Gvrose ciqlts8 8 #48
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Gvrose ciqlts8 8 #48
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… prevent wrong idmap generation
The PTE_MAYBE_NG macro sets the nG page table bit according to the value
of "arm64_use_ng_mappings". This variable is currently placed in the
.bss section. create_init_idmap() is called before the .bss section
initialisation which is done in early_map_kernel(). Therefore,
data/test_prot in create_init_idmap() could be set incorrectly through
the PAGE_KERNEL -> PROT_DEFAULT -> PTE_MAYBE_NG macros.
# llvm-objdump-21 --syms vmlinux-gcc | grep arm64_use_ng_mappings
ffff800082f242a8 g O .bss 0000000000000001 arm64_use_ng_mappings
The create_init_idmap() function disassembly compiled with llvm-21:
// create_init_idmap()
ffff80008255c058: d10103ff sub sp, sp, #0x40
ffff80008255c05c: a9017bfd stp x29, x30, [sp, #0x10]
ffff80008255c060: a90257f6 stp x22, x21, [sp, #0x20]
ffff80008255c064: a9034ff4 stp x20, x19, [sp, #0x30]
ffff80008255c068: 910043fd add x29, sp, #0x10
ffff80008255c06c: 90003fc8 adrp x8, 0xffff800082d54000
ffff80008255c070: d280e06a mov x10, #0x703 // =1795
ffff80008255c074: 91400409 add x9, x0, #0x1, lsl #12 // =0x1000
ffff80008255c078: 394a4108 ldrb w8, [x8, #0x290] ------------- (1)
ffff80008255c07c: f2e00d0a movk x10, #0x68, lsl #48
ffff80008255c080: f90007e9 str x9, [sp, #0x8]
ffff80008255c084: aa0103f3 mov x19, x1
ffff80008255c088: aa0003f4 mov x20, x0
ffff80008255c08c: 14000000 b 0xffff80008255c08c <__pi_create_init_idmap+0x34>
ffff80008255c090: aa082d56 orr x22, x10, x8, lsl #11 -------- (2)
Note (1) is loading the arm64_use_ng_mappings value in w8 and (2) is set
the text or data prot with the w8 value to set PTE_NG bit. If the .bss
section isn't initialized, x8 could include a garbage value and generate
an incorrect mapping.
Annotate arm64_use_ng_mappings as __read_mostly so that it is placed in
the .data section.
Fixes: 84b04d3 ("arm64: kernel: Create initial ID map from C code")
Cc: [email protected] # 6.9.x
Tested-by: Nathan Chancellor <[email protected]>
Signed-off-by: Yeoreum Yun <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[[email protected]: use __read_mostly instead of __ro_after_init]
[[email protected]: slight tweaking of the code comment]
Signed-off-by: Catalin Marinas <[email protected]>
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Another PR to fix the PR checker - hopefully dependencies are correct this time.