From: Bernd Edlinger <bernd.edlinger@hotmail.de>
To: Andrew Burgess <aburgess@redhat.com>,
"gdb-patches@sourceware.org" <gdb-patches@sourceware.org>
Subject: Re: [PATCH] sim: riscv: Fix newlib issue with brk syscall
Date: Fri, 12 Apr 2024 13:41:58 +0200 [thread overview]
Message-ID: <AS8P193MB128551B1F3A51C4752C54E3FE4042@AS8P193MB1285.EURP193.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <878r1i6e9s.fsf@redhat.com>
On 4/12/24 12:55, Andrew Burgess wrote:
> Bernd Edlinger <bernd.edlinger@hotmail.de> writes:
>
>> There is an issue with riscv newlib which uses
>> a brk syscall when malloc is used, and when
>> this syscall is not implemented, the malloc fails.
>> This adds a simple handling for this syscall
>> in order to make newlib happy.
>> ---
>> sim/riscv/sim-main.c | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>>
>> diff --git a/sim/riscv/sim-main.c b/sim/riscv/sim-main.c
>> index 9c0d070aa60..4e3672505c6 100644
>> --- a/sim/riscv/sim-main.c
>> +++ b/sim/riscv/sim-main.c
>> @@ -30,6 +30,7 @@
>> #include "sim-main.h"
>> #include "sim-signal.h"
>> #include "sim-syscall.h"
>> +#include "target-newlib-syscall.h"
>>
>> #include "opcode/riscv.h"
>>
>> @@ -629,6 +630,14 @@ execute_i (SIM_CPU *cpu, unsigned_word iw, const struct riscv_opcode *op)
>> break;
>> case MATCH_ECALL:
>> TRACE_INSN (cpu, "ecall;");
>> + if (riscv_cpu->a7 == TARGET_NEWLIB_RISCV_SYS_brk)
>> + {
>> + TRACE_SYSCALL (cpu, "brk[%i](%#lx)", TARGET_NEWLIB_RISCV_SYS_brk,
>> + (long)riscv_cpu->a0);
>> + if (riscv_cpu->a0 == 0)
>> + riscv_cpu->a0 = DEFAULT_MEM_SIZE / 2;
>> + break;
>> + }
>
> This doesn't seem like the right solution. I would have expected some
> changes in sim/common/syscall.c in the function cb_syscall. This would
> mean that the syscall would be handled via the sim_syscall call below.
>
This is the only target that would need such a quirk, in the newlib
this was introduced for compatibility with qemu, (but funny thing the
fopen syscall from newlib does not work with qemu :) but I have not seen a
way to configure a callback from inside sim_syscall for such target-
specific thing. I just saw similar things in sim/bfin/interp.c
where a CB_SYS_mmap2 had to be implemented and apparently the complete
sim_syscall was cloned into bfin_syscall which looked more ugly than this.
From there I took the idea to start the dynamic memory area at
DEFAULT_MEM_SIZE / 2, which I also just did because I have not seen
an easy way to find the end of the data segment.
Thanks
Bernd.
> Thanks,
> Andrew
>
>> riscv_cpu->a0 = sim_syscall (cpu, riscv_cpu->a7, riscv_cpu->a0,
>> riscv_cpu->a1, riscv_cpu->a2, riscv_cpu->a3);
>> break;
>> --
>> 2.25.1
>
prev parent reply other threads:[~2024-04-12 11:40 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-10 7:17 Bernd Edlinger
2024-04-12 10:55 ` Andrew Burgess
2024-04-12 11:41 ` Bernd Edlinger [this message]
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