[RFC PATCH v1 4/4] powerpc/static_call: Implement inline static calls
From: Christophe Leroy <hidden>
Date: 2022-05-25 15:59:13
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), objtool, static branch/call, the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Josh Poimboeuf, Peter Zijlstra, Jason Baron, Alice Ryhl, Linus Torvalds
Implement inline static calls: - Put a 'bl' to the destination function - Put a 'nop' when the destination function is NULL - Put a 'li r3,0' when the destination is the RET0 function For the time being it only works if the destination is within 32Mb from the caller. Signed-off-by: Christophe Leroy <redacted> --- arch/powerpc/Kconfig | 1 + arch/powerpc/include/asm/static_call.h | 2 + arch/powerpc/kernel/static_call.c | 41 ++++++++++++------- tools/objtool/arch/powerpc/include/arch/elf.h | 1 + 4 files changed, 31 insertions(+), 14 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 5ef8bf8eb202..3257a1c258d8 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig@@ -246,6 +246,7 @@ config PPC select HAVE_STACKPROTECTOR if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2) select HAVE_STACKPROTECTOR if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13) select HAVE_STATIC_CALL if PPC32 + select HAVE_STATIC_CALL_INLINE if PPC32 select HAVE_SYSCALL_TRACEPOINTS select HAVE_VIRT_CPU_ACCOUNTING select HUGETLB_PAGE_SIZE_VARIABLE if PPC_BOOK3S_64 && HUGETLB_PAGE
diff --git a/arch/powerpc/include/asm/static_call.h b/arch/powerpc/include/asm/static_call.h
index de1018cc522b..e3d5d3823dac 100644
--- a/arch/powerpc/include/asm/static_call.h
+++ b/arch/powerpc/include/asm/static_call.h@@ -26,4 +26,6 @@ #define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) __PPC_SCT(name, "blr") #define ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name) __PPC_SCT(name, "b .+20") +#define CALL_INSN_SIZE 4 + #endif /* _ASM_POWERPC_STATIC_CALL_H */
diff --git a/arch/powerpc/kernel/static_call.c b/arch/powerpc/kernel/static_call.c
index 863a7aa24650..fd25954cfd24 100644
--- a/arch/powerpc/kernel/static_call.c
+++ b/arch/powerpc/kernel/static_call.c@@ -9,25 +9,38 @@ void arch_static_call_transform(void *site, void *tramp, void *func, bool tail) int err; bool is_ret0 = (func == __static_call_return0); unsigned long target = (unsigned long)(is_ret0 ? tramp + PPC_SCT_RET0 : func); - bool is_short = is_offset_in_branch_range((long)target - (long)tramp); - - if (!tramp) - return; mutex_lock(&text_mutex); - if (func && !is_short) { - err = patch_instruction(tramp + PPC_SCT_DATA, ppc_inst(target)); - if (err) - goto out; + if (tramp) { + bool is_short = is_offset_in_branch_range((long)target - (long)tramp); + + if (func && !is_short) { + err = patch_instruction(tramp + PPC_SCT_DATA, ppc_inst(target)); + if (err) + goto out; + } + + if (!func) + err = patch_instruction(tramp, ppc_inst(PPC_RAW_BLR())); + else if (is_short) + err = patch_branch(tramp, target, 0); + else + err = patch_instruction(tramp, ppc_inst(PPC_RAW_NOP())); } - if (!func) - err = patch_instruction(tramp, ppc_inst(PPC_RAW_BLR())); - else if (is_short) - err = patch_branch(tramp, target, 0); - else - err = patch_instruction(tramp, ppc_inst(PPC_RAW_NOP())); + if (site) { + bool is_short = is_offset_in_branch_range((long)func - (long)site); + + if (!func) + err = patch_instruction(site, ppc_inst(PPC_RAW_NOP())); + else if (is_ret0) + err = patch_instruction(site, ppc_inst(PPC_RAW_LI(_R3, 0))); + else if (is_short) + err = patch_branch(site, target, BRANCH_SET_LINK); + else + panic("%s: function %pS is out of reach of %pS\n", __func__, func, site); + } out: mutex_unlock(&text_mutex);
diff --git a/tools/objtool/arch/powerpc/include/arch/elf.h b/tools/objtool/arch/powerpc/include/arch/elf.h
index 3c8ebb7d2a6b..18784c764c14 100644
--- a/tools/objtool/arch/powerpc/include/arch/elf.h
+++ b/tools/objtool/arch/powerpc/include/arch/elf.h@@ -4,5 +4,6 @@ #define _OBJTOOL_ARCH_ELF #define R_NONE R_PPC_NONE +#define R_REL32 R_PPC_REL32 #endif /* _OBJTOOL_ARCH_ELF */
--
2.35.3