From: Haibo Li <haibo.li@xxxxxxxxxxxx>
[ Upstream commit fa3eeb638de0c1a9d2d860e5b48259facdd65176 ]
When unwind instruction is 0xb2,the subsequent instructions
are uleb128 bytes.
For now,it uses only the first uleb128 byte in code.
For vsp increments of 0x204~0x400,use one uleb128 byte like below:
0xc06a00e4 <unwind_test_work>: 0x80b27fac
Compact model index: 0
0xb2 0x7f vsp = vsp + 1024
0xac pop {r4, r5, r6, r7, r8, r14}
For vsp increments larger than 0x400,use two uleb128 bytes like below:
0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c
Compact model index: 1
0xb2 0x81 0x01 vsp = vsp + 1032
0xac pop {r4, r5, r6, r7, r8, r14}
The unwind works well since the decoded uleb128 byte is also 0x81.
For vsp increments larger than 0x600,use two uleb128 bytes like below:
0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c
Compact model index: 1
0xb2 0x81 0x02 vsp = vsp + 1544
0xac pop {r4, r5, r6, r7, r8, r14}
In this case,the decoded uleb128 result is 0x101(vsp=0x204+(0x101<<2)).
While the uleb128 used in code is 0x81(vsp=0x204+(0x81<<2)).
The unwind aborts at this frame since it gets incorrect vsp.
To fix this,add uleb128 decode to cover all the above case.
Signed-off-by: Haibo Li <haibo.li@xxxxxxxxxxxx>
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Reviewed-by: Alexandre Mergnat <amergnat@xxxxxxxxxxxx>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/arm/kernel/unwind.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index 53be7ea6181b3..9d2192156087b 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -308,6 +308,29 @@ static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl,
return URC_OK;
}
+static unsigned long unwind_decode_uleb128(struct unwind_ctrl_block *ctrl)
+{
+ unsigned long bytes = 0;
+ unsigned long insn;
+ unsigned long result = 0;
+
+ /*
+ * unwind_get_byte() will advance `ctrl` one instruction at a time, so
+ * loop until we get an instruction byte where bit 7 is not set.
+ *
+ * Note: This decodes a maximum of 4 bytes to output 28 bits data where
+ * max is 0xfffffff: that will cover a vsp increment of 1073742336, hence
+ * it is sufficient for unwinding the stack.
+ */
+ do {
+ insn = unwind_get_byte(ctrl);
+ result |= (insn & 0x7f) << (bytes * 7);
+ bytes++;
+ } while (!!(insn & 0x80) && (bytes != sizeof(result)));
+
+ return result;
+}
+
/*
* Execute the current unwind instruction.
*/
@@ -361,7 +384,7 @@ static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
if (ret)
goto error;
} else if (insn == 0xb2) {
- unsigned long uleb128 = unwind_get_byte(ctrl);
+ unsigned long uleb128 = unwind_decode_uleb128(ctrl);
ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
} else {
--
2.39.2
