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Message-Id: <20230424194911.264850-4-heiko.stuebner@vrull.eu>
Date: Mon, 24 Apr 2023 21:49:10 +0200
From: Heiko Stuebner <heiko@...ech.de>
To: palmer@...belt.com, linux-riscv@...ts.infradead.org,
paul.walmsley@...ive.com
Cc: heiko@...ech.de, kito.cheng@...ive.com, jrtc27@...c27.com,
conor.dooley@...rochip.com, matthias.bgg@...il.com,
heinrich.schuchardt@...onical.com, greentime.hu@...ive.com,
nick.knight@...ive.com, christoph.muellner@...ll.eu,
philipp.tomsich@...ll.eu, richard.henderson@...aro.org,
arnd@...db.de, linux-kernel@...r.kernel.org,
Heiko Stuebner <heiko.stuebner@...ll.eu>
Subject: [PATCH 3/4] RISC-V: export the ISA string of the running machine in the aux vector
From: Heiko Stuebner <heiko.stuebner@...ll.eu>
Already defined aux-vectors regarding the machine type are AT_PLATFORM
and AT_BASE_PLATFORM. PPC already uses AT_BASE_PLATFORM to identify the
real platform the system is running on, so do a similar thing on RISC-V
and export the ISA string of the running machine via this aux-vector
element.
This way userspace can possibly adapt to extensions that allow it to
run certain loads more performantly.
Signed-off-by: Heiko Stuebner <heiko.stuebner@...ll.eu>
---
arch/riscv/include/asm/elf.h | 10 ++++++++++
arch/riscv/kernel/cpu.c | 12 ++++++++++++
2 files changed, 22 insertions(+)
diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
index 30e7d2455960..820ef627e83d 100644
--- a/arch/riscv/include/asm/elf.h
+++ b/arch/riscv/include/asm/elf.h
@@ -78,6 +78,16 @@ extern unsigned long elf_hwcap;
#define COMPAT_ELF_PLATFORM (NULL)
+/*
+ * ELF_PLATFORM indicates the ISA supported by the platform, but has
+ * special meaning to ld.so .
+ * Expose the ISA string including all usable extensions via
+ * ELF_BASE_PLATFORM instead and allow userspace to adapt to them
+ * if needed.
+ */
+#define ELF_BASE_PLATFORM (riscv_base_platform)
+extern const char *riscv_base_platform;
+
#ifdef CONFIG_MMU
#define ARCH_DLINFO \
do { \
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 06c2f587a176..71770563199f 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -118,8 +118,12 @@ static int riscv_cpuinfo_starting(unsigned int cpu)
return 0;
}
+const char *riscv_base_platform = NULL;
+static char *riscv_create_isa_string(void);
+
static int __init riscv_cpuinfo_init(void)
{
+ char *isa_str;
int ret;
ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "riscv/cpuinfo:starting",
@@ -129,6 +133,14 @@ static int __init riscv_cpuinfo_init(void)
return ret;
}
+ /*
+ * Create the isa-string with the common set of extensions over
+ * all harts, to expose as AT_BASE_PLATFORM in the aux vector.
+ */
+ isa_str = riscv_create_isa_string();
+ if (!IS_ERR(isa_str))
+ riscv_base_platform = isa_str;
+
return 0;
}
arch_initcall(riscv_cpuinfo_init);
--
2.39.0
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