Messages in this thread | | | Subject | Re: [RFC PATCH 0/3] Mark literal strings in __init / __exit code | From | Joe Perches <> | Date | Tue, 24 Jun 2014 12:37:00 -0700 |
| |
On Tue, 2014-06-24 at 21:13 +0200, Mathias Krause wrote: > On 24 June 2014 16:31, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote: [] > > gcc already seems to contain infrastructure for this kind of thing, so > > maybe it doesn't even require a plugin, but simply a little coordination > > with the gcc folks. This snippet from gcc internals seems relevant: > > > > -- Target Hook: section * TARGET_ASM_FUNCTION_RODATA_SECTION (tree > > DECL) > > Return the readonly data section associated with 'DECL_SECTION_NAME > > (DECL)'. The default version of this function selects > > '.gnu.linkonce.r.name' if the function's section is > > '.gnu.linkonce.t.name', '.rodata.name' if function is in > > '.text.name', and the normal readonly-data section otherwise. > > > > 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.
> I still strongly believe it's better to do this manually.
Maybe.
It'd work with any version of the compiler that way too.
It's a pretty simple transform.
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.
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);
etc...
There are maybe 200 or so __exit ones.
| |