On 24 June 2014 21:37, Joe Perches <[email protected]> wrote: > On Tue, 2014-06-24 at 21:13 +0200, Mathias Krause wrote: >> I don't think it's that easy. You cannot simply put all strings into >> the .init.rodata section when code currently gets emitted to >> .init.text. The reason is because strings used in __init code might be >> referenced later on, too. For example, the name passed to >> class_create() won't be copied. If that one would go into the >> .init.rodata section automatically, we would have dangling pointers >> after the .init.* memory got freed. Therefore a compiler driven >> approach would need to be implemented as a compiler extension, a gcc >> plugin to handle such cases -- know when a string can safely be put >> into the .init.rodata section and when not. But that decision is not >> as easy as Joe might think it would be. How would the plugin know >> which strings to put into the .init.rodata section? Would it only >> handle the ones passed to printk()? > > Yes.
Well, I would like to handle the easy ones, too. E.g. strings used in parameter parsing, i.e. strcmp()s. >> I still strongly believe it's better to do this manually. > > Maybe. > > It'd work with any version of the compiler that way too. That's a much stronger argument, IMHO. It'll work with gcc < 4.5 and clang, even. And, it does not require us to maintain compatibility to the repeating gcc plugin API breakage. > It's a pretty simple transform. Indeed, it is. > I believe this will show most all of the __init > uses of printks: > > $ grep-2.5.4 -rP --include=*.[ch] -n '\b__init\b[^\n][^\}]+\n}' * | \ > grep -P '^[\w\/\.]+:\d+:|\bprintk\b|\bpr_[a-z]+' | \ > grep -P -B1 '\bprintk\b|\bpr_[a-z]+' > > This shows a little more than a 1000 __init printks > treewide that could be converted. A simple awk script found additional 5399 pr_<level> calls in __init code and 188 calls in __exit code. So it's worth it, IMHO. > > For example: > arch/ia64/include/asm/cyclone.h:6:extern void __init cyclone_setup(void); > printk(KERN_ERR "Cyclone Counter: System not configured" > -- > arch/ia64/kernel/acpi.c:66:static unsigned long __init acpi_find_rsdp(void) > printk(KERN_WARNING PREFIX > -- > arch/ia64/kernel/acpi.c:366:static int __init acpi_parse_madt(struct > acpi_table > printk(KERN_INFO PREFIX "Local APIC address %p\n", ipi_base_addr); > Those might benefit twice from the change by being converted to pi_<level> calls along the way. So it's a win-win on all sides, no? > etc... > > There are maybe 200 or so __exit ones. > Yeah, the __exit ones are used less. Nonetheless, they should be converted, too. For completeness, at least. Thanks, Mathias -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
