Messages in this thread Patch in this message | | | From | Christophe Leroy <> | Subject | [PATCH v3 01/41] powerpc/traps: Declare unrecoverable_exception() as __noreturn | Date | Fri, 12 Mar 2021 12:50:10 +0000 (UTC) |
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unrecoverable_exception() is never expected to return, most callers have an infiniteloop in case it returns.
Ensure it really never returns by terminating it with a BUG(), and declare it __no_return.
It always GCC to really simplify functions calling it. In the exemple below, it avoids the stack frame in the likely fast path and avoids code duplication for the exit.
With this patch:
00000348 <interrupt_exit_kernel_prepare>: 348: 81 43 00 84 lwz r10,132(r3) 34c: 71 48 00 02 andi. r8,r10,2 350: 41 82 00 2c beq 37c <interrupt_exit_kernel_prepare+0x34> 354: 71 4a 40 00 andi. r10,r10,16384 358: 40 82 00 20 bne 378 <interrupt_exit_kernel_prepare+0x30> 35c: 80 62 00 70 lwz r3,112(r2) 360: 74 63 00 01 andis. r3,r3,1 364: 40 82 00 28 bne 38c <interrupt_exit_kernel_prepare+0x44> 368: 7d 40 00 a6 mfmsr r10 36c: 7c 11 13 a6 mtspr 81,r0 370: 7c 12 13 a6 mtspr 82,r0 374: 4e 80 00 20 blr 378: 48 00 00 00 b 378 <interrupt_exit_kernel_prepare+0x30> 37c: 94 21 ff f0 stwu r1,-16(r1) 380: 7c 08 02 a6 mflr r0 384: 90 01 00 14 stw r0,20(r1) 388: 48 00 00 01 bl 388 <interrupt_exit_kernel_prepare+0x40> 388: R_PPC_REL24 unrecoverable_exception 38c: 38 e2 00 70 addi r7,r2,112 390: 3d 00 00 01 lis r8,1 394: 7c c0 38 28 lwarx r6,0,r7 398: 7c c6 40 78 andc r6,r6,r8 39c: 7c c0 39 2d stwcx. r6,0,r7 3a0: 40 a2 ff f4 bne 394 <interrupt_exit_kernel_prepare+0x4c> 3a4: 38 60 00 01 li r3,1 3a8: 4b ff ff c0 b 368 <interrupt_exit_kernel_prepare+0x20>
Without this patch:
00000348 <interrupt_exit_kernel_prepare>: 348: 94 21 ff f0 stwu r1,-16(r1) 34c: 93 e1 00 0c stw r31,12(r1) 350: 7c 7f 1b 78 mr r31,r3 354: 81 23 00 84 lwz r9,132(r3) 358: 71 2a 00 02 andi. r10,r9,2 35c: 41 82 00 34 beq 390 <interrupt_exit_kernel_prepare+0x48> 360: 71 29 40 00 andi. r9,r9,16384 364: 40 82 00 28 bne 38c <interrupt_exit_kernel_prepare+0x44> 368: 80 62 00 70 lwz r3,112(r2) 36c: 74 63 00 01 andis. r3,r3,1 370: 40 82 00 3c bne 3ac <interrupt_exit_kernel_prepare+0x64> 374: 7d 20 00 a6 mfmsr r9 378: 7c 11 13 a6 mtspr 81,r0 37c: 7c 12 13 a6 mtspr 82,r0 380: 83 e1 00 0c lwz r31,12(r1) 384: 38 21 00 10 addi r1,r1,16 388: 4e 80 00 20 blr 38c: 48 00 00 00 b 38c <interrupt_exit_kernel_prepare+0x44> 390: 7c 08 02 a6 mflr r0 394: 90 01 00 14 stw r0,20(r1) 398: 48 00 00 01 bl 398 <interrupt_exit_kernel_prepare+0x50> 398: R_PPC_REL24 unrecoverable_exception 39c: 80 01 00 14 lwz r0,20(r1) 3a0: 81 3f 00 84 lwz r9,132(r31) 3a4: 7c 08 03 a6 mtlr r0 3a8: 4b ff ff b8 b 360 <interrupt_exit_kernel_prepare+0x18> 3ac: 39 02 00 70 addi r8,r2,112 3b0: 3d 40 00 01 lis r10,1 3b4: 7c e0 40 28 lwarx r7,0,r8 3b8: 7c e7 50 78 andc r7,r7,r10 3bc: 7c e0 41 2d stwcx. r7,0,r8 3c0: 40 a2 ff f4 bne 3b4 <interrupt_exit_kernel_prepare+0x6c> 3c4: 38 60 00 01 li r3,1 3c8: 4b ff ff ac b 374 <interrupt_exit_kernel_prepare+0x2c>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Reviewed-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/include/asm/interrupt.h | 2 +- arch/powerpc/kernel/traps.c | 5 ++++- 2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h index e8d09a841373..232a4847f596 100644 --- a/arch/powerpc/include/asm/interrupt.h +++ b/arch/powerpc/include/asm/interrupt.h @@ -436,7 +436,7 @@ DECLARE_INTERRUPT_HANDLER_NMI(hmi_exception_realmode); DECLARE_INTERRUPT_HANDLER_ASYNC(TAUException); -void unrecoverable_exception(struct pt_regs *regs); +void __noreturn unrecoverable_exception(struct pt_regs *regs); void replay_system_reset(void); void replay_soft_interrupts(void); diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index a44a30b0688c..a1c14680ed5a 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -2170,11 +2170,14 @@ DEFINE_INTERRUPT_HANDLER(SPEFloatingPointRoundException) * in the MSR is 0. This indicates that SRR0/1 are live, and that * we therefore lost state by taking this exception. */ -void unrecoverable_exception(struct pt_regs *regs) +void __noreturn unrecoverable_exception(struct pt_regs *regs) { pr_emerg("Unrecoverable exception %lx at %lx (msr=%lx)\n", regs->trap, regs->nip, regs->msr); die("Unrecoverable exception", regs, SIGABRT); + /* die() should not return */ + for (;;) + ; } #if defined(CONFIG_BOOKE_WDT) || defined(CONFIG_40x) -- 2.25.0
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