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Use ELF_BASE_PLATFORM to pass ISA level

PATCH Applied YunQiang Su 2 participants 2 messages Mar 7, 2020 – Mar 19, 2020

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YunQiang Su

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PATCH v3 1/1 Use ELF_BASE_PLATFORM to pass ISA level

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 <[email protected]>
Reviewed-by Jiaxun Yang <[email protected]>
---
 arch/mips/include/asm/elf.h  |  3 +++
 arch/mips/kernel/cpu-probe.c | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+)
arch/mips/include/asm/elf.h +3 -0
index f8f44b1a6cbb..5aa29ced6970 100644
@@ -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.
arch/mips/kernel/cpu-probe.c +18 -0
index 6ab6b03d35ba..82577d4e4ba1 100644
@@ -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)
 {
Signature · 1 line
2.25.1
maintainer Applied
#1 lore raw
Quoted 19 lines · 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.

Quoted 8 lines

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 <[email protected]>
Reviewed-by Jiaxun Yang <[email protected]>

---

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

Thomas.

Signature · 2 lines
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]