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Date:   Thu, 17 Mar 2022 11:59:15 +0100
From:   Petr Mladek <pmladek@suse.com>
To:     Maninder Singh <maninder1.s@samsung.com>
Cc:     mcgrof@kernel.org, rostedt@goodmis.org, senozhatsky@chromium.org,
        andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk,
        akpm@linux-foundation.org, wangkefeng.wang@huawei.com,
        v.narang@samsung.com, swboyd@chromium.org, ojeda@kernel.org,
        linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org,
        avimalin@gmail.com, atomlin@redhat.com, keescook@chromium.org,
        ndesaulniers@google.com, rdunlap@infradead.org, void@manifault.com
Subject: Re: [PATCH 1/1 module-next] kallsyms: enhance %pS/s/b printing when
 KALLSYSMS is disabled
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References: <CGME20220316043552epcas5p29b0723b7c55a3bcc9b4d858660e45933@epcas5p2.samsung.com>
 <20220316043540.677128-1-maninder1.s@samsung.com>
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On Wed 2022-03-16 10:05:40, Maninder Singh wrote:
> print module information when KALLSYMS is disabled.
> 
> No change for %pB, as it needs to know symbol name to adjust address
> value which can't be done without KALLSYMS.
> 
> (A) original output with KALLSYMS:
> [8.842129] ps function_1 [crash]
> [8.842735] pS function_1+0x4/0x2c [crash]
> [8.842890] pSb function_1+0x4/0x2c [crash b367e79021b9f3b0172f9a36d4261c1f528ca1b3]
> [8.843175] pB function_1+0x4/0x2c [crash]
> [8.843362] pBb function_1+0x4/0x2c [crash b367e79021b9f3b0172f9a36d4261c1f528ca1b3]
> 
> (B) original output without KALLSYMS:
> [12.487424] ps 0xffff800000eb008c
> [12.487598] pS 0xffff800000eb008c
> [12.487723] pSb 0xffff800000eb008c
> [12.487850] pB 0xffff800000eb008c
> [12.487967] pBb 0xffff800000eb008c
> 
> (C) With patched kernel
> with KALLYSMS:
> [41.974576] ps function_1 [crash]
> [41.975173] pS function_1+0x4/0x2c [crash]
> [41.975386] pSb function_1+0x4/0x2c [crash a8b20caaec9635b316cf4812f6b55598fe2b7cee]
> [41.975879] pB function_1+0x4/0x2c [crash]
> [41.976076] pBb function_1+0x4/0x2c [crash a8b20caaec9635b316cf4812f6b55598fe2b7cee]
> 
> without KALLSYMS:
> [9.624152] ps 0xffff800001bd008c [crash]	// similar to original, no changes
> [9.624548] pS 0x(____ptrval____)+0x8c [crash]   // base address hashed and offset is without hash
> [9.624847] pSb 0x(____ptrval____)+0x8c [crash a8b20caaec9635b316cf4812f6b55598fe2b7cee]
> [9.625388] pB 0x(____ptrval____)+0x8c [crash]
> [9.625594] pBb 0x(____ptrval____)+0x8c [crash a8b20caaec9635b316cf4812f6b55598fe2b7cee]
> 
> with disable hashing:
> [8.563916] ps 0xffff800000f2008c [crash]
> [8.564574] pS 0xffff800000f20000+0x8c [crash]
> [8.564749] pSb 0xffff800000f20000+0x8c [crash 3423a8993a7033fb79e5add14bf9d8d6b56330ca]
> [8.565008] pB 0xffff800000f20000+0x8c [crash]
> [8.565154] pBb 0xffff800000f20000+0x8c [crash 3423a8993a7033fb79e5add14bf9d8d6b56330ca]
> 
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -979,33 +979,92 @@ char *bdev_name(char *buf, char *end, struct block_device *bdev,
>  }
>  #endif
>  
> +#if !defined(CONFIG_KALLSYMS) && defined(CONFIG_MODULES)
> +static int sprint_module_info(char *buf, unsigned long value,
> +			     int modbuildid, int backtrace, int symbol)
> +{
> +	struct module *mod;
> +	unsigned long offset;
> +	void *base;
> +	char *modname;
> +	int len;
> +	const unsigned char *buildid = NULL;
> +	bool add_offset;
> +
> +	if (is_ksym_addr(value))
> +		return 0;
> +
> +	if (backtrace || symbol)
> +		add_offset = true;
> +	else
> +		add_offset = false;
> +
> +	preempt_disable();
> +	mod = __module_address(value);
> +	if (mod) {
> +		modname = mod->name;
> +#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
> +		if (modbuildid)
> +			buildid = mod->build_id;
> +#endif
> +		if (add_offset) {
> +			base = mod->core_layout.base;
> +			offset = value - (unsigned long)base;
> +		}
> +	}
> +	preempt_enable();
> +	if (!mod)
> +		return 0;

I think that some earlier version of the patch allowed to print
also the address from vmlinux with the offset. My concern was
that it would show non-hashed base pointer. IMHO, it is fine
to show it hashed.

> +
> +	/* address belongs to module */
> +	if (add_offset)
> +		len = sprintf(buf, "0x%p+0x%lx", base, offset);
> +	else
> +		len = sprintf(buf, "0x%lx", value);
> +
> +	return len + fill_name_build_id(buf, modname, modbuildid, buildid, len);
> +}

Otherwise, it looks good to me. I did also some basic testing.
The vmlinux address with offset can be added by a followup patch.
Feel free to use:

Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr