arm: print instructions pointed to by pc

PATCH Superseded Heinrich Schuchardt 4 participants 5 messages May 10, 2018 – May 24, 2018 Arm (32-bit)

Share & tools

Heinrich Schuchardt

author

2018-05-10 14:38 UTC #0 lore raw

PATCH v2 1/1 arm: print instructions pointed to by pc

If an exception occurs in a loaded image and the relocation offset is unknown, it is helful to know the instructions pointed to by the program counter. This patch adds the missing output.

A possible output is:

    *pc: fb de f7 e7 1e ff 2f e1 01 00 50 e3 f0 4d 2d e9 01 80 a0 e1

The output can be disassembled with
xxd -pc -r - > a.out $(CROSS_COMPILE)objdump -D -marm -b binary a.out

Signed-off-by Heinrich Schuchardt <[email protected]>

---
v2
print bytes not halfwords

---
 arch/arm/lib/interrupts.c | 7 +++++++
 1 file changed, 7 insertions(+)

arch/arm/lib/interrupts.c +7 -0

index 28ba3f14f36..25489e34462 100644
@@ -59,6 +59,9 @@ static void show_efi_loaded_images(struct pt_regs *regs)
 void show_regs (struct pt_regs *regs)
 {
 	unsigned long __maybe_unused flags;
+	/* The least significant bit chooses thumb, remove it. */
+	u8 *pc = (u8 *)(instruction_pointer(regs) & ~1);
+	int i;
 	const char __maybe_unused *processor_modes[] = {
 	"USER_26",	"FIQ_26",	"IRQ_26",	"SVC_26",
 	"UK4_26",	"UK5_26",	"UK6_26",	"UK7_26",

@@ -96,6 +99,10 @@ void show_regs (struct pt_regs *regs)
 		fast_interrupts_enabled (regs) ? "on" : "off",
 		processor_modes[processor_mode (regs)],
 		thumb_mode (regs) ? " (T)" : "");
+	printf("*pc:");
+	for (i = 0; i < 24; ++i)
+		printf(" %02x", pc[i]);
+	printf("\n");
 }
 
 /* fixup PC to point to the instruction leading to the exception */

Signature · 1 line

2.14.2

Tuomas Tynkkynen

2018-05-13 12:22 UTC #1 lore raw

PATCH v2 1/1 arm: print instructions pointed to by pc

Hi,

Quoted 7 lines · On Thu, 10 May 2018 16:38:30 +0200 Heinrich Schuchardt <[email protected]>…

If an exception occurs in a loaded image and the relocation offset is unknown, it is helful to know the instructions pointed to by the program counter. This patch adds the missing output.
A possible output is:
    *pc: fb de f7 e7 1e ff 2f e1 01 00 50 e3 f0 4d 2d e9 01 80 a0 e1

Quoted 8 lines

The output can be disassembled with
xxd -pc -r - > a.out $(CROSS_COMPILE)objdump -D -marm -b binary a.out
Signed-off-by Heinrich Schuchardt <[email protected]>
---
v2
print bytes not halfwords

Note that Linux already comes with a scripts/decodecode tool where you paste the output of an Oops and it disassembles the "Code: " line from the dump. So I'd vote for importing scripts/decodecode from Linux and making U-Boot's output compatible with Linux.

Marek Vasut

2018-05-13 14:45 UTC #2 lore raw

PATCH v2 1/1 arm: print instructions pointed to by pc

Quoted 21 lines · Tuomas Tynkkynen

Hi,
Quoted 7 lines · On Thu, 10 May 2018 16:38:30 +0200 Heinrich Schuchardt <[email protected]>…
If an exception occurs in a loaded image and the relocation offset is unknown, it is helful to know the instructions pointed to by the program counter. This patch adds the missing output.
A possible output is:
    *pc: fb de f7 e7 1e ff 2f e1 01 00 50 e3 f0 4d 2d e9 01 80 a0 e1
Quoted 8 lines
The output can be disassembled with
xxd -pc -r - > a.out $(CROSS_COMPILE)objdump -D -marm -b binary a.out
Signed-off-by Heinrich Schuchardt <[email protected]>
---
v2
print bytes not halfwords

Quoted 4 lines

Note that Linux already comes with a scripts/decodecode tool where you paste the output of an Oops and it disassembles the "Code: " line from the dump. So I'd vote for importing scripts/decodecode from Linux and making U-Boot's output compatible with Linux.

Sounds good.

btw if you get exception because the memory at PC is inaccessible, this will trigger a double-fault I think.

Signature · 2 lines

Best regards,
Marek Vasut

Alexander Graf

2018-05-24 08:57 UTC #3 lore raw

PATCH v2 1/1 arm: print instructions pointed to by pc

Quoted 27 lines · Marek Vasut

Quoted 21 lines · Tuomas Tynkkynen
Hi,
Quoted 7 lines · On Thu, 10 May 2018 16:38:30 +0200 Heinrich Schuchardt <[email protected]>…
If an exception occurs in a loaded image and the relocation offset is unknown, it is helful to know the instructions pointed to by the program counter. This patch adds the missing output.
A possible output is:
    *pc: fb de f7 e7 1e ff 2f e1 01 00 50 e3 f0 4d 2d e9 01 80 a0 e1
Quoted 8 lines
The output can be disassembled with
xxd -pc -r - > a.out $(CROSS_COMPILE)objdump -D -marm -b binary a.out
Signed-off-by Heinrich Schuchardt <[email protected]>
---
v2
print bytes not halfwords
Quoted 4 lines
Note that Linux already comes with a scripts/decodecode tool where you paste the output of an Oops and it disassembles the "Code: " line from the dump. So I'd vote for importing scripts/decodecode from Linux and making U-Boot's output compatible with Linux.

Quoted 4 lines

Sounds good.
btw if you get exception because the memory at PC is inaccessible, this will trigger a double-fault I think.

Yes, but it will only trigger it at the end of the handler at which point we're panicking anyways, no?

Alex

Marek Vasut

2018-05-24 09:06 UTC #4 lore raw

PATCH v2 1/1 arm: print instructions pointed to by pc

Quoted 30 lines · Alexander Graf

Quoted 27 lines · Marek Vasut
Quoted 25 lines · Tuomas Tynkkynen
Hi,
Quoted 7 lines · On Thu, 10 May 2018 16:38:30 +0200 Heinrich Schuchardt <[email protected]>…
If an exception occurs in a loaded image and the relocation offset is unknown, it is helful to know the instructions pointed to by the program counter. This patch adds the missing output.
A possible output is:
    *pc: fb de f7 e7 1e ff 2f e1 01 00 50 e3 f0 4d 2d e9 01 80 a0 e1
Quoted 8 lines
The output can be disassembled with
xxd -pc -r - > a.out $(CROSS_COMPILE)objdump -D -marm -b binary a.out
Signed-off-by Heinrich Schuchardt <[email protected]>
---
v2
print bytes not halfwords
Note that Linux already comes with a scripts/decodecode tool where you paste the output of an Oops and it disassembles the "Code: " line from the dump. So I'd vote for importing scripts/decodecode from Linux and making U-Boot's output compatible with Linux.

Quoted 7 lines

Quoted 4 lines
Sounds good.
btw if you get exception because the memory at PC is inaccessible, this will trigger a double-fault I think.
Yes, but it will only trigger it at the end of the handler at which point we're panicking anyways, no?

Linux prints the faulting function at the top.

Signature · 2 lines

Best regards,
Marek Vasut