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riscv: vdso: Add symbols for the alternative section boundaries

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Currently the alternative sections are extracted from the vDSO
binaries at runtime. This has runtime overhead and also doesn't
work for the compat vDSO.

Extract the offsets of the alternative section during the build with the
existing symbol extraction machinery.

Also add dummy symbols as fallback.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://patch.msgid.link/20260630-riscv-vdso32-alternative-v1-1-a32fd89b7b1c@linutronix.de
Signed-off-by: Paul Walmsley <pjw@kernel.org>
This commit is contained in:
Thomas Weißschuh 2026-08-07 19:24:33 -06:00 committed by Paul Walmsley
parent f61959a3a8
commit 7f2a7bbcd9
2 changed files with 8 additions and 0 deletions
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6
arch/riscv/include/asm/vdso.h
View File

@ -19,10 +19,14 @@
#ifdef CONFIG_MMU
#include <generated/vdso-offsets.h>
#else
extern size_t __vdso_alternatives_start_offset, __vdso_alternatives_end_offset;
#endif
#ifdef CONFIG_RISCV_USER_CFI
#include <generated/vdso-cfi-offsets.h>
#else
extern size_t __vdso_alternatives_start_cfi_offset, __vdso_alternatives_end_cfi_offset;
#endif
#ifdef CONFIG_RISCV_USER_CFI
@ -41,6 +45,8 @@
#define COMPAT_VDSO_SYMBOL(base, name) \
(void __user *)((unsigned long)(base) + compat__vdso_##name##_offset)
#else
extern size_t compat__vdso_alternatives_start_offset, compat__vdso_alternatives_end_offset;
#endif /* CONFIG_COMPAT */
extern char vdso_start[], vdso_end[];

2
arch/riscv/kernel/vdso/vdso.lds.S
View File

@ -45,9 +45,11 @@ SECTIONS
.text : { *(.text .text.*) } :text
. = ALIGN(4);
__vdso_alternatives_start = .;
.alternative : {
*(.alternative)
}
__vdso_alternatives_end = .;
}
/*