riscv: Remove support for variable page sizes

System Internals / glibc - Florian Weimer [redhat.com] - 7 October 2019 17:03 EDT

_dl_var_init is used to patch the read-only data section after relocation. Several architectures use this to update GLRO(page_size) with the correct value for the static dlopen case, where _rtld_global_ro has not been initialized by the dynamic loader.

RISC-V does not need this. The RISC-V Instruction Set Manual,
Volume II: Privileged Architecture, Document Version 20190608-Priv-MSU-Ratified says this:

After much deliberation, we have settled on a conventional page size of 4 KiB for both RV32 and RV64. We expect this decision to ease the porting of low-level runtime software and device drivers. The TLB reach problem is ameliorated by transparent superpage support in modern operating systems [2]. Additionally, multi-level TLB hierarchies are quite inexpensive relative to the multi-level cache hierarchies whose address space they map.

[2] Juan Navarro, Sitaram Iyer, Peter Druschel, and Alan Cox. Practical, transparent operating system support for superpages. SIGOPS Oper. Syst. Rev., 36(SI):89–104, December 2002.

This means that the initialization of _rtld_global_ro._dl_page_size in elf/rtld.c with EXEC_PAGESIZE is sufficient for RISC-V.

921abe4729 riscv: Remove support for variable page sizes
ChangeLog | 8 +++
sysdeps/unix/sysv/linux/riscv/Makefile | 4 --
sysdeps/unix/sysv/linux/riscv/dl-static.c | 84 -------------------------------
sysdeps/unix/sysv/linux/riscv/ldsodefs.h | 32 ------------
4 files changed, 8 insertions(+), 120 deletions(-)

Upstream: sourceware.org


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