Hello!
libfdt fdt_num_mem_rsv() results in an unaligned access crash because
the code "fdt64_to_cpu(_fdt_mem_rsv(fdt, i)->size" uses an aligned
64-bit read from an unaligned address. The platform is aarch64. The
following is the generated code for fdt64_to_cpu():
1181ec: f94004e1 ldr x1, [x7, #8]
1181f0: 910040e7 add x7, x7, #0x10
1181f4: d3505c23 ubfx x3, x1, #16, #8
1181f8: d3483c22 ubfx x2, x1, #8, #8
1181fc: d3585c63 lsl x3, x3, #40
118200: d378fc26 lsr x6, x1, #56
118204: d3609c25 ubfx x5, x1, #32, #8
118208: aa02c062 orr x2, x3, x2, lsl #48
11820c: aa01e0c6 orr x6, x6, x1, lsl #56
118210: 53187c24 lsr w4, w1, #24
118214: d370dc23 ubfx x3, x1, #48, #8
118218: d3689ca5 lsl x5, x5, #24
11821c: aa060042 orr x2, x2, x6
118220: aa0480a4 orr x4, x5, x4, lsl #32
118224: d368bc21 ubfx x1, x1, #40, #8
118228: d378dc63 lsl x3, x3, #8
11822c: aa040042 orr x2, x2, x4
118230: aa014061 orr x1, x3, x1, lsl #16
118234: aa010041 orr x1, x2, x1
The first instruction crashes because x7 is 4-byte aligned, but not
8-byte aligned.
I'm not sure where the bug is. Is fdt64_to_cpu() supposed to convert the
access to non-aligned and not doing its job properly?
We're using GCC 7.1.0.
--
Cyril
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