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Thu, 23 Jan 2025 10:04:11 +0000 (GMT) Message-ID: <7cfe94c9-4ca5-48b1-ab53-bc08fcf8fbc0@linux.ibm.com> Date: Thu, 23 Jan 2025 15:34:11 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/6] kexec: Initialize ELF lowest address to ULONG_MAX To: Sourabh Jain , linuxppc-dev@lists.ozlabs.org Cc: Andrew Morton , Madhavan Srinivasan , Mahesh Salgaonkar , Michael Ellerman , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Baoquan He References: <20250121115442.1278458-1-sourabhjain@linux.ibm.com> <20250121115442.1278458-2-sourabhjain@linux.ibm.com> Content-Language: en-US From: Hari Bathini In-Reply-To: <20250121115442.1278458-2-sourabhjain@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: iVIl_PKY5o8bpvR2QGLyZcy1lwgBkRvv X-Proofpoint-ORIG-GUID: iVIl_PKY5o8bpvR2QGLyZcy1lwgBkRvv X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-23_04,2025-01-22_02,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 clxscore=1011 mlxscore=0 impostorscore=0 lowpriorityscore=0 adultscore=0 suspectscore=0 mlxlogscore=999 malwarescore=0 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501230076 On 21/01/25 5:24 pm, Sourabh Jain wrote: > kexec_elf_load() loads an ELF executable and sets the address of the > lowest PT_LOAD section to the address held by the lowest_load_addr > function argument. > > To determine the lowest PT_LOAD address, a local variable lowest_addr > (type unsigned long) is initialized to UINT_MAX. After loading each > PT_LOAD, its address is compared to lowest_addr. If a loaded PT_LOAD > address is lower, lowest_addr is updated. However, setting lowest_addr > to UINT_MAX won't work when the kernel image is loaded above 4G, as the > returned lowest PT_LOAD address would be invalid. This is resolved by > initializing lowest_addr to ULONG_MAX instead. > > This issue was discovered while implementing crashkernel high/low > reservation on the PowerPC architecture. > Acked-by: Hari Bathini > Fixes: a0458284f062 ("powerpc: Add support code for kexec_file_load()") > Cc: Andrew Morton > Cc: Hari Bathini > Cc: Madhavan Srinivasan > Cc: Mahesh Salgaonkar > Cc: Michael Ellerman > Cc: kexec@lists.infradead.org > Cc: linuxppc-dev@lists.ozlabs.org > Cc: linux-kernel@vger.kernel.org > Acked-by: Baoquan He > Signed-off-by: Sourabh Jain > --- > kernel/kexec_elf.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/kexec_elf.c b/kernel/kexec_elf.c > index d3689632e8b9..3a5c25b2adc9 100644 > --- a/kernel/kexec_elf.c > +++ b/kernel/kexec_elf.c > @@ -390,7 +390,7 @@ int kexec_elf_load(struct kimage *image, struct elfhdr *ehdr, > struct kexec_buf *kbuf, > unsigned long *lowest_load_addr) > { > - unsigned long lowest_addr = UINT_MAX; > + unsigned long lowest_addr = ULONG_MAX; > int ret; > size_t i; >