| Message ID | 20190514122456.28559-13-julien.grall@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen/arm: Clean-up & fixes in boot/mm code | expand |
On 14.05.19 15:24, Julien Grall wrote: > The boot code is using r2 and r3 to hold the page-table entry value. > While r2 is always updated before storing the value, this is not always > the case for r3. > > Thankfully today, r3 will always be zero when we care. But this is > difficult to track and error-prone. > > So always zero r3 within the few instructions before the write the > page-table entry. > > Signed-off-by: Julien Grall <julien.grall@arm.com> > > --- > Changes in v2: > - Use 0x0 instead of 0 > - Remove a duplicate mov r3, #0 > --- Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>
On Tue, 14 May 2019, Julien Grall wrote: > The boot code is using r2 and r3 to hold the page-table entry value. > While r2 is always updated before storing the value, this is not always > the case for r3. > > Thankfully today, r3 will always be zero when we care. But this is > difficult to track and error-prone. > > So always zero r3 within the few instructions before the write the > page-table entry. > > Signed-off-by: Julien Grall <julien.grall@arm.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> > --- > Changes in v2: > - Use 0x0 instead of 0 > - Remove a duplicate mov r3, #0 > --- > xen/arch/arm/arm32/head.S | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S > index 3448817aab..18ded49a04 100644 > --- a/xen/arch/arm/arm32/head.S > +++ b/xen/arch/arm/arm32/head.S > @@ -270,6 +270,7 @@ cpu_init_done: > orr r2, r2, #PT_UPPER(MEM) /* r2:r3 := section map */ > orr r2, r2, #PT_LOWER(MEM) > lsl r1, r1, #3 /* r1 := Slot offset */ > + mov r3, #0x0 > strd r2, r3, [r4, r1] /* Mapping of paddr(start) */ > mov r6, #1 /* r6 := identity map now in place */ > > @@ -372,11 +373,11 @@ paging: > > /* Add UART to the fixmap table */ > ldr r1, =xen_fixmap /* r1 := vaddr (xen_fixmap) */ > - mov r3, #0 > lsr r2, r11, #THIRD_SHIFT > lsl r2, r2, #THIRD_SHIFT /* 4K aligned paddr of UART */ > orr r2, r2, #PT_UPPER(DEV_L3) > orr r2, r2, #PT_LOWER(DEV_L3) /* r2:r3 := 4K dev map including UART */ > + mov r3, #0x0 > strd r2, r3, [r1, #(FIXMAP_CONSOLE*8)] /* Map it in the first fixmap's slot */ > 1: > > @@ -388,6 +389,7 @@ paging: > orr r2, r2, #PT_LOWER(PT) /* r2:r3 := table map of xen_fixmap */ > ldr r4, =FIXMAP_ADDR(0) > mov r4, r4, lsr #(SECOND_SHIFT - 3) /* r4 := Slot for FIXMAP(0) */ > + mov r3, #0x0 > strd r2, r3, [r1, r4] /* Map it in the fixmap's slot */ > > /* Use a virtual address to access the UART. */ > -- > 2.11.0 >
diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S index 3448817aab..18ded49a04 100644 --- a/xen/arch/arm/arm32/head.S +++ b/xen/arch/arm/arm32/head.S @@ -270,6 +270,7 @@ cpu_init_done: orr r2, r2, #PT_UPPER(MEM) /* r2:r3 := section map */ orr r2, r2, #PT_LOWER(MEM) lsl r1, r1, #3 /* r1 := Slot offset */ + mov r3, #0x0 strd r2, r3, [r4, r1] /* Mapping of paddr(start) */ mov r6, #1 /* r6 := identity map now in place */ @@ -372,11 +373,11 @@ paging: /* Add UART to the fixmap table */ ldr r1, =xen_fixmap /* r1 := vaddr (xen_fixmap) */ - mov r3, #0 lsr r2, r11, #THIRD_SHIFT lsl r2, r2, #THIRD_SHIFT /* 4K aligned paddr of UART */ orr r2, r2, #PT_UPPER(DEV_L3) orr r2, r2, #PT_LOWER(DEV_L3) /* r2:r3 := 4K dev map including UART */ + mov r3, #0x0 strd r2, r3, [r1, #(FIXMAP_CONSOLE*8)] /* Map it in the first fixmap's slot */ 1: @@ -388,6 +389,7 @@ paging: orr r2, r2, #PT_LOWER(PT) /* r2:r3 := table map of xen_fixmap */ ldr r4, =FIXMAP_ADDR(0) mov r4, r4, lsr #(SECOND_SHIFT - 3) /* r4 := Slot for FIXMAP(0) */ + mov r3, #0x0 strd r2, r3, [r1, r4] /* Map it in the fixmap's slot */ /* Use a virtual address to access the UART. */
The boot code is using r2 and r3 to hold the page-table entry value. While r2 is always updated before storing the value, this is not always the case for r3. Thankfully today, r3 will always be zero when we care. But this is difficult to track and error-prone. So always zero r3 within the few instructions before the write the page-table entry. Signed-off-by: Julien Grall <julien.grall@arm.com> --- Changes in v2: - Use 0x0 instead of 0 - Remove a duplicate mov r3, #0 --- xen/arch/arm/arm32/head.S | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)