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Subject[PATCH 4.14 33/95] arm64: module-plts: factor out PLT generation code for ftrace
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

commit 7e8b9c1d2e2f5f45db7d40b50d14f606097c25de upstream.

To allow the ftrace trampoline code to reuse the PLT entry routines,
factor it out and move it into asm/module.h.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/include/asm/module.h | 44 ++++++++++++++++++++++++++++++++++++++++
arch/arm64/kernel/module-plts.c | 38 +---------------------------------
2 files changed, 46 insertions(+), 36 deletions(-)

--- a/arch/arm64/include/asm/module.h
+++ b/arch/arm64/include/asm/module.h
@@ -45,4 +45,48 @@ extern u64 module_alloc_base;
#define module_alloc_base ((u64)_etext - MODULES_VSIZE)
#endif

+struct plt_entry {
+ /*
+ * A program that conforms to the AArch64 Procedure Call Standard
+ * (AAPCS64) must assume that a veneer that alters IP0 (x16) and/or
+ * IP1 (x17) may be inserted at any branch instruction that is
+ * exposed to a relocation that supports long branches. Since that
+ * is exactly what we are dealing with here, we are free to use x16
+ * as a scratch register in the PLT veneers.
+ */
+ __le32 mov0; /* movn x16, #0x.... */
+ __le32 mov1; /* movk x16, #0x...., lsl #16 */
+ __le32 mov2; /* movk x16, #0x...., lsl #32 */
+ __le32 br; /* br x16 */
+};
+
+static inline struct plt_entry get_plt_entry(u64 val)
+{
+ /*
+ * MOVK/MOVN/MOVZ opcode:
+ * +--------+------------+--------+-----------+-------------+---------+
+ * | sf[31] | opc[30:29] | 100101 | hw[22:21] | imm16[20:5] | Rd[4:0] |
+ * +--------+------------+--------+-----------+-------------+---------+
+ *
+ * Rd := 0x10 (x16)
+ * hw := 0b00 (no shift), 0b01 (lsl #16), 0b10 (lsl #32)
+ * opc := 0b11 (MOVK), 0b00 (MOVN), 0b10 (MOVZ)
+ * sf := 1 (64-bit variant)
+ */
+ return (struct plt_entry){
+ cpu_to_le32(0x92800010 | (((~val ) & 0xffff)) << 5),
+ cpu_to_le32(0xf2a00010 | ((( val >> 16) & 0xffff)) << 5),
+ cpu_to_le32(0xf2c00010 | ((( val >> 32) & 0xffff)) << 5),
+ cpu_to_le32(0xd61f0200)
+ };
+}
+
+static inline bool plt_entries_equal(const struct plt_entry *a,
+ const struct plt_entry *b)
+{
+ return a->mov0 == b->mov0 &&
+ a->mov1 == b->mov1 &&
+ a->mov2 == b->mov2;
+}
+
#endif /* __ASM_MODULE_H */
--- a/arch/arm64/kernel/module-plts.c
+++ b/arch/arm64/kernel/module-plts.c
@@ -11,21 +11,6 @@
#include <linux/module.h>
#include <linux/sort.h>

-struct plt_entry {
- /*
- * A program that conforms to the AArch64 Procedure Call Standard
- * (AAPCS64) must assume that a veneer that alters IP0 (x16) and/or
- * IP1 (x17) may be inserted at any branch instruction that is
- * exposed to a relocation that supports long branches. Since that
- * is exactly what we are dealing with here, we are free to use x16
- * as a scratch register in the PLT veneers.
- */
- __le32 mov0; /* movn x16, #0x.... */
- __le32 mov1; /* movk x16, #0x...., lsl #16 */
- __le32 mov2; /* movk x16, #0x...., lsl #32 */
- __le32 br; /* br x16 */
-};
-
static bool in_init(const struct module *mod, void *loc)
{
return (u64)loc - (u64)mod->init_layout.base < mod->init_layout.size;
@@ -40,33 +25,14 @@ u64 module_emit_plt_entry(struct module
int i = pltsec->plt_num_entries;
u64 val = sym->st_value + rela->r_addend;

- /*
- * MOVK/MOVN/MOVZ opcode:
- * +--------+------------+--------+-----------+-------------+---------+
- * | sf[31] | opc[30:29] | 100101 | hw[22:21] | imm16[20:5] | Rd[4:0] |
- * +--------+------------+--------+-----------+-------------+---------+
- *
- * Rd := 0x10 (x16)
- * hw := 0b00 (no shift), 0b01 (lsl #16), 0b10 (lsl #32)
- * opc := 0b11 (MOVK), 0b00 (MOVN), 0b10 (MOVZ)
- * sf := 1 (64-bit variant)
- */
- plt[i] = (struct plt_entry){
- cpu_to_le32(0x92800010 | (((~val ) & 0xffff)) << 5),
- cpu_to_le32(0xf2a00010 | ((( val >> 16) & 0xffff)) << 5),
- cpu_to_le32(0xf2c00010 | ((( val >> 32) & 0xffff)) << 5),
- cpu_to_le32(0xd61f0200)
- };
+ plt[i] = get_plt_entry(val);

/*
* Check if the entry we just created is a duplicate. Given that the
* relocations are sorted, this will be the last entry we allocated.
* (if one exists).
*/
- if (i > 0 &&
- plt[i].mov0 == plt[i - 1].mov0 &&
- plt[i].mov1 == plt[i - 1].mov1 &&
- plt[i].mov2 == plt[i - 1].mov2)
+ if (i > 0 && plt_entries_equal(plt + i, plt + i - 1))
return (u64)&plt[i - 1];

pltsec->plt_num_entries++;

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