ARM: assembler: define a Kconfig symbol for group relocation support

Nathan reports the group relocations go out of range in pathological
cases such as allyesconfig kernels, which have little chance of actually
booting but are still used in validation.

So add a Kconfig symbol for this feature, and make it depend on
!COMPILE_TEST.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 359a3b85c8b37b9e864a3671ae9c7365db365855..70ab8d807032f873dcfd959f93e4cbd073186b14 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -128,7 +128,7 @@ config ARM
        select RTC_LIB
        select SYS_SUPPORTS_APM_EMULATION
        select THREAD_INFO_IN_TASK
-       select HAVE_ARCH_VMAP_STACK if MMU && (!LD_IS_LLD || LLD_VERSION >= 140000)
+       select HAVE_ARCH_VMAP_STACK if MMU && ARM_HAS_GROUP_RELOCS
        select TRACE_IRQFLAGS_SUPPORT if !CPU_V7M
        # Above selects are sorted alphabetically; please add new ones
        # according to that.  Thanks.
@@ -140,6 +140,17 @@ config ARM
          Europe.  There is an ARM Linux project with a web page at
          <http://www.arm.linux.org.uk/>.
 
+config ARM_HAS_GROUP_RELOCS
+       def_bool y
+       depends on !LD_IS_LLD || LLD_VERSION >= 140000
+       depends on !COMPILE_TEST
+       help
+         Whether or not to use R_ARM_ALU_PC_Gn or R_ARM_LDR_PC_Gn group
+         relocations, which have been around for a long time, but were not
+         supported in LLD until version 14. The combined range is -/+ 256 MiB,
+         which is usually sufficient, but not for allyesconfig, so we disable
+         this feature when doing compile testing.
+
 config ARM_HAS_SG_CHAIN
        bool
 

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 59d7b9e819346d3a55e82b3fdb6bde1a7900902a..9998718a49ca2253324fb5a1f568d3d8480c60ba 100644 (file)
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -656,8 +656,8 @@ THUMB(      orr     \reg , \reg , #PSR_T_BIT        )
 
        .macro          __ldst_va, op, reg, tmp, sym, cond
 #if __LINUX_ARM_ARCH__ >= 7 || \
-    (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS)) || \
-    (defined(CONFIG_LD_IS_LLD) && CONFIG_LLD_VERSION < 140000)
+    !defined(CONFIG_ARM_HAS_GROUP_RELOCS) || \
+    (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
        mov_l           \tmp, \sym, \cond
        \op\cond        \reg, [\tmp]
 #else
@@ -716,8 +716,8 @@ THUMB(      orr     \reg , \reg , #PSR_T_BIT        )
         */
        .macro          ldr_this_cpu, rd:req, sym:req, t1:req, t2:req
 #if __LINUX_ARM_ARCH__ >= 7 || \
-    (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS)) || \
-    (defined(CONFIG_LD_IS_LLD) && CONFIG_LLD_VERSION < 140000)
+    !defined(CONFIG_ARM_HAS_GROUP_RELOCS) || \
+    (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
        this_cpu_offset \t1
        mov_l           \t2, \sym
        ldr             \rd, [\t1, \t2]

diff --git a/arch/arm/include/asm/current.h b/arch/arm/include/asm/current.h
index 2f9d79214b25bb592fc2a198783715ca4a9939d6..131a89bbec6ba8f802196fda7be684d188b7862c 100644 (file)
--- a/arch/arm/include/asm/current.h
+++ b/arch/arm/include/asm/current.h
@@ -37,8 +37,8 @@ static inline __attribute_const__ struct task_struct *get_current(void)
 #ifdef CONFIG_CPU_V6
            "1:                                                 \n\t"
            "   .subsection 1                                   \n\t"
-#if !(defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS)) && \
-    !(defined(CONFIG_LD_IS_LLD) && CONFIG_LLD_VERSION < 140000)
+#if defined(CONFIG_ARM_HAS_GROUP_RELOCS) && \
+    !(defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
            "2: " LOAD_SYM_ARMV6(%0, __current) "               \n\t"
            "   b       1b                                      \n\t"
 #else
@@ -55,8 +55,8 @@ static inline __attribute_const__ struct task_struct *get_current(void)
 #endif
            : "=r"(cur));
 #elif __LINUX_ARM_ARCH__>= 7 || \
-      (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS)) || \
-      (defined(CONFIG_LD_IS_LLD) && CONFIG_LLD_VERSION < 140000)
+      !defined(CONFIG_ARM_HAS_GROUP_RELOCS) || \
+      (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
        cur = __current;
 #else
        asm(LOAD_SYM_ARMV6(%0, __current) : "=r"(cur));

diff --git a/arch/arm/include/asm/percpu.h b/arch/arm/include/asm/percpu.h
index 28961d60877da960d07dc104481b5e053aa22dfb..a09034ae45a1c8c2677b24cf6891167aabbb6258 100644 (file)
--- a/arch/arm/include/asm/percpu.h
+++ b/arch/arm/include/asm/percpu.h
@@ -38,8 +38,8 @@ static inline unsigned long __my_cpu_offset(void)
 #ifdef CONFIG_CPU_V6
            "1:                                                 \n\t"
            "   .subsection 1                                   \n\t"
-#if !(defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS)) && \
-    !(defined(CONFIG_LD_IS_LLD) && CONFIG_LLD_VERSION < 140000)
+#if defined(CONFIG_ARM_HAS_GROUP_RELOCS) && \
+    !(defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
            "2: " LOAD_SYM_ARMV6(%0, __per_cpu_offset) "        \n\t"
            "   b       1b                                      \n\t"
 #else

diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index 4d33a7acf617e3e3318d9f86a36ef050d910ea18..549abcedf795178a6e17244ed086d64f26f8a890 100644 (file)
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -68,6 +68,7 @@ bool module_exit_section(const char *name)
                strstarts(name, ".ARM.exidx.exit");
 }
 
+#ifdef CONFIG_ARM_HAS_GROUP_RELOCS
 /*
  * This implements the partitioning algorithm for group relocations as
  * documented in the ARM AArch32 ELF psABI (IHI 0044).
@@ -103,6 +104,7 @@ static u32 get_group_rem(u32 group, u32 *offset)
        } while (group--);
        return shift;
 }
+#endif
 
 int
 apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
@@ -118,7 +120,9 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
                unsigned long loc;
                Elf32_Sym *sym;
                const char *symname;
+#ifdef CONFIG_ARM_HAS_GROUP_RELOCS
                u32 shift, group = 1;
+#endif
                s32 offset;
                u32 tmp;
 #ifdef CONFIG_THUMB2_KERNEL
@@ -249,6 +253,7 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
                        *(u32 *)loc = __opcode_to_mem_arm(tmp);
                        break;
 
+#ifdef CONFIG_ARM_HAS_GROUP_RELOCS
                case R_ARM_ALU_PC_G0_NC:
                        group = 0;
                        fallthrough;
@@ -296,7 +301,7 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
                        }
                        *(u32 *)loc = __opcode_to_mem_arm((tmp & ~0xfff) | offset);
                        break;
-
+#endif
 #ifdef CONFIG_THUMB2_KERNEL
                case R_ARM_THM_CALL:
                case R_ARM_THM_JUMP24: