From: guoren@kernel.org To: anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, conor.dooley@microchip.com, heiko@sntech.de, rostedt@goodmis.org, mhiramat@kernel.org, jolsa@redhat.com, bp@suse.de, jpoimboe@kernel.org, suagrfillet@gmail.com, andy.chiu@sifive.com, mark.rutland@arm.com Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Guo Ren <guoren@kernel.org> Subject: [PATCH V4 1/7] riscv: ftrace: Fixup panic by disabling preemption Date: Mon, 28 Nov 2022 22:32:24 -0500 [thread overview] Message-ID: <20221129033230.255947-2-guoren@kernel.org> (raw) In-Reply-To: <20221129033230.255947-1-guoren@kernel.org> From: Andy Chiu <andy.chiu@sifive.com> In RISCV, we must use an AUIPC + JALR pair to encode an immediate, forming a jump that jumps to an address over 4K. This may cause errors if we want to enable kernel preemption and remove dependency from patching code with stop_machine(). For example, if a task was switched out on auipc. And, if we changed the ftrace function before it was switched back, then it would jump to an address that has updated 11:0 bits mixing with previous XLEN:12 part. p: patched area performed by dynamic ftrace ftrace_prologue: p| REG_S ra, -SZREG(sp) p| auipc ra, 0x? ------------> preempted ... change ftrace function ... p| jalr -?(ra) <------------- switched back p| REG_L ra, -SZREG(sp) func: xxx ret Fixes: afc76b8b8011 ("riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT") Signed-off-by: Andy Chiu <andy.chiu@sifive.com> Signed-off-by: Guo Ren <guoren@kernel.org> --- @Andy, could you give the patch a Signed-off-by? I just copy your most important comment, so the first author should be you. First, let's fix the problem caused by my previous patch, and you can continue your ftrace preemption work. --- arch/riscv/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 7cd981f96f48..1d0e5838b11b 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -280,7 +280,7 @@ config ARCH_RV64I select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_GRAPH_TRACER - select HAVE_FUNCTION_TRACER if !XIP_KERNEL + select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION select SWIOTLB if MMU endchoice -- 2.36.1
WARNING: multiple messages have this Message-ID (diff)
From: guoren@kernel.org To: anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, conor.dooley@microchip.com, heiko@sntech.de, rostedt@goodmis.org, mhiramat@kernel.org, jolsa@redhat.com, bp@suse.de, jpoimboe@kernel.org, suagrfillet@gmail.com, andy.chiu@sifive.com, mark.rutland@arm.com Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Guo Ren <guoren@kernel.org> Subject: [PATCH V4 1/7] riscv: ftrace: Fixup panic by disabling preemption Date: Mon, 28 Nov 2022 22:32:24 -0500 [thread overview] Message-ID: <20221129033230.255947-2-guoren@kernel.org> (raw) In-Reply-To: <20221129033230.255947-1-guoren@kernel.org> From: Andy Chiu <andy.chiu@sifive.com> In RISCV, we must use an AUIPC + JALR pair to encode an immediate, forming a jump that jumps to an address over 4K. This may cause errors if we want to enable kernel preemption and remove dependency from patching code with stop_machine(). For example, if a task was switched out on auipc. And, if we changed the ftrace function before it was switched back, then it would jump to an address that has updated 11:0 bits mixing with previous XLEN:12 part. p: patched area performed by dynamic ftrace ftrace_prologue: p| REG_S ra, -SZREG(sp) p| auipc ra, 0x? ------------> preempted ... change ftrace function ... p| jalr -?(ra) <------------- switched back p| REG_L ra, -SZREG(sp) func: xxx ret Fixes: afc76b8b8011 ("riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT") Signed-off-by: Andy Chiu <andy.chiu@sifive.com> Signed-off-by: Guo Ren <guoren@kernel.org> --- @Andy, could you give the patch a Signed-off-by? I just copy your most important comment, so the first author should be you. First, let's fix the problem caused by my previous patch, and you can continue your ftrace preemption work. --- arch/riscv/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 7cd981f96f48..1d0e5838b11b 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -280,7 +280,7 @@ config ARCH_RV64I select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_GRAPH_TRACER - select HAVE_FUNCTION_TRACER if !XIP_KERNEL + select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION select SWIOTLB if MMU endchoice -- 2.36.1 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2022-11-29 3:32 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-11-29 3:32 [PATCH V4 0/7] riscv: ftrace: Fixup ftrace detour code & Optimization guoren 2022-11-29 3:32 ` guoren 2022-11-29 3:32 ` guoren [this message] 2022-11-29 3:32 ` [PATCH V4 1/7] riscv: ftrace: Fixup panic by disabling preemption guoren 2022-11-29 3:32 ` [PATCH V4 2/7] riscv: ftrace: Remove wasted nops for !RISCV_ISA_C guoren 2022-11-29 3:32 ` guoren 2022-11-29 3:32 ` [PATCH V4 3/7] riscv: ftrace: Reduce the detour code size to half guoren 2022-11-29 3:32 ` guoren 2022-11-29 3:32 ` [PATCH V4 4/7] riscv: ftrace: Add ftrace_graph_func guoren 2022-11-29 3:32 ` guoren 2022-11-29 3:32 ` [PATCH V4 5/7] riscv: ftrace: Make ftrace_caller call ftrace_graph_func guoren 2022-11-29 3:32 ` guoren 2022-11-29 3:32 ` [PATCH V4 6/7] riscv: ftrace: Add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support guoren 2022-11-29 3:32 ` guoren 2022-11-29 12:03 ` Song Shuai 2022-11-29 12:03 ` Song Shuai 2022-11-30 7:29 ` Guo Ren 2022-11-30 7:29 ` Guo Ren 2022-12-01 20:02 ` Conor Dooley 2022-12-01 20:02 ` Conor Dooley 2022-12-01 20:06 ` Palmer Dabbelt 2022-12-01 20:06 ` Palmer Dabbelt 2022-12-01 20:15 ` Conor Dooley 2022-12-01 20:15 ` Conor Dooley 2022-11-29 3:32 ` [PATCH V4 7/7] samples: ftrace: Add riscv support for SAMPLE_FTRACE_DIRECT[_MULTI] guoren 2022-11-29 3:32 ` guoren
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