On Tue, Mar 12, 2019 at 10:08:16PM +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.pa...@wdc.com> > --- > arch/riscv/kernel/head.S | 1 + > arch/riscv/mm/init.c | 71 ++++++++++++++++++++++++++-------------- > 2 files changed, 47 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..f35299f2f3d5 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -172,55 +172,76 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t > phys, pgprot_t prot) > } > } > > -asmlinkage void __init setup_vm(void) > +static inline void *__early_va(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));
This is (void *)__pa(va), isn't it? > + return (void *)va; The below usage suggests that __early_va() should be used solely for addresses inside the kernel. What will happen if the accesses is outside that range? Isn't it a BUG()? > +} > + > +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 = __early_va(trampoline_pg_dir, load_pa); > + map_pa = (uintptr_t)__early_va(trampoline_pmd, load_pa); This reads a bit strange: pa = va() BTW, I think you could keep the pa local variable instead of introducing map_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 = __early_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 = (uintptr_t)__early_va(swapper_pmd, load_pa); > + pgdp[o] = pfn_pgd(PFN_DOWN(map_pa) + i, tableprot); > } > + pmdp = __early_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 = (uintptr_t)__early_va(fixmap_pmd, load_pa); > + pgdp[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = > + pfn_pgd(PFN_DOWN(map_pa), tableprot); > + pmdp = __early_va(fixmap_pmd, load_pa); > + map_pa = (uintptr_t)__early_va(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 = __early_va(trampoline_pg_dir, load_pa); > + pgdp[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] = > + pfn_pgd(PFN_DOWN(load_pa), prot); > + > + pgdp = __early_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 = (uintptr_t)__early_va(fixmap_pte, load_pa); > + pgdp[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = > + pfn_pgd(PFN_DOWN(map_pa), tableprot); > #endif > } > -- > 2.17.1 > -- Sincerely yours, Mike.