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riscv: Access gd with inline assembly when building with LTO or Clang

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Similar to AArch64's case, Clang may wrongly fold accesses to gd pointer
which is defined with register qualifier into constants, breaking
various components.

This patch defines gd as a macro when building with Clang or LTO, which
expands to get_gd() that accesses gp pointer in assembly, making RISC-V
ports function properly and preparing for introduction of LTO in the
future. Board initialization code is also adapted for non-assignable gd.

Reported-by: Nathaniel Hourt <I@nathaniel.land>
Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
This commit is contained in:
Yao Zi
2025-04-27 14:50:11 +00:00
committed by Leo Yu-Chi Liang
parent 6016308094
commit 307666be28
4 changed files with 33 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
arch/riscv/cpu/cpu.c
View File

@@ -18,6 +18,7 @@
#include <asm/hwcap.h>
#include <asm/cpufeature.h>
#include <asm/cache.h>
#include <asm/global_data.h>
#include <dm/uclass-internal.h>
#include <linux/bitops.h>
#include <linux/log2.h>
@@ -746,3 +747,8 @@ __weak int cleanup_before_linux(void)
return 0;
}
void arch_setup_gd(gd_t *new_gd)
{
set_gd(new_gd);
}

19
arch/riscv/include/asm/global_data.h
View File

@@ -14,6 +14,7 @@
#include <asm/smp.h>
#include <asm/u-boot.h>
#include <compiler.h>
#include <config.h>
/* Architecture-specific global data */
struct arch_global_data {
@@ -47,8 +48,26 @@ struct arch_global_data {
#include <asm-generic/global_data.h>
#if defined(__clang__) || CONFIG_IS_ENABLED(LTO)
#define DECLARE_GLOBAL_DATA_PTR
#define gd get_gd()
static inline gd_t *get_gd(void)
{
gd_t *gd_ptr;
__asm__ volatile ("mv %0, gp\n" : "=r" (gd_ptr));
return gd_ptr;
}
#else
#define DECLARE_GLOBAL_DATA_PTR register gd_t *gd asm ("gp")
#endif
static inline void set_gd(volatile gd_t *gd_ptr)
{
#ifdef CONFIG_64BIT

4
common/board_r.c
View File

@@ -815,7 +815,9 @@ void board_init_r(gd_t *new_gd, ulong dest_addr)
if (CONFIG_IS_ENABLED(X86_64) && !IS_ENABLED(CONFIG_EFI_APP))
arch_setup_gd(new_gd);
#if !defined(CONFIG_X86) && !defined(CONFIG_ARM) && !defined(CONFIG_ARM64)
#if defined(CONFIG_RISCV)
set_gd(new_gd);
#elif !defined(CONFIG_X86) && !defined(CONFIG_ARM) && !defined(CONFIG_ARM64)
gd = new_gd;
#endif
gd->flags &= ~GD_FLG_LOG_READY;

7
common/init/board_init.c
View File

@@ -13,8 +13,11 @@
DECLARE_GLOBAL_DATA_PTR;
/* Unfortunately x86 or ARM can't compile this code as gd cannot be assigned */
#if !defined(CONFIG_X86) && !defined(CONFIG_ARM)
/*
* Unfortunately x86, ARM and RISC-V can't compile this code as gd is defined
* as macro and cannot be assigned.
*/
#if !defined(CONFIG_X86) && !defined(CONFIG_ARM) && !defined(CONFIG_RISCV)
__weak void arch_setup_gd(struct global_data *gd_ptr)
{
gd = gd_ptr;