Messages in this thread | | | From | Nick Desaulniers <> | Date | Fri, 28 Apr 2023 11:22:48 -0700 | Subject | Re: [PATCH] arm64: kernel: remove SHF_WRITE|SHF_EXECINSTR from .idmap.text |
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On Fri, Apr 28, 2023 at 11:17 AM Ard Biesheuvel <ardb@kernel.org> wrote: > > Hi Nick, > > On Fri, 28 Apr 2023 at 19:09, <ndesaulniers@google.com> wrote: > > > > commit d54170812ef1 ("arm64: fix .idmap.text assertion for large kernels") > > modified some of the section assembler directives that declare > > .idmap.text to be SHF_ALLOC instead of > > SHF_ALLOC|SHF_WRITE|SHF_EXECINSTR. > > > > This patch fixes up the remaining stragglers that were left behind. > > > > Because .idmap.text is merged into .text, > > Nit: this is no longer the case: the ID map code is never executed via > the kernel mapping, so we moved it into a special .rodata.text section > that contains all generated code that should not have an executable > mapping by default, but only when it gets copied and/or mapped into a > different executable region.
Ah, sorry, I see IDMAP_TEXT is being placed in .rodata.text in arch/arm64/kernel/vmlinux.lds.S, so it's just the synthetic .got then that's affecting .text. So Fangrui's patch is meant to address that. https://lore.kernel.org/linux-arm-kernel/20230428050442.180913-1-maskray@google.com/
In that case, I'll drop this paragraph starting with "Because"; I misspelled symbolizing anyways.
> > This doesn't impact the correctness of the patch, so with this > paragraph clarified: > > Reviewed-by: Ard Biesheuvel <ardb@kernel.org> > > > > LLD will retain the > > SHF_EXECINSTR on .text, in addition to the synthetic .got. This doesn't > > matter to the kernel loader, but syzkaller is having trouble symboling > > such sections. Clean this up while we additionally fix up syzkaller. Add > > Fixes tag so that this doesn't precede related change in stable. > > > > Fixes: d54170812ef1 ("arm64: fix .idmap.text assertion for large kernels") > > Reported-by: Greg Thelen <gthelen@google.com> > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > > --- > > arch/arm64/kernel/cpu-reset.S | 2 +- > > arch/arm64/kernel/sleep.S | 2 +- > > arch/arm64/mm/proc.S | 6 +++--- > > 3 files changed, 5 insertions(+), 5 deletions(-) > > > > diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S > > index 6b752fe89745..c87445dde674 100644 > > --- a/arch/arm64/kernel/cpu-reset.S > > +++ b/arch/arm64/kernel/cpu-reset.S > > @@ -14,7 +14,7 @@ > > #include <asm/virt.h> > > > > .text > > -.pushsection .idmap.text, "awx" > > +.pushsection .idmap.text, "a" > > > > /* > > * cpu_soft_restart(el2_switch, entry, arg0, arg1, arg2) > > diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S > > index 2ae7cff1953a..2aa5129d8253 100644 > > --- a/arch/arm64/kernel/sleep.S > > +++ b/arch/arm64/kernel/sleep.S > > @@ -97,7 +97,7 @@ SYM_FUNC_START(__cpu_suspend_enter) > > ret > > SYM_FUNC_END(__cpu_suspend_enter) > > > > - .pushsection ".idmap.text", "awx" > > + .pushsection ".idmap.text", "a" > > SYM_CODE_START(cpu_resume) > > mov x0, xzr > > bl init_kernel_el > > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S > > index 91410f488090..c2cb437821ca 100644 > > --- a/arch/arm64/mm/proc.S > > +++ b/arch/arm64/mm/proc.S > > @@ -167,7 +167,7 @@ alternative_else_nop_endif > > SYM_FUNC_END(cpu_do_resume) > > #endif > > > > - .pushsection ".idmap.text", "awx" > > + .pushsection ".idmap.text", "a" > > > > .macro __idmap_cpu_set_reserved_ttbr1, tmp1, tmp2 > > adrp \tmp1, reserved_pg_dir > > @@ -201,7 +201,7 @@ SYM_FUNC_END(idmap_cpu_replace_ttbr1) > > > > #define KPTI_NG_PTE_FLAGS (PTE_ATTRINDX(MT_NORMAL) | SWAPPER_PTE_FLAGS) > > > > - .pushsection ".idmap.text", "awx" > > + .pushsection ".idmap.text", "a" > > > > .macro kpti_mk_tbl_ng, type, num_entries > > add end_\type\()p, cur_\type\()p, #\num_entries * 8 > > @@ -400,7 +400,7 @@ SYM_FUNC_END(idmap_kpti_install_ng_mappings) > > * Output: > > * Return in x0 the value of the SCTLR_EL1 register. > > */ > > - .pushsection ".idmap.text", "awx" > > + .pushsection ".idmap.text", "a" > > SYM_FUNC_START(__cpu_setup) > > tlbi vmalle1 // Invalidate local TLB > > dsb nsh > > > > --- > > base-commit: 22b8cc3e78f5448b4c5df00303817a9137cd663f > > change-id: 20230428-awx-c73f4bde79c4 > > > > Best regards, > > -- > > Nick Desaulniers <ndesaulniers@google.com> > >
-- Thanks, ~Nick Desaulniers
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