Messages in this thread | | | From | Albert Ou <> | Subject | Re: [PATCH] riscv: Fix memblock reservation for device tree blob | Date | Tue, 08 Oct 2019 16:31:17 -0700 |
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On 2019-10-08 15:38:15 -0700, Palmer Dabbelt <palmer@sifive.com> wrote: > 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? >
v2 was sent last week and has already been applied as 922b0375fc93fb1a20c5617e37c389c26bbccb70 by Paul.
-- Albert Ou
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