Messages in this thread | | | Subject | Re: [PATCH 2/2] hexdump: add a new dump prefix DUMP_PREFIX_ADDRESS_LOW16 | From | "Leizhen (ThunderTown)" <> | Date | Fri, 11 Aug 2023 15:31:09 +0800 |
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On 2023/8/9 15:05, Leizhen (ThunderTown) wrote: > > > On 2023/8/9 12:10, Sergey Senozhatsky wrote: >> On (23/08/08 15:52), Leizhen (ThunderTown) wrote: >>>>> I find the "before" much easier to read than the "after". >>> >>> I added the boot option no_hash_pointers, so "before" can print the >>> address. Otherwise, just print the 32-bit hash value, as shown below: >> >> >>> [ 14.872153] dump memory at sp=ffff800080903aa0: >> >> This line is not guaranteed to be printed. If you get >> "** N printk messages dropped **" instead then the >> ADDRESS_LOW16 math doesn't work.
I have a new idea. Replace DUMP_PREFIX_ADDRESS_LOW16 with DUMP_PREFIX_CUSTOM. Let the user to specify the format string.
For example: pr_info("dump memory at sp=%px:\n", sp); print_hex_dump(KERN_INFO, "%s%16hx: %s\n", DUMP_PREFIX_CUSTOM, 16, 1, sp, 16, false); print_hex_dump(KERN_INFO, "%s%16x: %s\n", DUMP_PREFIX_CUSTOM, 16, 1, sp, 16, false); print_hex_dump(KERN_INFO, "%s%px: %s\n", DUMP_PREFIX_CUSTOM, 16, 1, sp, 16, false);
dump memory at sp=ffff80008091baa0: baa0: c0 ba 91 80 00 80 ff ff d4 38 16 ce fc a7 ff ff 8091baa0: c0 ba 91 80 00 80 ff ff d4 38 16 ce fc a7 ff ff ffff80008091baa0: c0 ba 91 80 00 80 ff ff d4 38 16 ce fc a7 ff ff
> > Anyone is vulnerable in the face of nature. Even DUMP_PREFIX_ADDRESS, > without the preface, no one know what's dumped. In any case, > DUMP_PREFIX_ADDRESS_LOW16 has its own unique value in this ecosystem. > The only regret is that it has a slightly longer name than others. > Maybe it could be DUMP_PREFIX_ADDRLOW or something. > > By the way, would you consider changing %p to %px in case DUMP_PREFIX_ADDRESS? > >> >>> Actually, I added DUMP_PREFIX_ADDRESS_LOW16 because of another scene: >>> slab kmalloc-512 start ffff3b3c0094e800 pointer offset 168 size 512 >>> e888: 00400000 00000000 000f7704 00000000 >>> e898: 000f7704 00000000 12345678 00000000 >>> e8a8: 00000000 00000000 00000000 00000000 >>> e8b8: 9abcdef0 00000000 00507dd0 00000000 >>> >>> Here, the start address ffff3b3c0094e800 of slab object is printed by %px, >>> the address of the error data is at p=ffff3b3c0094e8a8 = ffff3b3c0094e800 + offset 168. >>> To locate the problem, dump up to 64 bytes centered on 'p'. >> . >> >
-- Regards, Zhen Lei
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