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)); + return (void *)va; +} + +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); + 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