Re: getxpid() parent lookup is broken
From: Al Viro <viro@ZenIV.linux.org.uk>
Date: 2012-05-29 14:18:39
Subsystem:
alpha port, the rest · Maintainers:
Richard Henderson, Matt Turner, Magnus Lindholm, Linus Torvalds
On Tue, May 29, 2012 at 03:09:43PM +0100, Al Viro wrote:
On Tue, May 29, 2012 at 12:55:10AM -0400, Matt Turner wrote:quoted
I recently looked at this gentoo bug -- https://bugs.gentoo.org/show_bug.cgi?id=405829 and then came across this email and the two patches. They seem possibly related. It looks like Al said he thought he had a better way of fixing the problem, but then I'm not sure if his patches surfaced or not. Also possibly related, Tobias and Michael have seen some RCU stalls with recent kernels. Looks like getxpid needs an update?Umm... Let me see if I can find it... Here:
[snip] BTW, there's another completely untested patch bouncing around in the local tree - takes kernel_execve() out of entry.S
diff --git a/arch/alpha/kernel/alpha_ksyms.c b/arch/alpha/kernel/alpha_ksyms.c
index d96e742..b77b813 100644
--- a/arch/alpha/kernel/alpha_ksyms.c
+++ b/arch/alpha/kernel/alpha_ksyms.c@@ -52,7 +52,6 @@ EXPORT_SYMBOL(alpha_write_fp_reg_s); /* entry.S */ EXPORT_SYMBOL(kernel_thread); -EXPORT_SYMBOL(kernel_execve); /* Networking helper routines. */ EXPORT_SYMBOL(csum_tcpudp_magic);
diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S
index 4074645..a8c9db8 100644
--- a/arch/alpha/kernel/entry.S
+++ b/arch/alpha/kernel/entry.S@@ -663,58 +663,6 @@ kernel_thread: br ret_to_kernel .end kernel_thread -/* - * kernel_execve(path, argv, envp) - */ - .align 4 - .globl kernel_execve - .ent kernel_execve -kernel_execve: - /* We can be called from a module. */ - ldgp $gp, 0($27) - lda $sp, -(32+SIZEOF_PT_REGS+8)($sp) - .frame $sp, 32+SIZEOF_PT_REGS+8, $26, 0 - stq $26, 0($sp) - stq $16, 8($sp) - stq $17, 16($sp) - stq $18, 24($sp) - .prologue 1 - - lda $16, 32($sp) - lda $17, 0 - lda $18, SIZEOF_PT_REGS - bsr $26, memset !samegp - - /* Avoid the HAE being gratuitously wrong, which would cause us - to do the whole turn off interrupts thing and restore it. */ - ldq $2, alpha_mv+HAE_CACHE - stq $2, 152+32($sp) - - ldq $16, 8($sp) - ldq $17, 16($sp) - ldq $18, 24($sp) - lda $19, 32($sp) - bsr $26, do_execve !samegp - - ldq $26, 0($sp) - bne $0, 1f /* error! */ - - /* Move the temporary pt_regs struct from its current location - to the top of the kernel stack frame. See copy_thread for - details for a normal process. */ - lda $16, 0x4000 - SIZEOF_PT_REGS($8) - lda $17, 32($sp) - lda $18, SIZEOF_PT_REGS - bsr $26, memmove !samegp - - /* Take that over as our new stack frame and visit userland! */ - lda $sp, 0x4000 - SIZEOF_PT_REGS($8) - br $31, ret_from_sys_call - -1: lda $sp, 32+SIZEOF_PT_REGS+8($sp) - ret -.end kernel_execve - /* * Special system calls. Most of these are special in that they either
diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c
index 153d3fc..d6fde98 100644
--- a/arch/alpha/kernel/process.c
+++ b/arch/alpha/kernel/process.c@@ -455,3 +455,22 @@ get_wchan(struct task_struct *p) } return pc; } + +int kernel_execve(const char *path, const char *const argv[], const char *const envp[]) +{ + /* Avoid the HAE being gratuitously wrong, which would cause us + to do the whole turn off interrupts thing and restore it. */ + struct pt_regs regs = {.hae = alpha_mv.hae_cache}; + int err = do_execve(path, argv, envp, ®s); + if (!err) { + struct pt_regs *p = current_pt_regs(); + /* copy regs to normal position and off to userland we go... */ + *p = regs; + __asm__ __volatile__ ( + "mov %0, $sp;" + "br $31, ret_from_sys_call" + : : "r"(p)); + } + return err; +} +EXPORT_SYMBOL(kernel_execve);