search for: parainstructions

Is it OK for section .parainstructions to reference exit.text? I'm seeing: WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after '' (at offset 0x0) WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after ''...

Is it OK for section .parainstructions to reference exit.text? I'm seeing: WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after '' (at offset 0x0) WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after ''...

...With the exception of the "drivers/ide/pci/atiixp:FFFF05", none of these > warnings is present in Linus' tree. yes, lots of new section mismatch warnings. A large number of them are due to the paravirt patches: WARNING: vmlinux - Section mismatch: reference to .init.text: from .parainstructions between '__start_parainstructions' (at offset 0xc0458470) and '__stop_parainstructions' WARNING: vmlinux - Section mismatch: reference to .init.text: from .parainstructions between '__start_parainstructions' (at offset 0xc0458478) and '__stop_parainstructions' WARNIN...

...With the exception of the "drivers/ide/pci/atiixp:FFFF05", none of these > warnings is present in Linus' tree. yes, lots of new section mismatch warnings. A large number of them are due to the paravirt patches: WARNING: vmlinux - Section mismatch: reference to .init.text: from .parainstructions between '__start_parainstructions' (at offset 0xc0458470) and '__stop_parainstructions' WARNING: vmlinux - Section mismatch: reference to .init.text: from .parainstructions between '__start_parainstructions' (at offset 0xc0458478) and '__stop_parainstructions' WARNIN...

...our main sets of patches in this series: > > 1. PV-ops management (patches 1-10, 20): mostly infrastructure and > refactoring pieces to make paravirt patching usable at runtime. For the > most part scoped under CONFIG_PARAVIRT_RUNTIME. > > Patches 1-7, to persist part of parainstructions in memory: > "x86/paravirt: Specify subsection in PVOP macros" > "x86/paravirt: Allow paravirt patching post-init" > "x86/paravirt: PVRTOP macros for PARAVIRT_RUNTIME" > "x86/alternatives: Refactor alternatives_smp_module* > "x86...

...pe, p->instr, p->len); + /* Pad the rest with nops */ + diff = p->len - used; + for (i = used; diff > 0; diff -= k, i += k) { + k = diff; + if (k > ASM_NOP_MAX) + k = ASM_NOP_MAX; + memcpy(p->instr + i, noptable[k], k); + } + } +} +extern struct paravirt_patch __start_parainstructions[], + __stop_parainstructions[]; +#else +void apply_paravirt(struct paravirt_patch *start, struct paravirt_patch *end) +{ +} +extern char __start_parainstructions[], __stop_parainstructions[]; +#endif /* CONFIG_PARAVIRT */ + void __init alternative_instructions(void) { apply_alternatives(__alt_i...

...pe, p->instr, p->len); + /* Pad the rest with nops */ + diff = p->len - used; + for (i = used; diff > 0; diff -= k, i += k) { + k = diff; + if (k > ASM_NOP_MAX) + k = ASM_NOP_MAX; + memcpy(p->instr + i, noptable[k], k); + } + } +} +extern struct paravirt_patch __start_parainstructions[], + __stop_parainstructions[]; +#else +void apply_paravirt(struct paravirt_patch *start, struct paravirt_patch *end) +{ +} +extern char __start_parainstructions[], __stop_parainstructions[]; +#endif /* CONFIG_PARAVIRT */ + void __init alternative_instructions(void) { apply_alternatives(__alt_i...

...his removes _some_ of the paravirt macro maze, but most of it needs to stay due to the need of hiding the call instructions from the compiler in order to avoid needless register save/restore. What is going away is the nasty stacking of alternative and paravirt patching and (of course) the special .parainstructions linker section. I have tested the series on bare metal and as Xen PV domain to still work. RFC because I'm quite sure there will be some objtool work needed (at least removing the specific paravirt handling). Juergen Gross (3): x86/paravirt: move some functions and defines to alternative...

...his removes _some_ of the paravirt macro maze, but most of it needs to stay due to the need of hiding the call instructions from the compiler in order to avoid needless register save/restore. What is going away is the nasty stacking of alternative and paravirt patching and (of course) the special .parainstructions linker section. I have tested the series on bare metal and as Xen PV domain to still work. RFC because I'm quite sure there will be some objtool work needed (at least removing the specific paravirt handling). Juergen Gross (3): x86/paravirt: move some functions and defines to alternative...

..._clobber] "i" (clobber) - -/* - * Generate some code, and mark it as patchable by the - * apply_paravirt() alternate instruction patcher. - */ -#define _paravirt_alt(insn_string, type, clobber) \ - "771:\n\t" insn_string "\n" "772:\n" \ - ".pushsection .parainstructions,\"a\"\n" \ - _ASM_ALIGN "\n" \ - _ASM_PTR " 771b\n" \ - " .byte " type "\n" \ - " .byte 772b-771b\n" \ - " .short " clobber "\n" \ - ".popsection\n" - -/* Generate patchable code, with t...

Hi Andi, Here's a little batch of cleanups: - re-enable VDSO when PARAVIRT is enabled - make the parainstructions symbols match the other altinstructions naming convention - add kernel command-line options to disable altinstructions for smp and pv_ops Oh, and I'm mailing your noreplacement patch back at you, for no particularly good reason. J --

Hi Andi, Here's a little batch of cleanups: - re-enable VDSO when PARAVIRT is enabled - make the parainstructions symbols match the other altinstructions naming convention - add kernel command-line options to disable altinstructions for smp and pv_ops Oh, and I'm mailing your noreplacement patch back at you, for no particularly good reason. J --

Thanks to Andrew for pointing these out. This patch moves the parvirtprobe section into .init.data: it's only used in very very early boot, and for similar reasons, puts lguest_maybe_init and lguest_memory_setup in init.text. As well as fixing some warnings, this frees up a tiny bit more memory. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> diff -r ecec388180b2

Thanks to Andrew for pointing these out. This patch moves the parvirtprobe section into .init.data: it's only used in very very early boot, and for similar reasons, puts lguest_maybe_init and lguest_memory_setup in init.text. As well as fixing some warnings, this frees up a tiny bit more memory. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> diff -r ecec388180b2

...runtime code. This mismatch hurts debuggability and makes the assembly code harder to understand. It also causes the ORC unwinder to produce KASAN warnings like: BUG: KASAN: stack-out-of-bounds in deref_stack_reg+0x123/0x140 This warning is due to the fact that objtool doesn't know about parainstructions, so it doesn't know about the "pushfq; pop %rax" sequence above. Prepare to fix both of these issues (debuggability and ORC KASAN warnings) by adding a paravirt alternatives infrastructure to put the native instructions in .text by default. Then, when booting on a hypervisor, replac...

..._clobber] "i" (clobber) +/* + * Generate some code, and mark it as patchable by the + * apply_paravirt() alternate instruction patcher. + */ +#define _paravirt_alt(insn_string, type, clobber) \ + "771:\n\t" insn_string "\n" "772:\n" \ + ".pushsection .parainstructions,\"a\"\n" \ + _ASM_ALIGN "\n" \ + _ASM_PTR " 771b\n" \ + " .byte " type "\n" \ + " .byte 772b-771b\n" \ + " .short " clobber "\n" \ + ".popsection\n" + /* Generate patchable code, with t...

...tructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) { + __alt_instructions = .; *(.altinstructions) + __alt_instructions_end = .; } - __alt_instructions_end = .; .altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) { *(.altinstr_replacement) } + . = ALIGN(8); + .parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) { + __start_parainstructions = .; + *(.parainstructions) + __stop_parainstructions = .; + } /* .exit.text is discard at runtime, not link time, to deal with references from .altinstructions and .eh_frame */ .exit.text : AT(ADDR(.exit.text) -...

...tructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) { + __alt_instructions = .; *(.altinstructions) + __alt_instructions_end = .; } - __alt_instructions_end = .; .altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) { *(.altinstr_replacement) } + . = ALIGN(8); + .parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) { + __start_parainstructions = .; + *(.parainstructions) + __stop_parainstructions = .; + } /* .exit.text is discard at runtime, not link time, to deal with references from .altinstructions and .eh_frame */ .exit.text : AT(ADDR(.exit.text) -...

...mmon runtime cases (everything except Xen and vSMP), vmlinux disassembly now matches what the actual runtime code looks like. This improves debuggability and kernel developer sanity (a precious resource). - It fixes a KASAN warning in the ORC unwinder due to objtool not understanding the .parainstructions stuff. - It's hopefully a first step in simplifying paravirt patching by getting rid of .parainstructions, pv ops, and apply_paravirt() completely. (I think Xen can be changed to set CPU feature bits to specify which ops it needs during early boot, then those ops can be patched in usi...

...mmon runtime cases (everything except Xen and vSMP), vmlinux disassembly now matches what the actual runtime code looks like. This improves debuggability and kernel developer sanity (a precious resource). - It fixes a KASAN warning in the ORC unwinder due to objtool not understanding the .parainstructions stuff. - It's hopefully a first step in simplifying paravirt patching by getting rid of .parainstructions, pv ops, and apply_paravirt() completely. (I think Xen can be changed to set CPU feature bits to specify which ops it needs during early boot, then those ops can be patched in usi...