| Message ID | 20170630153502.3327030-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> On 30 Jun 2017, at 15:34, Arnd Bergmann <arnd@arndb.de> wrote: > > With the new task struct randomization, we can run into a build > failure for certain random seeds: > > arch/arm/kernel/entry-armv.S: Assembler messages: > arch/arm/kernel/entry-armv.S:803: Error: bad immediate value for offset (4096) > > Only two constants in asm-offset.h are affected, and I'm changing > both of them here to work correctly in all configurations. > > One more macro has the problem, but is currently unused, so this > removes it instead of adding complexity. > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > Fixes: c33d8b12fbbd ("task_struct: Allow randomized layout") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > arch/arm/kernel/entry-armv.S | 5 ++++- > arch/arm/mm/proc-macros.S | 10 ++++------ > 2 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S > index 9f157e7c51e7..db6d22b23bd8 100644 > --- a/arch/arm/kernel/entry-armv.S > +++ b/arch/arm/kernel/entry-armv.S > @@ -797,7 +797,10 @@ ENTRY(__switch_to) > #if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) > ldr r7, [r2, #TI_TASK] > ldr r8, =__stack_chk_guard > - ldr r7, [r7, #TSK_STACK_CANARY] > + .if (TSK_STACK_CANARY > PAGE_MASK) Shouldn't this be ~PAGE_MASK? I think .if (TSK_STACK_CANARY & PAGE_MASK) != 0 is better and clearer as well > + add r7, r7, #TSK_STACK_CANARY & PAGE_MASK > + .endif > + ldr r7, [r7, #TSK_STACK_CANARY & ~PAGE_MASK] > #endif > #ifdef CONFIG_CPU_USE_DOMAINS > mcr p15, 0, r6, c3, c0, 0 @ Set domain register > diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S > index 0d40c285bd86..2c5f2a0a708b 100644 > --- a/arch/arm/mm/proc-macros.S > +++ b/arch/arm/mm/proc-macros.S > @@ -25,11 +25,6 @@ > ldr \rd, [\rn, #VMA_VM_FLAGS] > .endm > > - .macro tsk_mm, rd, rn > - ldr \rd, [\rn, #TI_TASK] > - ldr \rd, [\rd, #TSK_ACTIVE_MM] > - .endm > - > /* > * act_mm - get current->active_mm > */ > @@ -37,7 +32,10 @@ > bic \rd, sp, #8128 > bic \rd, \rd, #63 > ldr \rd, [\rd, #TI_TASK] > - ldr \rd, [\rd, #TSK_ACTIVE_MM] > + .if (TSK_ACTIVE_MM > PAGE_MASK) > + add \rd, \rd, #TSK_ACTIVE_MM & PAGE_MASK > + .endif > + ldr \rd, [\rd, #TSK_ACTIVE_MM & ~PAGE_MASK] > .endm > > /* > -- > 2.9.0 >
On Fri, Jun 30, 2017 at 03:49:41PM +0000, Ard Biesheuvel wrote: > > > > On 30 Jun 2017, at 15:34, Arnd Bergmann <arnd@arndb.de> wrote: > > > > With the new task struct randomization, we can run into a build > > failure for certain random seeds: > > > > arch/arm/kernel/entry-armv.S: Assembler messages: > > arch/arm/kernel/entry-armv.S:803: Error: bad immediate value for offset (4096) > > > > Only two constants in asm-offset.h are affected, and I'm changing > > both of them here to work correctly in all configurations. > > > > One more macro has the problem, but is currently unused, so this > > removes it instead of adding complexity. > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > Fixes: c33d8b12fbbd ("task_struct: Allow randomized layout") > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > > --- > > arch/arm/kernel/entry-armv.S | 5 ++++- > > arch/arm/mm/proc-macros.S | 10 ++++------ > > 2 files changed, 8 insertions(+), 7 deletions(-) > > > > diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S > > index 9f157e7c51e7..db6d22b23bd8 100644 > > --- a/arch/arm/kernel/entry-armv.S > > +++ b/arch/arm/kernel/entry-armv.S > > @@ -797,7 +797,10 @@ ENTRY(__switch_to) > > #if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) > > ldr r7, [r2, #TI_TASK] > > ldr r8, =__stack_chk_guard > > - ldr r7, [r7, #TSK_STACK_CANARY] > > + .if (TSK_STACK_CANARY > PAGE_MASK) > > Shouldn't this be ~PAGE_MASK? > > I think > > .if (TSK_STACK_CANARY & PAGE_MASK) != 0 > > is better and clearer as well It's not really that much clearer - what has any of this got to do with the size of a page? Just because a definition appears to be numerically the same, it doesn't mean it should be used! The LDR instruction takes a maximum of a 12-bit constant. This 12-bit constant has nothing to do with the page size; it's been that way since the early ARMs that knew nothing about page tables. Please instead create a LDR_IMM12_MASK or similar definition for this.
On Fri, Jun 30, 2017 at 5:49 PM, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: >> On 30 Jun 2017, at 15:34, Arnd Bergmann <arnd@arndb.de> wrote: >> >> With the new task struct randomization, we can run into a build >> failure for certain random seeds: >> >> arch/arm/kernel/entry-armv.S: Assembler messages: >> arch/arm/kernel/entry-armv.S:803: Error: bad immediate value for offset (4096) >> >> Only two constants in asm-offset.h are affected, and I'm changing >> both of them here to work correctly in all configurations. >> >> One more macro has the problem, but is currently unused, so this >> removes it instead of adding complexity. >> >> Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >> Fixes: c33d8b12fbbd ("task_struct: Allow randomized layout") >> Signed-off-by: Arnd Bergmann <arnd@arndb.de> >> --- >> arch/arm/kernel/entry-armv.S | 5 ++++- >> arch/arm/mm/proc-macros.S | 10 ++++------ >> 2 files changed, 8 insertions(+), 7 deletions(-) >> >> diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S >> index 9f157e7c51e7..db6d22b23bd8 100644 >> --- a/arch/arm/kernel/entry-armv.S >> +++ b/arch/arm/kernel/entry-armv.S >> @@ -797,7 +797,10 @@ ENTRY(__switch_to) >> #if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) >> ldr r7, [r2, #TI_TASK] >> ldr r8, =__stack_chk_guard >> - ldr r7, [r7, #TSK_STACK_CANARY] >> + .if (TSK_STACK_CANARY > PAGE_MASK) > > Shouldn't this be ~PAGE_MASK? > > I think > > .if (TSK_STACK_CANARY & PAGE_MASK) != 0 > > is better and clearer as well Right, sorry about that. Russell also pointed out that PAGE_MASK is not the best constant for this, as the MMU page size is independent of the definition of the immediate arguments. I'll fix both and resend. Arnd
On 30 June 2017 at 15:55, Russell King - ARM Linux <linux@armlinux.org.uk> wrote: > On Fri, Jun 30, 2017 at 03:49:41PM +0000, Ard Biesheuvel wrote: >> >> >> > On 30 Jun 2017, at 15:34, Arnd Bergmann <arnd@arndb.de> wrote: >> > >> > With the new task struct randomization, we can run into a build >> > failure for certain random seeds: >> > >> > arch/arm/kernel/entry-armv.S: Assembler messages: >> > arch/arm/kernel/entry-armv.S:803: Error: bad immediate value for offset (4096) >> > >> > Only two constants in asm-offset.h are affected, and I'm changing >> > both of them here to work correctly in all configurations. >> > >> > One more macro has the problem, but is currently unused, so this >> > removes it instead of adding complexity. >> > >> > Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >> > Fixes: c33d8b12fbbd ("task_struct: Allow randomized layout") >> > Signed-off-by: Arnd Bergmann <arnd@arndb.de> >> > --- >> > arch/arm/kernel/entry-armv.S | 5 ++++- >> > arch/arm/mm/proc-macros.S | 10 ++++------ >> > 2 files changed, 8 insertions(+), 7 deletions(-) >> > >> > diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S >> > index 9f157e7c51e7..db6d22b23bd8 100644 >> > --- a/arch/arm/kernel/entry-armv.S >> > +++ b/arch/arm/kernel/entry-armv.S >> > @@ -797,7 +797,10 @@ ENTRY(__switch_to) >> > #if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) >> > ldr r7, [r2, #TI_TASK] >> > ldr r8, =__stack_chk_guard >> > - ldr r7, [r7, #TSK_STACK_CANARY] >> > + .if (TSK_STACK_CANARY > PAGE_MASK) >> >> Shouldn't this be ~PAGE_MASK? >> >> I think >> >> .if (TSK_STACK_CANARY & PAGE_MASK) != 0 >> >> is better and clearer as well > > It's not really that much clearer - what has any of this got to do with > the size of a page? Just because a definition appears to be numerically > the same, it doesn't mean it should be used! > > The LDR instruction takes a maximum of a 12-bit constant. This 12-bit > constant has nothing to do with the page size; it's been that way since > the early ARMs that knew nothing about page tables. > > Please instead create a LDR_IMM12_MASK or similar definition for this. > Yes, good point.
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 9f157e7c51e7..db6d22b23bd8 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -797,7 +797,10 @@ ENTRY(__switch_to) #if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) ldr r7, [r2, #TI_TASK] ldr r8, =__stack_chk_guard - ldr r7, [r7, #TSK_STACK_CANARY] + .if (TSK_STACK_CANARY > PAGE_MASK) + add r7, r7, #TSK_STACK_CANARY & PAGE_MASK + .endif + ldr r7, [r7, #TSK_STACK_CANARY & ~PAGE_MASK] #endif #ifdef CONFIG_CPU_USE_DOMAINS mcr p15, 0, r6, c3, c0, 0 @ Set domain register diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S index 0d40c285bd86..2c5f2a0a708b 100644 --- a/arch/arm/mm/proc-macros.S +++ b/arch/arm/mm/proc-macros.S @@ -25,11 +25,6 @@ ldr \rd, [\rn, #VMA_VM_FLAGS] .endm - .macro tsk_mm, rd, rn - ldr \rd, [\rn, #TI_TASK] - ldr \rd, [\rd, #TSK_ACTIVE_MM] - .endm - /* * act_mm - get current->active_mm */ @@ -37,7 +32,10 @@ bic \rd, sp, #8128 bic \rd, \rd, #63 ldr \rd, [\rd, #TI_TASK] - ldr \rd, [\rd, #TSK_ACTIVE_MM] + .if (TSK_ACTIVE_MM > PAGE_MASK) + add \rd, \rd, #TSK_ACTIVE_MM & PAGE_MASK + .endif + ldr \rd, [\rd, #TSK_ACTIVE_MM & ~PAGE_MASK] .endm /*
With the new task struct randomization, we can run into a build failure for certain random seeds: arch/arm/kernel/entry-armv.S: Assembler messages: arch/arm/kernel/entry-armv.S:803: Error: bad immediate value for offset (4096) Only two constants in asm-offset.h are affected, and I'm changing both of them here to work correctly in all configurations. One more macro has the problem, but is currently unused, so this removes it instead of adding complexity. Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Fixes: c33d8b12fbbd ("task_struct: Allow randomized layout") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- arch/arm/kernel/entry-armv.S | 5 ++++- arch/arm/mm/proc-macros.S | 10 ++++------ 2 files changed, 8 insertions(+), 7 deletions(-)