91 lines
2.8 KiB
Diff
91 lines
2.8 KiB
Diff
From 40c112ed0d7d0577d2f84851c1f7b8157b3bd2f5 Mon Sep 17 00:00:00 2001
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From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Date: Mon, 31 Oct 2022 15:46:38 -0300
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Subject: [PATCH] elf: Remove allocate use on _dl_debug_printf
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The maximum number of directives is already limited by the maximum
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value of iovec, and current padding usage on _dl_map_object_from_fd
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specifies a value of 16 (2 times sizeof (void *)) in hexa, which is
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less than the INT_STRLEN_BOUND(void *) (20 for LP64).
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This works if pointers are larger than 8 bytes, for instance 16.
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In this case the maximum padding would be 32 and the IFMTSIZE would
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be 40.
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The resulting code does use a slightly larger static stack, the
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output of -fstack-usage (for x86_64):
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* master:
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dl-printf.c:35:1:_dl_debug_vdprintf 1344 dynamic
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* patch:
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dl-printf.c:36:1:_dl_debug_vdprintf 2416 static
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However, there is an improvement in code generation:
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* master
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text data bss dec hex filename
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330900 3309 ced elf/dl-printf.os
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* patch
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text data bss dec hex filename
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315100 3151 c4f elf/dl-printf.os
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Checked on x86_64-linux-gnu.
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Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
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---
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elf/dl-misc.c | 15 +++++++--------
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1 file changed, 7 insertions(+), 8 deletions(-)
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diff --git a/elf/dl-misc.c b/elf/dl-misc.c
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index a11d11d5..4a33737c 100644
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--- a/elf/dl-misc.c
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+++ b/elf/dl-misc.c
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@@ -34,6 +34,7 @@
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#include <_itoa.h>
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#include <dl-writev.h>
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#include <not-cancel.h>
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+#include <intprops.h>
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/* Read the whole contents of FILE into new mmap'd space with given
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protections. *SIZEP gets the size of the file. On error MAP_FAILED
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@@ -79,6 +80,9 @@ _dl_debug_vdprintf (int fd, int tag_p, const char *fmt, va_list arg)
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{
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# define NIOVMAX 64
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struct iovec iov[NIOVMAX];
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+ /* Maximum size for 'd', 'u', and 'x' including padding. */
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+ enum { IFMTSIZE = INT_STRLEN_BOUND(void *) };
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+ char ifmtbuf[NIOVMAX][IFMTSIZE];
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int niov = 0;
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pid_t pid = 0;
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char pidbuf[12];
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@@ -143,6 +147,8 @@ _dl_debug_vdprintf (int fd, int tag_p, const char *fmt, va_list arg)
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if (*fmt == '*')
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{
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width = va_arg (arg, int);
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+ /* The maximum padding accepted is up to pointer size. */
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+ assert (width < IFMTSIZE);
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++fmt;
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}
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@@ -203,14 +209,7 @@ _dl_debug_vdprintf (int fd, int tag_p, const char *fmt, va_list arg)
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#endif
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}
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- /* We use alloca() to allocate the buffer with the most
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- pessimistic guess for the size. Using alloca() allows
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- having more than one integer formatting in a call. */
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- int size = 1 + 3 * sizeof (unsigned long int);
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- if (width + 1 > size)
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- size = width + 1;
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- char *buf = (char *) alloca (size);
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- char *endp = &buf[size];
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+ char *endp = &ifmtbuf[niov][IFMTSIZE];
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char *cp = _itoa (num, endp, *fmt == 'x' ? 16 : 10, 0);
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/* Pad to the width the user specified. */
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--
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2.33.0
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