Messages in this thread | | | From | Haibo Li <> | Subject | Re: [PATCH] ARM:unwind:fix unwind abort for uleb128 case | Date | Thu, 13 Apr 2023 15:19:25 +0800 |
| |
> On 07/04/2023 05:33, Haibo Li wrote: > > 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@mediatek.com> > > --- > > arch/arm/kernel/unwind.c | 19 +++++++++++++++++-- > > 1 file changed, 17 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c index > > 53be7ea6181b..e5796a5acba1 100644 > > --- a/arch/arm/kernel/unwind.c > > +++ b/arch/arm/kernel/unwind.c > > @@ -20,7 +20,6 @@ > > #warning Change compiler or disable ARM_UNWIND option. > > #endif > > #endif /* __CHECKER__ */ > > - > > Why delete this line ? It may be changed by mistake.I will restore it. > > > #include <linux/kernel.h> > > #include <linux/init.h> > > #include <linux/export.h> > > @@ -308,6 +307,22 @@ 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 result = 0; > > + unsigned long insn; > > + unsigned long bytes = 0; > > Alphabetical order please. get it. > > > + > > + do { > > + insn = unwind_get_byte(ctrl); > > + result |= (insn & 0x7f) << (bytes * 7); > > + bytes++; > > + if (bytes == sizeof(result)) > > + break; > > + } while (!!(insn & 0x80)); > > + > > + return result; > > +} > > Please add a blank line for readability. OK. > > > /* > > * Execute the current unwind instruction. > > */ > > @@ -361,7 +376,7 @@ 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 { > > Great job! I'm aligned with Linus Walleij's feedback about the need of few > comments to explain the decode loop, even if your code is clear, light and > robust. Thanks for reviewing the patch.I will add the comment in later patch. >
| |