| Message ID | 1477585631-18574-2-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
On 27/10/16 17:27, Ard Biesheuvel wrote: > Commit 0e0ed6406e61 ("powerpc/modules: Module CRC relocation fix causes > perf issues") fixed an issue with relocatable PIE kernels in a way that > essentially reintroduced the issue again for 32-bit builds. > > Since the chosen approach does is not applicable to 32-bit, fix the > issue by updating the runtime relocation routine to ignore the load > offset for the interval [__start___kcrctab, __stop___kcrctab_gpl_future), > which is where the CRCs reside. This ensures that the values of the CRC > pseudo-symbols are no longer made dependent on the runtime load offset. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Ard, These changes look good to me (having originally written the code). Reviewed-by : Suzuki K Poulose <suzuki.poulose@arm.com> Cheers Suzuki > --- > arch/powerpc/kernel/reloc_32.S | 36 +++++++++++++++++--- > 1 file changed, 32 insertions(+), 4 deletions(-) > > diff --git a/arch/powerpc/kernel/reloc_32.S b/arch/powerpc/kernel/reloc_32.S > index f366fedb0872..150686b9febb 100644 > --- a/arch/powerpc/kernel/reloc_32.S > +++ b/arch/powerpc/kernel/reloc_32.S > @@ -87,12 +87,12 @@ eodyn: /* End of Dyn Table scan */ > * Work out the current offset from the link time address of .rela > * section. > * cur_offset[r7] = rela.run[r9] - rela.link [r7] > - * _stext.link[r12] = _stext.run[r10] - cur_offset[r7] > - * final_offset[r3] = _stext.final[r3] - _stext.link[r12] > + * _stext.link[r11] = _stext.run[r10] - cur_offset[r7] > + * final_offset[r3] = _stext.final[r3] - _stext.link[r11] > */ > subf r7, r7, r9 /* cur_offset */ > - subf r12, r7, r10 > - subf r3, r12, r3 /* final_offset */ > + subf r11, r7, r10 > + subf r3, r11, r3 /* final_offset */ > > subf r8, r6, r8 /* relaz -= relaent */ > /* > @@ -101,6 +101,21 @@ eodyn: /* End of Dyn Table scan */ > * r13 - points to the symbol table > */ > > +#ifdef CONFIG_MODVERSIONS > + /* > + * Treat R_PPC_RELATIVE relocations differently when they target the > + * interval [__start___kcrctab, __stop___kcrctab_gpl_future): in this > + * case, the relocated quantities are CRC pseudo-symbols, which should > + * be preserved as-is, rather than be modified to take the runtime > + * offset into account. > + */ > + lwz r10, (p_kcrc_start - 0b)(r12) > + lwz r11, (p_kcrc_stop - 0b)(r12) > + subf r12, r7, r12 /* link time addr of 0b */ > + add r10, r10, r12 > + add r11, r11, r12 > +#endif > + > /* > * Check if we have a relocation based on symbol > * r5 will hold the value of the symbol. > @@ -135,7 +150,15 @@ get_type: > bne hi16 > lwz r4, 0(r9) /* r_offset */ > lwz r0, 8(r9) /* r_addend */ > +#ifdef CONFIG_MODVERSIONS > + cmplw r4, r10 > + blt do_add > + cmplw r4, r11 > + blt skip_add > +do_add: > +#endif > add r0, r0, r3 /* final addend */ > +skip_add: > stwx r0, r4, r7 /* memory[r4+r7]) = (u32)r0 */ > b nxtrela /* continue */ > > @@ -207,3 +230,8 @@ p_dyn: .long __dynamic_start - 0b > p_rela: .long __rela_dyn_start - 0b > p_sym: .long __dynamic_symtab - 0b > p_st: .long _stext - 0b > + > +#ifdef CONFIG_MODVERSIONS > +p_kcrc_start: .long __start___kcrctab - 0b > +p_kcrc_stop: .long __stop___kcrctab_gpl_future - 0b > +#endif >
diff --git a/arch/powerpc/kernel/reloc_32.S b/arch/powerpc/kernel/reloc_32.S index f366fedb0872..150686b9febb 100644 --- a/arch/powerpc/kernel/reloc_32.S +++ b/arch/powerpc/kernel/reloc_32.S @@ -87,12 +87,12 @@ eodyn: /* End of Dyn Table scan */ * Work out the current offset from the link time address of .rela * section. * cur_offset[r7] = rela.run[r9] - rela.link [r7] - * _stext.link[r12] = _stext.run[r10] - cur_offset[r7] - * final_offset[r3] = _stext.final[r3] - _stext.link[r12] + * _stext.link[r11] = _stext.run[r10] - cur_offset[r7] + * final_offset[r3] = _stext.final[r3] - _stext.link[r11] */ subf r7, r7, r9 /* cur_offset */ - subf r12, r7, r10 - subf r3, r12, r3 /* final_offset */ + subf r11, r7, r10 + subf r3, r11, r3 /* final_offset */ subf r8, r6, r8 /* relaz -= relaent */ /* @@ -101,6 +101,21 @@ eodyn: /* End of Dyn Table scan */ * r13 - points to the symbol table */ +#ifdef CONFIG_MODVERSIONS + /* + * Treat R_PPC_RELATIVE relocations differently when they target the + * interval [__start___kcrctab, __stop___kcrctab_gpl_future): in this + * case, the relocated quantities are CRC pseudo-symbols, which should + * be preserved as-is, rather than be modified to take the runtime + * offset into account. + */ + lwz r10, (p_kcrc_start - 0b)(r12) + lwz r11, (p_kcrc_stop - 0b)(r12) + subf r12, r7, r12 /* link time addr of 0b */ + add r10, r10, r12 + add r11, r11, r12 +#endif + /* * Check if we have a relocation based on symbol * r5 will hold the value of the symbol. @@ -135,7 +150,15 @@ get_type: bne hi16 lwz r4, 0(r9) /* r_offset */ lwz r0, 8(r9) /* r_addend */ +#ifdef CONFIG_MODVERSIONS + cmplw r4, r10 + blt do_add + cmplw r4, r11 + blt skip_add +do_add: +#endif add r0, r0, r3 /* final addend */ +skip_add: stwx r0, r4, r7 /* memory[r4+r7]) = (u32)r0 */ b nxtrela /* continue */ @@ -207,3 +230,8 @@ p_dyn: .long __dynamic_start - 0b p_rela: .long __rela_dyn_start - 0b p_sym: .long __dynamic_symtab - 0b p_st: .long _stext - 0b + +#ifdef CONFIG_MODVERSIONS +p_kcrc_start: .long __start___kcrctab - 0b +p_kcrc_stop: .long __stop___kcrctab_gpl_future - 0b +#endif
Commit 0e0ed6406e61 ("powerpc/modules: Module CRC relocation fix causes perf issues") fixed an issue with relocatable PIE kernels in a way that essentially reintroduced the issue again for 32-bit builds. Since the chosen approach does is not applicable to 32-bit, fix the issue by updating the runtime relocation routine to ignore the load offset for the interval [__start___kcrctab, __stop___kcrctab_gpl_future), which is where the CRCs reside. This ensures that the values of the CRC pseudo-symbols are no longer made dependent on the runtime load offset. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/powerpc/kernel/reloc_32.S | 36 +++++++++++++++++--- 1 file changed, 32 insertions(+), 4 deletions(-) -- 2.7.4