Messages in this thread | | | From | Nadav Amit <> | Subject | Re: [PATCH 2/6] x86: bug: prevent gcc distortions | Date | Fri, 18 May 2018 14:22:41 +0000 |
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Peter Zijlstra <peterz@infradead.org> wrote:
> On Thu, May 17, 2018 at 09:13:58AM -0700, Nadav Amit wrote: >> +asm(".macro __BUG_FLAGS ins:req file:req line:req flags:req size:req\n" >> + "1:\t \\ins\n\t" >> + ".pushsection __bug_table,\"aw\"\n" >> + "2:\t "__BUG_REL(1b) "\t# bug_entry::bug_addr\n\t" >> + __BUG_REL(\\file) "\t# bug_entry::file\n\t" >> + ".word \\line" "\t# bug_entry::line\n\t" >> + ".word \\flags" "\t# bug_entry::flags\n\t" >> + ".org 2b+\\size\n\t" >> + ".popsection\n\t" >> + ".endm"); >> + >> +#define _BUG_FLAGS(ins, flags) \ >> do { \ >> + asm volatile("__BUG_FLAGS \"" ins "\" %c0 %c1 %c2 %c3" \ >> + : : "i" (__FILE__), "i" (__LINE__), \ >> + "i" (flags), \ >> "i" (sizeof(struct bug_entry))); \ >> } while (0) > > This is an awesome hack, but is there really nothing we can do to make > it more readable? Esp, that global asm doing the macro definition is a > pain to read. > > Also, can we pretty please used named operands in 'new' code?
It is hard to make the code readable in C, readable in the generated asm, and to follow the coding style imposed by checkpatch (e.g., no space between the newline and the asm argument before it).
I considered wrapping the asm macro in a C macro, but AFAIK C macros cannot emit backslashes.
I thought of suggesting to change “ins” into a vararg and removing the escaped double-quotes in the C macro, but you ask to use named operands.
So I am out of ideas. Do you have anything else in mind?
Thanks, Nadav | |