Messages in this thread | | | Date | Thu, 13 Apr 2023 15:28:07 +0200 | Subject | Re: [PATCH v2] ARM:unwind:fix unwind abort for uleb128 case | From | AngeloGioacchino Del Regno <> |
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Il 13/04/23 09:34, Haibo Li ha scritto: > 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> > --- > v2: > - As Linus Walleij and Alexandre Mergnat suggested,add comments for unwind_decode_uleb128 > - As Alexandre Mergnat suggested,change variables declaration in Alphabetical order > --- > 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 53be7ea6181b..f37e55fcf81d 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, > + * we loop until we get an instruction byte where bit 7 is not set. > + * Note:It decodes max 4 bytes to output 28bits data. > + * 28bits data(0xfffffff) covers vsp increments of 1073742336. > + * It is sufficent for unwinding stack. > + */
/* * 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++;
also, I would do ...
} while (!!(insn & 0x80) && bytes != sizeof(result));
...compressing the code and not creating any human readability concern.
after which, you can get my
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
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