Re: [PATCH v1 1/4] xen: introduce CONFIG_GENERIC_BUG_FRAME

[Oleksii <oleksii.kurochko@xxxxxxxxx>]

Hello Jan and community,

I experimented and switched RISC-V to x86 implementation. All that I
changed in x86 implementation for RISC-V was _ASM_BUGFRAME_TEXT. Other
things are the same as for x86.

For RISC-V it is fine to skip '%c' modifier so _ASM_BUGFRAME_TEXT will
look like:

#define _ASM_BUGFRAME_TEXT(second_frame) \
    ".Lbug%=: ebreak\n"   
    ".pushsection .bug_frames.%[bf_type], \"a\", @progbits\n"
    ".p2align 2\n"
    ".Lfrm%=:\n"
    ".long (.Lbug%= - .Lfrm%=) + %[bf_line_hi]\n"
    ".long (%[bf_ptr] - .Lfrm%=) + %[bf_line_lo]\n"
    ".if " #second_frame "\n"
    ".long 0, %[bf_msg] - .Lfrm%=\n"
    ".endif\n"
    ".popsection\n"

The only thing I am worried about is:

#define _ASM_BUGFRAME_INFO(type, line, ptr, msg) \
  [bf_type] "i" (type), ...
because as I understand it can be an issue with 'i' modifier in case of
PIE. I am not sure that Xen enables PIE somewhere but still...
If it is not an issue then we can use x86 implementation as a generic
one.

Could you please share your thoughts about that?

~ Oleksii