| Message ID | 20221212095523.52683-18-julien@xen.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen/arm: Don't switch TTBR while the MMU is on | expand |
On Mon, 12 Dec 2022, Julien Grall wrote: > From: Julien Grall <jgrall@amazon.com> > > At the moment, we are only checking that only some part of .text.header > is part of the identity mapping. However, this doesn't take into account > the litteral pool which will be located at the end of the section. ^ literal > While we could try to avoid using a literal pool, in the near future we > will also want to use an identity mapping for switch_ttbr(). > > Not everything in .text.header requires to be part of the identity > mapping. But it is below a page size (i.e. 4KB) so take a shortcut and > check that .text.header is smaller than a page size. > > With that _end_boot can be removed as it is now unused. Take the > pportunity to avoid assuming that a page size is always 4KB in the ^ opportunity > error message and comment. > > Signed-off-by: Julien Grall <jgrall@amazon.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> > --- > > Changes in v3: > - Patch added > --- > xen/arch/arm/arm32/head.S | 2 -- > xen/arch/arm/arm64/head.S | 2 -- > xen/arch/arm/xen.lds.S | 10 +++++++--- > 3 files changed, 7 insertions(+), 7 deletions(-) > > diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S > index 2658625bc775..e47f90f15b3d 100644 > --- a/xen/arch/arm/arm32/head.S > +++ b/xen/arch/arm/arm32/head.S > @@ -730,8 +730,6 @@ fail: PRINT("- Boot failed -\r\n") > b 1b > ENDPROC(fail) > > -GLOBAL(_end_boot) > - > /* > * Switch TTBR > * r1:r0 ttbr > diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S > index 23c2c7491db2..663f5813b12e 100644 > --- a/xen/arch/arm/arm64/head.S > +++ b/xen/arch/arm/arm64/head.S > @@ -812,8 +812,6 @@ fail: PRINT("- Boot failed -\r\n") > b 1b > ENDPROC(fail) > > -GLOBAL(_end_boot) > - > /* > * Switch TTBR > * > diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S > index ae8c3b4c6c5f..3f7ebd19f3ed 100644 > --- a/xen/arch/arm/xen.lds.S > +++ b/xen/arch/arm/xen.lds.S > @@ -32,7 +32,9 @@ SECTIONS > _start = .; > .text : { > _stext = .; /* Text section */ > + _idmap_start = .; > *(.text.header) > + _idmap_end = .; > > *(.text.cold) > *(.text.unlikely .text.*_unlikely .text.unlikely.*) > @@ -225,10 +227,12 @@ SECTIONS > } > > /* > - * We require that Xen is loaded at a 4K boundary, so this ensures that any > - * code running on the boot time identity map cannot cross a section boundary. > + * We require that Xen is loaded at a page boundary, so this ensures that any > + * code running on the identity map cannot cross a section boundary. > */ > -ASSERT( _end_boot - start <= PAGE_SIZE, "Boot code is larger than 4K") > +ASSERT(IS_ALIGNED(_idmap_start, PAGE_SIZE), "_idmap_start should be page-aligned") > +ASSERT(_idmap_end - _idmap_start <= PAGE_SIZE, "Identity mapped code is larger than a page size") > + > /* > * __init_[begin|end] MUST be at word size boundary otherwise we cannot > * write fault instructions in the space properly. > -- > 2.38.1 >
diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S index 2658625bc775..e47f90f15b3d 100644 --- a/xen/arch/arm/arm32/head.S +++ b/xen/arch/arm/arm32/head.S @@ -730,8 +730,6 @@ fail: PRINT("- Boot failed -\r\n") b 1b ENDPROC(fail) -GLOBAL(_end_boot) - /* * Switch TTBR * r1:r0 ttbr diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S index 23c2c7491db2..663f5813b12e 100644 --- a/xen/arch/arm/arm64/head.S +++ b/xen/arch/arm/arm64/head.S @@ -812,8 +812,6 @@ fail: PRINT("- Boot failed -\r\n") b 1b ENDPROC(fail) -GLOBAL(_end_boot) - /* * Switch TTBR * diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S index ae8c3b4c6c5f..3f7ebd19f3ed 100644 --- a/xen/arch/arm/xen.lds.S +++ b/xen/arch/arm/xen.lds.S @@ -32,7 +32,9 @@ SECTIONS _start = .; .text : { _stext = .; /* Text section */ + _idmap_start = .; *(.text.header) + _idmap_end = .; *(.text.cold) *(.text.unlikely .text.*_unlikely .text.unlikely.*) @@ -225,10 +227,12 @@ SECTIONS } /* - * We require that Xen is loaded at a 4K boundary, so this ensures that any - * code running on the boot time identity map cannot cross a section boundary. + * We require that Xen is loaded at a page boundary, so this ensures that any + * code running on the identity map cannot cross a section boundary. */ -ASSERT( _end_boot - start <= PAGE_SIZE, "Boot code is larger than 4K") +ASSERT(IS_ALIGNED(_idmap_start, PAGE_SIZE), "_idmap_start should be page-aligned") +ASSERT(_idmap_end - _idmap_start <= PAGE_SIZE, "Identity mapped code is larger than a page size") + /* * __init_[begin|end] MUST be at word size boundary otherwise we cannot * write fault instructions in the space properly.