[PATCH v4 5/6] powerpc/64: Add support for out-of-line static calls
Benjamin Gray
bgray at linux.ibm.com
Mon Oct 10 11:29:56 AEDT 2022
Implement static call support for 64 bit V2 ABI. This requires making
sure the TOC is kept correct across kernel-module boundaries. As a
secondary concern, it tries to use the local entry point of a target
wherever possible. It does so by checking if both tramp & target are
kernel code, and falls back to detecting the common global entry point
patterns if modules are involved. Detecting the global entry point is
also required for setting the local entry point as the trampoline
target: if we cannot detect the local entry point, then we need to
convservatively initialise r12 and use the global entry point.
The trampolines are marked with `.localentry NAME, 1` to make the
linker save and restore the TOC on each call to the trampoline. This
allows the trampoline to safely target functions with different TOC
values.
However this directive also implies the TOC is not initialised on entry
to the trampoline. The kernel TOC is easily found in the PACA, but not
an arbitrary module TOC. Therefore the trampoline implementation depends
on whether it's in the kernel or not. If in the kernel, we initialise
the TOC using the PACA. If in a module, we have to initialise the TOC
with zero context, so it's quite expensive.
Signed-off-by: Benjamin Gray <bgray at linux.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy at csgroup.eu>
---
arch/powerpc/Kconfig | 14 ++-
arch/powerpc/include/asm/code-patching.h | 1 +
arch/powerpc/include/asm/static_call.h | 80 +++++++++++++-
arch/powerpc/kernel/Makefile | 3 +-
arch/powerpc/kernel/static_call.c | 130 +++++++++++++++++++++--
5 files changed, 216 insertions(+), 12 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 4c466acdc70d..962e36ec34ec 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -102,6 +102,18 @@ config GENERIC_HWEIGHT
bool
default y
+config TOOLCHAIN_SUPPORTS_LOCALENTRY1
+ bool
+ depends on PPC64_ELF_ABI_V2
+ default y if LD_VERSION >= 23200 || LLD_VERSION >= 110000
+ help
+ A section of the ELF symbol st_other field can be given the value 1
+ using the directive '.localentry NAME, 1' to mean the local and global
+ entry points are the same, and r2 should be treated as caller-saved.
+
+ Older versions of Clang and binutils do not recognise this form of the
+ directive and will error if it is used.
+
config PPC
bool
default y
@@ -248,7 +260,7 @@ config PPC
select HAVE_SOFTIRQ_ON_OWN_STACK
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 if PPC32 || (PPC64_ELF_ABI_V2 && TOOLCHAIN_SUPPORTS_LOCALENTRY1)
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/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index 170bfa848c7c..cb4629e55e57 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -152,6 +152,7 @@ int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src);
bool is_conditional_branch(ppc_inst_t instr);
#define OP_RT_RA_MASK 0xffff0000UL
+#define OP_SI_MASK 0x0000ffffUL
#define LIS_R2 (PPC_RAW_LIS(_R2, 0))
#define ADDIS_R2_R12 (PPC_RAW_ADDIS(_R2, _R12, 0))
#define ADDI_R2_R2 (PPC_RAW_ADDI(_R2, _R2, 0))
diff --git a/arch/powerpc/include/asm/static_call.h b/arch/powerpc/include/asm/static_call.h
index de1018cc522b..3d6e82200cb7 100644
--- a/arch/powerpc/include/asm/static_call.h
+++ b/arch/powerpc/include/asm/static_call.h
@@ -2,12 +2,75 @@
#ifndef _ASM_POWERPC_STATIC_CALL_H
#define _ASM_POWERPC_STATIC_CALL_H
+#ifdef CONFIG_PPC64_ELF_ABI_V2
+
+#ifdef MODULE
+
+#define __PPC_SCT(name, inst) \
+ asm(".pushsection .text, \"ax\" \n" \
+ ".align 6 \n" \
+ ".globl " STATIC_CALL_TRAMP_STR(name) " \n" \
+ ".localentry " STATIC_CALL_TRAMP_STR(name) ", 1 \n" \
+ STATIC_CALL_TRAMP_STR(name) ": \n" \
+ " mflr 11 \n" \
+ " bcl 20, 31, $+4 \n" \
+ "0: mflr 12 \n" \
+ " mtlr 11 \n" \
+ " addi 12, 12, (" STATIC_CALL_TRAMP_STR(name) " - 0b) \n" \
+ " addis 2, 12, (.TOC.-" STATIC_CALL_TRAMP_STR(name) ")@ha \n" \
+ " addi 2, 2, (.TOC.-" STATIC_CALL_TRAMP_STR(name) ")@l \n" \
+ " " inst " \n" \
+ " ld 12, (2f - " STATIC_CALL_TRAMP_STR(name) ")(12) \n" \
+ " mtctr 12 \n" \
+ " bctr \n" \
+ "1: li 3, 0 \n" \
+ " blr \n" \
+ ".balign 8 \n" \
+ "2: .8byte 0 \n" \
+ ".type " STATIC_CALL_TRAMP_STR(name) ", @function \n" \
+ ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
+ ".popsection \n")
+
+#else /* KERNEL */
+
+#define __PPC_SCT(name, inst) \
+ asm(".pushsection .text, \"ax\" \n" \
+ ".align 5 \n" \
+ ".globl " STATIC_CALL_TRAMP_STR(name) " \n" \
+ ".localentry " STATIC_CALL_TRAMP_STR(name) ", 1 \n" \
+ STATIC_CALL_TRAMP_STR(name) ": \n" \
+ " ld 2, 16(13) \n" \
+ " " inst " \n" \
+ " addis 12, 2, 2f at toc@ha \n" \
+ " ld 12, 2f at toc@l(12) \n" \
+ " mtctr 12 \n" \
+ " bctr \n" \
+ "1: li 3, 0 \n" \
+ " blr \n" \
+ ".balign 8 \n" \
+ "2: .8byte 0 \n" \
+ ".type " STATIC_CALL_TRAMP_STR(name) ", @function \n" \
+ ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
+ ".popsection \n")
+
+#endif /* MODULE */
+
+#define PPC_SCT_INST_MODULE 28 /* Offset of instruction to update */
+#define PPC_SCT_RET0_MODULE 44 /* Offset of label 1 */
+#define PPC_SCT_DATA_MODULE 56 /* Offset of label 2 (aligned) */
+
+#define PPC_SCT_INST_KERNEL 4 /* Offset of instruction to update */
+#define PPC_SCT_RET0_KERNEL 24 /* Offset of label 1 */
+#define PPC_SCT_DATA_KERNEL 32 /* Offset of label 2 (aligned) */
+
+#elif defined(CONFIG_PPC32)
+
#define __PPC_SCT(name, inst) \
asm(".pushsection .text, \"ax\" \n" \
".align 5 \n" \
".globl " STATIC_CALL_TRAMP_STR(name) " \n" \
STATIC_CALL_TRAMP_STR(name) ": \n" \
- inst " \n" \
+ " " inst " \n" \
" lis 12,2f at ha \n" \
" lwz 12,2f at l(12) \n" \
" mtctr 12 \n" \
@@ -19,11 +82,20 @@
".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
".popsection \n")
-#define PPC_SCT_RET0 20 /* Offset of label 1 */
-#define PPC_SCT_DATA 28 /* Offset of label 2 */
+#define PPC_SCT_INST_MODULE 0 /* Offset of instruction to update */
+#define PPC_SCT_RET0_MODULE 20 /* Offset of label 1 */
+#define PPC_SCT_DATA_MODULE 28 /* Offset of label 2 */
+
+#define PPC_SCT_INST_KERNEL PPC_SCT_INST_MODULE
+#define PPC_SCT_RET0_KERNEL PPC_SCT_RET0_MODULE
+#define PPC_SCT_DATA_KERNEL PPC_SCT_DATA_MODULE
+
+#else /* !CONFIG_PPC64_ELF_ABI_V2 && !CONFIG_PPC32 */
+#error "Unsupported ABI"
+#endif /* CONFIG_PPC64_ELF_ABI_V2 */
#define ARCH_DEFINE_STATIC_CALL_TRAMP(name, func) __PPC_SCT(name, "b " #func)
#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 ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name) __PPC_SCT(name, "b 1f")
#endif /* _ASM_POWERPC_STATIC_CALL_H */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 06d2d1f78f71..a30d0d0f5499 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -128,8 +128,9 @@ extra-y += vmlinux.lds
obj-$(CONFIG_RELOCATABLE) += reloc_$(BITS).o
-obj-$(CONFIG_PPC32) += entry_32.o setup_32.o early_32.o static_call.o
+obj-$(CONFIG_PPC32) += entry_32.o setup_32.o early_32.o
obj-$(CONFIG_PPC64) += dma-iommu.o iommu.o
+obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o
obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_BOOTX_TEXT) += btext.o
obj-$(CONFIG_SMP) += smp.o
diff --git a/arch/powerpc/kernel/static_call.c b/arch/powerpc/kernel/static_call.c
index 863a7aa24650..9211b2e189bb 100644
--- a/arch/powerpc/kernel/static_call.c
+++ b/arch/powerpc/kernel/static_call.c
@@ -1,33 +1,151 @@
// SPDX-License-Identifier: GPL-2.0
+#include <linux/bitops.h>
#include <linux/memory.h>
#include <linux/static_call.h>
#include <asm/code-patching.h>
+static long sign_extend_long(unsigned long value, int index)
+{
+ if (sizeof(long) == 8)
+ return sign_extend64(value, index);
+ else
+ return sign_extend32(value, index);
+}
+
+static void *ppc_function_toc(u32 *func)
+{
+ if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2)) {
+ /* There are two common global entry sequences we handle below
+ *
+ * 1. addis r2, r12, SI1
+ * addi r2, SI2
+ *
+ * 2. lis r2, SI1
+ * addi r2, SI2
+ *
+ * Where r12 contains the global entry point address (it is otherwise
+ * uninitialised, so doesn't matter what value we use if this is not
+ * a separate global entry point).
+ *
+ * Here we simulate running the given sequence and return the result it
+ * would calculate. If the sequence is not recognised we return NULL.
+ */
+ u32 insn1 = *func;
+ u32 insn2 = *(func + 1);
+ unsigned long op_regs1 = insn1 & OP_RT_RA_MASK;
+ unsigned long op_regs2 = insn2 & OP_RT_RA_MASK;
+ unsigned long si1 = insn1 & OP_SI_MASK;
+ unsigned long si2 = insn2 & OP_SI_MASK;
+ unsigned long imm1 = sign_extend_long(si1 << 16, 31);
+ unsigned long imm2 = sign_extend_long(si2, 15);
+ unsigned long addr = 0;
+
+ /* Simulate the first instruction */
+ if (op_regs1 == ADDIS_R2_R12)
+ addr += (unsigned long)func + imm1;
+ else if (op_regs1 == LIS_R2)
+ addr += imm1;
+ else
+ return NULL;
+
+ /* Simulate the second instruction */
+ if (op_regs2 == ADDI_R2_R2)
+ addr += imm2;
+ else
+ return NULL;
+
+ return (void *)addr;
+ }
+
+ return NULL;
+}
+
+static bool shares_toc(void *func1, void *func2)
+{
+ if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2)) {
+ void *func1_toc;
+ void *func2_toc;
+
+ if (func1 == NULL || func2 == NULL)
+ return false;
+
+ /* Assume the kernel only uses a single TOC */
+ if (core_kernel_text((unsigned long)func1) &&
+ core_kernel_text((unsigned long)func2))
+ return true;
+
+ /* Fall back to calculating the TOC from common patterns
+ * if modules are involved
+ */
+ func1_toc = ppc_function_toc(func1);
+ func2_toc = ppc_function_toc(func2);
+ return func1_toc != NULL && func2_toc != NULL && func1_toc == func2_toc;
+ }
+
+ return true;
+}
+
+static void *get_inst_addr(void *tramp)
+{
+ return tramp + (core_kernel_text((unsigned long)tramp)
+ ? PPC_SCT_INST_KERNEL
+ : PPC_SCT_INST_MODULE);
+}
+
+static void *get_ret0_addr(void *tramp)
+{
+ return tramp + (core_kernel_text((unsigned long)tramp)
+ ? PPC_SCT_RET0_KERNEL
+ : PPC_SCT_RET0_MODULE);
+}
+
+static void *get_data_addr(void *tramp)
+{
+ return tramp + (core_kernel_text((unsigned long) tramp)
+ ? PPC_SCT_DATA_KERNEL
+ : PPC_SCT_DATA_MODULE);
+}
+
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);
+ bool is_short;
+ void *target = is_ret0 ? get_ret0_addr(tramp) : func;
+ void *tramp_inst = get_inst_addr(tramp);
if (!tramp)
return;
+ if (is_ret0)
+ is_short = true;
+ else if (shares_toc(tramp, target))
+ is_short = is_offset_in_branch_range(
+ (long)ppc_function_entry(target) - (long)tramp_inst);
+ else
+ /* Combine out-of-range with not sharing a TOC. Though it's possible
+ * an out-of-range target shares a TOC, handling this separately
+ * complicates the trampoline. It's simpler to always use the global
+ * entry point in this case.
+ */
+ is_short = false;
+
mutex_lock(&text_mutex);
if (func && !is_short) {
- err = patch_instruction(tramp + PPC_SCT_DATA, ppc_inst(target));
+ err = patch_ulong(get_data_addr(tramp), (unsigned long)target);
if (err)
goto out;
}
if (!func)
- err = patch_instruction(tramp, ppc_inst(PPC_RAW_BLR()));
+ err = patch_instruction(tramp_inst, ppc_inst(PPC_RAW_BLR()));
else if (is_short)
- err = patch_branch(tramp, target, 0);
+ err = patch_branch(tramp_inst, ppc_function_entry(target), 0);
else
- err = patch_instruction(tramp, ppc_inst(PPC_RAW_NOP()));
+ err = patch_instruction(tramp_inst, ppc_inst(PPC_RAW_NOP()));
+
out:
mutex_unlock(&text_mutex);
--
2.37.3
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