| Message ID | 1428674035-26603-2-git-send-email-ard.biesheuvel@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Ard, On Fri, Apr 10, 2015 at 02:53:45PM +0100, Ard Biesheuvel wrote: > Commit ea8c2e112445 ("arm64: Extend the idmap to the whole kernel > image") changed the early page table code so that the entire kernel > Image is covered by the identity map. This allows functions that > need to enable or disable the MMU to reside anywhere in the kernel > Image. > > However, this change has the unfortunate side effect that the Image > cannot cross a physical 512 MB alignment boundary anymore, since the > early page table code cannot deal with the Image crossing a /virtual/ > 512 MB alignment boundary. > > So instead, reduce the ID map to a single page, that is populated by > the contents of the .idmap.text section. Only three functions reside > there at the moment: __enable_mmu(), cpu_resume_mmu() and cpu_reset(). It would be worth mentioning in the cover letter which branch this is based on (arm64 for-next/core?), given the __enable_mmu + __turn_mmu_on folding isn't in mainline yet. > If new code is introduced that needs to manipulate the MMU state, it > should be added to this section as well. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Other than the minor nit below this looks good to me, and I've given it a spin on Juno with 4K and 64K pages. Assuming you can fix that up: Reviewed-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Mark Rutland <mark.rutland@arm.com> > @@ -669,6 +669,7 @@ ENDPROC(__secondary_switched) > * > * other registers depend on the function called upon completion > */ > + .section ".idmap.text", #alloc, #execinstr We should use "ax" rather than #alloc, #execinstr to keep things consistent, unless there's some difference that I'm missing? I've tested the patch locally with all instances changed to "ax". Thanks, Mark.
On 13 April 2015 at 14:53, Mark Rutland <mark.rutland@arm.com> wrote: > Hi Ard, > > On Fri, Apr 10, 2015 at 02:53:45PM +0100, Ard Biesheuvel wrote: >> Commit ea8c2e112445 ("arm64: Extend the idmap to the whole kernel >> image") changed the early page table code so that the entire kernel >> Image is covered by the identity map. This allows functions that >> need to enable or disable the MMU to reside anywhere in the kernel >> Image. >> >> However, this change has the unfortunate side effect that the Image >> cannot cross a physical 512 MB alignment boundary anymore, since the >> early page table code cannot deal with the Image crossing a /virtual/ >> 512 MB alignment boundary. >> >> So instead, reduce the ID map to a single page, that is populated by >> the contents of the .idmap.text section. Only three functions reside >> there at the moment: __enable_mmu(), cpu_resume_mmu() and cpu_reset(). > > It would be worth mentioning in the cover letter which branch this is > based on (arm64 for-next/core?), given the __enable_mmu + __turn_mmu_on > folding isn't in mainline yet. > Ah yes. That just feels so long ago already :-) >> If new code is introduced that needs to manipulate the MMU state, it >> should be added to this section as well. >> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > Other than the minor nit below this looks good to me, and I've given it > a spin on Juno with 4K and 64K pages. Assuming you can fix that up: > > Reviewed-by: Mark Rutland <mark.rutland@arm.com> > Tested-by: Mark Rutland <mark.rutland@arm.com> > Thanks! >> @@ -669,6 +669,7 @@ ENDPROC(__secondary_switched) >> * >> * other registers depend on the function called upon completion >> */ >> + .section ".idmap.text", #alloc, #execinstr > > We should use "ax" rather than #alloc, #execinstr to keep things > consistent, unless there's some difference that I'm missing? > > I've tested the patch locally with all instances changed to "ax". > OK, I will change it. I have a personal preference for wordy when it comes to things like this (try googling for ax), but as far as I know, they are 100% equivalent.
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 19f915e8f6e0..f54125a95a6d 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -382,7 +382,7 @@ __create_page_tables: * Create the identity mapping. */ mov x0, x25 // idmap_pg_dir - adrp x3, KERNEL_START // __pa(KERNEL_START) + adrp x3, __idmap_text_start // __pa(__idmap_text_start) #ifndef CONFIG_ARM64_VA_BITS_48 #define EXTRA_SHIFT (PGDIR_SHIFT + PAGE_SHIFT - 3) @@ -405,11 +405,11 @@ __create_page_tables: /* * Calculate the maximum allowed value for TCR_EL1.T0SZ so that the - * entire kernel image can be ID mapped. As T0SZ == (64 - #bits used), + * entire ID map region can be mapped. As T0SZ == (64 - #bits used), * this number conveniently equals the number of leading zeroes in - * the physical address of KERNEL_END. + * the physical address of __idmap_text_end. */ - adrp x5, KERNEL_END + adrp x5, __idmap_text_end clz x5, x5 cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? b.ge 1f // .. then skip additional level @@ -424,8 +424,8 @@ __create_page_tables: #endif create_pgd_entry x0, x3, x5, x6 - mov x5, x3 // __pa(KERNEL_START) - adr_l x6, KERNEL_END // __pa(KERNEL_END) + mov x5, x3 // __pa(__idmap_text_start) + adr_l x6, __idmap_text_end // __pa(__idmap_text_end) create_block_map x0, x7, x3, x5, x6 /* @@ -669,6 +669,7 @@ ENDPROC(__secondary_switched) * * other registers depend on the function called upon completion */ + .section ".idmap.text", #alloc, #execinstr __enable_mmu: ldr x5, =vectors msr vbar_el1, x5 diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S index ede186cdd452..04dc9aa2831e 100644 --- a/arch/arm64/kernel/sleep.S +++ b/arch/arm64/kernel/sleep.S @@ -130,12 +130,14 @@ ENDPROC(__cpu_suspend_enter) /* * x0 must contain the sctlr value retrieved from restored context */ + .pushsection ".idmap.text", #alloc, #execinstr ENTRY(cpu_resume_mmu) ldr x3, =cpu_resume_after_mmu msr sctlr_el1, x0 // restore sctlr_el1 isb br x3 // global jump to virtual address ENDPROC(cpu_resume_mmu) + .popsection cpu_resume_after_mmu: mov x0, #0 // return zero on success ldp x19, x20, [sp, #16] diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index a2c29865c3fe..98073332e2d0 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -38,6 +38,12 @@ jiffies = jiffies_64; *(.hyp.text) \ VMLINUX_SYMBOL(__hyp_text_end) = .; +#define IDMAP_TEXT \ + . = ALIGN(SZ_4K); \ + VMLINUX_SYMBOL(__idmap_text_start) = .; \ + *(.idmap.text) \ + VMLINUX_SYMBOL(__idmap_text_end) = .; + /* * The size of the PE/COFF section that covers the kernel image, which * runs from stext to _edata, must be a round multiple of the PE/COFF @@ -95,6 +101,7 @@ SECTIONS SCHED_TEXT LOCK_TEXT HYPERVISOR_TEXT + IDMAP_TEXT *(.fixup) *(.gnu.warning) . = ALIGN(16); @@ -167,11 +174,13 @@ SECTIONS } /* - * The HYP init code can't be more than a page long, + * The HYP init code and ID map text can't be longer than a page each, * and should not cross a page boundary. */ ASSERT(__hyp_idmap_text_end - (__hyp_idmap_text_start & ~(SZ_4K - 1)) <= SZ_4K, "HYP init code too big or misaligned") +ASSERT(__idmap_text_end - (__idmap_text_start & ~(SZ_4K - 1)) <= SZ_4K, + "ID map text too big or misaligned") /* * If padding is applied before .head.text, virt<->phys conversions will fail. diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index cdd754e19b9b..09da618906a3 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -67,7 +67,7 @@ ENDPROC(cpu_cache_off) * * - loc - location to jump to for soft reset */ - .align 5 + .pushsection ".idmap.text", #alloc, #execinstr ENTRY(cpu_reset) mrs x1, sctlr_el1 bic x1, x1, #1 @@ -75,6 +75,7 @@ ENTRY(cpu_reset) isb ret x0 ENDPROC(cpu_reset) + .popsection ENTRY(cpu_soft_restart) /* Save address of cpu_reset() and reset address */
Commit ea8c2e112445 ("arm64: Extend the idmap to the whole kernel image") changed the early page table code so that the entire kernel Image is covered by the identity map. This allows functions that need to enable or disable the MMU to reside anywhere in the kernel Image. However, this change has the unfortunate side effect that the Image cannot cross a physical 512 MB alignment boundary anymore, since the early page table code cannot deal with the Image crossing a /virtual/ 512 MB alignment boundary. So instead, reduce the ID map to a single page, that is populated by the contents of the .idmap.text section. Only three functions reside there at the moment: __enable_mmu(), cpu_resume_mmu() and cpu_reset(). If new code is introduced that needs to manipulate the MMU state, it should be added to this section as well. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/kernel/head.S | 13 +++++++------ arch/arm64/kernel/sleep.S | 2 ++ arch/arm64/kernel/vmlinux.lds.S | 11 ++++++++++- arch/arm64/mm/proc.S | 3 ++- 4 files changed, 21 insertions(+), 8 deletions(-)