| Message ID | 20190321094710.16552-3-anup.patel@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Boot RISC-V kernel from any 4KB aligned address | expand |
On Thu, Mar 21, 2019 at 09:47:47AM +0000, Anup Patel wrote: > The setup_vm() must access kernel symbols in a position independent way > because it will be called from head.S with MMU off. > > If we compile kernel with cmodel=medany then PC-relative addressing will > be used in setup_vm() to access kernel symbols so it works perfectly fine. > > Although, if we compile kernel with cmodel=medlow then either absolute > addressing or PC-relative addressing (based on whichever requires fewer > instructions) is used to access kernel symbols in setup_vm(). This can > break setup_vm() whenever any absolute addressing is used to access > kernel symbols. > > With the movement of setup_vm() from kernel/setup.c to mm/init.c, the > setup_vm() is now broken for cmodel=medlow but it works perfectly fine > for cmodel=medany. > > This patch fixes setup_vm() and makes it independent of GCC code model > by accessing kernel symbols relative to kernel load address instead of > assuming PC-relative addressing. > > Fixes: 6f1e9e946f0b ("RISC-V: Move setup_vm() to mm/init.c") > Signed-off-by: Anup Patel <anup.patel@wdc.com> > --- > arch/riscv/kernel/head.S | 1 + > arch/riscv/mm/init.c | 73 ++++++++++++++++++++++++++-------------- > 2 files changed, 49 insertions(+), 25 deletions(-) > > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S > index fe884cd69abd..7966262b4f9d 100644 > --- a/arch/riscv/kernel/head.S > +++ b/arch/riscv/kernel/head.S > @@ -62,6 +62,7 @@ clear_bss_done: > > /* Initialize page tables and relocate to virtual addresses */ > la sp, init_thread_union + THREAD_SIZE > + la a0, _start > call setup_vm > call relocate > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index b379a75ac6a6..e38f8195e45b 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -172,55 +172,78 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) > } > } > > -asmlinkage void __init setup_vm(void) > +static inline void *__load_addr(void *ptr, uintptr_t load_pa) > { > extern char _start; > + uintptr_t va = (uintptr_t)ptr; > + uintptr_t sz = (uintptr_t)(&_end) - (uintptr_t)(&_start); > + > + if (va >= PAGE_OFFSET && va <= (PAGE_OFFSET + sz)) > + return (void *)(load_pa + (va - PAGE_OFFSET)); > + return (void *)va; > +} > + > +#define __load_va(ptr, load_pa) __load_addr(ptr, load_pa) > +#define __load_pa(ptr, load_pa) ((uintptr_t)__load_addr(ptr, load_pa)) > + > +asmlinkage void __init setup_vm(uintptr_t load_pa) > +{ > uintptr_t i; > - uintptr_t pa = (uintptr_t) &_start; > +#ifndef __PAGETABLE_PMD_FOLDED > + pmd_t *pmdp; > +#endif > + pgd_t *pgdp; > + phys_addr_t map_pa; > + pgprot_t tableprot = __pgprot(_PAGE_TABLE); > pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC); > > - va_pa_offset = PAGE_OFFSET - pa; > - pfn_base = PFN_DOWN(pa); > + va_pa_offset = PAGE_OFFSET - load_pa; > + pfn_base = PFN_DOWN(load_pa); > > /* Sanity check alignment and size */ > BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0); > - BUG_ON((pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0); > + BUG_ON((load_pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0); > > #ifndef __PAGETABLE_PMD_FOLDED > - trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = > - pfn_pgd(PFN_DOWN((uintptr_t)trampoline_pmd), > - __pgprot(_PAGE_TABLE)); > - trampoline_pmd[0] = pfn_pmd(PFN_DOWN(pa), prot); > + pgdp = __load_va(trampoline_pg_dir, load_pa); > + map_pa = __load_pa(trampoline_pmd, load_pa); > + pgdp[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = Can we use pgd_index(PAGE_OFFSET) here as index to PGD? > + pfn_pgd(PFN_DOWN(map_pa), tableprot); It seems that __load_pa result is always used with PFN_DOWN(), it's worth adding __load_pfn(). Then the last two statements become map_pfn = __load_pfn(trampoline_pmd, load_pa); pgdp[pgd_index(PAGE_OFFSET)] = pfn_pgd(map_pfn, tableprot); This applies to most of the mappings below as well. > + trampoline_pmd[0] = pfn_pmd(PFN_DOWN(load_pa), prot); > + > + pgdp = __load_va(swapper_pg_dir, load_pa); > > for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) { > size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i; > > - swapper_pg_dir[o] = > - pfn_pgd(PFN_DOWN((uintptr_t)swapper_pmd) + i, > - __pgprot(_PAGE_TABLE)); > + map_pa = __load_pa(swapper_pmd, load_pa); > + pgdp[o] = pfn_pgd(PFN_DOWN(map_pa) + i, tableprot); > } > + pmdp = __load_va(swapper_pmd, load_pa); > for (i = 0; i < ARRAY_SIZE(swapper_pmd); i++) > - swapper_pmd[i] = pfn_pmd(PFN_DOWN(pa + i * PMD_SIZE), prot); > + pmdp[i] = pfn_pmd(PFN_DOWN(load_pa + i * PMD_SIZE), prot); > > - swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = > - pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pmd), > - __pgprot(_PAGE_TABLE)); > + map_pa = __load_pa(fixmap_pmd, load_pa); > + pgdp[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = > + pfn_pgd(PFN_DOWN(map_pa), tableprot); > + pmdp = __load_va(fixmap_pmd, load_pa); > + map_pa = __load_pa(fixmap_pte, load_pa); > fixmap_pmd[(FIXADDR_START >> PMD_SHIFT) % PTRS_PER_PMD] = > - pfn_pmd(PFN_DOWN((uintptr_t)fixmap_pte), > - __pgprot(_PAGE_TABLE)); > + pfn_pmd(PFN_DOWN(map_pa), tableprot); > #else > - trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = > - pfn_pgd(PFN_DOWN(pa), prot); > + pgdp = __load_va(trampoline_pg_dir, load_pa); > + pgdp[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = > + pfn_pgd(PFN_DOWN(load_pa), prot); > > + pgdp = __load_va(swapper_pg_dir, load_pa); > for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) { > size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i; > > - swapper_pg_dir[o] = > - pfn_pgd(PFN_DOWN(pa + i * PGDIR_SIZE), prot); > + pgdp[o] = pfn_pgd(PFN_DOWN(load_pa + i * PGDIR_SIZE), prot); > } > > - swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = > - pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pte), > - __pgprot(_PAGE_TABLE)); > + map_pa = __load_pa(fixmap_pte, load_pa); > + pgdp[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = > + pfn_pgd(PFN_DOWN(map_pa), tableprot); > #endif > } > -- > 2.17.1 >
On Sat, Mar 23, 2019 at 9:15 PM Mike Rapoport <rppt@linux.ibm.com> wrote: > > On Thu, Mar 21, 2019 at 09:47:47AM +0000, Anup Patel wrote: > > The setup_vm() must access kernel symbols in a position independent way > > because it will be called from head.S with MMU off. > > > > If we compile kernel with cmodel=medany then PC-relative addressing will > > be used in setup_vm() to access kernel symbols so it works perfectly fine. > > > > Although, if we compile kernel with cmodel=medlow then either absolute > > addressing or PC-relative addressing (based on whichever requires fewer > > instructions) is used to access kernel symbols in setup_vm(). This can > > break setup_vm() whenever any absolute addressing is used to access > > kernel symbols. > > > > With the movement of setup_vm() from kernel/setup.c to mm/init.c, the > > setup_vm() is now broken for cmodel=medlow but it works perfectly fine > > for cmodel=medany. > > > > This patch fixes setup_vm() and makes it independent of GCC code model > > by accessing kernel symbols relative to kernel load address instead of > > assuming PC-relative addressing. > > > > Fixes: 6f1e9e946f0b ("RISC-V: Move setup_vm() to mm/init.c") > > Signed-off-by: Anup Patel <anup.patel@wdc.com> > > --- > > arch/riscv/kernel/head.S | 1 + > > arch/riscv/mm/init.c | 73 ++++++++++++++++++++++++++-------------- > > 2 files changed, 49 insertions(+), 25 deletions(-) > > > > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S > > index fe884cd69abd..7966262b4f9d 100644 > > --- a/arch/riscv/kernel/head.S > > +++ b/arch/riscv/kernel/head.S > > @@ -62,6 +62,7 @@ clear_bss_done: > > > > /* Initialize page tables and relocate to virtual addresses */ > > la sp, init_thread_union + THREAD_SIZE > > + la a0, _start > > call setup_vm > > call relocate > > > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > > index b379a75ac6a6..e38f8195e45b 100644 > > --- a/arch/riscv/mm/init.c > > +++ b/arch/riscv/mm/init.c > > @@ -172,55 +172,78 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) > > } > > } > > > > -asmlinkage void __init setup_vm(void) > > +static inline void *__load_addr(void *ptr, uintptr_t load_pa) > > { > > extern char _start; > > + uintptr_t va = (uintptr_t)ptr; > > + uintptr_t sz = (uintptr_t)(&_end) - (uintptr_t)(&_start); > > + > > + if (va >= PAGE_OFFSET && va <= (PAGE_OFFSET + sz)) > > + return (void *)(load_pa + (va - PAGE_OFFSET)); > > + return (void *)va; > > +} > > + > > +#define __load_va(ptr, load_pa) __load_addr(ptr, load_pa) > > +#define __load_pa(ptr, load_pa) ((uintptr_t)__load_addr(ptr, load_pa)) > > + > > +asmlinkage void __init setup_vm(uintptr_t load_pa) > > +{ > > uintptr_t i; > > - uintptr_t pa = (uintptr_t) &_start; > > +#ifndef __PAGETABLE_PMD_FOLDED > > + pmd_t *pmdp; > > +#endif > > + pgd_t *pgdp; > > + phys_addr_t map_pa; > > + pgprot_t tableprot = __pgprot(_PAGE_TABLE); > > pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC); > > > > - va_pa_offset = PAGE_OFFSET - pa; > > - pfn_base = PFN_DOWN(pa); > > + va_pa_offset = PAGE_OFFSET - load_pa; > > + pfn_base = PFN_DOWN(load_pa); > > > > /* Sanity check alignment and size */ > > BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0); > > - BUG_ON((pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0); > > + BUG_ON((load_pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0); > > > > #ifndef __PAGETABLE_PMD_FOLDED > > - trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = > > - pfn_pgd(PFN_DOWN((uintptr_t)trampoline_pmd), > > - __pgprot(_PAGE_TABLE)); > > - trampoline_pmd[0] = pfn_pmd(PFN_DOWN(pa), prot); > > + pgdp = __load_va(trampoline_pg_dir, load_pa); > > + map_pa = __load_pa(trampoline_pmd, load_pa); > > + pgdp[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = > > Can we use pgd_index(PAGE_OFFSET) here as index to PGD? > > > + pfn_pgd(PFN_DOWN(map_pa), tableprot); > > It seems that __load_pa result is always used with PFN_DOWN(), it's worth > adding __load_pfn(). Then the last two statements become > > map_pfn = __load_pfn(trampoline_pmd, load_pa); > pgdp[pgd_index(PAGE_OFFSET)] = pfn_pgd(map_pfn, tableprot); > > This applies to most of the mappings below as well. Thanks for the comments. I am going to drop this patch because we have other patch which uses "CFLAGS_init.o := -cmodel=medany" in mm/Makefile Regards, Anup
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index fe884cd69abd..7966262b4f9d 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -62,6 +62,7 @@ clear_bss_done: /* Initialize page tables and relocate to virtual addresses */ la sp, init_thread_union + THREAD_SIZE + la a0, _start call setup_vm call relocate diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index b379a75ac6a6..e38f8195e45b 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -172,55 +172,78 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) } } -asmlinkage void __init setup_vm(void) +static inline void *__load_addr(void *ptr, uintptr_t load_pa) { extern char _start; + uintptr_t va = (uintptr_t)ptr; + uintptr_t sz = (uintptr_t)(&_end) - (uintptr_t)(&_start); + + if (va >= PAGE_OFFSET && va <= (PAGE_OFFSET + sz)) + return (void *)(load_pa + (va - PAGE_OFFSET)); + return (void *)va; +} + +#define __load_va(ptr, load_pa) __load_addr(ptr, load_pa) +#define __load_pa(ptr, load_pa) ((uintptr_t)__load_addr(ptr, load_pa)) + +asmlinkage void __init setup_vm(uintptr_t load_pa) +{ uintptr_t i; - uintptr_t pa = (uintptr_t) &_start; +#ifndef __PAGETABLE_PMD_FOLDED + pmd_t *pmdp; +#endif + pgd_t *pgdp; + phys_addr_t map_pa; + pgprot_t tableprot = __pgprot(_PAGE_TABLE); pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC); - va_pa_offset = PAGE_OFFSET - pa; - pfn_base = PFN_DOWN(pa); + va_pa_offset = PAGE_OFFSET - load_pa; + pfn_base = PFN_DOWN(load_pa); /* Sanity check alignment and size */ BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0); - BUG_ON((pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0); + BUG_ON((load_pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0); #ifndef __PAGETABLE_PMD_FOLDED - trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = - pfn_pgd(PFN_DOWN((uintptr_t)trampoline_pmd), - __pgprot(_PAGE_TABLE)); - trampoline_pmd[0] = pfn_pmd(PFN_DOWN(pa), prot); + pgdp = __load_va(trampoline_pg_dir, load_pa); + map_pa = __load_pa(trampoline_pmd, load_pa); + pgdp[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = + pfn_pgd(PFN_DOWN(map_pa), tableprot); + trampoline_pmd[0] = pfn_pmd(PFN_DOWN(load_pa), prot); + + pgdp = __load_va(swapper_pg_dir, load_pa); for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) { size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i; - swapper_pg_dir[o] = - pfn_pgd(PFN_DOWN((uintptr_t)swapper_pmd) + i, - __pgprot(_PAGE_TABLE)); + map_pa = __load_pa(swapper_pmd, load_pa); + pgdp[o] = pfn_pgd(PFN_DOWN(map_pa) + i, tableprot); } + pmdp = __load_va(swapper_pmd, load_pa); for (i = 0; i < ARRAY_SIZE(swapper_pmd); i++) - swapper_pmd[i] = pfn_pmd(PFN_DOWN(pa + i * PMD_SIZE), prot); + pmdp[i] = pfn_pmd(PFN_DOWN(load_pa + i * PMD_SIZE), prot); - swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = - pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pmd), - __pgprot(_PAGE_TABLE)); + map_pa = __load_pa(fixmap_pmd, load_pa); + pgdp[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = + pfn_pgd(PFN_DOWN(map_pa), tableprot); + pmdp = __load_va(fixmap_pmd, load_pa); + map_pa = __load_pa(fixmap_pte, load_pa); fixmap_pmd[(FIXADDR_START >> PMD_SHIFT) % PTRS_PER_PMD] = - pfn_pmd(PFN_DOWN((uintptr_t)fixmap_pte), - __pgprot(_PAGE_TABLE)); + pfn_pmd(PFN_DOWN(map_pa), tableprot); #else - trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = - pfn_pgd(PFN_DOWN(pa), prot); + pgdp = __load_va(trampoline_pg_dir, load_pa); + pgdp[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = + pfn_pgd(PFN_DOWN(load_pa), prot); + pgdp = __load_va(swapper_pg_dir, load_pa); for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) { size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i; - swapper_pg_dir[o] = - pfn_pgd(PFN_DOWN(pa + i * PGDIR_SIZE), prot); + pgdp[o] = pfn_pgd(PFN_DOWN(load_pa + i * PGDIR_SIZE), prot); } - swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = - pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pte), - __pgprot(_PAGE_TABLE)); + map_pa = __load_pa(fixmap_pte, load_pa); + pgdp[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = + pfn_pgd(PFN_DOWN(map_pa), tableprot); #endif }
The setup_vm() must access kernel symbols in a position independent way because it will be called from head.S with MMU off. If we compile kernel with cmodel=medany then PC-relative addressing will be used in setup_vm() to access kernel symbols so it works perfectly fine. Although, if we compile kernel with cmodel=medlow then either absolute addressing or PC-relative addressing (based on whichever requires fewer instructions) is used to access kernel symbols in setup_vm(). This can break setup_vm() whenever any absolute addressing is used to access kernel symbols. With the movement of setup_vm() from kernel/setup.c to mm/init.c, the setup_vm() is now broken for cmodel=medlow but it works perfectly fine for cmodel=medany. This patch fixes setup_vm() and makes it independent of GCC code model by accessing kernel symbols relative to kernel load address instead of assuming PC-relative addressing. Fixes: 6f1e9e946f0b ("RISC-V: Move setup_vm() to mm/init.c") Signed-off-by: Anup Patel <anup.patel@wdc.com> --- arch/riscv/kernel/head.S | 1 + arch/riscv/mm/init.c | 73 ++++++++++++++++++++++++++-------------- 2 files changed, 49 insertions(+), 25 deletions(-)