Date: Fri, 17 Jan 2020 17:03:25 +0000 (UTC) From: Mitchell Horne <mhorne@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r356835 - head/sys/riscv/riscv Message-ID: <202001171703.00HH3P52055181@repo.freebsd.org>
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Author: mhorne Date: Fri Jan 17 17:03:25 2020 New Revision: 356835 URL: https://svnweb.freebsd.org/changeset/base/356835 Log: RISC-V: fix global pointer assignment at boot As part of the RISC-V ABI, the gp register is expected to initialized with the address of __global_pointer$ as early as possible. This allows loads and stores from .sdata to be relaxed based on the value of gp. In locore.S we do this initialization twice, once each for va and mpva. However, in both cases the initialization is preceded by an la instruction, which in theory could be relaxed by the linker. Move the initialization of gp to be slightly earlier (before la cpu_exception_handler), and add an additional gp initialization at the very beginning of _start, before virtual memory is set up. Reported by: jrtc27 Reviewed by: jrtc27 Differential Revision: https://reviews.freebsd.org/D23139 Modified: head/sys/riscv/riscv/locore.S Modified: head/sys/riscv/riscv/locore.S ============================================================================== --- head/sys/riscv/riscv/locore.S Fri Jan 17 16:48:20 2020 (r356834) +++ head/sys/riscv/riscv/locore.S Fri Jan 17 17:03:25 2020 (r356835) @@ -53,6 +53,12 @@ .text .globl _start _start: + /* Set the global pointer */ +.option push +.option norelax + lla gp, __global_pointer$ +.option pop + /* Get the physical address kernel loaded to */ lla t0, virt_map ld t1, 0(t0) @@ -168,6 +174,11 @@ _start: .align 2 va: + /* Set the global pointer again, this time with the virtual address. */ +.option push +.option norelax + lla gp, __global_pointer$ +.option pop /* Setup supervisor trap vector */ la t0, cpu_exception_handler @@ -177,12 +188,6 @@ va: li t0, 0 csrw sscratch, t0 - /* Set the global pointer */ -.option push -.option norelax - la gp, __global_pointer$ -.option pop - /* Initialize stack pointer */ la s3, initstack_end mv sp, s3 @@ -322,6 +327,12 @@ ENTRY(mpentry) .align 2 mpva: + /* Set the global pointer again, this time with the virtual address. */ +.option push +.option norelax + lla gp, __global_pointer$ +.option pop + /* Setup supervisor trap vector */ la t0, cpu_exception_handler csrw stvec, t0 @@ -329,12 +340,6 @@ mpva: /* Ensure sscratch is zero */ li t0, 0 csrw sscratch, t0 - - /* Set the global pointer */ -.option push -.option norelax - la gp, __global_pointer$ -.option pop call init_secondary END(mpentry)
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