Messages in this thread | | | Date | Tue, 10 Jan 2012 10:59:42 +0800 | From | "tiejun.chen" <> | Subject | Re: [PATCH 1/1] kmemleak/module: only scan the existed data section |
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Catalin Marinas wrote: > On 28 December 2011 08:11, Tiejun Chen <tiejun.chen@windriver.com> wrote: >> We should only scan the sections containing data and it's size is not >> zero as well. >> >> Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com> >> --- >> �kernel/module.c | � �2 ++ >> �1 files changed, 2 insertions(+), 0 deletions(-) >> >> diff --git a/kernel/module.c b/kernel/module.c >> index 12cfa2b..0b93c30 100644 >> --- a/kernel/module.c >> +++ b/kernel/module.c >> @@ -2045,6 +2045,8 @@ static void kmemleak_load_module(struct module *mod, Elf_Ehdr *hdr, >> � � � � � � � �if (strncmp(secstrings + sechdrs[i].sh_name, ".data", 5) != 0 >> � � � � � � � � � �&& strncmp(secstrings + sechdrs[i].sh_name, ".bss", 4) != 0) >> � � � � � � � � � � � �continue; >> + � � � � � � � if (sechdrs[i].sh_size == 0) >> + � � � � � � � � � � � continue; >> >> � � � � � � � �kmemleak_scan_area((void *)sechdrs[i].sh_addr, >> � � � � � � � � � � � � � � � � � sechdrs[i].sh_size, GFP_KERNEL); > > I would rather move this check to kmemleak.c. But why would it be > needed? Performance? A zero-size area shouldn't be scanned anyway.
When we call layout_sections() to calculate sh_entsize, often a zero-sized .data/.bss section would be ordered as a middle of all valid sections. For example, ------ Symbol Addr size
.init. 0xf96d3000 ...... .data(or .bss) 0xf96d3180 0 ...... 0xf96d4000
If so kmemleak_scan_area(0xf96d3180,0,GFP_KERNEL) is fine as we expect since 0xf96d3180 is always within a valid address scopes summarized all section, 0xf96d3000 ~ 0xf96d4000. But sometimes if that is arranged as a last section: ----- Symbol Addr size
.init. 0xf96d3000 ...... .data(or .bss) 0xf96d3180 0
An then the following call trace is triggered ...... kmemleak: Adding scan area to unknown object at 0xf96d3180 Call Trace: [e9095de0] [c0008588] show_stack+0x68/0x1d8 (unreliable) [e9095e30] [c0690094] dump_stack+0x2c/0x44 [e9095e40] [c015a190] kmemleak_scan_area+0x128/0x184 [e9095e70] [c00a145c] load_module+0xa98/0x1c04 [e9095f10] [c00a2650] sys_init_module+0x88/0x24c [e9095f40] [c0012f7c] ret_from_syscall+0x0/0x4 --- Exception: c01 at 0xff63564 LR = 0x10003414
Tiejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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