| Message ID | 20231115203401.2495875-27-iii@linux.ibm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | kmsan: Enable on s390 | expand |
On Wed, Nov 15, 2023 at 9:35 PM Ilya Leoshkevich <iii@linux.ibm.com> wrote: > > The pages for the KMSAN metadata associated with most kernel mappings > are taken from memblock by the common code. However, vmalloc and module > metadata needs to be defined by the architectures. > > Be a little bit more careful than x86: allocate exactly MODULES_LEN > for the module shadow and origins, and then take 2/3 of vmalloc for > the vmalloc shadow and origins. This ensures that users passing small > vmalloc= values on the command line do not cause module metadata > collisions. > > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> > --- > arch/s390/boot/startup.c | 8 ++++++++ > arch/s390/include/asm/pgtable.h | 10 ++++++++++ > 2 files changed, 18 insertions(+) > > diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c > index 8104e0e3d188..297c1062372a 100644 > --- a/arch/s390/boot/startup.c > +++ b/arch/s390/boot/startup.c > @@ -253,9 +253,17 @@ static unsigned long setup_kernel_memory_layout(void) > MODULES_END = round_down(__abs_lowcore, _SEGMENT_SIZE); > MODULES_VADDR = MODULES_END - MODULES_LEN; > VMALLOC_END = MODULES_VADDR; > +#ifdef CONFIG_KMSAN > + VMALLOC_END -= MODULES_LEN * 2; > +#endif > > /* allow vmalloc area to occupy up to about 1/2 of the rest virtual space left */ > vmalloc_size = min(vmalloc_size, round_down(VMALLOC_END / 2, _REGION3_SIZE)); > +#ifdef CONFIG_KMSAN > + /* take 2/3 of vmalloc area for KMSAN shadow and origins */ > + vmalloc_size = round_down(vmalloc_size / 3, PAGE_SIZE); Is it okay that vmalloc_size is only aligned on PAGE_SIZE? E.g. above the alignment is _REGION3_SIZE.
On Thu, Nov 16, 2023 at 04:03:13PM +0100, Alexander Potapenko wrote: Hi Alexander! > > /* allow vmalloc area to occupy up to about 1/2 of the rest virtual space left */ > > vmalloc_size = min(vmalloc_size, round_down(VMALLOC_END / 2, _REGION3_SIZE)); > > +#ifdef CONFIG_KMSAN > > + /* take 2/3 of vmalloc area for KMSAN shadow and origins */ > > + vmalloc_size = round_down(vmalloc_size / 3, PAGE_SIZE); > Is it okay that vmalloc_size is only aligned on PAGE_SIZE? > E.g. above the alignment is _REGION3_SIZE. Good question! This patch does not break anything, although the _REGION3_SIZE alignment would be consistent here. Yet, we might rethink this whole code piece and the next version would reflect that. Thanks!
diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c index 8104e0e3d188..297c1062372a 100644 --- a/arch/s390/boot/startup.c +++ b/arch/s390/boot/startup.c @@ -253,9 +253,17 @@ static unsigned long setup_kernel_memory_layout(void) MODULES_END = round_down(__abs_lowcore, _SEGMENT_SIZE); MODULES_VADDR = MODULES_END - MODULES_LEN; VMALLOC_END = MODULES_VADDR; +#ifdef CONFIG_KMSAN + VMALLOC_END -= MODULES_LEN * 2; +#endif /* allow vmalloc area to occupy up to about 1/2 of the rest virtual space left */ vmalloc_size = min(vmalloc_size, round_down(VMALLOC_END / 2, _REGION3_SIZE)); +#ifdef CONFIG_KMSAN + /* take 2/3 of vmalloc area for KMSAN shadow and origins */ + vmalloc_size = round_down(vmalloc_size / 3, PAGE_SIZE); + VMALLOC_END -= vmalloc_size * 2; +#endif VMALLOC_START = VMALLOC_END - vmalloc_size; /* split remaining virtual space between 1:1 mapping & vmemmap array */ diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index 601e87fa8a9a..d764abeb9e6d 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -107,6 +107,16 @@ static inline int is_module_addr(void *addr) return 1; } +#ifdef CONFIG_KMSAN +#define KMSAN_VMALLOC_SIZE (VMALLOC_END - VMALLOC_START) +#define KMSAN_VMALLOC_SHADOW_START VMALLOC_END +#define KMSAN_VMALLOC_ORIGIN_START (KMSAN_VMALLOC_SHADOW_START + \ + KMSAN_VMALLOC_SIZE) +#define KMSAN_MODULES_SHADOW_START (KMSAN_VMALLOC_ORIGIN_START + \ + KMSAN_VMALLOC_SIZE) +#define KMSAN_MODULES_ORIGIN_START (KMSAN_MODULES_SHADOW_START + MODULES_LEN) +#endif + /* * A 64 bit pagetable entry of S390 has following format: * | PFRA |0IPC| OS |
The pages for the KMSAN metadata associated with most kernel mappings are taken from memblock by the common code. However, vmalloc and module metadata needs to be defined by the architectures. Be a little bit more careful than x86: allocate exactly MODULES_LEN for the module shadow and origins, and then take 2/3 of vmalloc for the vmalloc shadow and origins. This ensures that users passing small vmalloc= values on the command line do not cause module metadata collisions. Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> --- arch/s390/boot/startup.c | 8 ++++++++ arch/s390/include/asm/pgtable.h | 10 ++++++++++ 2 files changed, 18 insertions(+)