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From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
	Jiri Olsa <jolsa@kernel.org>
Subject: [PATCH v2 1/9] powerpc: Remove __kernel_text_address() in show_instructions()
Date: Wed,  1 Feb 2023 11:04:23 +0100	[thread overview]
Message-ID: <4fd69ef7945518c3e27f96b95046a5c1468d35bf.1675245773.git.christophe.leroy@csgroup.eu> (raw)

That test was introducted in 2006 by
commit 00ae36de49cc ("[POWERPC] Better check in show_instructions").
At that time, there was no BPF progs.

As seen in message of commit 89d21e259a94 ("powerpc/bpf/32: Fix Oops
on tail call tests"), when a page fault occurs in test_bpf.ko for
instance, the code is dumped as XXXXXXXXs. Allthough
__kernel_text_address() checks is_bpf_text_address(), it seems it is
not enough.

Today, show_instructions() uses get_kernel_nofault() to read the code,
so there is no real need for additional verifications.

ARM64 and x86 don't do any additional check before dumping
instructions. Do the same and remove __kernel_text_address()
in show_instructions().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/process.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index c22cc234672f..effe9697905d 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1405,8 +1405,7 @@ static void show_instructions(struct pt_regs *regs)
 	for (i = 0; i < NR_INSN_TO_PRINT; i++) {
 		int instr;
 
-		if (!__kernel_text_address(pc) ||
-		    get_kernel_nofault(instr, (const void *)pc)) {
+		if (get_kernel_nofault(instr, (const void *)pc)) {
 			pr_cont("XXXXXXXX ");
 		} else {
 			if (nip == pc)
-- 
2.39.1


WARNING: multiple messages have this Message-ID (diff)
From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Hao Luo <haoluo@google.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Song Liu <song@kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	John Fastabend <john.fastabend@gmail.com>,
	linux-kernel@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Stanislav Fomichev <sdf@google.com>, Jiri Olsa <jolsa@kernel.org>,
	KP Singh <kpsingh@kernel.org>, Yonghong Song <yhs@fb.com>,
	bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH v2 1/9] powerpc: Remove __kernel_text_address() in show_instructions()
Date: Wed,  1 Feb 2023 11:04:23 +0100	[thread overview]
Message-ID: <4fd69ef7945518c3e27f96b95046a5c1468d35bf.1675245773.git.christophe.leroy@csgroup.eu> (raw)

That test was introducted in 2006 by
commit 00ae36de49cc ("[POWERPC] Better check in show_instructions").
At that time, there was no BPF progs.

As seen in message of commit 89d21e259a94 ("powerpc/bpf/32: Fix Oops
on tail call tests"), when a page fault occurs in test_bpf.ko for
instance, the code is dumped as XXXXXXXXs. Allthough
__kernel_text_address() checks is_bpf_text_address(), it seems it is
not enough.

Today, show_instructions() uses get_kernel_nofault() to read the code,
so there is no real need for additional verifications.

ARM64 and x86 don't do any additional check before dumping
instructions. Do the same and remove __kernel_text_address()
in show_instructions().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/process.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index c22cc234672f..effe9697905d 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1405,8 +1405,7 @@ static void show_instructions(struct pt_regs *regs)
 	for (i = 0; i < NR_INSN_TO_PRINT; i++) {
 		int instr;
 
-		if (!__kernel_text_address(pc) ||
-		    get_kernel_nofault(instr, (const void *)pc)) {
+		if (get_kernel_nofault(instr, (const void *)pc)) {
 			pr_cont("XXXXXXXX ");
 		} else {
 			if (nip == pc)
-- 
2.39.1


             reply	other threads:[~2023-02-01 10:05 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-01 10:04 Christophe Leroy [this message]
2023-02-01 10:04 ` [PATCH v2 1/9] powerpc: Remove __kernel_text_address() in show_instructions() Christophe Leroy
2023-02-01 10:04 ` [PATCH v2 2/9] powerpc/bpf/32: No need to zeroise r4 when not doing tail call Christophe Leroy
2023-02-01 10:04   ` Christophe Leroy
2023-02-01 10:04 ` [PATCH v2 3/9] powerpc/bpf/32: Only set a stack frame when necessary Christophe Leroy
2023-02-01 10:04   ` Christophe Leroy
2023-02-01 10:04 ` [PATCH v2 4/9] powerpc/bpf/32: BPF prog is never called with more than one arg Christophe Leroy
2023-02-01 10:04   ` Christophe Leroy
2023-02-01 10:04 ` [PATCH v2 5/9] powerpc/bpf: Perform complete extra passes to update addresses Christophe Leroy
2023-02-01 10:04   ` Christophe Leroy
2023-02-01 10:04 ` [PATCH v2 6/9] powerpc/bpf: Only pad length-variable code at initial pass Christophe Leroy
2023-02-01 10:04   ` Christophe Leroy
2023-02-01 10:04 ` [PATCH v2 7/9] powerpc/bpf/32: Optimise some particular const operations Christophe Leroy
2023-02-01 10:04   ` Christophe Leroy
2023-02-01 10:04 ` [PATCH v2 8/9] powerpc/bpf/32: introduce a second source register for ALU operations Christophe Leroy
2023-02-01 10:04   ` Christophe Leroy
2023-02-01 10:04 ` [PATCH v2 9/9] powerpc/bpf/32: perform three operands " Christophe Leroy
2023-02-01 10:04   ` Christophe Leroy
2023-02-15 12:40 ` [PATCH v2 1/9] powerpc: Remove __kernel_text_address() in show_instructions() Michael Ellerman
2023-02-15 12:40   ` Michael Ellerman

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