From 8645370af18979123d9e94e3ed215d23dd740721 Mon Sep 17 00:00:00 2001 From: Palmer Dabbelt Date: Thu, 13 Jan 2022 18:10:19 -0800 Subject: [PATCH] RISC-V: Document the degree of position independence that medany affords The code generated by -mcmodel=medany is defined to be position-independent, but is not guaranteed to function correctly when linked into position-independent executables or libraries. See the recent discussion at the psABI specification [1] for more details. It would be better to reject these invalid sequences when linking, but as pointed out in a recent LD bug [2] there may be some compatibility issues related to the PCREL_HI20 relocations used to initialize GP. Given the complexity here it's unlikely we'll be able to reject these sequences any time soon, so instead just document that these may not work. [1]: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/issues/245 [2]: https://sourceware.org/bugzilla/show_bug.cgi?id=28789 gcc/ChangeLog: * doc/invoke.texi (RISC-V -mcmodel=medany): Document the degree of position independence that -mcmodel=medany affords. Signed-off-by: Palmer Dabbelt --- gcc/doc/invoke.texi | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index fb3dec4ab0c..ec291c06542 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -27772,6 +27772,10 @@ Generate code for the medium-any code model. The program and its statically defined symbols must be within any single 2 GiB address range. Programs can be statically or dynamically linked. +The code generated by the medium-any code model is position-independent, but is +not guaranteed to function correctly when linked into position-independent +executables or libraries. + @item -mexplicit-relocs @itemx -mno-exlicit-relocs Use or do not use assembler relocation operators when dealing with symbolic