[PATCH v3] Use ELF_BASE_PLATFORM to pass ISA level

[PATCH v3] Use ELF_BASE_PLATFORM to pass ISA level

[YunQiang Su]

Some userland application/program runtime/dynamic loaded need to
know about the current ISA level to use the best runtime.
While kernel doesn't provides this info.

ELF_PLATFORM only provides some info about the CPU, with very few info,
for example, the value is "mips" for both 24Kc and P6600.

Currently ELF_BASE_PLATFORM is not used by MIPS (only by powerpc).
So we cant set its value as:
  mips2, mips3, mips4, mips5,
  mips32, mips32r2, mips32r6
  mips64, mips64r2, mips64r6
Then in userland, we can get it by:
  getauxval(AT_BASE_PLATFORM)

The only problem is that it seems has different defination than ppc:
  on ppc, it is the mircoarchitecture
while now we use it as ISA level on MIPS.

v2->v3:
  no need to init static data with 0.
v1->v2:
  add Signed-off-by and Reviewer-by Jiaxun Yang.

Signed-off-by: YunQiang Su <syq@debian.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
 arch/mips/include/asm/elf.h  |  3 +++
 arch/mips/kernel/cpu-probe.c | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index f8f44b1a6cbb..5aa29ced6970 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -445,6 +445,9 @@ extern unsigned int elf_hwcap;
 #define ELF_PLATFORM  __elf_platform
 extern const char *__elf_platform;
 
+#define ELF_BASE_PLATFORM  __elf_base_platform
+extern const char *__elf_base_platform;
+
 /*
  * See comments in asm-alpha/elf.h, this is the same thing
  * on the MIPS.
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index 6ab6b03d35ba..82577d4e4ba1 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -513,6 +513,13 @@ static inline void set_elf_platform(int cpu, const char *plat)
 		__elf_platform = plat;
 }
 
+static inline void set_elf_base_platform(const char *plat)
+{
+	if(__elf_base_platform == NULL) {
+		__elf_base_platform = plat;
+	}
+}
+
 static inline void cpu_probe_vmbits(struct cpuinfo_mips *c)
 {
 #ifdef __NEED_VMBITS_PROBE
@@ -527,36 +534,46 @@ static void set_isa(struct cpuinfo_mips *c, unsigned int isa)
 	switch (isa) {
 	case MIPS_CPU_ISA_M64R2:
 		c->isa_level |= MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2;
+		set_elf_base_platform("mips64r2");
 		/* fall through */
 	case MIPS_CPU_ISA_M64R1:
 		c->isa_level |= MIPS_CPU_ISA_M32R1 | MIPS_CPU_ISA_M64R1;
+		set_elf_base_platform("mips64");
 		/* fall through */
 	case MIPS_CPU_ISA_V:
 		c->isa_level |= MIPS_CPU_ISA_V;
+		set_elf_base_platform("mips5");
 		/* fall through */
 	case MIPS_CPU_ISA_IV:
 		c->isa_level |= MIPS_CPU_ISA_IV;
+		set_elf_base_platform("mips4");
 		/* fall through */
 	case MIPS_CPU_ISA_III:
 		c->isa_level |= MIPS_CPU_ISA_II | MIPS_CPU_ISA_III;
+		set_elf_base_platform("mips3");
 		break;
 
 	/* R6 incompatible with everything else */
 	case MIPS_CPU_ISA_M64R6:
 		c->isa_level |= MIPS_CPU_ISA_M32R6 | MIPS_CPU_ISA_M64R6;
+		set_elf_base_platform("mips64r6");
 		/* fall through */
 	case MIPS_CPU_ISA_M32R6:
 		c->isa_level |= MIPS_CPU_ISA_M32R6;
+		set_elf_base_platform("mips32r6");
 		/* Break here so we don't add incompatible ISAs */
 		break;
 	case MIPS_CPU_ISA_M32R2:
 		c->isa_level |= MIPS_CPU_ISA_M32R2;
+		set_elf_base_platform("mips32r2");
 		/* fall through */
 	case MIPS_CPU_ISA_M32R1:
 		c->isa_level |= MIPS_CPU_ISA_M32R1;
+		set_elf_base_platform("mips32");
 		/* fall through */
 	case MIPS_CPU_ISA_II:
 		c->isa_level |= MIPS_CPU_ISA_II;
+		set_elf_base_platform("mips2");
 		break;
 	}
 }
@@ -2113,6 +2130,7 @@ EXPORT_SYMBOL(__ua_limit);
 
 const char *__cpu_name[NR_CPUS];
 const char *__elf_platform;
+const char *__elf_base_platform;
 
 void cpu_probe(void)
 {
-- 
2.25.1

Re: [PATCH v3] Use ELF_BASE_PLATFORM to pass ISA level

[Thomas Bogendoerfer]

On Sat, Mar 07, 2020 at 10:39:45AM +0800, YunQiang Su wrote:
> Some userland application/program runtime/dynamic loaded need to
> know about the current ISA level to use the best runtime.
> While kernel doesn't provides this info.
> 
> ELF_PLATFORM only provides some info about the CPU, with very few info,
> for example, the value is "mips" for both 24Kc and P6600.
> 
> Currently ELF_BASE_PLATFORM is not used by MIPS (only by powerpc).
> So we cant set its value as:
>   mips2, mips3, mips4, mips5,
>   mips32, mips32r2, mips32r6
>   mips64, mips64r2, mips64r6
> Then in userland, we can get it by:
>   getauxval(AT_BASE_PLATFORM)
> 
> The only problem is that it seems has different defination than ppc:
>   on ppc, it is the mircoarchitecture
> while now we use it as ISA level on MIPS.
> 
> v2->v3:
>   no need to init static data with 0.
> v1->v2:
>   add Signed-off-by and Reviewer-by Jiaxun Yang.
> 
> Signed-off-by: YunQiang Su <syq@debian.org>
> Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---

Applied to mips-next. BTW I prefer to have the changelog below the ---

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]