On Fri, May 20, 2016 at 11:22:40AM +0800, Xiaqing (A) wrote:
在 2016/5/19 21:18, Catalin Marinas 写道:
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c index 3808470486f3..6bda9d30a769 100644 --- a/arch/arm64/kernel/cpuinfo.c +++ b/arch/arm64/kernel/cpuinfo.c @@ -22,6 +22,7 @@
#include <linux/bitops.h> #include <linux/bug.h> +#include <linux/elf.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/personality.h> @@ -104,6 +105,8 @@ static const char *const compat_hwcap2_str[] = { static int c_show(struct seq_file *m, void *v) { int i, j;
bool compat = is_compat_task() ||
personality(current->personality) == PER_LINUX32;for_each_online_cpu(i) { struct cpuinfo_arm64 *cpuinfo = &per_cpu(cpu_data, i);
@@ -115,6 +118,9 @@ static int c_show(struct seq_file *m, void *v) * "processor". Give glibc what it expects. */ seq_printf(m, "processor\t: %d\n", i);
if (compat)seq_printf(m, "model name\t: ARMv8 Processor rev %d (%s)\n",MIDR_REVISION(midr), COMPAT_ELF_PLATFORM);seq_printf(m, "BogoMIPS\t: %lu.%02lu\n", loops_per_jiffy / (500000UL/HZ),
@@ -127,7 +133,7 @@ static int c_show(struct seq_file *m, void *v) * software which does already (at least for 32-bit). */ seq_puts(m, "Features\t:");
if (personality(current->personality) == PER_LINUX32) {
if (compat) {#ifdef CONFIG_COMPAT for (j = 0; compat_hwcap_str[j]; j++) if (compat_elf_hwcap & (1 << j)) ------------------8<---------------------
With the above, a compat task or a native one with PER_LINUX32 personality would get:
processor : 0 model name : ARMv8 Processor rev 0 (v8l) BogoMIPS : 100.00 Features : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt lpae evtstrm aes pmull sha1 sha2 crc32 CPU implementer : 0x41 CPU architecture: 8 CPU variant : 0x0 CPU part : 0xd03 CPU revision : 0
I have tested with your patch, the app still can not start up at all.
I'm sorry I didn't explan this exactly before, those apps are 32-bit android apps(com.tencent.pao etc.). They want to get the information as "*D m3e : GetCPUType:AArch64 Processor rev 0 (aarch64)*" and I'm sure the process is forked by zygote not zygote64 in android M.
So, these 32-bit applications would never run on an arm32 kernel (because with my patch, compat /proc/cpuinfo is the same as the native arm32 kernel)? How did they get into this situation?
I recall from some past discussions with Google on this aspect that there are indeed applications parsing /proc/cpuinfo but the 32-bit zygote would set PER_LINUX32 so that child processes would inherit it and always get the compat /proc/cpuinfo. I don't follow the Android developments, so I can't tell whether this personality setting is in place.
While we did change the /proc/cpuinfo 64-bit format slightly in 3.19, I find it insane that there are 32-bit applications relying on always running under a 64-bit kernel.