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Subject[PATCH 1/4] LoongArch: Use trampoline for exception handlers and kill la.abs
Date
From: Xi Ruoyao <xry111@xry111.site>

Use a trampoline as an exception handlers, which can kill some use of
la.abs in preparation for the subsequent support of the PIE kernel.

Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
---
arch/loongarch/include/asm/stackframe.h | 8 +++----
arch/loongarch/include/asm/uaccess.h | 1 -
arch/loongarch/kernel/entry.S | 6 +++---
arch/loongarch/kernel/genex.S | 20 +++++++++---------
arch/loongarch/kernel/head.S | 2 +-
arch/loongarch/kernel/traps.c | 4 +++-
arch/loongarch/mm/tlbex.S | 28 +++++++------------------
7 files changed, 29 insertions(+), 40 deletions(-)

diff --git a/arch/loongarch/include/asm/stackframe.h b/arch/loongarch/include/asm/stackframe.h
index 4ca953062b5b..96c94035b5d0 100644
--- a/arch/loongarch/include/asm/stackframe.h
+++ b/arch/loongarch/include/asm/stackframe.h
@@ -76,8 +76,8 @@
* kernelsp array for it. It stores the current sp in t0 and loads the
* new value in sp.
*/
- .macro get_saved_sp docfi=0
- la.abs t1, kernelsp
+ .macro get_saved_sp docfi=0
+ la.pcrel t1, kernelsp
#ifdef CONFIG_SMP
csrrd t0, PERCPU_BASE_KS
LONG_ADD t1, t1, t0
@@ -89,8 +89,8 @@
LONG_L sp, t1, 0
.endm

- .macro set_saved_sp stackp temp temp2
- la.abs \temp, kernelsp
+ .macro set_saved_sp stackp temp temp2
+ la.pcrel \temp, kernelsp
#ifdef CONFIG_SMP
LONG_ADD \temp, \temp, u0
#endif
diff --git a/arch/loongarch/include/asm/uaccess.h b/arch/loongarch/include/asm/uaccess.h
index 255899d4a7c3..0d22991ae430 100644
--- a/arch/loongarch/include/asm/uaccess.h
+++ b/arch/loongarch/include/asm/uaccess.h
@@ -22,7 +22,6 @@
extern u64 __ua_limit;

#define __UA_ADDR ".dword"
-#define __UA_LA "la.abs"
#define __UA_LIMIT __ua_limit

/*
diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S
index d53b631c9022..ca01afdbec3f 100644
--- a/arch/loongarch/kernel/entry.S
+++ b/arch/loongarch/kernel/entry.S
@@ -18,9 +18,9 @@
.text
.cfi_sections .debug_frame
.align 5
-SYM_FUNC_START(handle_syscall)
+SYM_FUNC_START(handle_sys)
csrrd t0, PERCPU_BASE_KS
- la.abs t1, kernelsp
+ la.pcrel t1, kernelsp
add.d t1, t1, t0
move t2, sp
ld.d sp, t1, 0
@@ -66,7 +66,7 @@ SYM_FUNC_START(handle_syscall)
bl do_syscall

RESTORE_ALL_AND_RET
-SYM_FUNC_END(handle_syscall)
+SYM_FUNC_END(handle_sys)

SYM_CODE_START(ret_from_fork)
bl schedule_tail # a0 = struct task_struct *prev
diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S
index 75e5be807a0d..d3df0fa725a2 100644
--- a/arch/loongarch/kernel/genex.S
+++ b/arch/loongarch/kernel/genex.S
@@ -32,9 +32,8 @@ SYM_FUNC_START(__arch_cpu_idle)
SYM_FUNC_END(__arch_cpu_idle)

SYM_FUNC_START(handle_vint)
- BACKUP_T0T1
SAVE_ALL
- la.abs t1, __arch_cpu_idle
+ la.pcrel t1, __arch_cpu_idle
LONG_L t0, sp, PT_ERA
/* 32 byte rollback region */
ori t0, t0, 0x1f
@@ -43,8 +42,7 @@ SYM_FUNC_START(handle_vint)
LONG_S t0, sp, PT_ERA
1: move a0, sp
move a1, sp
- la.abs t0, do_vint
- jirl ra, t0, 0
+ bl do_vint
RESTORE_ALL_AND_RET
SYM_FUNC_END(handle_vint)

@@ -67,12 +65,10 @@ SYM_FUNC_END(except_vec_cex)
.macro BUILD_HANDLER exception handler prep
.align 5
SYM_FUNC_START(handle_\exception)
- BACKUP_T0T1
SAVE_ALL
build_prep_\prep
move a0, sp
- la.abs t0, do_\handler
- jirl ra, t0, 0
+ bl do_\handler
RESTORE_ALL_AND_RET
SYM_FUNC_END(handle_\exception)
.endm
@@ -89,7 +85,11 @@ SYM_FUNC_END(except_vec_cex)
BUILD_HANDLER watch watch none
BUILD_HANDLER reserved reserved none /* others */

-SYM_FUNC_START(handle_sys)
- la.abs t0, handle_syscall
+SYM_FUNC_START(handler_trampoline)
+ csrwr t0, EXCEPTION_KS0
+ csrwr t1, EXCEPTION_KS1
+ pcaddi t0, 0
+ ld.d t0, t0, 16
jr t0
-SYM_FUNC_END(handle_sys)
+ nop
+SYM_FUNC_END(handler_trampoline)
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index 57bada6b4e93..aa6181714ec3 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -117,7 +117,7 @@ SYM_CODE_START(smpboot_entry)
li.w t0, 0x00 # FPE=0, SXE=0, ASXE=0, BTE=0
csrwr t0, LOONGARCH_CSR_EUEN

- la.abs t0, cpuboot_data
+ la.pcrel t0, cpuboot_data
ld.d sp, t0, CPU_BOOT_STACK
ld.d tp, t0, CPU_BOOT_TINFO

diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index 7ea62faeeadb..0e8faaca3679 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -61,6 +61,7 @@ extern asmlinkage void handle_lasx(void);
extern asmlinkage void handle_reserved(void);
extern asmlinkage void handle_watch(void);
extern asmlinkage void handle_vint(void);
+extern asmlinkage void handler_trampoline(void);

static void show_backtrace(struct task_struct *task, const struct pt_regs *regs,
const char *loglvl, bool user)
@@ -716,7 +717,8 @@ void per_cpu_trap_init(int cpu)
/* Install CPU exception handler */
void set_handler(unsigned long offset, void *addr, unsigned long size)
{
- memcpy((void *)(eentry + offset), addr, size);
+ memcpy((void *)(eentry + offset), &handler_trampoline, 24);
+ memcpy((void *)(eentry + offset + 24), &addr, 8);
local_flush_icache_range(eentry + offset, eentry + offset + size);
}

diff --git a/arch/loongarch/mm/tlbex.S b/arch/loongarch/mm/tlbex.S
index 58781c6e4191..cfaacdac518c 100644
--- a/arch/loongarch/mm/tlbex.S
+++ b/arch/loongarch/mm/tlbex.S
@@ -24,8 +24,7 @@
move a0, sp
REG_S a2, sp, PT_BVADDR
li.w a1, \write
- la.abs t0, do_page_fault
- jirl ra, t0, 0
+ bl do_page_fault
RESTORE_ALL_AND_RET
SYM_FUNC_END(tlb_do_page_fault_\write)
.endm
@@ -34,20 +33,16 @@
tlb_do_page_fault 1

SYM_FUNC_START(handle_tlb_protect)
- BACKUP_T0T1
SAVE_ALL
move a0, sp
move a1, zero
csrrd a2, LOONGARCH_CSR_BADV
REG_S a2, sp, PT_BVADDR
- la.abs t0, do_page_fault
- jirl ra, t0, 0
+ bl do_page_fault
RESTORE_ALL_AND_RET
SYM_FUNC_END(handle_tlb_protect)

SYM_FUNC_START(handle_tlb_load)
- csrwr t0, EXCEPTION_KS0
- csrwr t1, EXCEPTION_KS1
csrwr ra, EXCEPTION_KS2

/*
@@ -116,7 +111,7 @@ smp_pgtable_change_load:

#ifdef CONFIG_64BIT
vmalloc_load:
- la.abs t1, swapper_pg_dir
+ la.pcrel t1, swapper_pg_dir
b vmalloc_done_load
#endif

@@ -187,13 +182,10 @@ tlb_huge_update_load:
nopage_tlb_load:
dbar 0
csrrd ra, EXCEPTION_KS2
- la.abs t0, tlb_do_page_fault_0
- jr t0
+ b tlb_do_page_fault_0
SYM_FUNC_END(handle_tlb_load)

SYM_FUNC_START(handle_tlb_store)
- csrwr t0, EXCEPTION_KS0
- csrwr t1, EXCEPTION_KS1
csrwr ra, EXCEPTION_KS2

/*
@@ -263,7 +255,7 @@ smp_pgtable_change_store:

#ifdef CONFIG_64BIT
vmalloc_store:
- la.abs t1, swapper_pg_dir
+ la.pcrel t1, swapper_pg_dir
b vmalloc_done_store
#endif

@@ -336,13 +328,10 @@ tlb_huge_update_store:
nopage_tlb_store:
dbar 0
csrrd ra, EXCEPTION_KS2
- la.abs t0, tlb_do_page_fault_1
- jr t0
+ b tlb_do_page_fault_1
SYM_FUNC_END(handle_tlb_store)

SYM_FUNC_START(handle_tlb_modify)
- csrwr t0, EXCEPTION_KS0
- csrwr t1, EXCEPTION_KS1
csrwr ra, EXCEPTION_KS2

/*
@@ -411,7 +400,7 @@ smp_pgtable_change_modify:

#ifdef CONFIG_64BIT
vmalloc_modify:
- la.abs t1, swapper_pg_dir
+ la.pcrel t1, swapper_pg_dir
b vmalloc_done_modify
#endif

@@ -483,8 +472,7 @@ tlb_huge_update_modify:
nopage_tlb_modify:
dbar 0
csrrd ra, EXCEPTION_KS2
- la.abs t0, tlb_do_page_fault_1
- jr t0
+ b tlb_do_page_fault_1
SYM_FUNC_END(handle_tlb_modify)

SYM_FUNC_START(handle_tlb_refill)
--
2.37.1
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