drop the two CFI-related > > > patches from this set so I can merge the others next week. > > > > > > > Two CFI-related patches? > > > > What's the other than "objtool: Add CONFIG_CFI_CLANG support"? > > I was referring to patches 10 and 11: > > objtool: Move unsuffixed symbol conversion to a helper function > objtool: Add CONFIG_CFI_CLANG support > OK, thanks. I will test with a revert of these two patches in another scenario where I have problems with Clang's IAS but not with GNU AS. - Sedat - > You can just drop those patches from your testing (and don't test with > CFI). > > > Do you plan (or offer) a v3 of objtool-vmlinux? > > Not unless there are any more comments. > > -- > Josh > > -- > You received this message because you are subscribed to the Google Groups > "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clang-built-linux+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/clang-built-linux/20210123024634.qu62tyq3nkqusken%40treble.
Re: [PATCH v2 00/20] objtool: vmlinux.o and CLANG LTO support
On Sat, Jan 23, 2021 at 03:31:20AM +0100, Sedat Dilek wrote: > On Sat, Jan 23, 2021 at 3:26 AM Josh Poimboeuf wrote: > > > > On Fri, Jan 22, 2021 at 05:32:43PM -0800, Nick Desaulniers wrote: > > > > In this specific case, find_func_by_offset returns NULL for > > > > .text..L.cfi.jumptable.43 at addend 0x8, because Clang doesn't emit > > > > jump table symbols for static functions: > > > > > > > > <__typeid__ZTSFjmiE_global_addr>: > > > >0: e9 00 00 00 00 jmpq 5 > > > > <__typeid__ZTSFjmiE_global_addr+0x5> > > > > 1: R_X86_64_PLT32 io_serial_in-0x4 > > > >5: cc int3 > > > >6: cc int3 > > > >7: cc int3 > > > >8: e9 00 00 00 00 jmpq d > > > > <__typeid__ZTSFjmiE_global_addr+0xd> > > > > 9: R_X86_64_PLT32 mem32_serial_in-0x4 > > > >d: cc int3 > > > >e: cc int3 > > > >f: cc int3 > > > > > > > > Nick, do you remember if there were plans to change this? > > > > > > Do you have a link to any previous discussion to help jog my mind; I > > > don't really remember this one. > > > > > > Is it that `__typeid__ZTSFjmiE_global_addr` is the synthesized jump > > > table, and yet there is no `__typeid__ZTSFjmiE_global_addr` entry in > > > the symbol table? > > > > I think he means there's not a 'mem32_serial_in.cfi_jt' symbol at > > '__typeid__ZTSFjmiE_global_addr+8'. Probably more aggressive symbol > > pruning from the assembler. > > > > It's fine though. I just need to rewrite the CFI support a bit. > > > > But that can come later. For now I'll just drop the two CFI-related > > patches from this set so I can merge the others next week. > > > > Two CFI-related patches? > > What's the other than "objtool: Add CONFIG_CFI_CLANG support"? I was referring to patches 10 and 11: objtool: Move unsuffixed symbol conversion to a helper function objtool: Add CONFIG_CFI_CLANG support You can just drop those patches from your testing (and don't test with CFI). > Do you plan (or offer) a v3 of objtool-vmlinux? Not unless there are any more comments. -- Josh
Re: [PATCH v2 00/20] objtool: vmlinux.o and CLANG LTO support
On Sat, Jan 23, 2021 at 3:26 AM Josh Poimboeuf wrote: > > On Fri, Jan 22, 2021 at 05:32:43PM -0800, Nick Desaulniers wrote: > > > In this specific case, find_func_by_offset returns NULL for > > > .text..L.cfi.jumptable.43 at addend 0x8, because Clang doesn't emit > > > jump table symbols for static functions: > > > > > > <__typeid__ZTSFjmiE_global_addr>: > > >0: e9 00 00 00 00 jmpq 5 > > > <__typeid__ZTSFjmiE_global_addr+0x5> > > > 1: R_X86_64_PLT32 io_serial_in-0x4 > > >5: cc int3 > > >6: cc int3 > > >7: cc int3 > > >8: e9 00 00 00 00 jmpq d > > > <__typeid__ZTSFjmiE_global_addr+0xd> > > > 9: R_X86_64_PLT32 mem32_serial_in-0x4 > > >d: cc int3 > > >e: cc int3 > > >f: cc int3 > > > > > > Nick, do you remember if there were plans to change this? > > > > Do you have a link to any previous discussion to help jog my mind; I > > don't really remember this one. > > > > Is it that `__typeid__ZTSFjmiE_global_addr` is the synthesized jump > > table, and yet there is no `__typeid__ZTSFjmiE_global_addr` entry in > > the symbol table? > > I think he means there's not a 'mem32_serial_in.cfi_jt' symbol at > '__typeid__ZTSFjmiE_global_addr+8'. Probably more aggressive symbol > pruning from the assembler. > > It's fine though. I just need to rewrite the CFI support a bit. > > But that can come later. For now I'll just drop the two CFI-related > patches from this set so I can merge the others next week. > Two CFI-related patches? What's the other than "objtool: Add CONFIG_CFI_CLANG support"? Do you plan (or offer) a v3 of objtool-vmlinux? Thanks. - Sedat - [1] https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git/commit/?h=objtool-vmlinux-v2=d743f4b36e120c06506567a9f87a062ae03da47f
Re: [PATCH v2 00/20] objtool: vmlinux.o and CLANG LTO support
On Fri, Jan 22, 2021 at 05:32:43PM -0800, Nick Desaulniers wrote: > > In this specific case, find_func_by_offset returns NULL for > > .text..L.cfi.jumptable.43 at addend 0x8, because Clang doesn't emit > > jump table symbols for static functions: > > > > <__typeid__ZTSFjmiE_global_addr>: > >0: e9 00 00 00 00 jmpq 5 > > <__typeid__ZTSFjmiE_global_addr+0x5> > > 1: R_X86_64_PLT32 io_serial_in-0x4 > >5: cc int3 > >6: cc int3 > >7: cc int3 > >8: e9 00 00 00 00 jmpq d > > <__typeid__ZTSFjmiE_global_addr+0xd> > > 9: R_X86_64_PLT32 mem32_serial_in-0x4 > >d: cc int3 > >e: cc int3 > >f: cc int3 > > > > Nick, do you remember if there were plans to change this? > > Do you have a link to any previous discussion to help jog my mind; I > don't really remember this one. > > Is it that `__typeid__ZTSFjmiE_global_addr` is the synthesized jump > table, and yet there is no `__typeid__ZTSFjmiE_global_addr` entry in > the symbol table? I think he means there's not a 'mem32_serial_in.cfi_jt' symbol at '__typeid__ZTSFjmiE_global_addr+8'. Probably more aggressive symbol pruning from the assembler. It's fine though. I just need to rewrite the CFI support a bit. But that can come later. For now I'll just drop the two CFI-related patches from this set so I can merge the others next week. -- Josh
Re: [PATCH v2 00/20] objtool: vmlinux.o and CLANG LTO support
On Fri, Jan 22, 2021 at 1:17 PM Sami Tolvanen wrote: > > Hi Josh, > > On Fri, Jan 22, 2021 at 7:42 AM Josh Poimboeuf wrote: > > > > On Thu, Jan 21, 2021 at 11:38:54PM +0100, Sedat Dilek wrote: > > > On Thu, Jan 21, 2021 at 10:29 PM Josh Poimboeuf > > > wrote: > > > > > > > > v2: > > > > - fix commit description for why xen hypervisor page contents don't > > > > matter [Juergen] > > > > - annotate indirect jumps as safe instead of converting them to > > > > retpolines [Andrew, Juergen] > > > > - drop patch 1 - fake jumps no longer exist > > > > - add acks > > > > > > > > Based on tip/objtool/core. > > > > > > > > > > > > Add support for proper vmlinux.o validation, which will be needed for > > > > Sami's upcoming x86 LTO set. (And vmlinux validation is the future for > > > > objtool anyway, for other reasons.) > > > > > > > > This isn't 100% done -- most notably, crypto still needs to be supported > > > > -- but I think this gets us most of the way there. > > > > > > > > This can also be found at > > > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git > > > > objtool-vmlinux > > > > > > > > > > Should this be s/objtool-vmlinux/objtool-vmlinux-v2 ? > > > > Indeed: > > > > git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git > > objtool-vmlinux-v2 > > I tested v2 on top of the LTO tree and with allyesconfig + relevant > crypto configs disabled, and I only see the warnings I reported > earlier. > > I also tested this on top of the CFI tree and with LTO+CFI enabled, I > can reproduce the segfault Sedat reported in the previous thread. This > happens because find_unsuffixed_func is called with a NULL sym in > read_relocs: > > Program received signal SIGSEGV, Segmentation fault. > find_unsuffixed_func (elf=elf@entry=0x755a5010, sym=0x0, > suffix=0x416cbf ".cfi_jt", func=func@entry=0x7fffd5f0) at > elf.c:274 > 274 loc = strstr(sym->name, suffix); > (gdb) bt > #0 find_unsuffixed_func (elf=elf@entry=0x755a5010, sym=0x0, > suffix=0x416cbf ".cfi_jt", func=func@entry=0x7fffd5f0) at > elf.c:274 > #1 0x0040d8f8 in read_relocs (elf=0x755a5010) at elf.c:637 > ... > > In this specific case, find_func_by_offset returns NULL for > .text..L.cfi.jumptable.43 at addend 0x8, because Clang doesn't emit > jump table symbols for static functions: > > <__typeid__ZTSFjmiE_global_addr>: >0: e9 00 00 00 00 jmpq 5 <__typeid__ZTSFjmiE_global_addr+0x5> > 1: R_X86_64_PLT32 io_serial_in-0x4 >5: cc int3 >6: cc int3 >7: cc int3 >8: e9 00 00 00 00 jmpq d <__typeid__ZTSFjmiE_global_addr+0xd> > 9: R_X86_64_PLT32 mem32_serial_in-0x4 >d: cc int3 >e: cc int3 >f: cc int3 > > Nick, do you remember if there were plans to change this? Do you have a link to any previous discussion to help jog my mind; I don't really remember this one. Is it that `__typeid__ZTSFjmiE_global_addr` is the synthesized jump table, and yet there is no `__typeid__ZTSFjmiE_global_addr` entry in the symbol table? -- Thanks, ~Nick Desaulniers
Re: [PATCH v2 00/20] objtool: vmlinux.o and CLANG LTO support
Hi Josh, On Fri, Jan 22, 2021 at 7:42 AM Josh Poimboeuf wrote: > > On Thu, Jan 21, 2021 at 11:38:54PM +0100, Sedat Dilek wrote: > > On Thu, Jan 21, 2021 at 10:29 PM Josh Poimboeuf wrote: > > > > > > v2: > > > - fix commit description for why xen hypervisor page contents don't > > > matter [Juergen] > > > - annotate indirect jumps as safe instead of converting them to > > > retpolines [Andrew, Juergen] > > > - drop patch 1 - fake jumps no longer exist > > > - add acks > > > > > > Based on tip/objtool/core. > > > > > > > > > Add support for proper vmlinux.o validation, which will be needed for > > > Sami's upcoming x86 LTO set. (And vmlinux validation is the future for > > > objtool anyway, for other reasons.) > > > > > > This isn't 100% done -- most notably, crypto still needs to be supported > > > -- but I think this gets us most of the way there. > > > > > > This can also be found at > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git > > > objtool-vmlinux > > > > > > > Should this be s/objtool-vmlinux/objtool-vmlinux-v2 ? > > Indeed: > > git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git > objtool-vmlinux-v2 I tested v2 on top of the LTO tree and with allyesconfig + relevant crypto configs disabled, and I only see the warnings I reported earlier. I also tested this on top of the CFI tree and with LTO+CFI enabled, I can reproduce the segfault Sedat reported in the previous thread. This happens because find_unsuffixed_func is called with a NULL sym in read_relocs: Program received signal SIGSEGV, Segmentation fault. find_unsuffixed_func (elf=elf@entry=0x755a5010, sym=0x0, suffix=0x416cbf ".cfi_jt", func=func@entry=0x7fffd5f0) at elf.c:274 274 loc = strstr(sym->name, suffix); (gdb) bt #0 find_unsuffixed_func (elf=elf@entry=0x755a5010, sym=0x0, suffix=0x416cbf ".cfi_jt", func=func@entry=0x7fffd5f0) at elf.c:274 #1 0x0040d8f8 in read_relocs (elf=0x755a5010) at elf.c:637 ... In this specific case, find_func_by_offset returns NULL for .text..L.cfi.jumptable.43 at addend 0x8, because Clang doesn't emit jump table symbols for static functions: <__typeid__ZTSFjmiE_global_addr>: 0: e9 00 00 00 00 jmpq 5 <__typeid__ZTSFjmiE_global_addr+0x5> 1: R_X86_64_PLT32 io_serial_in-0x4 5: cc int3 6: cc int3 7: cc int3 8: e9 00 00 00 00 jmpq d <__typeid__ZTSFjmiE_global_addr+0xd> 9: R_X86_64_PLT32 mem32_serial_in-0x4 d: cc int3 e: cc int3 f: cc int3 Nick, do you remember if there were plans to change this? Sami
Re: [PATCH v2 00/20] objtool: vmlinux.o and CLANG LTO support
On Thu, Jan 21, 2021 at 11:38:54PM +0100, Sedat Dilek wrote: > On Thu, Jan 21, 2021 at 10:29 PM Josh Poimboeuf wrote: > > > > v2: > > - fix commit description for why xen hypervisor page contents don't > > matter [Juergen] > > - annotate indirect jumps as safe instead of converting them to > > retpolines [Andrew, Juergen] > > - drop patch 1 - fake jumps no longer exist > > - add acks > > > > Based on tip/objtool/core. > > > > > > Add support for proper vmlinux.o validation, which will be needed for > > Sami's upcoming x86 LTO set. (And vmlinux validation is the future for > > objtool anyway, for other reasons.) > > > > This isn't 100% done -- most notably, crypto still needs to be supported > > -- but I think this gets us most of the way there. > > > > This can also be found at > > > > git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git > > objtool-vmlinux > > > > Should this be s/objtool-vmlinux/objtool-vmlinux-v2 ? Indeed: git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git objtool-vmlinux-v2 -- Josh
Re: [PATCH v2 00/20] objtool: vmlinux.o and CLANG LTO support
On Thu, Jan 21, 2021 at 10:29 PM Josh Poimboeuf wrote: > > v2: > - fix commit description for why xen hypervisor page contents don't > matter [Juergen] > - annotate indirect jumps as safe instead of converting them to > retpolines [Andrew, Juergen] > - drop patch 1 - fake jumps no longer exist > - add acks > > Based on tip/objtool/core. > > > Add support for proper vmlinux.o validation, which will be needed for > Sami's upcoming x86 LTO set. (And vmlinux validation is the future for > objtool anyway, for other reasons.) > > This isn't 100% done -- most notably, crypto still needs to be supported > -- but I think this gets us most of the way there. > > This can also be found at > > git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git > objtool-vmlinux > Should this be s/objtool-vmlinux/objtool-vmlinux-v2 ? - Sedat - > And for more testing it can be combined with Sami's x86 LTO patches: > > https://github.com/samitolvanen/linux clang-lto > > > Josh Poimboeuf (20): > objtool: Fix error handling for STD/CLD warnings > objtool: Fix retpoline detection in asm code > objtool: Fix ".cold" section suffix check for newer versions of GCC > objtool: Support retpoline jump detection for vmlinux.o > x86/ftrace: Add UNWIND_HINT_FUNC annotation for ftrace_stub > objtool: Assume only ELF functions do sibling calls > objtool: Add asm version of STACK_FRAME_NON_STANDARD > objtool: Combine UNWIND_HINT_RET_OFFSET and UNWIND_HINT_FUNC > objtool: Add xen_start_kernel() to noreturn list > objtool: Move unsuffixed symbol conversion to a helper function > objtool: Add CONFIG_CFI_CLANG support > x86/xen: Support objtool validation in xen-asm.S > x86/xen: Support objtool vmlinux.o validation in xen-head.S > x86/xen/pvh: Annotate indirect branch as safe > x86/ftrace: Support objtool vmlinux.o validation in ftrace_64.S > x86/acpi: Annotate indirect branch as safe > x86/acpi: Support objtool validation in wakeup_64.S > x86/power: Annotate indirect branches as safe > x86/power: Move restore_registers() to top of the file > x86/power: Support objtool validation in hibernate_asm_64.S > > arch/x86/include/asm/unwind_hints.h | 13 +--- > arch/x86/kernel/acpi/Makefile | 1 - > arch/x86/kernel/acpi/wakeup_64.S | 4 + > arch/x86/kernel/ftrace_64.S | 8 +- > arch/x86/lib/retpoline.S | 2 +- > arch/x86/platform/pvh/head.S | 2 + > arch/x86/power/Makefile | 1 - > arch/x86/power/hibernate_asm_64.S | 103 +- > arch/x86/xen/Makefile | 1 - > arch/x86/xen/xen-asm.S| 29 +--- > arch/x86/xen/xen-head.S | 5 +- > include/linux/objtool.h | 13 +++- > tools/include/linux/objtool.h | 13 +++- > tools/objtool/arch/x86/decode.c | 4 +- > tools/objtool/arch/x86/special.c | 2 +- > tools/objtool/check.c | 89 -- > tools/objtool/elf.c | 88 -- > tools/objtool/include/objtool/check.h | 12 ++- > tools/objtool/include/objtool/elf.h | 2 +- > 19 files changed, 240 insertions(+), 152 deletions(-) > > -- > 2.29.2 >
