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riscv establishes 2 virtual mappings:
- early_pg_dir maps the kernel which allows to discover the system
memory
- swapper_pg_dir installs the final mapping (linear mapping included)
We used to map the dtb in early_pg_dir using DTB_EARLY_BASE_VA, and this
mapping was not carried over in swapper_pg_dir. It happens that
early_init_fdt_scan_reserved_mem() must be called before swapper_pg_dir is
setup otherwise we could allocate reserved memory defined in the dtb.
And this function initializes reserved_mem variable with addresses that
lie in the early_pg_dir dtb mapping: when those addresses are reused
with swapper_pg_dir, this mapping does not exist and then we trap.
The previous "fix" was incorrect as early_init_fdt_scan_reserved_mem()
must be called before swapper_pg_dir is set up otherwise we could
allocate in reserved memory defined in the dtb.
So move the dtb mapping in the fixmap region which is established in
early_pg_dir and handed over to swapper_pg_dir.
Fixes: 922b0375fc93 ("riscv: Fix memblock reservation for device tree blob")
Fixes: 8f3a2b4a96dc ("RISC-V: Move DT mapping outof fixmap")
Fixes: 50e63dd8ed92 ("riscv: fix reserved memory setup")
Reported-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/all/f8e67f82-103d-156c-deb0-d6d6e2756f5e@microchip.com/
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230329081932.79831-2-alexghiti@rivosinc.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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RISC-V has been supporting the "sv57" address translation mode for a
while, but is has not been added to the VM layout documentation. Let
us fix that.
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20221118171556.1612190-1-bjorn@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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sv48 was just introduced, so add its virtual memory layout to the
documentation.
Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Now that KASAN_SHADOW_OFFSET is defined at compile time as a config,
this value must remain constant whatever the size of the virtual address
space, which is only possible by pushing this region at the end of the
address space next to the kernel mapping.
Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Andreas reported commit fc8504765ec5 ("riscv: bpf: Avoid breaking W^X")
breaks booting with one kind of defconfig, I reproduced a kernel panic
with the defconfig:
[ 0.138553] Unable to handle kernel paging request at virtual address ffffffff81201220
[ 0.139159] Oops [#1]
[ 0.139303] Modules linked in:
[ 0.139601] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc5-default+ #1
[ 0.139934] Hardware name: riscv-virtio,qemu (DT)
[ 0.140193] epc : __memset+0xc4/0xfc
[ 0.140416] ra : skb_flow_dissector_init+0x1e/0x82
[ 0.140609] epc : ffffffff8029806c ra : ffffffff8033be78 sp : ffffffe001647da0
[ 0.140878] gp : ffffffff81134b08 tp : ffffffe001654380 t0 : ffffffff81201158
[ 0.141156] t1 : 0000000000000002 t2 : 0000000000000154 s0 : ffffffe001647dd0
[ 0.141424] s1 : ffffffff80a43250 a0 : ffffffff81201220 a1 : 0000000000000000
[ 0.141654] a2 : 000000000000003c a3 : ffffffff81201258 a4 : 0000000000000064
[ 0.141893] a5 : ffffffff8029806c a6 : 0000000000000040 a7 : ffffffffffffffff
[ 0.142126] s2 : ffffffff81201220 s3 : 0000000000000009 s4 : ffffffff81135088
[ 0.142353] s5 : ffffffff81135038 s6 : ffffffff8080ce80 s7 : ffffffff80800438
[ 0.142584] s8 : ffffffff80bc6578 s9 : 0000000000000008 s10: ffffffff806000ac
[ 0.142810] s11: 0000000000000000 t3 : fffffffffffffffc t4 : 0000000000000000
[ 0.143042] t5 : 0000000000000155 t6 : 00000000000003ff
[ 0.143220] status: 0000000000000120 badaddr: ffffffff81201220 cause: 000000000000000f
[ 0.143560] [<ffffffff8029806c>] __memset+0xc4/0xfc
[ 0.143859] [<ffffffff8061e984>] init_default_flow_dissectors+0x22/0x60
[ 0.144092] [<ffffffff800010fc>] do_one_initcall+0x3e/0x168
[ 0.144278] [<ffffffff80600df0>] kernel_init_freeable+0x1c8/0x224
[ 0.144479] [<ffffffff804868a8>] kernel_init+0x12/0x110
[ 0.144658] [<ffffffff800022de>] ret_from_exception+0x0/0xc
[ 0.145124] ---[ end trace f1e9643daa46d591 ]---
After some investigation, I think I found the root cause: commit
2bfc6cd81bd ("move kernel mapping outside of linear mapping") moves
BPF JIT region after the kernel:
| #define BPF_JIT_REGION_START PFN_ALIGN((unsigned long)&_end)
The &_end is unlikely aligned with PMD size, so the front bpf jit
region sits with part of kernel .data section in one PMD size mapping.
But kernel is mapped in PMD SIZE, when bpf_jit_binary_lock_ro() is
called to make the first bpf jit prog ROX, we will make part of kernel
.data section RO too, so when we write to, for example memset the
.data section, MMU will trigger a store page fault.
To fix the issue, we need to ensure the BPF JIT region is PMD size
aligned. This patch acchieve this goal by restoring the BPF JIT region
to original position, I.E the 128MB before kernel .text section. The
modification to kasan_init.c is inspired by Alexandre.
Fixes: fc8504765ec5 ("riscv: bpf: Avoid breaking W^X")
Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
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This new document presents the RISC-V virtual memory layout and is based
one the x86 one: it describes the different limits of the different regions
of the virtual address space.
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
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