Messages in this thread | | | Date | Tue, 08 Oct 2019 15:38:15 -0700 (PDT) | Subject | Re: [PATCH] riscv: Fix memblock reservation for device tree blob | From | Palmer Dabbelt <> |
| |
On Fri, 20 Sep 2019 21:34:57 PDT (-0700), anup@brainfault.org wrote: > On Sat, Sep 21, 2019 at 6:30 AM Albert Ou <aou@eecs.berkeley.edu> wrote: >> >> This fixes an error with how the FDT blob is reserved in memblock. >> An incorrect physical address calculation exposed the FDT header to >> unintended corruption, which typically manifested with of_fdt_raw_init() >> faulting during late boot after fdt_totalsize() returned a wrong value. >> Systems with smaller physical memory sizes more frequently trigger this >> issue, as the kernel is more likely to allocate from the DMA32 zone >> where bbl places the DTB after the kernel image. >> >> Commit 671f9a3e2e24 ("RISC-V: Setup initial page tables in two stages") >> changed the mapping of the DTB to reside in the fixmap area. >> Consequently, early_init_fdt_reserve_self() cannot be used anymore in >> setup_bootmem() since it relies on __pa() to derive a physical address, >> which does not work with dtb_early_va that is no longer a valid kernel >> logical address. >> >> The reserved[0x1] region shows the effect of the pointer underflow >> resulting from the __pa(initial_boot_params) offset subtraction: >> >> [ 0.000000] MEMBLOCK configuration: >> [ 0.000000] memory size = 0x000000001fe00000 reserved size = 0x0000000000a2e514 >> [ 0.000000] memory.cnt = 0x1 >> [ 0.000000] memory[0x0] [0x0000000080200000-0x000000009fffffff], 0x000000001fe00000 bytes flags: 0x0 >> [ 0.000000] reserved.cnt = 0x2 >> [ 0.000000] reserved[0x0] [0x0000000080200000-0x0000000080c2dfeb], 0x0000000000a2dfec bytes flags: 0x0 >> [ 0.000000] reserved[0x1] [0xfffffff080100000-0xfffffff080100527], 0x0000000000000528 bytes flags: 0x0 >> >> With the fix applied: >> >> [ 0.000000] MEMBLOCK configuration: >> [ 0.000000] memory size = 0x000000001fe00000 reserved size = 0x0000000000a2e514 >> [ 0.000000] memory.cnt = 0x1 >> [ 0.000000] memory[0x0] [0x0000000080200000-0x000000009fffffff], 0x000000001fe00000 bytes flags: 0x0 >> [ 0.000000] reserved.cnt = 0x2 >> [ 0.000000] reserved[0x0] [0x0000000080200000-0x0000000080c2dfeb], 0x0000000000a2dfec bytes flags: 0x0 >> [ 0.000000] reserved[0x1] [0x0000000080e00000-0x0000000080e00527], 0x0000000000000528 bytes flags: 0x0 > > Thanks for catching this issue. > > Most of us did not notice this issue most likely because: > 1. We generally have good enough RAM on QEMU and SiFive Unleashed > 2. Most of people use OpenSBI FW_JUMP on QEMU and U-Boot on > SiFive Unleashed to boot in Linux which places FDT quite far away > from Linux kernel end > > Linux ARM64 kernel also uses FIXMAP to access FDT and over there > as well early_init_fdt_reserve_self() is not used. > >> >> Fixes: 671f9a3e2e24 ("RISC-V: Setup initial page tables in two stages") >> Signed-off-by: Albert Ou <aou@eecs.berkeley.edu> >> --- >> arch/riscv/mm/init.c | 13 ++++++++++++- >> 1 file changed, 12 insertions(+), 1 deletion(-) >> >> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c >> index f0ba713..52d007c 100644 >> --- a/arch/riscv/mm/init.c >> +++ b/arch/riscv/mm/init.c >> @@ -11,6 +11,7 @@ >> #include <linux/swap.h> >> #include <linux/sizes.h> >> #include <linux/of_fdt.h> >> +#include <linux/libfdt.h> >> >> #include <asm/fixmap.h> >> #include <asm/tlbflush.h> >> @@ -82,6 +83,8 @@ static void __init setup_initrd(void) >> } >> #endif /* CONFIG_BLK_DEV_INITRD */ >> >> +static phys_addr_t __dtb_pa __initdata; > > May be dtb_early_pa will be more consistent name > instead of __dtb_pa because it matches dtb_early_va > used below. > >> + >> void __init setup_bootmem(void) >> { >> struct memblock_region *reg; >> @@ -117,7 +120,12 @@ void __init setup_bootmem(void) >> setup_initrd(); >> #endif /* CONFIG_BLK_DEV_INITRD */ >> >> - early_init_fdt_reserve_self(); >> + /* >> + * Avoid using early_init_fdt_reserve_self() since __pa() does >> + * not work for DTB pointers that are fixmap addresses >> + */ >> + memblock_reserve(__dtb_pa, fdt_totalsize(dtb_early_va)); >> + >> early_init_fdt_scan_reserved_mem(); >> memblock_allow_resize(); >> memblock_dump_all(); >> @@ -333,6 +341,7 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size) >> "not use absolute addressing." >> #endif >> >> + > > Please remove this newline addition. > >> asmlinkage void __init setup_vm(uintptr_t dtb_pa) >> { >> uintptr_t va, end_va; >> @@ -393,6 +402,8 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) >> >> /* Save pointer to DTB for early FDT parsing */ >> dtb_early_va = (void *)fix_to_virt(FIX_FDT) + (dtb_pa & ~PAGE_MASK); >> + /* Save physical address for memblock reservation */ >> + __dtb_pa = dtb_pa; >> } >> >> static void __init setup_vm_final(void) >> -- >> 2.7.4 >> >> >> _______________________________________________ >> linux-riscv mailing list >> linux-riscv@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-riscv > > This deserves to be stable kernel fix as well. > You should add: > Cc: stable@vger.kernel.org > in your commit description. > > Apart from minor nits above. > > Reviewed-by: Anup Patel <anup@brainfault.org> > > I tried this patch for both RV64 and RV32 on QEMU with > Yocto rootfs. > > Tested-by: Anup Patel <anup@brainfault.org> > > Regards, > Anup
Albert: Do you plan on spinning a v2 of the patch set?
| |