From a959cb4e648986a903fff8d72b0eb3483d2a937b Mon Sep 17 00:00:00 2001 From: Bruno Haible Date: Sun, 10 Jul 2022 23:19:03 +0200 Subject: [PATCH] sigsegv: Optimize stackvma implementation for AIX 7. Reported by Neha Jain in via Eric Blake. * lib/stackvma.c: For AIX, add implementation that uses /proc/$pid/map, based on lib/vma-iter.c. (sigsegv_get_vma): Use it on AIX 7 or higher. --- ChangeLog | 10 ++ lib/stackvma.c | 301 ++++++++++++++++++++++++++++++++++++++++++++++++- lib/vma-iter.c | 8 +- 3 files changed, 312 insertions(+), 7 deletions(-) diff --git a/ChangeLog b/ChangeLog index c9d1deb5dd..12abc601b0 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,13 @@ +2022-07-10 Bruno Haible + + sigsegv: Optimize stackvma implementation for AIX 7. + Reported by Neha Jain in + + via Eric Blake. + * lib/stackvma.c: For AIX, add implementation that uses /proc/$pid/map, + based on lib/vma-iter.c. + (sigsegv_get_vma): Use it on AIX 7 or higher. + 2022-07-10 Bruno Haible vma-iter: Add support for AIX 7. diff --git a/lib/stackvma.c b/lib/stackvma.c index 4d0e08616a..aab3575c4c 100644 --- a/lib/stackvma.c +++ b/lib/stackvma.c @@ -46,7 +46,7 @@ || defined __FreeBSD_kernel__ || defined __FreeBSD__ || defined __DragonFly__ \ || defined __NetBSD__ \ || (defined __APPLE__ && defined __MACH__) \ - || defined __sgi || defined __sun \ + || defined _AIX || defined __sgi || defined __sun \ || defined __CYGWIN__ || defined __HAIKU__ /* This file contains the proximity test function for the simple cases, where @@ -1465,17 +1465,312 @@ sigsegv_get_vma (uintptr_t req_address, struct vma_struct *vma) return -1; } -/* -------------------------------------------------------------------------- */ +/* ----------------------------- stackvma-aix.c ----------------------------- */ #elif defined _AIX /* AIX */ +# include /* getpagesize, getpid, close, read */ +# include /* EINTR */ +# include /* open */ +# include /* memcpy */ +# include +# include /* mmap, munmap */ +# include /* prmap_t */ +# include /* uname */ + +struct callback_locals +{ + uintptr_t address; + struct vma_struct *vma; +# if STACK_DIRECTION < 0 + uintptr_t prev; +# else + int stop_at_next_vma; +# endif + int retval; +}; + +static int +callback (struct callback_locals *locals, uintptr_t start, uintptr_t end) +{ +# if STACK_DIRECTION < 0 + if (locals->address >= start && locals->address <= end - 1) + { + locals->vma->start = start; + locals->vma->end = end; + locals->vma->prev_end = locals->prev; + locals->retval = 0; + return 1; + } + locals->prev = end; +# else + if (locals->stop_at_next_vma) + { + locals->vma->next_start = start; + locals->stop_at_next_vma = 0; + return 1; + } + if (locals->address >= start && locals->address <= end - 1) + { + locals->vma->start = start; + locals->vma->end = end; + locals->retval = 0; + locals->stop_at_next_vma = 1; + return 0; + } +# endif + return 0; +} + +/* Iterate over the virtual memory areas of the current process. + If such iteration is supported, the callback is called once for every + virtual memory area, in ascending order, with the following arguments: + - LOCALS is the same argument as passed to vma_iterate. + - START is the address of the first byte in the area, page-aligned. + - END is the address of the last byte in the area plus 1, page-aligned. + Note that it may be 0 for the last area in the address space. + If the callback returns 0, the iteration continues. If it returns 1, + the iteration terminates prematurely. + This function may open file descriptors, but does not call malloc(). + Return 0 if all went well, or -1 in case of error. */ +/* This code is a simplified copy (no handling of protection flags) of the + code in gnulib's lib/vma-iter.c. */ +static int +vma_iterate (struct callback_locals *locals) +{ + /* On AIX, there is a /proc/$pic/map file, that contains records of type + prmap_t, defined in . In older versions of AIX, it lists + only the virtual memory areas that are connected to a file, not the + anonymous ones. But at least since AIX 7.1, it is well usable. */ + + char fnamebuf[6+10+4+1]; + char *fname; + int fd; + size_t memneed; + + if (pagesize == 0) + init_pagesize (); + + /* Construct fname = sprintf (fnamebuf+i, "/proc/%u/map", getpid ()). */ + fname = fnamebuf + sizeof (fnamebuf) - (4+1); + memcpy (fname, "/map", 4+1); + { + unsigned int value = getpid (); + do + *--fname = (value % 10) + '0'; + while ((value = value / 10) > 0); + } + fname -= 6; + memcpy (fname, "/proc/", 6); + + fd = open (fname, O_RDONLY | O_CLOEXEC); + if (fd < 0) + return -1; + + /* The contents of /proc//map contains a number of prmap_t entries, + then an entirely null prmap_t entry, then a heap of NUL terminated + strings. + Documentation: https://www.ibm.com/docs/en/aix/7.1?topic=files-proc-file + We read the entire contents, but look only at the prmap_t entries and + ignore the tail part. */ + + for (memneed = 2 * pagesize; ; memneed = 2 * memneed) + { + /* Allocate memneed bytes of memory. + We cannot use alloca here, because not much stack space is guaranteed. + We also cannot use malloc here, because a malloc() call may call mmap() + and thus pre-allocate available memory. + So use mmap(), and ignore the resulting VMA if it occurs among the + resulting VMAs. (Normally it doesn't, because it was allocated after + the open() call.) */ + void *auxmap; + unsigned long auxmap_start; + unsigned long auxmap_end; + ssize_t nbytes; + + auxmap = (void *) mmap ((void *) 0, memneed, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (auxmap == (void *) -1) + { + close (fd); + return -1; + } + auxmap_start = (unsigned long) auxmap; + auxmap_end = auxmap_start + memneed; + + /* Read the contents of /proc//map in a single system call. + This guarantees a consistent result (no duplicated or omitted + entries). */ + retry: + do + nbytes = read (fd, auxmap, memneed); + while (nbytes < 0 && errno == EINTR); + if (nbytes <= 0) + { + munmap (auxmap, memneed); + close (fd); + return -1; + } + if (nbytes == memneed) + { + /* Need more memory. */ + munmap (auxmap, memneed); + if (lseek (fd, 0, SEEK_SET) < 0) + { + close (fd); + return -1; + } + } + else + { + if (read (fd, (char *) auxmap + nbytes, 1) > 0) + { + /* Oops, we had a short read. Retry. */ + if (lseek (fd, 0, SEEK_SET) < 0) + { + munmap (auxmap, memneed); + close (fd); + return -1; + } + goto retry; + } + + /* We now have the entire contents of /proc//map in memory. */ + prmap_t* maps = (prmap_t *) auxmap; + + /* The entries are not sorted by address. Therefore + 1. Extract the relevant information into an array. + 2. Sort the array in ascending order. + 3. Invoke the callback. */ + typedef struct + { + uintptr_t start; + uintptr_t end; + } + vma_t; + /* Since 2 * sizeof (vma_t) <= sizeof (prmap_t), we can reuse the + same memory. */ + vma_t *vmas = (vma_t *) auxmap; + + vma_t *vp = vmas; + { + prmap_t* mp; + for (mp = maps;;) + { + unsigned long start, end; + + start = (unsigned long) mp->pr_vaddr; + end = start + mp->pr_size; + if (start == 0 && end == 0 && mp->pr_mflags == 0) + break; + /* Discard empty VMAs and kernel VMAs. */ + if (start < end && (mp->pr_mflags & MA_KERNTEXT) == 0) + { + if (start <= auxmap_start && auxmap_end - 1 <= end - 1) + { + /* Consider [start,end-1] \ [auxmap_start,auxmap_end-1] + = [start,auxmap_start-1] u [auxmap_end,end-1]. */ + if (start < auxmap_start) + { + vp->start = start; + vp->end = auxmap_start; + vp++; + } + if (auxmap_end - 1 < end - 1) + { + vp->start = auxmap_end; + vp->end = end; + vp++; + } + } + else + { + vp->start = start; + vp->end = end; + vp++; + } + } + mp++; + } + } + + size_t nvmas = vp - vmas; + /* Sort the array in ascending order. + Better not call qsort(), since it may call malloc(). + Insertion-sort is OK in this case, despite its worst-case running + time of O(N²), since the number of VMAs will rarely be larger than + 1000. */ + { + size_t i; + for (i = 1; i < nvmas; i++) + { + /* Invariant: Here vmas[0..i-1] is sorted. */ + size_t j; + for (j = i; j > 0 && vmas[j - 1].start > vmas[j].start; j--) + { + vma_t tmp = vmas[j - 1]; + vmas[j - 1] = vmas[j]; + vmas[j] = tmp; + } + /* Invariant: Here vmas[0..i] is sorted. */ + } + } + + /* Invoke the callback. */ + { + size_t i; + for (i = 0; i < nvmas; i++) + { + vma_t *vpi = &vmas[i]; + if (callback (locals, vpi->start, vpi->end)) + break; + } + } + + munmap (auxmap, memneed); + break; + } + } + + close (fd); + return 0; +} + int sigsegv_get_vma (uintptr_t address, struct vma_struct *vma) { + struct utsname u; + if (uname (&u) >= 0 + /* && strcmp (u.sysname, "AIX") == 0 */ + && !(u.version[0] >= '1' && u.version[0] <= '6' && u.version[1] == '\0')) + { + /* AIX 7 or higher. */ + struct callback_locals locals; + locals.address = address; + locals.vma = vma; +#if STACK_DIRECTION < 0 + locals.prev = 0; +#else + locals.stop_at_next_vma = 0; +#endif + locals.retval = -1; + + vma_iterate (&locals); + if (locals.retval == 0) + { +#if !(STACK_DIRECTION < 0) + if (locals.stop_at_next_vma) + vma->next_start = 0; +#endif + vma->is_near_this = simple_is_near_this; + return 0; + } + } + return mincore_get_vma (address, vma); } -/* --------------------------- stackvma-procfs.h --------------------------- */ +/* --------------------------- stackvma-procfs.c --------------------------- */ #elif defined __sgi || defined __sun /* IRIX, Solaris */ diff --git a/lib/vma-iter.c b/lib/vma-iter.c index fca4626ee3..44fa2a3855 100644 --- a/lib/vma-iter.c +++ b/lib/vma-iter.c @@ -894,10 +894,10 @@ vma_iterate (vma_iterate_callback_fn callback, void *data) #elif defined _AIX /* AIX */ -/* On AIX, there is a /proc/$pic/map file, that contains records of type - prmap_t, defined in . In older versions of AIX, it lists - only the virtual memory areas that are connected to a file, not the - anonymous ones. But at least since AIX 7.1, it is well usable. */ + /* On AIX, there is a /proc/$pic/map file, that contains records of type + prmap_t, defined in . In older versions of AIX, it lists + only the virtual memory areas that are connected to a file, not the + anonymous ones. But at least since AIX 7.1, it is well usable. */ size_t pagesize; char fnamebuf[6+10+4+1]; -- 2.39.5